Scientists say they have uploaded a real genome to a quantum computer for the first time, marking an important step in applying the emerging technology to biology.

The researchers encoded the entire genome of the hepatitis D virus (HDV) onto a system powered by IBM's 156-qubit Heron quantum processing unit. This achievement came during the Quantum for Bio (Q4Bio) challenge, a competitive international research program designed to accelerate quantum computing applications for human health. The goal was to demonstrate that quantum computers could handle real-world genomic data in a format the machines could actually process.

A genome is naturally stored as a long sequence of letters (A, C, G, and T/U), whereas a quantum computer works with quantum states represented by qubits. Simply copying DNA letters into qubits is not enough; the information has to be transformed into a quantum representation that can be prepared, manipulated, and measured by the hardware.

The scientists with the Wellcome Sanger Institute converted the HDV genome into a quantum-compatible format, allowing quantum algorithms to analyze genetic information rather than just theoretical problems.

They said in a statement that they specifically targeted the most complex and variable genomes ‪—‬ tasks that can exceed the current capabilities of classical computers, including artificial intelligence (AI) systems.

Where quantum computing and biology intersect

"When we work with pangenomes, the information is presented in a form of a tangled maze, but we are building quantum algorithms to help find the best path through this maze when regular tools, such as classic computers, just get hopelessly stuck," said leader of the research team, Sergii Strelchuk, an associate professor at the Department of Computer Science at the University of Oxford.

"We’re aiming for a simple but game-changing idea by bringing quantum computing into the world of genomics."

The same researchers already demonstrated four key genomics capabilities on real quantum hardware within the same Q4Bio genomics project. They used data encoding to convert DNA sequences into a quantum-compatible format.

A step called sequence alignment mapped DNA fragments into reference genomes, while a process called pangenome assembly built genomes from multiple individuals' DNA data. They also used, phylogenetic tree construction to map evolutionary relationships among organisms.

The scientists chose HDV because it has a compact genome and is clinically relevant. Although its RNA folds into intricate secondary structures — rather than existing as a simple linear sequence — and it mutates rapidly (like many RNA viruses), HDV has one of the smallest known animal virus genomes — roughly 1,700 nucleotides of circular RNA.

It causes severe blood-borne liver infections through contact with infected bodily fluids, making it an ideal test case that balances complexity with practical biomedical importance, the team said.

Increasingly complex computations

The work also demonstrates that pangenomes — collections of genome sequences from many individuals of the same species — are where quantum computing truly shines. As more genomes join a pangenome, conventional computing resources can be overwhelmed due to combinatorial growth in complexity.

A pangenome is not just a collection of genomes stored side by side but a data structure that captures all the genetic variation across many individuals, strains, or populations. As more genomes are added, the amount of variation that must be represented, compared, and indexed grows rapidly.

Quantum machines may be better able to navigate this computational complexity because they can represent and process many possible genetic patterns at once in a way that might make certain large-scale comparison and search problems in genomics faster (or more efficient) than traditional computers.

In the future, faster and more powerful genomic analysis could let scientists rapidly track infectious diseases, improve their understanding of rare genetic disorders, and pinpoint disease-causing mutations, the team said. Loading the hepatitis D genome onto a quantum computer opens the door to solving biological problems that have been impossible for classical computers to tackle, James McCafferty, chief information officer at the Wellcome Sanger Institute, said in the statement.

Although the accomplishment is promising, practical applications may still be years away, Strelchuk and colleagues on the Q4Bio team said in the statement. The team wants to package these capabilities into a usable service that would allow the wider scientific community to upload data and choose between classical or quantum approaches (or both) to address computational challenges.

Can you match these ancient devices to their pictures? Find out with our computing quiz!

Scientists genetically tweaked a tiny, worm-like parasite to produce a life-saving antitoxin from inside a living host.

In a first-of-its-kind study, researchers modified the hookworm Ancylostoma ceylanicum so that it produces antibodies that partially neutralize the potent pufferfish poison tetrodotoxin.

The approach has so far been tested in hamsters, but the ultimate aim is to use it in people. In fact, the study was funded by the U.S. Department of Defense with a view to developing protective treatments for military personnel exposed to chemical or biological threats, such as tetrodotoxin, study co-author Alex Loukas, director of the Australian Institute of Tropical Health and Medicine at James Cook University, told Live Science.

That said, future work could see these worms engineered to produce a variety of other medications and excrete them inside the human body, the study authors wrote in a report published June 3 in Nature Communications. For instance, they could deliver long-term treatments for chronic diseases, such as type 2 diabetes or inflammatory bowel syndrome, Loukas suggested.

From parasite to antitoxin factory

Hookworms are one of humanity's oldest parasites and infect upwards of 400 million people globally, primarily in tropical regions. Like an internal leech, these small intestinal worms latch on to the inner wall of the gut to feed on blood, simultaneously releasing a variety of anti-inflammatory and immunosuppressant compounds to prevent the body from flushing them out.

Each worm is about 0.4 inches (1 centimeter) long and consumes less than two drops of blood a day, and healthy hosts often don't experience any symptoms of infection. The hookworm used in this study, A. ceylanicum, infects humans, dogs and cats.

"The hookworm has spent millions of years perfecting how to assure long-term survival inside a human host and how to get molecules out of its body and into ours," study co-author Makedonka Mitreva, professor at Washington University School of Medicine in St. Louis, Missouri, said in a statement.

The cocktail of compounds produced by these parasites has already shown some promise in treating metabolic disorders such as metabolic syndrome and type 2 diabetes, as well as celiac disease. However, studies so far have been restricted to molecules produced by the hookworms naturally.

The new work pushes this concept one step further. "We asked: What if we could add one more molecule to the roughly 1,000 things the worm already secretes, something therapeutically useful to people?" Mitreva said. "This study shows that's not just a concept. It works."

Using CRISPR gene-editing technology, the team inserted a gene coding for an antibody known to counteract the deadly pufferfish poison tetrodotoxin into the hookworm's genome at the egg stage. Mitreva's team had to carefully consider the placement of the gene, ensuring it didn't interfere with other critical regions of DNA, yet still promoted production and secretion of the new protein.

The team then infected hamsters with 80 to 100 of the modified parasite larvae. Upon maturation, the adult worms containing the newly inserted gene were able to produce the antibody and then secreted it into the hamster's bloodstream. Blood samples later taken from the infected hamsters partially neutralized the tetrodotoxin poison in lab experiments, showing compounds produced by the worm were active in the hamster.

On paper, the same approach could be used to secrete other antibodies or peptide drugs — which are short bits of protein — to directly treat gastrointestinal disorders, Loukas said.

"We're thinking about actively introducing antibodies that neutralize inflammatory hormones or cytokines," to treat conditions such as inflammatory bowel disease, he said. "You can also think about the possibility of a worm that secretes very very small quantities of food allergens to desensitize the host for childhood food allergies,” he added.

Looking forward, the team wants to extend the durability of the therapeutic molecules the worms release, since they can only make so much at a time, he noted.

While it may sound counterintuitive to infect a person with a parasite to help them feel better, hookworms actually have an excellent safety profile, Loukas said. A quirk of their biology means there is no chance of the infection getting out of control.

Hookworm larvae enter the body through the skin and migrate to the small intestine where they mature into adults, often living for years without noticeably impacting the host. Any eggs the adult parasites produce must hatch outside of the host; they exit in the host's stool. That means the number of adult worms in the body remains fairly constant.

What's more, with a single dose of a standard anti-worming treatment, the infection clears within 24 hours. So any hookworm-based treatments could be easily cleared from a person's system.

"It's exciting and it's really opening up an entirely new way of delivering and producing therapeutic molecules," Loukas said.

Indigenous Andeans in Peru may be able to digest potatoes and other starches more easily than anyone in the world, a new study finds.

Scientists discovered that Indigenous Andeans have more copies of the gene for saliva-based starch digestion enzymes — called amylase — than any other population worldwide. Natural selection drove the surge in amylase genes following the local domestication of potatoes around 10,000 years ago, according to the study published May 5 in the journal Nature Communications.

Amylase in humans' saliva breaks complex starch down into simple sugars, making the starch easier to digest. Populations worldwide differ in the number of gene copies that encode for amylase, but more copies means more amylase production and presumably, improved starch digestion.

On average, people around the world have seven copies of the amylase gene, but Indigenous Andeans in Peru possess an average of 10 copies. People with a higher number of amylase genes had a 1.24% higher chance of surviving and reproducing than those with fewer copies, the researchers wrote in the study.

While that number seems small, this is an "insanely high" adaptive advantage that would have compounded over each successive generation, study co-author Omer Gokcumen, a professor of biological sciences at the University of Buffalo, told Live Science.

Being able to digest amylase effectively was more than just passing gas when eating potatoes, Gokcumen said. The strong survival and reproductive advantage suggests either a substantial number of babies did not survive because the pregnancies were not successful, or people with more gene copies have more babies, he said. "It's actually a life or death kind of situation."

Variation in starch digestion

Beginning around 12,000 years ago, the ancient people living in the Andes had developed a slew of new adaptations, including the ability to live at high altitudes and digest new foods.

Previous analysis of the genomes of Peruvians of Indigenous South American ancestry revealed signs of selection for an intestinal starch digestion enzyme. That adaptation was likely the result of Indigenous Andean populations having domesticated potatoes as early as 10,000 years ago.

In 2024, Gokcumen and his team identified variation in the structure of salivary amylase genes across global populations. But the cause of that variation was unclear.

To figure out what caused the difference, in the new study, Gokcumen and his team created a map of salivary amylase gene copy numbers using genome data from 3,723 individuals from 85 global populations. They found that Peruvian Andeans and Akimel O'odham people in southern Arizona and northern Mexico had the highest average number of salivary amylase genes out of the populations they studied.

The researchers found that, beginning around 10,000 years ago, Indigenous Andean individuals with 10 or more copies of the salivary amylase gene had a 1.24% higher chance of surviving and reproducing than those with fewer copies — evidence that natural selection caused the elevated copy number in the Indigenous Andeans in their sample.

The Akimel O'odham samples also showed high copy numbers, but the researchers could not perform tests looking for signs of natural selection in this population as too few Akimel O'odham individuals were included in their sample.

The functional advantage of having more salivary amylase copies is unknown. Gokcumen said it could have something to do with the microbiome, metabolism and immune system. For instance, people with more copies of the gene may get more calories from cooked potatoes. He and his team are now running experiments to clarify these potential relationships, he said.

This is an "exciting and important study," Charles Lee, a human genomics expert at The Jackson Laboratory for Genomic Medicine in Connecticut who was not involved in the new study, told Live Science in an email.

The high copy numbers in the Akimel O'odham samples suggests that "different Indigenous American groups may have developed high amylase copy numbers in different ways, depending on their diets," Lee said.

Salivary amylase gene copy number variation is unlikely to be the only example of adaptive variation in gene structure, Lee added. "It is simply one of the best examples we currently have of how complex copy number variation can intersect with diet, culture and human evolution," he said.

Do you know where pumpkins and blueberries come from? Find out with our fruits and vegetables quiz!

Whether using family records, DNA tests or genealogy websites, many people can trace their family histories back generations. The world-record holder for the longest family tree is Chinese philosopher Confucius (551 to 479 B.C.), whose family tree extends more than 80 generations from his ancestors in the eighth century B.C. to his living descendants. That's almost 3,000 years.

But our species has been around for 300,000 years, based on scientific dates of the oldest known fossils. So how many generations do we go back as a species?

To find out, you need to know how long modern humans (Homo sapiens) have existed and the length of a generation, according to Matthew Hahn, a population geneticist at Indiana University Bloomington. The number of human generations that have lived would be equal to the time since H. sapiens emerged as a species divided by the length of a generation, also called the generation interval.

The generation interval is typically defined as the average age at which humans have children, Hahn said. It tends to be longer for men than for women because men can have children later in life, Hahn explained.

There are many estimates of our species' generation interval, each of which produces a different answer to the question of how many human generations have come before us.

For example, a 2003 study of Icelanders published in the American Journal of Human Genetics based generation interval estimates on the country's extensive records from churches and other sources. Using these records, researchers at the company deCODE Genetics created a genealogical database of the country's entire population. They found that the average generation interval in Iceland over the past 300 years was 30.3 years.

A 2005 study used data about the average age at which European women had children between 1960 and 2000 and estimated the generation intervals for men to arrive at an average generation interval of 29.1 years.

But those are estimates of the generation interval in the recent past. A study led by Hahn and published in the journal Science Advances in 2023 estimated the generation interval over the past 250,000 years. Hahn's study put together data from two others. A 2017 study of Icelanders, also led by deCODE Genetics and published in the journal Nature, found that as parents age, the blend of mutations that arise in their children changes. Using this data, Hahn and colleagues built a model of the mix of new mutations that you would expect to find in a group of people according to the generation interval at the time.

"If you know the types of mutations that individuals leave to their children according to their age, if you have a collection of mutations, you can try to estimate how old the mixture of individuals was," Hahn said.

A 2020 study in the journal PLOS Biology estimated when millions of mutations found in humans today first arose. Hahn and colleagues grouped the mutations from the 2020 paper according to when they arose and then determined the blend of new mutations that popped up during each time period. With that information, they could estimate the generation interval for each time span. While the generation interval varied over the course of an estimated 250,000 years, it was an estimated 26.9 years, on average. Using that generation interval, there would have been an estimated 11,152 generations of humans over 300,000 years, Hahn said.

Moisès Coll Macià, an evolutionary biologist and population geneticist who works as a postdoctoral researcher at the Institute of Evolutionary Biology in Barcelona, Spain, told Live Science that while a generation interval of 26.9 years is "not unimaginable," he prefers to give a range of possible generation intervals.

In Coll Macià's view, the lower bound would be the generation interval for one of our closest living relatives, chimpanzees (Pan troglodytes). Because humans and chimps share a common ancestor that lived during the Miocene epoch (23 million to 5 million years ago), you would expect that past human generations would have had a generation interval somewhere between that of contemporary humans and that of contemporary chimps, Coll Macià said. Chimpanzees have an estimated generation time of about 24.6 years, according to a 2012 paper in the journal PNAS.

As for the upper bound in modern humans, Coll Macià suggested 26 to 30 years. That's based on a 2016 PNAS study that analyzed fragments of Neanderthal DNA found in ancient and contemporary human genomes to estimate the human generation interval across the past 45,000 years.

Based on Coll Macià's upper-bound generation interval of about 30 years, there have been at least 10,000 generations of humans. Based on the lower-bound generation interval of 24.6 years, there have been at most 12,195 generations. These numbers attest that the human family tree is pretty tall, however you look at it.

See how much you know about early humans with our human evolution quiz!

The Romans controlled much of Britain for nearly 400 years, but they left relatively little genetic evidence of their occupation, new ancient-DNA research reveals.

Instead, the Roman occupation, from A.D. 43 until about 410, seems to have changed the culture of their Britannia province, with most people native to Britain converting to Imperial Roman ways.

A preprint of the study was posted to the bioRxiv server April 29 and has not been published in a peer-reviewed journal yet. Some experts agree with the conclusions, but others are cautious.

However, some of the study's findings agree with the results of earlier genetic studies of the Germanic migration into Britain, Duncan Sayer, an archaeologist at the University of Lancashire in England, told Live Science.

"These results absolutely confirm the data we've had previously," said Sayer, who was not involved in the study.

For their investigations, the researchers looked at the genomes of more than 1,000 individuals who had been buried in Britain between 2550 B.C. and A.D. 1150. They found that Roman DNA — identified as having ancestral origins "outside Britain" — accounted for only about 20% of the genetic profile of individuals buried in Britain during its Roman era. By comparison, in the later Anglo-Saxon era, DNA from "Germanic" sources accounted for about 70% of the genetics of people buried there at that time.

These findings indicate that the native British interbred surprisingly little with people from elsewhere in the Roman Empire but often interbred with people of Anglo-Saxon origin, Sayer said.

"In the Roman period, although people are settling in Britain, it's not in quite the same way as Germanic speakers [Anglo-Saxons] are in the fifth and sixth centuries," James Gerrard, an archaeologist at Newcastle University in England who was not involved in the research, told Live Science.

The team who worked on the latest study said they also found very little genetic evidence of the later Viking Age in the North of England, when most of that region followed Danish traditions and was called the Danelaw: only about 4% of the genetic profiles of people buried in England at this time showed they had Iron Age Scandinavian ancestry, they reported.

Meanwhile, ancestries from Central and Southern Europe rose from the eighth century onward that signified more people migrated into England during the medieval period, the team wrote in the preprint.

Cultural transformation

The authors noted that "previous DNA sampling from Roman Britain has been relatively small-scale and regionally or context specific" and suggested that their "dataset bridges this gap."

But Gerrard, who was not involved in the study, cautioned that the new research might not give an accurate picture of Britain's genetic history.

To begin with, while the new study examined the DNA extracted from 1,039 people buried in Britain between the Bronze Age and medieval times — a span of roughly 3,700 years — only about 200 were from the Roman period.

This is a small sample size compared with archaeological investigations in Britain, where the origins of several thousand people buried during the Roman period have been examined over decades, he said.

In addition, the burials in the new research tended to be from cities, rather than from the countryside, where intermarriage rates may have differed. The results of the study might have also been skewed because the Roman presence would have been greater in the North of England, where many troops were stationed at camps, and in the East of England, where Roman urban settlements were more common, he said.

"We have a problem, I think, of whether ancient DNA is representative of the whole population," Gerrard said.

Celtic women

The Romans invaded and annexed most of Britain at the command of Emperor Claudius in A.D. 43, although his great-great-granduncle (by adoption) Julius Caesar led two short-lived invasions in 55 and 54 B.C. The Roman occupation ended in about A.D. 410, when Roman troops guarding the northern frontier were recalled to the continent to defend Roman territories against Germanic invasions.

Although the study found relatively little genetic evidence of the Roman occupation, the researchers noted that the Romans seemed to have had a marked effect on burial practices. Pre-Roman burials in Britain were often grouped by matrilineal relationships, perhaps reflecting the traditionally Celtic importance of women as the heads of their families, and the researchers found evidence that this practice continued for a time in the West of England — a native stronghold. Under this cultural tradition, women were relatively empowered and stayed in their ancestral homes, and the men they married moved into their communities.

But the DNA extracted from the remains in Roman-era cemeteries in Britain showed no such patterns, the researchers said, which might reflect traditional Roman patriarchal practices.

The authors of the new research declined a request from Live Science to comment, noting that they wanted to wait until the paper is published in a peer-reviewed journal before talking with the media.

What do you know about the Empire's conquest of the British Isles? Find out with our Roman Britain quiz!

Epigenetics, which means "above genetics," results in changes to the way an individual's genes act without involving changes to the DNA itself. For example, by adding molecules called methyl groups to DNA — a process called DNA methylation — epigenetics may turn genes on or off, or increase or decrease their activity.

Environmental factors ‪—‬ such as stress, diet and smoking ‪—‬ can fuel epigenetic modifications which can, in turn, lead to conditions such as colorectal cancer and heart disease.

But some of these epigenetic modifications can be reversed. This means that epigenetics can reveal potentially new and targeted ways of modifying disease risk, Alika Maunakea, a professor of anatomy, biochemistry and physiology at the University of Hawaii at Manoa, told Live Science.

Having grown up subsistence-living on a homestead in Hawaii, Maunakea said he learned from a young age that the environment plays a major role in shaping the health of the community.

Now, Maunakea has been researching epigenetics for over 20 years and heads the Maunakea Lab, which focuses on how environmental and epigenetic factors act at the molecular level to fuel health disparities. Live Science spoke with Maunakea to unpack how epigenetics affects health and what his research is uncovering about how epigenetics plays a role in driving health disparities in Native Hawaiians.

Sophie Berdugo: Can you explain how genetics and epigenetics interact in a health context?

Alika Maunakea: It's a little complicated because there's a lot of nuanced differences and variability in understanding the context behind disease risk that's not just shaped by genetic predisposition but also environmental factors and lifestyle, and even things that our grandparents experienced. That's where epigenetics comes in.

Epigenetics is this intermediate state between the environment and the genome, and it helps to regulate the genome. So, even if you carry a genetic risk, it doesn't necessarily mean that risk will play out.

They [genetics and epigenetics] relate to each other because there are certain regions in the genome where if there's a polymorphism — a change — in the sequence, that can sometimes cause a change in the epigenetic patterning. So there's this intertwined connection between the two. In some cases, it's hard to separate completely the genetic variability that's conferring a risk of a particular outcome with epigenetic variability that's contributing to that same risk.

If a lot of the epigenetic variability is contributing to that risk — rather than genetic variability — then there's a chance that there are lifestyle changes, things that you can modify at the individual level to reshape the epigenome, that would then help to reduce that risk. So there's still a lot of work [to be done] around understanding that connection, and it will require a multidisciplinary approach and integrating multiple types of data.

SB: What got you interested in this field?

AM: My great-grandmother was a Hawaiian healer — what we call "kahuna la'au lapa'au" — and she taught me "nā mea Hawai'i," so "all the things Hawaiian." There was a deep understanding and recognition for how maintaining a healthy built and natural environment around us actually does shape our own health and well-being.

I was really interested in understanding why our population, Native Hawaiians, has a higher prevalence of specific chronic conditions which we never had before Westernization, and trying to understand, why do we see it earlier, at a younger age, in our population compared to other populations? That was something that really bothered me. I wanted to understand that more at the cell and gene level, so I think I just gravitated naturally towards epigenetics because I think it explains that phenomenon.

My main goal is really to apply that information into more of a clinical, community-based setting where that information can be used to enable tools and approaches that would help reduce the onset of these disorders in our community.

What we're learning now is that, indeed, epigenetic processes can precede disease symptoms. We can actually identify some of the earlier indicators of disease trajectories before our clinical diagnosis, using epigenetic analyses. Trying to understand how that can play a role in enabling prevention is a real big thing in my lab right now.

SB: Which health conditions do you look at in your research?

AM: One of the conditions that we're looking at is type 2 diabetes, which has such a high prevalence amongst Native Hawaiians. It's three times higher than in other populations in the state, as well as an earlier onset of disorder: about 10 to 15 years younger where Native Hawaiians are diagnosed with type 2 diabetes compared to other populations in the state. [They also have] higher rates of mortality due to type 2 diabetes and other chronic conditions.

Pre-colonization [pre-Western contact in 1778], we never had [chronic conditions like type 2 diabetes] as an issue in our population. Our "kahuna la'au lapa'au" [Hawaiian healer], like my great-grandmother, had to invent new terms for them based on the phenotype [how the condition is presenting]. So we call it [type 2 diabetes] "mimi koko," which is "sweet blood."

It's unclear how much of our genotype is really related to that disease risk, but we think that environmental factors and the changes that happened after colonization and Westernization, and the changes in our lifestyle and our society — disruption and especially displacement — really drove us to this state where there's this higher incidence now of these conditions. And so we're trying to understand what, at the molecular level, is shaping those outcomes and how we can use that information to prevent that from happening in the first place.

One of the questions that really immediately came out was, what's really behind the earlier age of onset? Why do we not only have a higher prevalence, but why is it happening at a younger age? That question still remains to be clarified, but we think that certain traits, like obesity, modify that risk.

To get at that question, then, we really need to understand, at the molecular level, are there disruptions to the aging process in this population? Are there differences in vulnerabilities to aging in this population versus other populations that might be influenced by these environmental factors?

There's a phenomenon called "epigenetic aging," which Steve Horvath back in 2013 initially published a paper around, and identified that there are certain sites in the genome that are epigenetically regulated — by DNA methylation, in particular — that correlate with chronological age really well in a healthy population.

But there were some individuals that exhibited what we would call outliers in this relationship, where there were cases where individuals seem to have higher estimated epigenetic age compared to their chronological age. So they would seem [to be] biologically aging faster than they should be normally. And then there were also people at the opposite end, where their estimated epigenetic age actually appeared younger than their chronological age. And we think that corresponds to health in general.

We found something similar in the Native Hawaiian population: There's a higher frequency of individuals in the Native Hawaiian population that seem to be, at the molecular level, aging faster than they should be compared to other populations, such as white populations and Japanese American populations in the state of Hawaii.

And we know that corresponds to the higher prevalence of these chronic conditions that we see, like diabetes in the Native Hawaiians compared to these other populations, as well as some of these risk factors, like obesity. And we've seen it in our community. Individuals that are in socioeconomically poorer neighborhoods tend to have this accelerated aging.

We're learning that there are certain individual-level lifestyle factors that can actually potentially modify that [epigenetic] risk. We have identified that even amongst Native Hawaiians that are living in socioeconomically poorer areas, at the individual level, if there's a higher degree of physical activity as well as education — and even in some cases, nutrition — there tends to be closer-to-normal biological aging amongst those individuals even within that population.

And so that told us that while there's a higher risk for individuals that have this accelerated aging of diseases like diabetes, that risk could be potentially modified by engaging in healthier lifestyle changes.

Now we're not only seeing that there's this disparity and potentially a mechanism that might underlie that disparity but some clues into potentially what types of environmental factors might be shaping that molecular process.

We have one pilot study that we published a few years ago showing clearly that amongst Native Hawaiians that are diabetic, when they engage in a lifestyle intervention that includes social support, in particular, they not only improve their glycemic control — which is the main purpose of this intervention, really — through this lifestyle modification over a 12-week period, but we also showed that the cells that relate to inflammation, the behavior of those cells, is actually modified by that intervention, and they actually seem to be less inflamed. [Glycemic control is the management of blood glucose levels.]

The epigenomes of those cells are also being modified to a pattern that's similar to a nondiabetic-like state.

So we think those cells play a role in the pathology and the etiology [cause] of the disease and metabolic dysregulation in diabetic individuals. But we also think that modifying their inflammatory state might actually help with improving the glycemic control. So we're trying to understand how much of the epigenetic patterning might be associated with that [inflammation].

We're finding very clear associations that indicate that potentially we can use that information also to identify more effective interventions that might actually target this [epigenetic] process, where we can reduce the inflammatory state of these individuals at the cellular and molecular level.

We're really hoping that it can be useful for prevention, because we can identify these really early, before the clinical diagnosis. [Editor's note: These findings have not been published in a peer-reviewed journal.] And we think that if we can do that at the individual level, especially in a high-risk population, then we can recommend appropriate interventions — or optimize those interventions that exist — to target changes in the epigenome that then have this effect on the physiology and the outcomes of the condition itself. So that's something we're trying to develop further.

SB: How resource-intensive is it to inspect an individual's epigenome?

AM: It is resource-heavy, unfortunately, at this stage. So I think that it will take time to develop new technologies and tools that are more targeted and that can be used in more of a clinical setting.

But with genome sequencing being more cost-effective than it ever was before and the reduced cost that it's now moving towards, that does increase the feasibility to adopt some of these approaches.

Editor's note: This interview has been condensed and edited for clarity.

Fingerprinting transformed police investigations by making it possible to place a suspect at a crime scene with physical evidence. Similarly, genome sequencing has changed how disease detectives study outbreaks by allowing them to read a pathogen's genes as a biological record of where it came from and how it spread.

One way to think about sequencing is to imagine a virus or bacteria's genome as a recipe book. Each gene is a recipe for making a protein. When scientists sequence a pathogen, they read the order of the genetic letters in those recipes.

Over time, small changes appear in the recipes as the pathogen mutates. By comparing those changes in samples collected from different places and times, researchers can determine which infections are related and estimate when and where the pathogen entered a population.

Scientists have used sequencing in this way to track outbreaks of COVID-19, Ebola, mpox and foodborne illnesses. This information helps public health investigators connect cases that might otherwise seem unrelated.

Still, genomic sequencing has limits. It can show that different pathogen strains are related, but it cannot fully explain why an outbreak began in one place, why it spread in a particular direction, or how human behavior shaped its course. Answering those questions requires combining genomic data with historical records, archaeological artifacts, trade records and epidemiological investigations.

I am a chemist and the author of "Diseases Without Borders: Plagues, Pandemics, and Beyond," a book for young adults on infectious disease and the ways it has shaped human history. In my research, I've found that while the genome can help researchers trace the evolutionary trail of a pathogen, other fields are needed to explain the environmental conditions that allowed this trail to become an outbreak.

Ancient DNA tells only part of the story

Advances in DNA sequencing and extraction over the past decade have made it possible to recover fragments of ancient DNA from bones and teeth. Researchers can use these genomes to study a metaphorical molecular fossil record of microbial evolution.

The Black Death, one of the deadliest pandemics in history, shows both the power and the limits of sequencing.

The infectious disease behind the Black Death, plague, is caused by the bacterium Yersinia pestis. DNA recovered from the teeth of people buried more than 5,000 years ago in what is now Sweden revealed the existence of an ancestral form of Y. pestis that had not yet adapted to fleas.

About 2,000 years later, the bacterium made an important evolutionary shift: It gained the ability to survive in fleas and pass back and forth between humans, rats and other mammals via flea bites. That change made the pathogen far more dangerous and helped pave the way for three great plague pandemics that followed: the Justinianic Plague from the sixth to eighth century; the Black Death and later waves from the 1300s into the 1700s; and the third pandemic from the 19th to mid-20th centuries.

But how and why did plague emerge and move through human societies with such devastating results? Genetic results alone are not enough to answer these questions.

When gravestones become genetic evidence

Geneticists needed archaeologists, paleoclimatologists and historians to complete the picture of the plague pandemics. The genome revealed the lineage. Other disciplines supplied the historical and environmental context.

Two 14th-century graveyards in what is now Kyrgyzstan provide a striking example of how historical evidence can guide genetic investigations into the origins of a pandemic.

Historian Philip Slavin noticed archival records pointing to an unusual number of gravestones from 1338 and 1339. Some of those tombstones explicitly referred to a pestilence as the cause of death.

That clue led to the next stage of the investigation, where archaeologist Maria Spyrou and her team extracted and sequenced ancient DNA from the skeletal remains of seven people buried in the graves and found genetic traces of Yersinia pestis in three of the skeletons. These strains were close precursors of the strain linked to the Black Death and ancestors of several modern Y. pestis lineages.

This major finding was still not the whole story. It could explain where the Black Death pandemic began but not how the disease spread across Asia to Europe. Researchers found a potential answer to this question in artifacts buried at the site, which included pearls from the Indian Ocean, Mediterranean coral and foreign coins. Those objects suggested that the region was connected to long-distance trade networks.

Once the gravestones, skeletal remains, written records and trade goods were considered together, a richer picture emerged. Researchers could place the pathogen in a specific time and place and connect it to the networks of human movement that may have carried plague westward.

Sequencing provided the biological clue, revealing the pathogen’s identity and ancestry. History and archaeology turned that clue into a plausible narrative.

From ancient DNA to modern outbreaks

Genomic sequencing isn't limited to examining outbreak cold cases. It is also researchers' tool of choice for understanding new diseases.

When the first reported COVID-19 cases emerged in 2019, researchers quickly sequenced the virus and found that it was closely related to the virus that caused the 2002 SARS outbreak. This placed the new virus within a known family of pathogens.

Later genomic sequencing helped reveal the scale of a major superspreading event: the 2020 Biogen conference in Boston.

The biotech company Biogen brought together about 175 European and American executives at a moment when COVID-19 was only beginning to spread in the United States. In Europe, COVID-19 was also escalating, with northern Italy reporting locally transmitted clusters just days before the meeting. After the meeting, many Massachusetts cases were linked to the conference.

Researchers then analyzed thousands of viral genomes from patients in Massachusetts and elsewhere. One viral genome carried a unique genetic signature traceable to a European attendee at the conference. It matched viruses circulating in Europe but also had an additional mutation that appeared to have arisen during the attendee’s travel to Boston or early in the conference.

Because that altered sequence appeared only in people with direct or indirect ties to the meeting, it served as a genetic marker for the COVID-19 strain originating at the Biogen conference. By comparing it with other viral sequences in national databases, researchers tracked the strain associated with the conference to 29 states and several other countries.

Interviews and contact tracing alone couldn’t have made that chain of infection so clear because people may not know exactly when they were exposed, especially when infections spread through brief encounters, via travel or large meetings.

When genomes join the investigation

Genome sequencing has rewritten the history of disease by giving scientists a way to read a pathogen's own record of change.

It can link ancient graves to later pandemics and trace a modern outbreak from one conference room to cases across a continent.

But the greatest strength of genome sequencing lies in partnership. Sequencing does not replace history, archaeology or public health investigation. It gives them a new molecular partner.

Combining work from these fields produces a fuller and more accurate account of how disease moves through the world.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

In a first, researchers have sequenced genetic material from 400,000-year-old Homo erectus fossils — and the results reveal deep genetic links to both modern humans and the enigmatic Denisovans.

H. erectus was the earliest human ancestor to travel outside Africa and successfully spread into Europe, Asia and Oceania beginning 1.8 million years ago. With a relatively large brain and the ability to craft complex stone tools, H. erectus was the longest-lasting human ancestor until it disappeared around 108,000 years ago. But paleoanthropologists have long wondered if H. erectus overlapped and interbred with Homo sapiens, which evolved around 300,000 years ago in Africa.

In a new study published Wednesday (May 13) in the journal Nature, researchers detailed their analysis of dental enamel from six H. erectus skeletons discovered in three locations in China, all dating to about 400,000 years ago. The researchers extracted 11 different proteins from the enamel and identified hundreds of positions of amino acids, the building blocks of the proteins.

Two of those amino acid variants surprised the researchers — one was present in all six H. erectus individuals but not in any other human lineage, while the other was present in all H. erectus samples as well as in Denisovans, a group of archaic humans who lived in Asia and went extinct around 30,000 years ago. This amino acid variant was then passed from Denisovans to some H. sapiens groups through interbreeding tens of thousands of years ago.

The results are the first to show "deep genetic links" between these H. erectus individuals and present-day modern humans, the researchers wrote in a statement. The results are also a step forward for the relatively new technique called paleoproteomics, which allows scientists to sequence genetic material that lasts longer than DNA does.

"I don't believe that any previous DNA or proteomics have been done before" on H. erectus, study first author Qiaomei Fu, director of the Ancient DNA Laboratory at the Institute of Vertebrate Paleontology and Paleoanthropology, part of the Chinese Academy of Sciences, in Beijing, told Live Science in an email. But "how they evolved into modern humans and are related to the Denisovans, we really need to get DNA to understand that," she said.

DNA has a shorter shelf life than proteins do, and so far, researchers haven't found any H. erectus DNA that can be sequenced. However, Denisovan DNA has been sequenced.

The muddle in the middle

The Middle Pleistocene era (also called the Chibanian age) spanned from 774,000 to 129,000 years ago. During this era, a number of ancient human groups overlapped in Africa, Europe and Asia, including H. erectus, H. sapiens, Neanderthals and Denisovans, presenting paleoanthropologists with the difficult task of figuring out how they were all related — a confusion they call a "muddle."

"Scientists used to call this 'the muddle in the Middle Pleistocene,'" John Hawks, a paleoanthropologist at the University of Wisconsin-Madison who was not involved in the study, told Live Science in an email, "and now we know that muddling is just mixing." The new study of 400,000-year-old enamel proteins shows that mixing of different evolutionary branches was important to our evolution, "even earlier than DNA evidence can show us," Hawks said.

But what exactly the new results mean for the evolution of H. erectus — and the possibility that it interbred with modern H. sapiens in Eurasia — is still murky. "I think this raises the question of whether we know what Homo erectus even is," Hawks said.

Paleoanthropologists often define an ancient human species based on a group's physical features, such as the size and shape of their bones and teeth ‪—‬ a method called the "morphological species concept." But that way of determining species has been complicated by the rise in genomic analysis over the past two decades, which has revealed interbreeding among groups such as Neanderthals, Denisovans and modern humans, proving that there is some biological overlap among these groups.

But whereas the genetic information shared among groups around 50,000 years ago in Europe and Asia is relatively clear-cut thanks to DNA and genomic analysis, the newly revealed amino acid variations in 400,000-year-old fossils from China are just the first step in clarifying the "muddle in the Middle Pleistocene."

"What I'm concluding is that probably paleoanthropologists of the past were too willing to glom these Middle Pleistocene fossils from China into Homo erectus," Hawks said. "Many of these fossils are probably Denisovan relatives, or possibly they came from other groups we've been calling 'erectus' just because we don't really understand them."

The bottom line, according to Hawks, is that the new study is a great piece of work. "It's tough to look at data like these and not be impressed with the uncertainty of boundaries and the mixing between them in these past people," he said.

What do you know about early humans? Test your knowledge with our human origins quiz!

They sleep on our beds, steal our food, and generally rule the house. Between them, cats and dogs make up two-thirds of pet ownership worldwide. But which of the two companion animals are we more closely related to?

The answer depends on how you look at the question.

"From an evolutionary perspective we are equally related to dogs and cats," Mark Springer, a professor emeritus of evolution, ecology and organismal biology at the University of California, Riverside, told Live Science in an email.

Cats, dogs and humans are all mammals. In the mammalian family tree, which maps out how different mammal species are related to one another, both cats and dogs belong to the order Carnivora, while humans are primates. These two groups split from a common ancestor about 90 million to 95 million years ago, Springer said. Meanwhile, cats and dogs split from each other much later, around 55 million years ago.

In terms of common ancestry, "dogs and cats are more closely related to mammals such as pangolins, horses, cows, whales, bats, shrews and moles than they are to humans," Springer said. And "humans are more closely related to colugos [flying lemurs], tree shrews, rabbits, rats, and mice than they are to cats and dogs."

Genetic ties

Another way of deciding which species we are more closely related to is through a genetic lens.

If you measure how much the DNA code has changed over time, humans are about equally related to cats and dogs, William Murphy, a comparative genomicist at Texas A&M University, told Live Science in an email.

However, scientists also compare how DNA strands are organized within chromosomes. Here, a difference emerges.

Murphy explained that the ancestors of modern-day dogs went through extensive chromosome rearrangements over evolutionary time. (Such rearrangements are not unique to dogs; they occur across different animal and plant species, though scientists don't fully understand why some lineages rearrange faster than others.) Cats, on the other hand, retained a genome organization that's closer to ours. "In terms of how genes are arranged within chromosomes, humans and cats are twice as similar to each other as humans are to dogs," he said.

Because the way DNA is organized affects how genes are switched on and off, cats may be a better model than dogs for understanding human gene regulation, Murphy said.

That also makes them useful for studying genetic diseases. For example, polycystic kidney disease occurs in both humans and cats, and treatments developed for cats could help inform therapies for people.

Cats may also provide clues about cancer. A recent study found that cancer-related genes in cats are strikingly similar to those in humans, both in number and variety. One notable example involves a gene called FBXW7, which was mutated in more than half of the feline mammary tumors studied. In humans, mutations in the same gene are linked to worse outcomes in breast cancer

That said, dogs are also used to model and analyze human illness, including Alzheimer’s disease, idiopathic epilepsy, eye disease and heart disease.

Although cats may share more similarities with humans in gene regulation, to date more research has focused on dogs. This may be due in part to the fact that the complete feline genome became available later than the canine genome, as well as historical bias — cats have long been perceived as less cooperative in research settings.

So, which are we more closely related to? From an evolutionary standpoint, it's a tie, but genetically, at least in terms of genome structure, we are closer to cats.

How much of a cat fan are you? Find out by taking our cat quiz!

When the dinosaur-killing meteor hit Earth 66 million years ago, many flowering plants transformed into "hopeful monsters" to endure the resulting environmental crisis. Now, new research suggests that this was not the only time these plants responded this way. In nine separate events over the past 150 million years, flowering plants have duplicated their whole genome to give themselves a better chance of survival in the face of catastrophe.

The work could help scientists understand what will happen to flowering plants, which include most of the crops people eat, as the climate changes and organisms endure another environmental upheaval.

"Waves of whole genome duplications correlate with important geological events or periods in evolution," Yves Van de Peer, a genome biologist at Ghent University in Belgium and a co-author of the paper, told Live Science.

For almost a century, whole-genome duplication has puzzled scientists. Organisms that have more than two sets of genomes are called polyploids. Humans, which have two sets of chromosomes, are diploids. Polyploids are sometimes called "hopeful monsters" because they are "monstrously" different from their parent organisms — but have the potential to survive conditions that their parents cannot and, therefore, offer hope to a species.

But these organisms are a paradox, Van de Peer said. "When you go outside and start collecting plants, there is a very high chance that you will collect polyploid plants," which are plants that have undergone a whole genome duplication, he explained. "Nevertheless, when we analyze plant genomes, we find very little evidence for many whole-genome duplications that have survived in the longer term."

That's because whole-genome duplication is a risky gamble for a plant. "It's not an easy thing, from a cell biology point of view, to deal with," he said. "There are costs involved," such as larger cells, reduced fertility and other consequences. For this reason, polyploids are often seen as evolutionary dead ends because these mutations are unlikely to endure.

Many of the crops we eat are polyploids that humans have subconsciously selected over time because of their bigger fruit or ability to survive environmental stresses, Van de Peer said. But polyploid individuals struggle to compete with other members of their species when conditions are stable, so they die out during good times. But during difficult periods, polyploids may be able to adapt better, he said.

"Bursts throughout the history of plants"

In the new study, published Friday (May 8) in the journal Cell, the researchers analyzed the genomes of 470 flowering plants, called angiosperms. They hunted within those genomes for the remnants of whole-genome duplication. Ultimately, they discovered 132 independent duplication events over the past 150 million years and used information from fossilized plants, among other methods, to date when these events took place.

In 2009, Van de Peer and colleagues showed that duplication in a handful flowering plant species clustered around the meteor that killed the dinosaurs. However, the latest research shows that the blossoming of polyploid angiosperms was not a one-off event; it has occurred many times in the past 150 million years. The researchers identified at least nine clusters of duplication incidents, all of which corresponded to important environmental events.

"We see clusterings of whole genome duplications in time, and every time it corresponds with a described, important geological event, whether it's a global cooling period, whether it's a global warming period, or whether there's an extinction event," Van de Peer said.

Kevin Bird, a researcher who studies the evolutionary genomics of polyploids at Kew Garden in London and was not involved in the new study, said the new research helps build on past work. "The study's findings are a very exciting hint at how life survives and evolves through the most extreme periods in our planet's history," he said. "Given that the initial findings in 2009 were about a single cluster of ancient duplication events around 60-70 million years ago, it was a shock that they discovered evidence for as many as nine of these bursts throughout the history of plants."

However, he noted that the research should be a starting point for further investigation. "Overall, the work is done very carefully with some of the best methods currently available, but there is always a lot of uncertainty when you're projecting back hundreds of millions of years in the past," Bird told Live Science.

In the future, as the climate changes, research into polyploids is likely to become increasingly important, scientists say.

"Polyploids are better able to cope with stress, and stressful conditions can also induce polyploidy," said Douglas Soltis, a biologist at the Natural History Museum of Florida who was not involved in the research but who collaborates with Van De Peer. "The Anthropocene [human era] will be — and probably already is — a time of stress that will induce polyploidy and also select for polyploids."

Bird agreed that climate change could trigger another burst of genome duplications, but he noted that it would take millions of years to see how this burst will shape plant evolution. "What we might expect to see in the present is that polyploid populations are better able to tolerate the weather volatility, intensification and habitat degradation brought on by climate change and other human disturbances to habitats," he said.

Van De Peer and his team are artificially making polyploid plants and investigating how they respond to stress. "There must be a stress advantage in the polyploids, but there is so much that we still don't know about that," he said.

See how much you know about natural selection with our evolution quiz!

Nearly 180 years after they died of cold and starvation in the Canadian Arctic, four crewmembers who perished in the Franklin expedition have been identified thanks to genetic analyses that matched their DNA with that of living descendants.

Three of the victims were from HMS Erebus, one of the expedition's two vessels, and died at Erebus Bay, the researchers reported in a new study published Wednesday (May 6) in the Journal of Archaeological Science: Reports. The fourth victim, a captain on HMS Terror, is the first from that ship to be identified with DNA, according to a second study that was published Thursday (May 7) in the journal Polar Record.

The findings reveal that "none of the men [from HMS Erebus] were alone when they died," the researchers wrote in the first of those studies, adding that "it is our hope that additional identifications can be made to provide that kind of information to other descendants." Based on the location of the bodies, researchers believe that other survivors were still alive and nearby.

The Franklin expedition departed England in May 1845, with an aim of discovering a Northwest Passage, an Arctic route to connect the Atlantic and Pacific oceans. Sir John Franklin commanded the mission's two ships. However, the ships and their 129 crewmembers became stuck in ice off a Canadian archipelago in late 1846, and Franklin died June 11, 1847.

On April 22, 1848, the surviving 105 crewmembers left the ships off King William Island and tried to make it to the Canadian mainland, walking and dragging boats on sleds, but all of them died along the way.

Search expeditions launched over the following two decades found some human remains and artifacts, as did scientific expeditions launched in the 20th and 21st centuries, which finally led to the discovery of the long-lost ships.

The new DNA analysis sheds light on exactly where each ship's crew traveled in their doomed attempt to find safety. One victim, Harry Peglar, was "Captain of the Foretop on HMS Terror," the team found in their research. Papers belonging to Peglar were found on another man's body in 1859 and include poetry and descriptions of events on board the ships.

Peglar's remains were discovered about 125 miles (200 kilometers) from the frozen ships, meaning he had made it far into the remote wilderness. "What is known is that he died alone, dressed in the uniform of a steward," the researchers wrote in the Polar Record study.

The other three newly identified individuals are William Orren, an able seaman on HMS Erebus; David Young, a boy first class on HMS Erebus; and John Bridgens, a subordinate officer's steward on HMS Erebus.

According to historical records, Orren first went to sea in 1821, when he was just 15 years old. He served on HMS Swan in 1830 and HMS Alfred in 1831. "He wouldn't sail with the navy again for another 14 years, until he joined the crew of HMS Erebus in Woolwich on 19 March 1845 as an Able Seaman when he was 38 years old," the team wrote in the first study.

Historical records also say Orren was about 5 feet, 4 inches (1.63 meters) tall, with dark hair, a light complexion and brown eyes. A descendant of his sister provided the DNA that allowed him to be identified.

Young was 17 years old when he joined HMS Erebus. His father was also a navy sailor but wasn't posted to the Erebus expedition. The DNA used to identify him came from a descendant of one of his brothers.

Bridgens was born in 1818, and his father was a sailor who never married his mother. Bridgens was trained by his stepfather to be a hairdresser, but he went to sea instead. Records indicate that he first went to sea as a musician in 1829. He served aboard HMS Endymion in 1841, during a war with China, and "volunteered for the Franklin expedition in Woolwich on 20 March 1845, when he was 26 years old," the team wrote in the article. The DNA of a descendant of one of his half-sisters was used to identify the remains of Bridgens.

"He was 5 ft 6 inches [1.68 m] tall, with dark hair and hazel eyes," the researchers wrote in the study. "His seaman's ticket indicates that he was illiterate, which is further demonstrated by his marking his name with a cross on his allotment records."

Previous DNA studies identified other members of the Franklin expedition, including John Gregory, an engineer on the Erebus, and James Fitzjames, who became captain of the Erebus after Franklin's death and was likely cannibalized.

"For the living descendants, these findings provide previously unavailable details regarding the circumstances and locations of their relatives' deaths, as well as the identities of some of the shipmates who died with them," Douglas Stenton, an anthropologist at the University of Waterloo in Ontario and first author of the Journal of Archaeological Science: Reports paper, said in a statement.

The team's work continues, and the remains of more crewmembers may be identified.

The U.S. Food and Drug Administration (FDA) has approved the first-ever gene therapy for inherited deafness.

The therapy, called Otarmeni, is approved to treat a form of hearing loss caused by mutations in the OTOF gene, which codes for a protein called otoferlin. Cells in the inner ear need otoferlin to translate vibrations into signals that can be interpreted by the brain. When people carry two defective copies of the OTOF gene — one from each parent — this line of communication between the inner ear and brain is cut, resulting in severe-to-profound hearing loss.

Otarmeni is a one-time treatment that uses harmless viruses to deliver working copies of OTOF into the ear. In a trial including 20 participants, 16 showed improved hearing within six months, and one additional person showed improvement within a year of treatment.

Some participants improved to the point that they could hear whispers, while all the participants who responded to the therapy reached a level of hearing that does not typically require cochlear implantation — meaning the use of a device to bypass the inner ear and restore some hearing. Many people with this form of hearing loss get cochlear implants, but the implants don't perfectly replicate natural hearing and require maintenance over time.

Based on the trial results, Otarmeni was approved for both children and adults with OTOF-related hearing loss, the therapy's maker Regeneron announced Thursday (April 23). The company has said that the treatment itself will be free to patients in the U.S., not including out-of-pocket administration costs that might be dictated by a patient's doctor and insurance.

"The FDA approval of this gene therapy is a landmark moment for the field and, most importantly, for patients," said Zheng-Yi Chen, an associate scientist at the Eaton-Peabody Laboratories at Mass Eye and Ear and an associate professor at Harvard Medical School. Chen has been involved in a trial of a similar gene therapy for OTOF-related deafness in China.

Chen said the data from the trial "convincingly demonstrate both safety and efficacy." The approval process was very fast, he added, taking less than three years from when the first patient was dosed in 2023. (Otarmeni was approved through a special FDA "fast track" process, in part because there were no existing treatments for OTOF-related hearing loss that address its underlying cause.)

The speed "underscores both the robust clinical results and the urgent, unmet medical need for children with OTOF-mediated congenital hearing loss," Chen told Live Science. "We are incredibly encouraged by this milestone, which will serve as a catalyst to accelerate the development of future genetic therapies for hearing loss."

OTOF-related hearing loss affects about 50 newborns per year in the U.S. The new therapy is approved for those with two defective copies of the OTOF gene and no history of using a cochlear implant in the ear intended for treatment. Installing these implants damages the inner ear, so a gene therapy is unlikely to work; but those who have only one cochlear implant can get the gene therapy in the opposite ear.

Patients seeking the therapy must also have intact outer hair cells, which are special cells in the ear that act as amplifiers, increasing the movement of the eardrum in response to sound.

An international trial testing Otarmeni is still ongoing and is recruiting children under 18 in the U.S., United Kingdom, Spain, Germany and Japan.

"I've witnessed firsthand my trial participant responding to their mother’s voice, dancing to music and interacting with the world, and these moments are now possible for more children born with this specific form of hearing loss," Dr. A. Eliot Shearer, an otolaryngologist at Boston Children’s Hospital, associate professor at Harvard Medical School and trial runner, said in the Regeneron statement.

This article is for informational purposes only and is not meant to offer medical advice.

In the largest and longest trial of its kind, 90% of people who received an experimental gene therapy for congenital deafness showed marked improvements in their hearing over the next several years.

The trial, which involved 42 people and was conducted across eight sites in China, mostly involved children but also included three adults, two of whom responded well to the therapy. All of the participants started out with complete hearing loss. Although the children's hearing improved more than the adults' did, the trial results still suggest adults could benefit from the treatment. The trial was described Wednesday (April 22) in the journal Nature.

"In some patients, their recovery is so good, they reach completely normal [hearing]," said study co-author Zheng-Yi Chen, an associate scientist at the Eaton-Peabody Laboratories at Mass Eye and Ear and an associate professor at Harvard Medical School. "It would be like a completely blind patient having 20-20 vision back," Chen told Live Science.

These improvements in hearing appear to progress over time and then plateau and stabilize by around the one-year mark, Chen said. By now, 10 of the trial participants have been monitored for at least two years, and of those, all can hear normal-volume conversation — around 50 to 60 decibels — and five can hear whispers, he said.

Four of the 42 patients didn't show any improvements in their hearing after the treatment, and it's still unclear why. But given the therapy spurred improvement in most patients and that the improvement lasted a long time, Chen is excited for the next steps.

"I really foresee, in the next few years, that there'll be many different trials coming up for different types of genetic hearing loss," said Chen, who is a co-founder of Salubritas Therapeutics, a company developing regenerative therapies for sensory disorders. "We're just the beginning; we're really at a turning point in history."

Repairing the inner ear

About 1.5 in 1,000 children are born with hearing loss, though the exact prevalence varies by country. Up to 8% of these congenital hearing loss cases are caused by various loss-of-function mutations in the OTOF gene, which carries instructions for a protein called otoferlin.

This protein is critical to the ear's inner hair cells, which translate vibrations into signals that the brain can interpret. If a person carries two mutant copies of the OTOF gene — one from each parent — they'll have severe to profound hearing loss. People with severe hearing loss cannot hear normal-volume speech but can hear some loud sounds; those with profound hearing loss cannot hear speech spoken at any volume and can hear only very loud sounds, if any. (Deaf people mostly have profound hearing loss, which implies very little or no hearing, according to the World Health Organization.)

As such, speech development is often severely impacted in people with OTOF-related deafness, unless they're fitted with a cochlear implant at a young age. Cochlear implants are very effective at improving hearing, Chen said, "but it comes with a limitation in that it's mechanical, so the sound is very different." People's voices can sound a bit like Donald Duck's, and the nuances of music are very difficult to perceive, he noted. And as with any device, the implants experience wear and tear and require maintenance.

By contrast, the new gene therapy would likely be a one-and-done treatment and correct the underlying issue causing deafness: the defective OTOF gene. Using harmless viruses as delivery vehicles, the therapy distributes working copies of OTOF into the inner ear, thus restoring the hair cells' function.

In previous trials with 11 children, the therapy was both safe and effective, with most of the kids showing robust improvements in their hearing. However, those trials were only months long, raising questions about how long the improvements last and whether any side effects could show up down the line. The trial runners also wondered if the treatment could work for older patients.

"These are the three main questions: the duration, the safety and the patient population," Chen said. "The current study really addresses those."

The new trial included 39 children and teens, ages 9 months to 18 years, and three adults in their 20s and 30s. Most got the gene therapy in just one ear, as many currently or previously had a cochlear implant in the other ear. Six participants got the treatment in both ears.

No serious side effects were seen in any of the patients, although some experienced temporary upticks or declines in specific types of immune cells. A handful had mild vertigo, and one had some inflammation of the inner ear.

For most of the 38 participants who responded to the treatment, their hearing started to improve within weeks and then continued to increase over time. The team has two years of data on 15 of the treated ears, 100% of which can detect conversational speech and 60% can detect whispers.

Generally, participants under 18 had greater improvement than adults. Interestingly, one factor that seemed tied to the degree of hearing recovery was the condition of the participants' outer hair cells, which are different from inner hair cells. These cells act as amplifiers, increasing the motion of the eardrum in response to sound, Chen explained. In people who have had hearing loss for a long time, these cells' function may degrade, and that may affect how much hearing they can regain through the therapy, he suggested. But this idea warrants more study.

The participants whose hearing improved also gained better speech perception. In turn, being able to better hear speech enabled some participants to better produce speech themselves, with some learning to speak for the first time. The standout example was an 11-year-old girl with no history of using cochlear implants.

Following therapy, "she managed to develop some rudimentary capacity to speak, and she can say simple words," Chen said. "We want to know, with more rehabilitation down the road, what else can we do to help her."

Next steps

The team is now exploring whether it's feasible to give patients multiple doses of the therapy and if that boosts outcomes. Future trials could run even longer than this one, to see how well the improvements hold, and they could investigate why some patients don't respond to the treatment, Chen said.

Early tests hint that this gene therapy or others like it could be superior to cochlear implants in some respects — for instance, by enabling better music perception and speech detection in noisy environments. However, "I think the implant will remain the major treatment option for a long time to come," Chen noted, and some patients may not be good candidates for gene therapy.

Once a gene therapy is approved, this will become a choice for patients and their caregivers to weigh, in part because it's likely not possible to get gene therapy on an ear that previously had a cochlear implant installed, he said. That's because the installation physically damages the inner ear cells to some degree, although less-damaging surgical techniques are now being developed, he said.

Anecdotally, the children with one cochlear implant who had their second ear treated tended to prefer switching off their implants once their hearing improved, Chen added. "Often, they just don't wear the cochlear; they don't want to wear the cochlear. They just leave the other ear that was treated with gene therapy," he said.

This experimental therapy will now be tested in further trials and continue to move through China's drug approval process. Chen hopes it will someday be approved in the U.S., as well. That would likely require additional trials in the United States, as the Food and Drug Administration (FDA) often asks for extra data before approving therapies that have been cleared in other countries, he noted.

Meanwhile, Chen anticipates that a treatment made by Regeneron Pharmaceuticals could be the first gene therapy for deafness to earn approval from the FDA. Regeneron announced its intention to file for approval in 2025 and a decision is expected within a year, although the exact timing is unknown, Chen said.

"That'll be a major event for the field," he said.

Editor's note: Since this article was published, Regeneron's gene therapy for OTOF-related hearing loss has been approved by the FDA.

This article is for informational purposes only and is not meant to offer medical advice.

An extreme form of nausea and vomiting during pregnancy is linked to 10 genes, one of which is likely the main culprit behind the condition, according to the largest genetic study of its kind to date.

Most people experience some degree of nausea and vomiting during early pregnancy, but up to 10.8% have symptoms so severe that they stop being able to eat and drink and may even require hospitalization. This condition, called hyperemesis gravidarum (HG), can last throughout a person's entire pregnancy, but it currently lacks any Food and Drug Administration-approved treatments.

Now, a new study, published Tuesday (April 14) in the journal Nature Genetics, provides evidence that the gene for the hormone growth differentiation factor 15 (GDF15) is the leading cause of HG, which has been suggested in other studies.

The research also identified six additional genes with ties to the condition, including one that may control the production of glucagon-like peptide-1 (GPL-1), a hormone involved in regulating insulin and appetite. The gene is also the greatest known genetic risk factor for type 2 diabetes.

These findings could spur the development of new treatment options and targets for HG.

"It's going to be helpful as far as exploring new avenues for therapies and exploring ways to better predict, diagnose, treat and potentially prevent HG in the future," study first author Marlena Fejzo, an expert in HG at the Keck School of Medicine of the University of Southern California, told Live Science. Fejzo consults for a pharmaceutical company trialing a GDF15 drug.

Finding the cause of HG

The pregnancy hormone human chorionic gonadotropin (hCG) — the first hormone made by the placenta after conception — was long thought to underpin HG because its levels surge in early pregnancy. Estrogen was also suggested as a possible cause, as its levels also rise dramatically.

But recent research by Fejzo and her colleagues has zeroed in on GDF15 as a likely cause of HG. They've pinpointed specific mutations in the GDF15 gene that significantly boost the risk of the condition, with one rare mutation increasing the risk tenfold.

But because the researchers identified this genetic risk factor primarily using data from people of European ancestry, Fejzo said she wanted to see if the finding generalized to more diverse populations.

So, in the new study, the team combined data from nine independent studies of HG from across the U.S. and Europe. They compared the whole genomes and autosomes — the chromosomes excluding the X and Y sex chromosomes — of nearly 11,000 people with diagnosed HG and over 420,000 people with a history of pregnancy but no HG. Most data still came from individuals of European descent, but the datasets also included roughly 13,000 people of Asian ancestry, over 1,200 people of African ancestry, and 75 people of Latino ancestry.

The team found 10 genes associated with a heightened risk of HG, with the gene for GDF15 as the top signal across all populations, Fejzo said.

"These are associations, so we can't necessarily say that they're causative," she said. However, this study provides indirect evidence for a causal link between HG and GDF15, given the strength and generalizability of the signal, Fejzo said.

Ultimately this large study's findings, combined with the previous work by Fejzo's team and other groups, establishes a causal link between GDF15 and the condition, she said.

In a first, the researchers also identified an association with TCF7L2, the leading genetic risk factor for type 2 and gestational diabetes, which is new-onset high blood sugar in pregnancy. Previous research found that this gene may regulate GPL-1, the same hormone mimicked by drugs like Ozempic and Wegovy.

Fejzo said this discovery "seems like a fascinating new target to explore" to develop new drugs for HG.

Other genes pinpointed in the study are linked to learning and memory, while others are tied to wasting syndrome and appetite. No genetic links to hCG or estrogen were identified in the work, the authors wrote in the paper.

This "incredibly well-done" research "cements" the GDF15 pathway as the primary driver of HG across a wide and diverse population, said Dr. Andrew Housholder, an emergency physician who specializes in HG and consults for a pharmaceutical company trialing a GDF15 drug.

"It should finally end the discussion of HG as a sensitivity to hCG and estrogen," Housholder, who was not involved in the research, told Live Science in an email.

Each of the 10 genes identified "deserves deep study," he added. The fact that they span many major biological pathways, touching on everything from insulin signaling to learning, "really illustrates how complex a disease process HG is."

The exact reason learning and memory genes are linked is unclear, but one theory suggests they may play a part in wiring the extreme food aversion responses seen in people with HG, Fejzo said.

Fejzo and her team aim to launch a clinical trial this summer. It will involve giving metformin, a diabetes medication that increases GDF15, to patients with a history of HG. The patients being enrolled are planning to have more children in the near future, so the trial will test whether metformin desensitizes them to GDF15 ahead of conception. The hope would be to reduce their nausea and vomiting once they are pregnant.

While treatments are being explored, Fejzo said people can find guidance and support on the website of the Hyperemesis Education and Research (HER) Foundation, which supports research, advocacy and education on HG. Fejzo is a voluntary board member and the research director of the HER Foundation.

This article is for informational purposes only and is not meant to offer medical advice.

Over the past 10,000 years, natural selection has contributed to the evolution of nearly 500 genes in the DNA of West Eurasians, affecting their looks and susceptibility to different illnesses, a new study finds.

Natural selection in this group led to an increased frequency of light skin tone, red hair, and resistance to HIV and leprosy (also called Hansen's disease), and it decreased the frequency of male-pattern baldness and rheumatoid arthritis susceptibility, the new study of 16,000 genomes reveals. This discovery contradicts the long-standing view that recent human evolution was limited.

"Human evolution didn't slow down; we were just missing the signal," study first author Ali Akbari, a staff scientist at Harvard University, told Live Science in an email.

Evolutionary change can occur through a variety of mechanisms, including mutation; natural selection, in which traits that are advantageous to survival are passed to offspring; gene flow, in which genetic material is mixed between populations; and genetic drift, in which the frequency of a gene in a population changes due to random chance.

In a study published Wednesday (April 15) in the journal Nature, Akbari and colleagues developed a new statistical method to identify natural selection over an 18,000-year period in thousands of ancient and modern genomes from people living in West Eurasia, an area encompassing Europe and parts of western Asia, like Turkey.

"Previous work, based on the scars that natural selection leaves in present-day genomes, led to the view that directional selection was rare," Akbari said. But with large datasets like the one that the researchers amassed and methods that can separate the signal of natural selection from other evolutionary processes, "we can now detect small, consistent changes over time," he explained.

The researchers found evidence of natural selection in 479 gene variants in the West Eurasian genome dataset, 60% of which correspond with known traits in present-day people. Some of the gene variants that were strongly positively selected for are involved in expressing traits such as light skin tone, red hair, resistance to HIV and leprosy infections, and the B blood type. They also discovered genes related to a lower chance of male-pattern baldness and a lower risk of rheumatoid arthritis.

The results suggest that all of these variants were useful in the evolution of modern West Eurasian people — but the DNA does not help to explain exactly why these traits were useful. The increase in the frequency of light skin pigmentation probably reflects selection for increased synthesis of vitamin D in regions of low sunlight, the researchers wrote in the study. But it's harder to explain the rise in redheads. It is possible that red hair itself was not beneficial but rather that the genes for the trait are also associated with a more important adaptation.

Some traits were positively or negatively selected at different times, the researchers found. For several millennia, genes for tuberculosis susceptibility increased in frequency and then decreased around 3,500 years ago. Similarly, genes for susceptibility for multiple sclerosis increased until about 2,000 years ago and then decreased in frequency.

"This likely reflects changes in environment or selective pressures over time; for example, the introduction of new pathogens," Akbari said.

The researchers have made their data and methods — called AGES (Ancient Genome Selection) — freely available so that other scientists can expand on this work. Akbari said the research team now plans to explore other groups outside West Eurasia to better understand how the global human population evolved. They have already posted a preprint of a study investigating East Eurasia, which looked at people with East Asian ancestry; this research found similar patterns, Akbari said.

"What is likely to differ across regions is not whether selection occurred, but how local environments and cultural changes shaped it, including factors like diet, pathogens, and climate," Akbari said. "Extending this approach more broadly will help us understand how different historical pressures influenced human biology in different settings."

How much do you know about human evolution? Test your knowledge with our human evolution quiz!

Changing just one "letter" in the DNA of female mouse embryos triggers the development of male genitalia and testes, scientists have found.

"This is a remarkable finding because such a tiny change — just one DNA letter out of ~2.8 billion — was enough to produce a dramatic developmental outcome," senior study author Nitzan Gonen, a senior investigator at Bar-Ilan University in Israel who studies how sex is determined during embryonic development, said in a statement.

In early development, the emergence of male sexual characteristics relies on two key genes: SRY and SOX9. The first gene carries instructions for a protein that then interacts with and switches on the second. This activation of SOX9 triggers a chain reaction that causes testes and sperm-making cells to develop.

Back in 2018, Gonen and colleagues pinpointed another stretch of DNA that is important for this chain reaction. This snippet of DNA, called enhancer 13 (Enh13), doesn't carry instructions for any proteins. Instead, it acts as an "on-off" switch for SOX9. The SRY protein latches onto this switch, flipping it and sending SOX9 into overdrive.

In previous work, the researchers also found that, by eliminating this on-off switch, they could reverse the sex of male mouse embryos. Even though they carried XY sex chromosomes, the mice without Enh13 developed as females. Enh13's absence causes SOX9 activity to fall by about 80%, which prevents the development of testes and instead ushers the development of ovaries, the researchers reported. Tweaking only select bits of Enh13 has the same effect, the team found in a later study.

The scientists suspect that mutations in this on-off switch may contribute to certain differences of sexual development (DSD) in humans, which can cause a person's sex chromosomes and sexual characteristics to be mismatched. In particular, it was clear Enh13 might play a role in cases where XY individuals develop female characteristics, as they'd explored in mouse studies.

But some studies also hinted at a potential role in conditions that cause XX individuals to develop male features. And the new research, published Thursday (April 9) in the journal Nature Communications, backs up this latter idea.

The researchers tweaked Enh13 in female mouse embryos by either deleting three letters or inserting one letter into the portion of the on-off switch that SRY latches onto. Both of these modifications caused small testes and male external genitalia to develop in the female mice, although they also grew some ovarian tissue.

For male sex organs to develop, the mutation had to affect both copies of Enh13; cells carry two copies of chromosome 17, which Enh13 is found on. If only one copy was mutated, the XX mice developed normal ovaries and no male organs.

Typically, the SOX9 gene must be switched off for ovaries to develop properly, and XX embryos use various mechanisms to achieve that. The new study suggests that mutations in Enh13 can lift the brakes on SOX9, allowing the gene to activate to a small degree even without any SRY protein present.

Once activated, SOX9 can sustain and amplify its own activity, so "this minimal activation would be enough to trigger the self-amplification loop," the study authors wrote.

In the long run, these results could help scientists better understand how DSDs emerge in humans, the researchers say. For now, though, the work raises a number of hypotheses about Enh13's role in sex development in both males and females, and more research is needed to fully unpack its effects.

"Our findings show that it is not enough to look only at genes," Elisheva Abberbock, a doctoral student at Bar-Ilan University who led the research, said in the statement. "Important disease-causing mutations may also lie in the non-coding genome, in DNA regions that control gene activity rather than encode proteins."

This article is for informational purposes only and is not meant to offer medical advice.

In medieval Spain, two men were buried in a prehistoric stone monument that had been constructed millennia earlier. Now, a new analysis of these burials is revealing clues about their ancestry but also leaving some mysteries, such as which religion they practiced.

For example, one of the men was related not only to European populations but also to people living in the Middle East and North Africa, including two people who are still alive today, according to the new genetic analysis.

The burial place, the Dolmen de Menga, is a large megalithic monument used for burials. It was built in the fourth millennium B.C., during the Neolithic period, or New Stone Age. The existence of the dolmen has always been known and has been a topic of archaeological study since at least the 19th century.

In 2005, archaeologists unexpectedly found two additional burials within its atrium: one dating to around the eighth century or ninth century A.D. and another from around the 10th or 11th century, researchers wrote in a paper published in the February issue of the Journal of Archaeological Science: Reports.

Analysis of the remains found that the 10th- or 11th-century burial is of a man who was over 45 years old when he died. DNA tests showed that he had a mix of European, North African and Middle Eastern ancestry, the team found. The man's Y-chromosome lineage matches one that "has been present in Spain since at least the Chalcolithic," or Copper Age (3200 to 2200 B.C.) in Iberia, the researchers wrote in the new study.

When looking at this individual's maternal lineage through his mitochondrial DNA, the researchers found that it matched one from Europe that has been known in Iberia since the Early Neolithic but is also found in modern-day northwest Africa. In fact, the medieval man shares a specific mutation with two modern-day African individuals in a genetic database — one in Morocco and another in Algeria.

It's not surprising to find North African genes in a medieval man buried in Spain, the researchers wrote, noting that North African ancestry was "widespread" in southern Iberia from at least the third to fourth century, "probably connected with regular movement of people across the Mediterranean potentiated by Greek, Phoenician, and Carthaginian trade and, later, the Roman Empire," they wrote in the study.

From the eighth to the 11th century, when these medieval men were buried at the Dolmen de Menga, southern Spain was part of Al-Andalus, a Muslim kingdom in Iberia. A variety of religions ‪—‬ including Islam, Christianity, Judaism and paganism ‪—‬ were practiced within this kingdom, the team wrote in the paper.

"With the onset of the Islamic period in 711 CE, contacts with North Africa were probably more frequent, enabled by political events and shared cultural practices," the researchers wrote in the study.

The eighth- or ninth-century burial also appears to be of a man who was more than 45 years old, but his DNA was too fragmented for analysis; the researchers wrote that there was even an "intrusion of roots into some of the bones."

Religion unknown

Both individuals were buried in simple pits with no grave goods. "Their heads were lying on their right side, pointing to the southwest — in line with the monument's axis of symmetry — with their faces looking southeast," in the direction of Mecca, the team wrote in the study.

The "apparent symbolic alignment of the inhumations with the axis of symmetry of the Menga megalithic monument contrasts with Islamic necropolises in the area," the researchers wrote. The direction of the heads aligning with the dolmen itself is different from the other burials, study co-author Leonardo García Sanjuán, a professor in the Department of Prehistory and Archaeology at the University of Seville, told Live Science in an email

This leaves the question of which religion these two people practiced.

The "fact that both individuals were buried at the entrance of a monument which already at their time was extremely old, and with their heads pointing towards the interior of it, may be significant, indicating that these two men revered the dolmen," García Sanjuán said. "Altogether, this suggests that their world view may have been a mixture of Islamic and pagan [beliefs]."

Leonor Rocha, an archaeology professor at the University of Évora in Portugal who was not involved in the study, told Live Science that it "seems very interesting to me, especially because they have preserved bones and because of the DNA analysis." Rocha noted that the Alentejo region of southern Portugal also has evidence that people reused prehistoric megalithic monuments for burials during the Middle Ages, but no bones have been found there.

"In the Alentejo region, we have some evidence of reuse from that period, but unfortunately without preserved bones," Rocha said in an email.

It's possible that medieval people interpreted the dolmen as a cave, Yves Gleize, an archaeologist and biological anthropologist at the National Institute for Preventive Archaeological Research and the University of Bordeaux, told Live Science.

In the Muslim "world, the cave is an important place; for example, the prophet received the first revelations in the cave of Hira [near Mecca]," Gleize, who was not involved in the study, said in an email. He noted that caves were sometimes used as places of spiritual retreat.

Gleize added that he is interested in hearing more about the orientation of the burials and thinks it is best to be cautious about assigning them a specific religion.

Over 100 million people, and more than 30% of adults, suffer from some type of allergy in the United States, and that number is on the rise. But where are these allergies coming from? Do we inherit them, or do they result from environmental factors?

The answer involves a little of both, said Dr. Derek Chu, an allergy specialist at McMaster University in Ontario. Allergies occur when the immune system mistakes a harmless substance, such as pollen or a certain type of food, for a dangerous substance and attempts to get it out of the body. Once the body reacts this way toward an allergen, it will repeat the allergic response for every new exposure, unless there is a successful intervention.

"The body goes awry and is trained to do the wrong thing," Chu told Live Science.

According to Leah Kottyan, an immunologist at Cincinnati Children's Hospital, there are several main types of allergies. They include allergic dermatitis, which manifests through skin conditions such as rashes and hives; allergic asthma, which involves airway inflammation and the overproduction of mucus; allergic rhinitis, which results in sneezing and a stuffy nose; and food allergies, which can trigger a whole-body immune response. All of these responses could be driven by the same allergen, Kottyan noted. Moreover, people who have one type of allergic response are more likely to have others and more likely to be allergic to more than one thing.

According to Kottyan, there is almost certainly a genetic component to the development of allergies. Independent studies comparing the prevalence of allergies in identical and fraternal twins found that the identical twins were far more likely to exhibit similar allergies than the fraternal twins, indicating that their genetic makeup played a role. In one study, the identical twins had an average of 95% similarity between four different types of allergies, whereas fraternal twins had an average of around 37%.

However, the link between genetics and allergies is complicated. Allergic responses can be traced to mutations in hundreds of genes. One of the most studied such genes, known as filaggrin or FLG, affects the development of the skin's moisture barrier, Kottyan said. Mutations in FLG cause the moisture barrier to not act as it should. This increases a person's risk of developing eczema, allergic dermatitis and other types of allergies.

FLG mutations can put the skin in a compromised state, which can increase the skin's susceptibility in getting cuts and scrapes and from developing dry and cracked skin. When this compromised skin comes into contact with an allergen, the immune system is more likely to become sensitized improperly to that allergen, Kottyan said. This can cause an allergy to develop.

"Literally, when there's food on the baby's skin, the food is coming in through the damaged skin barrier, and the child is getting sensitized to that food through the skin," Kottyan told Live Science.

Environmental factors

Although allergic reactions have a genetic component, environmental factors — including exposure to different allergens — play a big role in how someone develops allergies.

"It doesn't track one to one," Chu told Live Science. In a recent study Chu co-authored, scientists investigated nongenetic risk factors for allergies, including the baby's method of delivery, early exposure to antibiotics, and when they were introduced to solid food.

Moreover, even people who inherit a tendency to develop allergies may not be allergic to the same things as their parents. Rather, whether the baby becomes allergic to peanuts, for example, will likely be determined by their early exposure to that allergen. There is now a FDA-approved immunotherapy treatment for children that centers on daily exposure to peanut proteins over a long period of time.

"If the immune system is exposed inconsistently, then it's not learning to tolerate what it's being exposed to, and instead it can easily end up misbehaving, leading to allergic reactions," Chu said.

The microbiome also plays a big role in the development of allergies. Scientists have found that early exposure to a wide variety of environmental microbes results in robust and healthy gut and skin microbiomes that are more tolerant of potential allergens. Without this diversity, or with a microbiome consisting of higher percentages of certain microbes, it is more likely that a person will develop conditions like eczema and food allergies.

A similar theory suggests that the eradication of many common parasites, and the more sterile environment many of us now live in, may have played a role in the uptick in allergy cases in the United States. With no parasites and fewer viruses and bad bacteria to go after, our immune systems may be developing too many allergy-fighting cells instead of the bacteria and virus-fighting ones.

Researchers like Chu and Kottyan are continuing to pinpoint the risk factors that can cause someone to develop allergies and test new preventive measures to help children grow into allergy-free adults. For now, Kottyan said, the best steps parents can take to prevent allergies in their children is to expose them to common allergens early and often and to take good care of their children's skin, especially in areas that are prone to dryness and eczema.

"Allergy genetics are not deterministic; they aren't going to say you absolutely are going to get a disease," Kottyan told Live Science. "It's not a life sentence."

This article is for informational purposes only and is not meant to offer medical or dietary advice.

Before Neanderthals went extinct, they experienced a major upheaval that resulted in just one of their genetic lineages surviving in Europe and then expanding across the continent, a new study shows.

The findings, published March 23 in the journal PNAS, may shed light on what ultimately doomed the Neanderthals.

Neanderthals were among the closest relatives of modern humans (Homo sapiens), with their lineages diverging around 500,000 years ago. Although Neanderthals once ranged across Eurasia, they are generally thought to have gone extinct about 40,000 years ago.

DNA recovered from Neanderthal fossils can shed light not just on their extinction but on their history in general. In the new study, researchers examined DNA from mitochondria in cells, which help generate energy for the body, and get passed down from mothers to offspring.

The scientists gathered 10 mitochondrial DNA sequences from Neanderthals excavated from six archaeological sites in Belgium, France, Germany and Serbia. They analyzed them alongside 49 Neanderthal mitochondrial DNA sequences released in previous research.

The team found that in Europe, where Neanderthals ultimately died out, several mitochondrial DNA lineages existed until about 65,000 years ago. After this point, these groups were replaced by a single Neanderthal mitochondrial genetic lineage originating from southwestern France. These "Late Neanderthals" proceeded to disperse across Europe.

"This tells us there was this major disruption in Neanderthal history," study senior author Cosimo Posth, a paleogeneticist at the University of Tübingen in Germany, told Live Science. "There was really a genetic transformation."

Posth noted that about 75,000 years ago, glaciers came to dominate Europe.

"We don't think our findings suggest that Neanderthals were migrating to the Mediterranean," he said. "We think Neanderthal groups in northern Europe perished, while a Neanderthal group that was already in southwestern France survived this climate change and then went on to expand across a broader region. Neanderthals had experienced multiple glaciations before, but the last one proved harsh on their survival."

The study also found that "there was a kind of genetic impoverishment among the Late Neanderthals," Posth said. "Since they appeared to emerge from this single group, their genetic diversity overall was reduced drastically compared to what came before — they were all extremely similar on a genetic level across Europe, from Spain to the Caucasus to northern Europe."

This low genetic diversity ‪—‬ which grew most pronounced about 42,000 years ago, shortly before Neanderthals generally died out ‪—‬ "might have played a role in their extinction," Posth noted. "We don't think there was a single reason the Neanderthals went extinct, but this lack of genetic diversity would have made them more predisposed to not really survive climatic changes and other disruptions."

Likewise, Neanderthal groups in the Altai Mountains of Siberia were more closely related to each other than to European Neanderthals, and these Siberian Neanderthals also had low genetic diversity and lived in small, isolated groups, another March 23 study published in the journal PNAS found.

Despite this low genetic diversity, the Late Neanderthals in Europe appeared quite diverse across sites in terms of their artifacts and art. "So after the Neanderthals re-expanded across Europe, we think that Late Neanderthal groups were not highly connected with each other," Posth said. "This would have led to more inbred groups, explaining the low genetic diversity, but also more cultural and archaeological diversity, since these groups were isolated and so would have developed more specialized cultures."

"We've seen evidence that Neanderthal populations replaced each other, and this paper really creates a ground story as to why that might be — because Neanderthals went extinct in places all the time, and then other Neanderthal groups went in and recolonized the same places," Fernando Villanea, a population geneticist at the University of Colorado Boulder who was not involved in the study, told Live Science.

Future research could seek to test these findings by analyzing DNA from Neanderthal cell nuclei instead of their mitochondria, Posth said. However, this will be a major challenge, as DNA from nuclei is several hundred times less abundant than DNA from mitochondria in cells.

Neanderthal quiz: How much do you know about our closest relatives?

Two Neanderthals present at the same cave site 10 millennia apart were distant relatives, a tiny 110,000-year-old bone fragment from the Altai Mountains in Siberia reveals. The fragment has also produced the fourth full genome of a Neanderthal to date, shedding light on how small and isolated Neanderthals were long before they disappeared around 40,000 years ago.

Researchers found the bone fragment in Denisova Cave, which both Neanderthals and Denisovans lived in off and on for nearly 300,000 years. In a study published Monday (March 23) in the journal PNAS, the researchers compared the genome of the 110,000-year-old Neanderthal male (called D17) with three other complete Neanderthal genomes to better understand Neanderthals' population structure.

The researchers compared the genome of D17 with the genome of a female Neanderthal (called D5) dated to 120,000 years ago from the same cave. They found that, while D5 was not a direct ancestor of D17, the two Neanderthals belonged to closely related lineages connected by a common ancestor. This distant biological relationship suggests Neanderthals had a long-term presence in the Altai region, the researchers said.

"But it is likely that Denisova Cave was part of a broader landscape used repeatedly by these Neanderthal populations over time, rather than a site occupied by a single, continuous group," study first author Diyendo Massilani, a genetics professor at the Yale School of Medicine, told Live Science in an email.

The study results also revealed that Neanderthals in the Altai region lived in very small and highly isolated populations of 50 or fewer people, as shown by stronger genetic markers of inbreeding. Specifically, researchers found that the individuals they analyzed had large sections of identical DNA, an indication that their parents were very closely related — as close as first cousins, for example.

The new research complements previous studies that showed Neanderthals lived in smaller and more isolated groups than our own species did. A 2022 study indicated that one Altai Neanderthal community numbered around 20 individuals, while another study provided evidence of a group being isolated for roughly 50,000 years. Many researchers have pointed to inbreeding and isolation as causes for Neanderthals' disappearance around 40,000 years ago. But the latest results suggest that Neanderthals also survived for long periods under extreme conditions of isolation and small population size.

Massiliani and colleagues also discovered that Altai Neanderthals were very different from later European Neanderthals. In their genetic analysis, the researchers found that Altai Neanderthal D17 was more closely related to D5 than either of them was to Neanderthals in Europe or to later populations in the Altai region. This suggests that Neanderthal populations from eastern and western Eurasia became genetically different from one another in a relatively short time frame and within a fairly small geographic area.

"Even though the individuals from which we have genomes were separated for only about 50,000 years on average, they reached levels of difference similar to what we see today between some of the most distinct human populations, like people from Central Africa and Papua New Guinea that separated about 300,000 years ago," Massilani said.

Likely because they were small and isolated, Neanderthal populations became genetically distinct from one another much more quickly, Massilani said. This may have been because in small, isolated groups, a process called genetic drift can cause random genetic changes to become more common over time.

"We already knew that Neanderthals were not a single, homogeneous population spread across Eurasia, but a patchwork of groups shaped by complex demographic processes, including divergence, migration, local extinctions and replacements," he said. "What is striking in our results is just how differentiated these populations could become."

The high amount of genetic separation and differences between groups may have limited Neanderthals' ability to adapt to environmental changes, Massilani said.

The study provides new details about how Neanderthal populations were structured, one expert said.

"To have two sequenced Neanderthals in such a close geographic place does bring new and more fine-grained insight" into their population, Léo Planche, a population geneticist at Paris-Saclay University's Interdisciplinary Laboratory for Digital Sciences who was not involved in the study, told Live Science in an email. "We start to have enough Neanderthal genomes to actually have some claim about their population structure. Populations are groups of individuals, so the more data the better."

Editor's note: This article was updated on March 27, 2026 to note that the vast majority of Neanderthals went extinct 40,000 years ago, not 34,000 years ago as was previously stated.

Neanderthal quiz: How much do you know about our closest relatives?

Humans have evolved the ability to live anywhere on Earth, thanks to gradual changes to our biology and our knack for developing new technologies, like clothes and shelter. This adaptability is often touted as being unique to our species, Homo sapiens.

In his new book, "Adaptable: How Your Unique Body Really Works and Why Our Biology Unites Us" (Penguin Random House, 2025), Herman Pontzer, a professor of evolutionary anthropology and global health at Duke University, explores how local environments work in tandem with genetics to produce the full spectrum of diversity we see in people today.

The book journeys through the human body and focuses just as much on what connects us as it does on the conditions required for differences to arise. Pontzer weaves in his work with contemporary hunter-gatherer populations, like the Hadza in Tanzania, to explore the lifestyles of pre-farming cultures and how the stark departure from these ways of life for many people today is making us sick.

"Adaptable" is a finalist for the PEN/E.O. Wilson Literary Science Writing Award, which celebrates excellence in nonfiction in the physical or biological sciences. The winner will be announced March 31 at the Literary Awards Ceremony and will receive a $10,000 cash prize.

Live Science spoke with Pontzer about his book and why understanding why and how diversity occurs is essential for questioning and challenging scientific misinformation.

Sophie Berdugo: Why did you decide to write the book now?

Herman Pontzer: In having conversations about "Burn" [Pontzer's book on the science of the metabolism (Penguin, 2022)], it became very clear to me that when you move outside of the ivory tower and start having these conversations more broadly, that there's just a lot of misunderstanding and misinformation about just how the body works in general. It's not just our metabolism. The metabolism is one of those blackbox things that we love to blame everything on and people don't really understand what it means or how it works.

SB: What is your favorite fact about the human body that you feel is completely underappreciated?

HP: I mean, where to start? Your kidneys. Kidneys are the forgotten essential workers of the body. And I could start anywhere, but let's start there ‪—‬ because if I say brains or hearts, people go, "Yeah, those are important; we know that."

Your kidneys, man: 180 liters [47.5 gallons] of water a day [are] filtered through your kidneys. All of the detox stuff that you think you're doing with the supplements you're taking, they're [your kidneys are] doing it for free and better. Somehow our bodies have learned to regulate water in a way that's different from the other apes, because we evolved in a dry environment. So, it's the interplay of water balance across our whole systems.

Spleens ‪—‬ let's do another unappreciated organ. Most people don't even know what their spleen does, I think. But among others, it's an immune function organ. Your spleen is this reservoir for red blood cells. And so, whether you're at altitude and you need a little bit more oxygen, your spleen gets bigger to be this bigger red blood cell reservoir for that.

There's this fascinating population called the Sama in the Philippines. They spend their lives on boats and in the ocean, and they forage underwater. And so there's been local adaptations, local evolution to give them bigger spleens [to have more blood oxygen when holding their breath for long periods under water when diving for food]. The alleles, the gene variants, that give them bigger spleens have become more common, and now people there have bigger spleens, on average, than everybody else.

Literally everywhere you look in the body, there's a story that I bet you haven't heard of.

SB: That case of the spleen being enlarged in this population in the Philippines is a great example of a local adaptation. Could you explain how these local adaptations occur?

HP: To talk about those local adaptations becomes a little bit tricky because they do happen, right? Certain populations do have a trait that gets more common there, or bigger or smaller, whatever it is. Natural selection can shape a trait in a population, but it's actually pretty rare because the conditions have to be just right.

So how do we do it? Local adaptation is just like any other kind of evolutionary adaptation. The reason a certain trait becomes common in a place is because it helps individuals there survive and reproduce. And that could be anything from being the right body shape and size to having a bigger spleen that helps you forage underwater. Anything that helps you survive and reproduce could end up as a local adaptation.

But the important thing here for why we see these localized events happening — and what makes them different from things that affect our whole species — is that it really has to be localized to a specific environment. It can't be that if the same trait is good everywhere, then that trait's going to spread because there's so much interbreeding, gene flow as we call it, that eventually if it's a good trait everywhere, it'll get everywhere.

So it has to be just good there. There has to be something about that trait that makes it really helpful right there but not other places. And that has to persist for generations and generations so that there's enough time for selection, because natural selection acts very slowly over generations. So it has to be good for survival and reproduction, has to be very localized and persistent for generations and generations.

Very few selection pressures meet all those criteria. Skin color is a good example of one that does ‪—‬ the best skin color to have in terms of ultraviolet light production. The darker your skin, the more protected you are against ultraviolet light damage versus having lighter skin if you need to be able to make more vitamin D, because that's the trade-off.

Those conditions have been around since the sun and the Earth have been where they are. There's always been more ultraviolet light at the equator and less towards the poles, and so that gradient has been really consistent. And then we see, surprisingly, a really consistent gradient in local populations' skin tone, how much melanin they make and, therefore, how dark their skin is.

[Then there are] things like high-altitude adaptations. The Himalayas have been thousands of meters tall since forever basically, for our purposes. And so humans living there have always had that selection pressure to be able to handle high altitude. And so you see altitude adaptations there. That's the kind of stories we see with local adaptation.

Where we get into trouble is when people talk about local adaptations with things like heart disease. There's been the argument in the '90s that Black Americans might be more likely to have heart disease because there's some localized set of alleles that affects their heart function that makes them more likely to develop hypertension and heart disease. Well, that doesn't make a lot of sense, because the selection pressures on the heart have been kind of the same for our whole species forever.

Same with all these ridiculous and really dangerous things about IQ evolution in different populations. Having a smart brain has been selected for — it's been a good idea — for our whole species since forever. And so any traits that make us have smarter brains are going to be selected for equally everywhere. Gene flow is going to push them all around.

SB: So hypothetically, if I was born with the same genetics but in the Philippines, like your earlier example, instead of the U.K., would the environment override the genetic hand I've been dealt?

HP: The way I try to talk about genetics in my classes and in the book is, your genetics — the hand you're dealt — kind of gives you a universe of possibilities where you could end up. Now, it's not unlimited. There's nothing that you could ever do to me that would have made me 8 feet [2.4 meters] tall, right? My parents could have given me all the best nutrition. I was never going to be 8 feet tall, or even 7 feet [2.1 m] tall, for that matter. So there are limits.

So I don't think of it as overriding. I think whether nature or nurture is what you see emerging more, it's almost always nurture. The environment usually has a much, much larger effect. But they really work together.

SB: What role does epigenetics play in shaping how you develop over developmental time, rather than evolutionary time?

HP: It's a wonderful example of nature and nurture working together because epigenetics is the environmental effects on your body that actually sort of change the way that your genes act for the rest of your life. An environmental experience, a stress, can affect the body in a way that it actually affects the genome, which affects your DNA so that a particular gene might be turned off or actually amplified. It can have different effects for the rest of your life.

But what's really interesting about epigenetics is this possibility that those changes might persist across generations. And so we know this is true in mice, that the epigenetic effects on the genome that we see within a lifetime are somehow transmitted to the offspring and they will have those same epigenetic effects. So the environment experienced by mom as she's growing up could actually affect her offspring when they're born and for their lives.

We have some interesting hints that it's also happening in humans. It's a really exciting space to watch in biology. I don't think we have the full answer yet for humans; it's just so hard to do the work because you're talking about studies that take decades, basically. But it's an exciting new frontier in the sort of nature-nurture interface.

SB: Would you mind explaining what evolutionary mismatches are, and why they're important?

HP: Our species evolved as hunter-gatherers. And so that environment's been the norm for humans for millions of years actually, even before we were Homo sapiens. Being a hunter-gatherer looks different depending on where you are in the world and what time frame we're talking about, but it always involves a lot of physical activity. It always involves foods that you're getting from the wild environment around you. It generally involves a fair amount of pathogens and stuff — the world's dirty out there in the wild. And so they're the kind of environments that our bodies are evolved to be best at because that's what shaped us.

Our environments today are so different from that, and that's the mismatch. The environment that I'm living in right now —‬ my house is climate controlled; I've got thousands of calories of food in the refrigerator; if I don't want to walk around too much today, I don't have to. I've got all sorts of antibacterial soaps and antibiotics if I need them.

Our environments have shifted so much that we're well outside the kind of micro-adjustments our bodies are used to making over a lifetime. And so our physiologies respond in ways that can be bad ‪—‬ so, heart disease, allergies, all sorts of modern ailments that we know didn't used to be common but are common now because of that mismatch.

SB: You mentioned how you see the human body as an anthropologist. You talk throughout the book about the Hadza and other contemporary hunter-gatherer populations. What can we learn about local adaptations from these populations?

HP: We are an incredibly diverse species. Our ability to adapt to our different environments and the cultural adaptations we see, the biological — that's our superpower. That's why there's 9 billion of us and not 9 billion of some other primate. We are as successful as we are because of this adaptability, this flexibility. And what that means is that if we only look to our own population, if I only did this book pulling what we could understand from my fellow Americans, it would be an impoverished book. There would be less to say, and we'd learn less about our bodies and ourselves because we wouldn't have the full extent of human diversity to pull from and learn from.

SB: Your book covers a lot of ground. What do you hope readers take away from it?

HP: More than anything, I hope it gives them the tool set to engage because they're going to put that book down, and the next day they're going to read the paper or be online, and they're going to see some new study about the brain or about diet or they're going to hear some headline about vaccines. And I want people to have a tool set to digest that, make sense of it, and ask the right questions about how we interpret all of this and move forward.

SB: What are those key questions that you hope readers will start to ask?

HP: First of all, to understand that diversity is multilayered. And so, just because I know the color of your skin, it doesn't mean I know anything else about you. I can understand something about that and why people's skin might be darker or lighter and understand that that's a separate question completely from hearts and heart health, or intelligence or anything, really. All these systems develop independently. So, when we think about diversity, we need to move away from the categories that we're taught and [away from] putting everybody in a bucket, and understand this is multilayered. It's true for yourself; it's true for everybody else.

Science has done a lot of work in the past couple hundred years, at least, on the human body to develop some really important consensus ideas around health. We know what kinds of diets keep us healthy. We know that vaccines keep us healthy. We can understand these things and move forward, comfortable in that knowledge. So the debates, for example, around vaccination, I think, are hurtful because we actually have been debating vaccines for 300 years at least, and the evidence is really clear that they're one of the biggest public health victories ever.

So both the kind of concrete details like that, but also the kind of mental tool kit to how we understand diversity. I think those are two different things to walk away with.

Editor's note: This interview has been condensed and edited for clarity.

The patient: Dr. John Graham, a professor of medical genetics and pediatrics at Cedars-Sinai in Los Angeles

The symptoms: Most newborn babies don't have any teeth, but Graham already had a few when he was born. These teeth fell out very shortly after birth, but adult teeth never replaced them — a condition known as tooth agenesis. With time, though, the rest of Graham's mouth filled with teeth.

What happened next: Throughout adolescence and adulthood, Graham contended with confidence issues and underwent multiple costly dental implants. And he was not alone — his mother and her siblings, as well as Graham's children and grandchildren, also had this condition, which strongly suggested the disorder was genetic.

After graduating from medical school, Graham set out to hunt for a genetic cause of the condition.

With the genome-sequencing tools available in 2010, Graham struggled to pinpoint the mutation hiding among the 20,000 or so protein-coding genes in the human genome. Those early sequencing tools from over a decade ago revealed that a long stretch of DNA sequences on chromosome 1 was likely involved, but this came with over 311 mutations to pore over, hardly narrowing down the search.

Some of those mutations may have even been sequencing errors. With the technology available, "the quality of data was just way too noisy," said Dr. Pedro Sanchez, director of pediatric medical genetics at Cedars-Sinai Guerin Children's.

Graham was preparing to retire and simultaneously stop searching for the problem gene when Sanchez offered to help Graham continue his pursuit.

"He was my mentor in medical school," Sanchez told Live Science. "He motivated me to go into medicine, into genetics." Graham had spent his career helping to diagnose other families' illnesses but had yet to pin down his own. "Right before he retired, I said, 'I have to do this for you,'" Sanchez said.

To narrow down the genetic cause, Sanchez and his colleagues sequenced and compared the genomes of two affected and two unaffected family members to isolate mutations unique to the individuals with missing teeth. One mutation fit those criteria, and it lay within the same stretch of chromosome 1 Graham had explored previously.

The diagnosis: The mutation caused a change to one letter in the gene that codes for a protein called keratinocyte differentiation factor 1 (KDF-1). The protein regulates the development of skin and teeth.

To validate the mutation as the correct one, the team sequenced the gene in 21 family members. They found that the variant appeared in 11 affected individuals and was absent in 10 unaffected people. That cemented the genetic variant as the likely cause.

Using computer modeling, Sanchez and his team simulated what shape the KDF-1 protein would take with and without this mutation present. This revealed that the mutation changed a critical building block within the protein, thus destabilizing and bending the protein out of shape. Such an overt change could cause the protein to lose or alter its function in tooth development, bringing about the condition. They reported this discovery in the International Dental Journal.

The treatment: Tooth agenesis remains incurable, but the discovery offered Graham and his family closure. Down the line, this discovery may lead to earlier diagnosis, the researchers think.

Sanchez also said the discovery could help with advocating for dental insurance providers to cover the cost of implants for affected patients, rather than treat implants as non-essential, cosmetic procedures. "Tooth agenesis is not a cheap problem to have," he noted, adding that it's important to cover dental operations because missing teeth could predispose teenagers to mental health issues. Tooth agenesis can also make chewing and speaking more difficult.

What makes the case unique: Tooth agenesis involving one tooth occurs in up to 10% of Americans, but the severe form affecting multiple teeth — as seen in Graham's family — occurs in less than 0.5% of people.

This rarity likely stems from the mutation's location: a critical site in the KDF-1 gene that evolution has left virtually untouched. In addition to studying the gene in humans, the team looked at 421 animal species and discovered that no more than 10 species had evolved a different gene variant at this site.

The doctors didn't just solve Graham's medical mystery; they mapped a crucial site on a protein important in human development.

For more intriguing medical cases, check out our Diagnostic Dilemma archives.

For decades, scientists have delved into the genetic causes of disease by studying patients with those diseases and their families, picking through their genomes in search of genetic mutations that could be the cause.

It's a method that has turned up hundreds of mutations, many thought to be responsible for diseases in almost 100% of the people carrying them. Such mutations have been linked to myriad conditions, from thyroid cancer to ovarian insufficiency to certain forms of diabetes.

But new research is finding that these so-called "monogenic diseases" actually aren't caused by single gene mutations at all. In fact, plenty of perfectly healthy people are walking around with these mutations and no sign of disease, population-based studies are revealing.

"It kind of challenges our standard dogma," said Caroline Wright, a professor of genomic medicine at the University of Exeter in England. Wright has found gene variants that seem to cause disease all the time in patient samples but only in a minority of people in the general population.

"In much of single-gene genetics we've often assumed that a particular genetic cause is necessary and sufficient, and everything else is irrelevant," Wright told Live Science. "And what we're seeing is that that's not necessarily true."

It's a finding that impacts both genetic counseling for patients with family histories of genetic disease and possible treatments for these disorders.

A complicated inheritance

In the mid-1800s, Gregor Mendel worked out the rules of inheritance with the help of pea plants, establishing the basics of modern genetics: Offspring receive a copy of each gene from each parent. In some cases, a gene is dominant, meaning just one copy is enough to ensure that the gene's instructions are expressed in the body. In others, it is recessive, meaning two copies are needed.

Beyond those basics, things get more complex, as not all genes are as simple as the "brown eyes dominant, blue eyes recessive" many people learn in middle school science class. Genes interact with one another and with environmental factors, and those interactions determine the person's phenotype, or traits. In practice, the likelihood that a person with a particular genotype, or combination of genes, expresses a particular phenotype is known as "penetrance."

Some diseases, known as monogenic diseases, have long been classified as having 100% penetrance, meaning people with a given gene mutation always get the disease. The lethal nervous system disorder Tay-Sachs disease, for example, is a recessive condition that develops in all babies with two copies of a particular mutated gene, one inherited from each parent.

Other conditions, such as Crohn's disease and schizophrenia, are classified as polygenic, meaning they arise from the interactions of hundreds to thousands of genes, as well as environmental factors. In polygenic conditions, there isn't a single genetic switch that determines if the person has the disease or not — rather, scientists calculate risk scores that try to take into account as much of the person's genetic spectrum as is understood. The higher the score, the higher the probability of disease.

Many rare diseases were once thought to be monogenic, on the same spectrum as Tay-Sachs. But now, research is showing they are more akin to schizophrenia. What's cracked this new knowledge open is the creation of huge genetic databases from healthy populations.

When gene sequencing was expensive, researchers were limited to looking at the genomes of people with diagnosed diseases and their families. Take inherited retinal degenerations, a constellation of conditions in which the layer of the eye containing light-sensing cells degrades, leading to early vision loss. By testing patients and their families, researchers found genes that were more common in people with the disorder and genes passed down in the family line that raised the risk of disease. Not all of these genes conferred a 100% risk of disease in these clinical samples, but many appeared to come close.

But that method suffers from what's known as "ascertainment bias," said Dr. Eric Pierce, director of the Ocular Genomics Institute at Mass Eye and Ear and an ophthalmologist at Harvard Medical School. Because you're only looking at people with the disorder, you may indeed see gene variants that are common in people with the disorder. But what you can't see is whether healthy people also carry the same variants.

Today, gene sequencing is cheap, and huge studies like the U.S. National Institutes of Health All of Us cohort and the U.K. Biobank collect genetic data and medical records from hundreds of thousands or millions of individuals, sometimes following them through time. These individuals are part of the "general population," meaning they are not specifically included in the cohorts because they have a particular medical condition.

Pierce and his colleague Dr. Elizabeth Rossin, an ophthalmologist and vitreoretinal surgeon at Mass General Hospital and Harvard University, looked in these databases for 167 gene variants thought to lead to severe vision loss almost all the time. What they found was that, in actuality, people with these gene variants had vision loss less than 30% of the time.

"That means for that other 70% of people there is something about the rest of their genome or environment that is changing the way they manifest," Rossin told Live Science.

The supporting cast

If the genes linked to the condition are lead actors, the rest of the genome and the environment are the supporting cast.

In patients and their relatives, the leading-actor genes tend to be shared. But so does the supporting cast. That makes the role of those secondary genes difficult to tease out. In the broader population, the supporting casts aren't the same, so scientists can start to probe the role of the rest of the genome in either protecting against disease or making a disorder more likely to emerge.

There is now a long list of single-gene variants that seem to be necessary to cause a disease, but not sufficient: They appear in almost everyone with the disease, but at the same time, don't seem to trouble most the people that carry them. For example, Wright and her colleagues have found that genetic variants that seemed to cause thyroid cancer in 95% of clinical populations only lead to disease in between 2% and 19% of the general population.

One study by Wright, not yet peer-reviewed, found that variants thought to cause "brittle bone disease," or osteogenesis imperfecta, almost 100% of the time may only cause the disorder about 21% to 40% of the time. Another finds similar results with variants thought to cause a rare childhood eye cancer. Other researchers have turned up the same patterns in mitochondrial diseases, certain inherited forms of diabetes, and ovarian insufficiency, a condition that causes early menopause.

On the flip side, sometimes these studies turn up more risk than expected in the general population. Huntington's disease is a degenerative neurological condition caused by a repeating genetic sequence in the Huntington's gene. It was initially thought to be inherited in an autosomal dominant pattern, meaning if you inherited at least one copy of the defective gene from your parents, you always got the disease.

Later research showed that the disease was somewhat dose-dependent; when people have 40 or more of these genetic repeats, they eventually develop the disease. But a 2016 study found that 1 in 400 people in the population carry 36 to 39 repeats of the gene — right on the edge of the threshold. Not all these people will develop Huntington's, but they are at higher risk, said Michael Hayden, a professor of medical genetics at the University of British Columbia who led that research.

This discovery led Hayden and his team to further study patients with Huntington's who carry 36 to 39 genetic repeats. They found that those at the highest risk of developing the disease earlier in life carry an additional variant nearby that essentially makes the gene act as if the repeated segment were longer.

The Huntington's research is an example of how population and patient samples can complement each other to lead scientists to new answers about how diseases develop.

In ovarian insufficiency, where more than 99% of genetic variants thought to cause the disease were also present in asymptomatic women, population studies also point to the need for better basic cellular research on the condition, said Anna Murray, a professor of human genetics at the University of Exeter in England who led that work. Many genes involved in that condition have multiple roles in the body and multiple interactions with other genes in tissues beyond the ovary, she said.

"Just because you can demonstrate that your variant affects a process [in the lab] doesn't actually necessarily mean that that's what is happening in your particular cell in that system," Murray told Live Science.

Individual risk

Studies of patient groups can reveal an upper bound on the risks of a genetic variant, Wright said, while population-level studies can provide a lower bound. The challenge is helping patients understand what this range means for their own personal risk — a question that researchers are trying to answer.

As genetic screening becomes more ubiquitous, understanding the meaning of individual variants is increasingly important. Parents doing IVF and screening embryos for health conditions, for example, might make very different decisions about which embryos to implant if they are told the risk of genetic disease from a particular variant is 100% versus 20%. Likewise, people getting genetic counseling need to understand if their risk of disease is truly as high as studies on patient populations would suggest, or if they have protective factors that bring their risk down.

The findings may also help refine gene therapy treatments that target specific disease-causing genes. Because these genes do cause the disease in some people, these gene therapies will continue to be important, Pierce said. But understanding the rest of the genetic milieu could help boost the effectiveness of such therapies.

"We might be able to predict more accurately who will respond best to genetic therapies," Pierce said. "We might also identify novel targets for therapies following the identification of the additional genetic factors that influence disease expression."

Rossin and Pierce are now working on large global collaborations to learn more about what modifies the genetic risk in retinal disorders. Other researchers are looking to do the same for disorders such as ovarian insufficiency.

Right now, there are limited treatment options for many of the conditions under study. That means that there may be few options for prevention or early treatment, even if the genes fueling the conditions are better understood.

But as more new treatment options emerge, it will be increasingly important to understand the nuances of risk for individual patients, Hayden said. Understanding that risk could help patients make decisions about preventative treatment.

"When therapies are available for those diseases, early treatment—and particularly early treatment for degenerative disease of the brain and the eye—is better than later, because you can't replace neurons," Hayden said. "So you'll want to know your risk."

DNA is often considered the ultimate indicator of our identity — a foolproof way to determine our origins and how we connect to our parents and previous generations of our family. But in this excerpt from "Hidden Guests: Migrating Cells and How the New Science of Microchimerism Is Redefining Human Identity" (Greystone Books, 2025), author and science journalist Lise Barnéoud explores an unusual case that exposes the limitations of DNA testing, when a maternity test suggested a woman was not the mother of the children she gave birth to.

Lydia Fairchild was 26 years old when she applied for welfare benefits to help her raise her two children on her own. As part of the application process, she had to undergo a maternity test. A few weeks later, she was called into a meeting with social services, where they accused her of not being the mother of her children.

"At first, I kind of laughed … But they were serious. I could just see the seriousness in their faces," Fairchild said. "DNA is 100% foolproof, and it doesn't lie," a social worker told her. "So who are you?"

At first, Fairchild was suspected of attempting to defraud the welfare system by inventing children. The state prosecutor launched an investigation and quickly confirmed that two children did indeed live with her. Could she have kidnapped them? Fairchild showed them photographs of herself pregnant. Her mother, her children's father, and her obstetrician all testified to the fact that she had given birth.

Could she be a surrogate mother who kept the children she'd carried? After three hearings in court, Fairchild feared the worst. "Every day it felt like it was going to be the last day I'd see them," she tearfully recounted. "I called every lawyer in the phone book. None of them believed me. It was my word against DNA. It was me against everyone."

Fairchild was pregnant with her third child at the time, and the judge asked that both mother and child be tested immediately after birth. And the impossible happened: Fairchild's third child, just emerged from her womb, was not her son either — genetically speaking.

At last, a lawyer agreed to help her. Alan Tindell asked Fairchild about her life, her relationships with her siblings, and her relationship with the father of her children. "Given her answers, I finally decided to believe her," Tindell explained. He soon came across a scientific article describing Karen Keegan's case and contacted the team in Boston to ask them to examine Fairchild. They first tested Fairchild's blood, but they found only one cell type, just as they had for Karen Keegan. They moved on to cells from her skin, hair, and cheek: still nothing.

Until the day they performed a cervical smear. There, they found cells with a different DNA, a DNA that matched Fairchild's children as well as her mother. They concluded that the second DNA must have come from a vanished twin sister. Fairchild could finally breathe. But how would her story have ended without Karen Keegan?

The oft-taught equation of "one individual, one genome" fails to capture the full complexity of reality. What seemed a long-established and unshakable certainty, even to me, has turned out to be imperfect knowledge in need of revision. We know too little about our own biology to have blind faith that DNA profiling will always reveal a person's identity or origins.

Our ultimate proof is far from foolproof. Yet it is very often used to determine relationships, prove or disprove paternity, evaluate applications for family reunification, or convict persons otherwise presumed innocent. "The overriding assumption in such circumstances is that a sample that fails to confirm genetic kinship is an indication of fraud, regardless of other substantiations of legitimate kinship relations," observes the British philosopher Margrit Shildrick, one of the few scholars to examine the social and legal consequences of microchimerism.

Why is some scientific knowledge so hastily dressed up as infallible truth? Do we not dwell enough on our own ignorance? And why do some fields of knowledge remain frozen by skepticism, even when new discoveries should allow us to dispel our doubts? The sociology of science has its work cut out for it.

It's impossible to know how many Karen Keegans and Lydia Fairchilds exist. Most of the time, the existence of chimeric cells from vanished twins goes unnoticed. If Keegan had not needed a kidney transplant, if Fairchild had not applied for welfare benefits, they never would have known that their gametes were "occupied" by cells other than their own.

Their children or grandchildren might have eventually discovered that a branch in their family tree appeared to be missing, that they had somehow inherited genes that neither of their parents possessed.

Today, we know of about a dozen cases of this phenomenon, known as germ-line chimerism: where chimeric cells are present in the tissues that form eggs or sperm. One such case involved an American man who learned through a paternity test that he could not be the father of his child, who was conceived via assisted reproduction. He was preparing to sue the clinic, believing himself to be the victim of a semen mix-up, when a more precise test revealed that he in fact shared 25% of his DNA with the child. In other words, he was the child's uncle, genetically speaking.

Further research showed that 10% of his sperm contained DNA from a vanished twin brother. "One of the most impactful consequences of this case study is to point out that some traditional paternity tests which have resulted in negative outcomes (the tested parent was excluded as the biological parent) may have been wrong, because the alleged parent may have undiagnosed chimerism," stress the researchers who chronicled his case.

Given the increasing use of these tests, it is likely that the paternity of other fathers has been wrongly contested. This is precisely the scenario depicted in the French TV series "Nona et ses filles," which aired in 2021. Nona, played by 70-year-old actress Miou-Miou, is pregnant when a genetic test reveals that her lover, André, cannot be the father of her child. They eventually learn that one of André's testicles contains sperm from a vanished twin brother. In the words of André, as he attempts to parse his situation, "So he's my nephew … but he's also my son."

When Neanderthals and modern humans first got together, they preferred pairings between Neanderthal men and human women, a new study of ancient and modern genomes suggests. The finding helps to explain why modern humans (Homo sapiens) have a relatively low level of Neanderthal genes and why those genes are found in some populations today and not in others.

Ever since the first modern-human and Neanderthal genomes were sequenced over 20 years ago, scientists have puzzled over "Neanderthal deserts," or places in the modern-human genome where Neanderthal genes are rare. The two groups interbred during a few periods after their ancestors split around 600,000 years ago. The result is that most non-African people on the planet today carry an average of 2% Neanderthal DNA, while some African groups have up to 1.5%, which was inherited from H. sapiens who mixed with Neanderthals in Eurasia and then moved to Africa.

But what has stymied experts is that the genes we inherited from Neanderthals are found only in tiny patches on our X chromosome, even though those genes appear in greater numbers across our other chromosomes. There are regions on the X chromosome — the sex chromosome that every human has at least one copy of — where no living humans have any Neanderthal ancestry.

"For years, we just assumed these deserts existed because certain Neanderthal genes were biologically 'toxic' to humans — as tends to be the case when species diverge — so we thought the genes may have caused health problems and were likely purged by natural selection," Alexander Platt, a population geneticist at the University of Pennsylvania, said in a statement.

But in a study published Thursday (Feb. 26) in the journal Science, Platt and colleagues concluded that the most plausible explanation for these "Neanderthal deserts" is actually mate preference, an evolutionary mechanism that is a major part of sexual selection. Biologists commonly illustrate the evolutionary result of mate preference with the large, colorful tail of the male peacock. Early humans and Neanderthals likely chose their mates for specific reasons as well.

DNA deep dive

The researchers analyzed the genomes of 73 women from three modern-day African populations that have no Neanderthal ancestry, including the !Xoo, Ju|'hoansi and Khoisan, and compared them with the genomes of a few Neanderthals. First, they looked at the Neanderthals' X chromosomes and found significantly higher amounts of modern-human ancestry there than on the other Neanderthal chromosomes. This result revealed that the lack of Neanderthal genes in the human X chromosome is not the result of incompatibility, which would have suggested Neanderthal genes caused modern humans problems and were eliminated through natural selection.

Rather, the surprisingly high amount of modern human DNA chunks found in Neanderthals can be explained by mate preference, the researchers concluded. Because females carry two X chromosomes and males carry only one, a preference for mating between female H. sapiens and male Neanderthals would mean fewer Neanderthal X chromosomes would enter the human gene pool, producing the pattern the researchers identified in the genomes.

But the reasons for the mate preference — and the direction of it — remain elusive.

"I have no idea whose preference is being expressed here," Platt told Live Science in an email.

Previous research into the Neanderthal Y chromosome — one of the two sex chromosomes of male individuals — indicates there was interbreeding between male H. sapiens and female Neanderthals. But it is apparent from the new study that, in effect, male Neanderthals and female H. sapiens liked each other more than female Neanderthals and male H. sapiens did.

"We simply don't have a genetic signature to discern beyond that at the moment," Platt said.

The researchers did not rule out more complicated evolutionary scenarios that might have combined natural selection, sex biases, mate preference and sex-specific migration to contribute to the "Neanderthal deserts" in the human genome.

Questions about the structure of Neanderthal and modern-human societies are also important to answer for a fuller understanding of mate choice in the past, as anthropologists and evolutionary biologists who have studied the phenomenon show that mate choice is partially learned.

The research team plans to "look at the evolution of the social structures and gender roles within Neanderthals," which "could conceivably shed some light on the picture," Platt said. "But I think we're a long way from knowing this."

Neanderthal quiz: How much do you know about our closest relatives?

Flipping a single genetic switch can make doting dads attack their offspring, at least in African striped mice, new research suggests. But the gene itself wasn't solely responsible for this switch from attentive to aggressive fathering; social conditions also played a role in how the male mice behaved.

The findings could reveal more about the genetic mechanisms that lead some species of mammals to act as caring fathers while others abandon their young. Active fathering is rare in mammals, with only 5% of the 6,000 mammalian species having involved dads. Because of this, scientists know far less about how paternal care works in mammals than they know about maternal care in mammals. African striped mice (Rhabdomys pumilio) are useful for studying mammalian paternal care because males show a wide range of behaviors toward pups, from huddling to keep pups warm to actively ignoring their progeny.

In a study published Feb. 18 in the journal Nature, researchers placed male African striped mice in cages either alone with a group of pups or in group housing with other dads and their pups. They found males kept in groups were more likely to ignore the pups or to try to kill them.

To determine the brain regions that mediated this behavior, the team exposed male mice to pups, then monitored their brain activity. They found the attentive dads had greater activity in one brain region, called the medial preoptic area (MPOA).

"Decades of work has shown that the MPOA acts as a hub for maternal care across mammals," lead author and postdoctoral researcher Dr. Forrest Rogers, a researcher at the Princeton Neuroscience Institute, told Live Science in an email.

The team then dissected the brains of the mice and measured gene activity in cells from the MPOA. From this, they discovered that a gene called Agouti was more active in males that attacked pups than in males that cared for the pups.

"Agouti is better known for its roles in skin pigmentation and metabolism, so discovering this previously unknown role in the brain for parenting behavior was exciting," Rogers said in a statement.

To confirm that Agouti expression was responsible for the transition between attentive and aggressive behavior, the team first exposed mice to pups, then injected a virus that amped up the expression of the Agouti gene in the MPOA. When the males were exposed again to pups, their behavior changed.

"We found that those males, when Agouti was increased, became aggressive toward pups," Rogers told Live Science in an email, suggesting that this gene was acting as a sort of "switch" that flipped between aggressive and caring behavior in mouse fathers.

While the Agouti gene found within the MPOA may have a strong link to the change in paternal care, Rogers cautioned that this molecular switch wasn't the whole story.

"It certainly seems that for some striped mice, increasing Agouti expression is sufficient to induce infanticide," he said. "However, we also found that there were other factors at play, for example, the current social housing, which could moderate this effect."

When the researchers moved males from group housing to solitary cages, Agouti levels dropped and caregiving increased, suggesting that the gene is influenced more by social context than by food availability.

While this study may have uncovered a possible genetic switch for fathering, there were key limitations. Notably, only male African striped mice were studied. And although fathering behavior varied within the species, the researchers cautioned against translating those findings to other species.

"While we won't rule out that Agouti could function similarly in other species (humans or others), there is no current evidence suggesting this specific function in humans (or other mammalian species)," Rogers said in his email to Live Science.

Kazakh folklore says that the body of Jochi, Genghis Khan's eldest son, lies in a mausoleum in the Ulytau region, in the country's central uplands. When archaeologists recently studied the body from the medieval mausoleum, though, they didn't find Jochi — but they did find a novel genetic lineage that may have been passed on by Genghis himself.

Genghis Khan, born Temüjin in the Khentii mountains of northeast Mongolia, was a central Asian warrior who founded the sprawling Mongol Empire in 1206. The Mongols' astounding horseback riding abilities and skill with bows and arrows enabled them to quickly conquer a territory stretching from the Pacific Ocean to Central Europe. Genghis Khan and his wife Börte had four sons and five daughters. Their eldest son, Jochi, was born around 1182 and died around 1227, shortly before Genghis' own death. The northwestern part of the Mongol Empire that Jochi (also spelled Joshi, Zhoshi and Jüshi) ruled was later known as the Golden Horde.

"The Golden Horde was ruled by the eldest son of Genghis Khan and his descendants for many, many generations," Ayken Askapuli, a biological anthropologist at the University of Wisconsin-Madison, told Live Science. "And so far, no ancient DNA data has been obtained from these individuals."

To try and unearth DNA from Genghis' close relations, Askapuli and colleagues investigated the folklore claims that Jochi, who died after falling from a horse in Ulytau, was buried in the eponymous mausoleum, which was built at least 70 years after his death. They published their findings Feb. 19 in the journal PNAS.

For the study, the researchers went to the Ulytau region and analyzed male skeletons from three medieval mausoleums reputedly belonging to Jochi and other men of the elite Golden Horde. The team examined these individuals' DNA to look at their Y chromosome data, which is passed from father to son.

Two of the male skeletons were carbon-dated to between 1286 and 1398, making them unlikely to be the children of Genghis Khan. But the researchers' DNA analysis did reveal that the two men shared a paternal lineage — also shared with a man who was carbon-dated to the 18th century — that is believed to be associated with Genghis Khan.

One issue with confirming this association, though, is that Genghis Khan's skeleton has never been found and no one knows where he was buried. "Nobody knows exactly what his Y DNA would look like," Askapuli said. "Not only from him, but his sons, his grandsons, immediate relatives — none of them are known. So this is an attempt to answer that question."

A previous study published in the American Journal of Human Genetics in 2003 showed that an unusual Y chromosome lineage that originated in Mongolia a millennium ago, called C3*, is now common in people who are living throughout what was once the Mongol Empire. Those researchers concluded that the lineage was likely carried by male descendants of Genghis Khan and that 0.5% of the world's male population today, or 1 in 200 men, may be descended from the famous warrior.

In the new analysis, Askapuli and colleagues found that the three men buried in the Golden Horde mausoleums were all paternally related and shared a recent ancestor in the C3* lineage.

"The Y chromosome haplotype they have belongs to the C3* cluster that was previously hypothesized to be Genghis Khan's," Askapuli said, "but this one is very rare in modern populations."

The C3* cluster is a very large genetic family — a fact that was not known in 2003. "It has many different branches," Askapuli explained, "and the Golden Horde elites have one of those branches."

The specific branch that the researchers found in the mausoleum skeletons is actually much more rare than the one discovered in 2003, meaning far fewer men living today are related to Genghis Khan than previously assumed.

The scientists also found that the individuals in the Golden Horde mausoleums could trace their ancestry largely to Ancient Northeast Asian (ANA) populations, with genetic contributions from the Kipchaks, a group of eastern Scythian-related nomads that lived in the Eurasian Steppe and were integrated into the Golden Horde in medieval times.

Although the exact Y chromosome lineage that Genghis Khan shared with his male descendants is still unknown, Askapuli believes that in the near future, researchers may be able to answer this question.

"If we have a tomb which is historically recorded and also have a tombstone that says that this individual belonged to the descendants of Genghis Khan, and then if we perform genetic tests on these individuals, I think it is possible to make a final conclusion," Askapuli said. "But it's not a simple story — it's complicated."

The past decade ushered in a surge of discovery in the field of human genetics — and simultaneously, more genetic technologies made their way out of the lab and into the consumer marketplace.

This tech includes at-home genetic tests for learning about health risks and ancestry, as well as polygenic embryo selection, which enables prospective parents undergoing in vitro fertilization (IVF) to predict the future traits of the resulting embryos. If these products work as advertised, they could improve health outcomes; but are they really as powerful as their marketing claims? And what impact could these technologies have on society if they're used irresponsibly?

In a new book, "What We Inherit: How New Technologies and Old Myths Are Shaping Our Genomic Future" (Princeton University Press, 2026), bioethicist Daphne Martschenko and sociologist Sam Trejo unpack persistent myths about genes that shape scientists' and the public's views of these technologies. They weigh up the possible pros and cons of using such tools, ultimately concluding that the field is in desperate need of regulation. They argue that allowing it to advance without guardrails could deepen existing social inequalities.

Live Science spoke with Martschenko and Trejo about their book and perspectives on genomic technologies, especially those aimed at consumers.

Nicoletta Lanese: What prompted you to write this book now?

Daphne Martschenko: We realized we were both similarly disillusioned by the bitter academic debate that was going on over whether and how to do genomic research on behaviors and social outcomes — this field of "social genomics" that we focus on in the book.

We also had a goal of wanting the public to understand these consumer products that are coming out — direct-to-consumer genetic testing, polygenic embryo selection. [We wanted people to] understand some of the science behind them and the limitations behind them so that they can make informed decisions when thinking about whether or not to access those technologies.

Sam Trejo: A lot of it has to do with [the fact that] we're pretty early on in this "post-genomic" era. We had the first genome sequence about 25 years ago, but it's only really been in the last 10, maybe 15, years that we've started to get large enough genomic databases to make rigorous discoveries — because the genome is so big, and each particular region of it actually has, it turns out, a very small contribution to most traits.

Now that the science is improving, our ability to take a person's genome — have them spit in a cup, process that information, and make predictions about a wide range of traits — is growing. It could be from how tall someone is going to be, how far they're going to go in school, their likelihood of developing Crohn's disease or schizophrenia. Over time, our ability to summarize a person's genetic predisposition has gotten better, and it's increasingly used in scientific research in a wide variety of ways.

But there are these lingering questions about, to what extent should we take these technologies that were designed for research and actually use them in the wider world?

NL: In the book, you address myths about genes and misconceptions around the influence of "nature versus nurture." Why was that important?

ST: In the book, we call this [the] "destiny myth," which summarizes the idea that a person's DNA affects their traits, their diseases, their life outcomes in simple, straightforward, immutable ways that are biological and distinct from the social and cultural aspects of their life — the idea that DNA is destiny, that if you have a genetic predisposition for something, then there's little that we can do about it.

What we try to do in that chapter is really drill down to, where are the origins of these misconceptions that we have about DNA? And these recent genomic discoveries that say, "Oh, we've identified the regions of the genome that are relevant for educational attainment or that are relevant for depression" — what do those actually mean?

The big story is, even though we're starting to identify many regions of the genome that correlate with, or even causally affect, a wide range of medical traits, social traits — even though that's true, we still don't really know why. We don't know the mechanisms that connect DNA differences to differences in people's life outcomes.

DM: When we talk about some of these downstream applications, like the use of polygenic scores in embryo selection, we discussed how the polygenic scores are a "black box predictor." [Editor's note: Polygenic scores predict the likelihood that a given trait or disease will emerge based on an individual's genome. Some companies offer polygenic scores for IVF embryos, enabling parents to select embryos with higher scores for desired traits.]

When Sam was saying that there's poor understanding of what causal mechanisms are, we don't know why a genome-wide association study flags variants that are associated with whatever the trait is that the researchers are looking at.

NL: Where might it be appropriate to use polygenic scores for health applications?

DM: I think there's more of an appetite for using polygenic scores for medical conditions like heart disease or type 2 diabetes. That's less controversial than, for example, using polygenic scores in something like embryo selection for intelligence, or offering direct-to-consumer genetic testing for a trait like intelligence.

Part of that is because of the long-standing history in which claims regarding genetic differences in socially valued traits, like intelligence, have been used for social harm. That's something that we talked through in the book: how the destiny myth and the "race myth" have been used to justify laws outlawing interracial marriage or legalize involuntary sterilization. [Editor's note: The authors define the "race myth" as the false belief that DNA differences divide humans into discrete and biologically distinct racial groups.]

ST: In the book, we talk about "application genetic screening," which would be used to stratify access to certain medical interventions or treatments based on polygenic scores. So, if you go to the cardiologist, they're going to assess your risk of having a heart attack in the next few years. Having a high genetic predisposition could be something that gets indexed by a polygenic score. That could be something that people are comfortable with doctors using to decide "What level of statins should I prescribe, or what other interventions are appropriate here?"

There's this idea that it's [polygenic scoring is] going to allow us to better target our resources to the people who need them the most. We're identifying this hidden risk for heart disease or these other negative traits that we can then help ameliorate. On balance, the use of polygenic scores in the clinic in this way could reduce the differences in outcomes between somebody who has a high risk for heart disease and a low risk for heart disease.

The flip side would be something like using polygenic scores for private school admissions. As far as Daphne and I can tell — or the experts that we've talked to — there's no kind of legislation that would prevent a private school from considering polygenic scores in addition to, you know, personal essays, past academic performance, in determining how to admit students. This isn't something that we're actually seeing in the world, but as a hypothetical application, I think this is something that would make many people uncomfortable.

NL: What would you flag as limitations of direct-to-consumer genetic tests?

DM: There are a number of companies that offer genetic tests for a wide range of traits. If you can imagine a trait, there's probably a company somewhere that is offering a genetic test for that. Things like facial attractiveness, athletic ability, political views, intelligence, heart health, brain health — you name it, there's a company that's trying to sell it to consumers.

One of the things that we point out is how companies offering these kinds of tests sometimes use the destiny myth to market the product they're selling. They overstate the role and relevance of DNA to make the consumers feel that this is really important information for them to have. We, in the book, debunk the destiny myth.

ST: There's also not a lot of transparency from the companies in terms of what datasets they are drawing upon, [or] how they analyze the samples that people are sending in, in order to spit out the genetic report that the consumer has purchased.

For most of the traits that people are interested in, aside from very specific diseases and disorders — Huntington's disease, cystic fibrosis, Tay-Sachs [disease], sickle cell [disease] — most human traits are polygenic, which is to say that many, many, many regions of the genome matter for shaping that trait. Sometimes, these direct-to-consumer tests will tell somebody that they have a very high genetic risk for some negative outcome, but they're only looking at three variants, when actually 10,000 variants matter.

So there's not clear information on these direct-to-consumer sites about how predictive or how accurate these tests are. And certainly some of them have accuracy that's close to zero [for specific traits] but are provided nonetheless.

NL: And what are the limitations of polygenic embryo selection?

ST: What polygenic embryo selection does is use these scores to try and change the expected characteristics of the child that the set of prospective parents will have. Before we decide which of these [IVF] embryos is actually going to be implanted and become a fully realized human child, we're going to genotype all of them. We're going to see which DNA they happen to inherit from each parent, and we're going to pick the embryo that we think has the "best" or "healthiest" genetic characteristics.

But importantly, how effective this technology is at present is limited by a lot of things. … The truth is, for most traits right now, its accuracy is quite limited.

Height [as a selectable trait] has two things going for it: One, we have very large sample sizes to train our polygenic scores on, partly because height is something that everybody has and it's easy to measure. And height is very heritable; it's very genetically influenced. In the U.S., about 80% of the variation in height is due to people's DNA, so it's kind of the best-case scenario. But some traits are much less genetically influenced.

Another important piece of the puzzle is the number of embryos that you're able to select from. If you're only selecting from a few embryos, then even if you pick the one that has the highest polygenic score for a particular trait, you're actually not going to get that big of a change, on average.

The technology relies on our ability to identify the regions of the genome that matter for a given trait … and polygenetic scores are trained on sample sizes of, ideally, millions of people. Typically, though, those people are from one particular region of the [human] family tree: the European ancestry region.

There's very limited portability of these products to other ancestries. The accuracy declines for Hispanic Americans, Asian Americans, Black Americans, who tend to have ancestry from different regions of this big family tree of humanity.

DM: I want to make clear that the "big family tree of humanity," and the genetic ancestry that researchers crudely draw over that family tree, is not synonymous with race. … The social process of race is where we look at physical, outward appearances of folks and make decisions about how we treat them and understand them. Race is a social process that's about power, and it's not the same thing as the great family tree of humanity.

NL: What are the big takeaways from this book?

DM: I would say, to the academic researchers who are enthusiastic about polygenic scores and how they might be deployed in the world, and for those who are more cautious and apprehensive, our message is that if we want to ensure that these technologies are used in ways that maximize good and minimize harms, it's very important that we take the time to really listen to each other and understand why we're disagreeing.

Something that Sam and I learned is that we didn't have to agree on everything in order to agree about the need for regulation of these technologies and to develop a preliminary framework for thinking about how we might go about that regulation.

In the last part of the book, we think about regulating the use of polygenic scores in not just embryo selection but also direct-to-consumer genetic testing and screening in settings like schools or financial lending. [On that front] we also have a message for policymakers, really calling for the need for greater regulation of this technology and offering a potential path forward for at least getting the conversation started.

For members of the public, a key goal is to help folks understand, when they go to a company like 23andMe or Ancestry and get their ancestry results, what is the information that they're receiving? How are these companies generating these tests, and what do I need to know so that I understand what the limitations of them are?

When it comes to the consumer products that are related to the social behavioral traits or to embryo selection, it's also about helping people understand, what is the science or lack of science behind some of these products — so again, consumers can make informed decisions about whether they want to spend their money to buy a genetic test for something like facial attractiveness or math ability, understanding the dearth of scientific evidence to support those kinds of consumer tests.

Editor's note: This interview has been lightly edited for length and clarity.

This article is for informational purposes only and is not meant to offer medical advice.

The technology sounds like it's been plucked from a science-fiction film — but it's all too real.

A number of companies now offer prospective parents the chance to "score" embryos fertilized through in vitro fertilization (IVF), based on the embryos' genetic profiles. This technology, called polygenic embryo selection, uses genetics to predict the likelihood that a given trait or disease will manifest in a baby-to-be. In theory, the technology could be leveraged to lower a child's risk of diseases with strong genetic components. But there are lingering questions about how well it works and whether it could deepen existing health disparities between groups.

Bioethicist Daphne Martschenko and sociologist Sam Trejo explore some of these questions in this excerpt from their book "What We Inherit: How New Technologies and Old Myths Are Shaping Our Genomic Future" (Princeton University Press, 2026).

For most traits and diseases, companies offering polygenic embryo selection are currently selling consumers little more than snake oil. However, in the coming decades, the accuracy of polygenic scores will likely improve. These improvements in accuracy will mean that a wider range of characteristics will become viable targets for polygenic embryo selection, raising a host of concerns. Among them, first and foremost is the potential exacerbation and, worse still, biological reification of structural inequality that could come from unequal access to the technology.

If the United States continues on its current path, polygenic embryo selection will only be available to those with enough money to afford IVF and will — at least for a time — be most effective in individuals of European ancestries. The high costs of IVF are prohibitively expensive for working- and middle-class Americans. A single cycle of IVF costs between $15,000 and $20,000 — and, at present, most couples undergoing IVF go through three or four cycles to be successful, with extra costs incurred to freeze embryos or use donor eggs. (However, because these couples are typically experiencing infertility, the extent to which these figures generalize the broader American population of prospective parents is uncertain.) Private health insurance coverage of IVF is typically limited and varies across states and employers. Medicaid, the public health insurance offered to low-income families in the United States, does not cover IVF at all.

Polygenic embryo selection only introduces further additional costs; Genomic Prediction, for instance, charges $1,000 per embryo analyzed, and Orchid Health charges $2,500. Heliospect charges up to $50,000 to test 100 embryos. If the status quo continues and polygenic embryo selection remains unregulated, then unequal access to the technology will cause structural inequality to grow. The racial and socioeconomic disparities of the world, both past and present, are not the result of systematic DNA differences across groups. If polygenic embryo selection continues to expand unchecked, then the frightening possibility exists that a new source of racial and economic structural inequality that is, in part, genetically produced will emerge.

As an example, consider health disparities. Because of the portability problem, polygenic embryo selection has decreased effectiveness in non-European ancestries. If, in the coming years, the use of the technology grows, those of non-European ancestries, like Pacific Islander Americans, will largely be excluded from any health benefits that embryo selection provides. Pacific Islander Americans (such as those from Guam or Samoa) are largely of Oceanian ancestries and occupy a unique portion of the Family Tree. They tend to have higher rates of diabetes, high blood pressure, and heart disease than White Americans — the Centers for Disease Control lists colonialism, poverty, and inadequate access to healthy foods, among other things, as key factors contributing to this disparity. However, if polygenic embryo selection continues to be less effective for Pacific Islander Americans, then this community could one day have systematically higher genetic risk for chronic health conditions than White Americans with European genetic ancestry, further worsening existing health disparities between Pacific Islander Americans and White Americans.

Imagine a similar dynamic playing out in educational settings. Today, children from working-class families are nearly twice as likely to not graduate from high school compared with children from upper-class families. Imagine how this disparity would grow if upper-class families (but not working-class families) were able to afford and utilize polygenic embryo selection to decrease the rate that their children suffered from learning disabilities, such as dyslexia and ADHD. Existing educational disparities between upper-class and lower-class American children would only worsen with disparate access to polygenic technologies.

Perhaps most concerning, if unequal access to embryo selection were to create class or racial disparities in genetic risk, then these differences would be passed onto future generations — potentially even compounding and accumulating over time. Richard Herrnstein and Charles Murray were dead wrong in 1994 when they wrote in "The Bell Curve" that genetic differences have naturally emerged between the American rich and poor or between White and Black Americans.

However, if care is not exercised, genetic differences between groups of people may emerge artificially through technologies like polygenic embryo selection. Troublingly, even the inaccurate and ineffective polygenic embryo selection that is occurring in the United States right now could spur the formation of new myths about group differences in genetic risk. The outsized power of genetic myths highlights how even just the perception that polygenic embryo selection has produced genetic differences between groups could become a problem in and of itself. In other words, if people believe that children born via polygenic embryo selection are materially dif­ferent from (or better than) children born without it, they may treat them differently — regardless of whether an actual difference exists. Scholars have shown that people can use the idea of genetic difference to disguise underlying racist, classist, and sexist attitudes.

Though concerns about polygenic embryo selection abound, it is important to also consider the potential upsides. Remember Sam's experiences with nerve damage and chronic pain from the previous chapter? A person's risk for chronic pain is meaningfully influenced by their DNA, and Sam's mom, Nina, has also suffered from sometimes debilitating chronic pain for most of her life. Being in pain is not a relative trait; one person hurting less is not inherently accompanied by another person hurting more. In a world where polygenic scores are accurate for individuals across the entire Family Tree, polygenic embryo selection could help reduce the rate of chronic pain in future generations. In such a world, Sam would have a hard time justifying a policy that prevented parents from accessing such a technology (and would even consider using it himself). The looming challenge is figuring out for which traits and under what circumstances polygenic embryo selection is and is not permissible.

This article is for informational purposes only and is not meant to offer medical advice.

"If I give you a diagnostic tool that lets you end up with a kid that has a three times higher chance of getting admitted to MIT, I think people are going to be interested."

Although it sounds like a line from a sci-fi movie, this is actually a quote from Steve Hsu, a physics professor at Michigan State University and co-founder of Genomic Prediction, a company that offers parents a new technology called polygenic embryo selection.

In the 1997 film "Gattaca," the kind of thinking reflected in Hsu's pitch led to a dystopia in which children were conceived in laboratories and society was divided into genetic haves and have-nots. When the film first came out, the reproductive technologies it depicted were science fiction — but today, they are rapidly becoming scientific realities.

Companies like Genomic Prediction, Orchid, Herasight, and Nucleus now offer polygenic embryo selection, a technology that sorts embryos by their genetics and predicts the eventual traits of babies-to-be. It is not the same as an older technology that screens embryos for chromosomal abnormalities and specific, single-gene genetic diseases, such as sickle cell and cystic fibrosis. By comparison, polygenic embryo selection aims to give prospective parents insight into a much wider range of traits, ranging from intelligence to heart disease to depression.

Hsu thinks this is just good business, and he's right –– in survey studies, many prospective parents have expressed interest in utilizing the technology. The question is whether we should let him sell it.

These tests rely on polygenic scores, summaries of thousands of tiny genetic influences, to try and predict the likelihood that a given trait will manifest. Polygenic scores are valuable tools for researchers seeking to better understand the influence of genetics on various diseases. But the predictive accuracy of existing polygenic scores varies substantially from trait to trait, and they are typically unreliable guides for predicting a person's future — let alone an embryo's.

Researchers have discovered that many of the supposedly genetic effects summarized in existing polygenic scores aren't biological at all. Rather, they reflect the fact that people who are genetically alike tend to also live in similar regions and share social and economic circumstances. Polygenic scores also don't work well for people who aren't represented in the training data — namely, people who aren’t of European ancestry.

But that isn't stopping companies from marketing their service as the responsible way to make babies.

Potential consequences of polygenic embryo selection

Despite their well-known scientific limitations, using polygenic scores to select embryos could fuel the belief that children conceived this way are inherently "better" than those conceived without them — akin to what we saw in "Gattaca."

Parents may have higher expectations of polygenic embryo-selected kids. Polygenic embryo-selected individuals might seek out potential spouses who have similarly been selected for. Meanwhile, those born without selection could face lower expectations, discrimination and the stigma of being deemed genetically inferior.

The ways in which we perceive one another, however unfounded, have a profound influence on our social interactions. There is, for instance, a long and disturbing history of using genetic science to legitimize harmful and inaccurate views of race and instigate racial violence.

Eventually, polygenic embryo selection will likely become more accurate at predicting traits as the genomic databases used in medical research grow larger and more diverse — though just how accurate will depend on the trait. That makes the current lack of regulation around the technology all the more troubling.

There are no agreed-upon standards for the threshold at which the underlying science will be accurate enough to justify its use in embryo selection. Little compels companies to be transparent about the specific scientific studies that their services are built upon. Misleading advertising faces few repercussions in practice. There's a reason the leading embryo selection companies are based in the United States: We don't have rules.

Meanwhile, other developed nations have taken a far more cautious regulatory approach. Countries like the U.K., Germany and France have banned polygenic embryo selection outright –– although loopholes still exist. These nations recognized early that leaving such consequential technology to market forces risks creating the exact dystopia "Gattaca" warned us about.

Prospective parents who suffer from conditions such as Crohn's disease or schizophrenia may see embryo selection as a way to reduce their child's chances of enduring a similar fate. It's difficult to justify avoiding embryo selection in these cases. But without a robust regulatory apparatus, screening for such conditions could inadvertently open the door to selection for far more troubling traits: intelligence, athleticism, or even skin tone.

At least two companies — Nucleus and Herasight — already offer embryo testing for intelligence.

Notably, as it stands, the technology is unaffordable to most Americans. Polygenic embryo selection requires undergoing IVF. A single IVF cycle costs tens of thousands of dollars and is not covered by Medicaid. Genetically testing each embryo prior to implantation adds thousands more to the overall price tag.

Given the wealthy can access the technology, as the effectiveness of polygenic embryo selection improves, existing social inequalities between rich and poor Americans could turn into biological ones.

Affluent Americans are already into the idea of utilizing embryo selection to "optimize" their best baby. Millions of dollars have been pumped into the industry from tech elites like Alexis Ohanian, Reddit co-founder and husband of the tennis superstar Serena Williams; and Brian Armstrong, co-founder of Coinbase. Notable clientele of polygenic embryo selection include OpenAI's Sam Altman and Tesla's Elon Musk.

Without regulation, key ethical and social questions raised by polygenic embryo selection will go unanswered: What kinds of traits should parents be allowed to select for? Could unreasonable expectations be placed on the children who were conceived with the technology? Are we quietly creating a genetic arms race that encodes existing social and economic inequalities into our very DNA?

Allowing companies to offer embryo selection will tilt social competition even further in favor of those already ahead. Regulation won't stop scientific progress, and in fact, it is essential for ensuring that progress benefits society rather than dividing it.

Opinion on Live Science gives you insight on the most important issues in science that affect you and the world around you today, written by experts and leading scientists in their field.

Men tend to lose the Y chromosome from their cells as they age. But because the Y bears few genes other than for male determination, it was thought this loss would not affect health.

But evidence has mounted over the past few years that when people who have a Y chromosome lose it, the loss is associated with serious diseases throughout the body, contributing to a shorter lifespan.

Loss of the Y in older men

New techniques to detect Y chromosome genes show frequent loss of the Y in tissues of older men. The increase with age is clear: 40% of 60-year-old men show loss of Y, but 57% of 90-year-olds. Environmental factors such as smoking and exposure to carcinogens also play a role.

Loss of Y occurs only in some cells, and their descendants never get it back. This creates a mosaic of cells with and without a Y in the body. Y-less cells grow faster than normal cells in culture, suggesting they may have an advantage in the body — and in tumors.

The Y chromosome is particularly prone to mistakes during cell division — it can be left behind in a little bag of membrane that gets lost. So we would expect that tissues with rapidly dividing cells would suffer more from loss of Y.

Why should loss of the gene-poor Y matter?

The human Y is an odd little chromosome, bearing only 51 protein-coding genes (not counting multiple copies), compared with the thousands on other chromosomes. It plays crucial roles in sex determination and sperm function, but was not thought to do much else.

The Y chromosome is frequently lost when cells are cultured in the lab. It is the only chromosome that can be lost without killing the cell. This suggests no specific functions encoded by Y genes are necessary for cellular growth and function.

Indeed, males of some marsupial species jettison the Y chromosome early in their development, and evolution seems to be rapidly dispensing with it. In mammals, the Y has been degrading for 150 million years and has already been lost and replaced in some rodents.

So the loss of Y in body tissue late in life should surely not be a drama.

Association of loss of Y with health problems

Despite its apparent uselessness to most cells in the body, evidence is accumulating that loss of Y is associated with severe health conditions, including cardiovascular and neurodegenerative diseases and cancer.

Loss of Y frequency in kidney cells is associated with kidney disease.

Several studies now show a relationship between loss of Y and cardiac disease. For instance, a very large German study found men over 60 with high frequencies of loss of Y had an increased risk of heart attacks.

Loss of Y has also been linked to death from COVID, which might explain the sex difference in mortality. A tenfold higher frequency of loss of Y has been found in Alzheimer's disease patients.

Several studies have documented associations of loss of Y with various cancers in men. It is also associated with a poorer outcome for those who do have cancer. Loss of Y is common in cancer cells themselves, among other chromosome anomalies.

Does loss of Y cause disease and mortality in older men?

Figuring out what causes the links between loss of Y and health problems is difficult. They might occur because health problems cause loss of Y, or perhaps a third factor might cause both.

Even strong associations can't prove causation. The association with kidney or heart disease could result from rapid cell division during organ repair, for instance.

Cancer associations might reflect a genetic predisposition for genome instability. Indeed, whole genome association studies show loss of Y frequency is about one-third genetic, involving 150 identified genes largely involved in cell cycle regulation and cancer susceptibility.

However, one mouse study points to a direct effect. Researchers transplanted Y-deficient blood cells into irradiated mice, which then displayed increased frequencies of age-related pathologies including poorer cardiac function and subsequent heart failure.

Similarly, loss of Y from cancer cells seems to affect cell growth and malignancy directly, possibly driving eye melanoma, which is more frequent in men.

Role of the Y in body cells

The clinical effects of loss of Y suggest the Y chromosome has important functions in body cells. But given how few genes it hosts, how?

The male-determining SRY gene found on the Y is expressed widely in the body. But the only effect ascribed to its activity in the brain is complicity in causing Parkinson's disease. And four genes essential for making sperm are active only in the testis.

But among the other 46 genes on the Y, several are widely expressed and have essential functions in gene activity and regulation. Several are known cancer suppressors.

These genes all have copies on the X chromosome, so both males and females have two copies. It may be that the absence of a second copy in Y-less cells causes some kind of dysregulation.

As well as these protein-coding genes, the Y contains many non-coding genes. These are transcribed into RNA molecules, but never translated into proteins. At least some of these non-coding genes seem to control the function of other genes.

This might explain why the Y chromosome can affect the activity of genes on many other chromosomes. Loss of Y affects expression of some genes in the cells that make blood cells, as well as others that regulate immune function. It may also indirectly affect differentiation of blood cell types and heart function.

The DNA of the human Y was only fully sequenced a couple of years ago – so in time we may track down how particular genes cause these negative health effects.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

A new study is the first to identify genetic variants linked with chromosomal abnormalities that can lead to pregnancy loss.

About half of pregnancy losses in the first trimester are caused by aneuploidy, a condition in which cells have an abnormal number of chromosomes. Studies show that aneuploidy is much more common in egg cells than in sperm cells and that it affects an increasing proportion of a person's eggs with age.

Aneuploidy in eggs can contribute to infertility and pregnancy loss in women, as well as genetic disorders in children, some of which can cause severe disability or death. But currently, little is understood about the individual factors linked to a greater risk of producing aneuploid eggs and, in turn, aneuploid embryos.

"I think that's a big blind spot for our field," said Rajiv McCoy, an associate professor of biology at Johns Hopkins University. McCoy and colleagues aimed to address this blind spot in a new study, published in January in the journal Nature.

They used clinical genetic testing data from over 139,000 embryos created for in vitro fertilization (IVF) to examine the relationship between maternal genetic variants and the incidence of aneuploid embryos. The dataset included 22,850 mothers, whose ages ranged from about 20 to nearly 56 years old. The average age was about 36 years old, around the age women's risk of producing aneuploid embryos sharply increases.

"We previously didn't have any very well-characterized associations between genetic variation in the mother's genome and risk of producing eggs with aneuploidy," McCoy told Live Science.

The researchers performed genome-wide association studies, meaning they looked for statistical links between gene variants carried by the study participants and certain traits — in this case, the incidence of aneuploidy. They also analyzed the transcriptome, meaning the RNA inside cells; this genetic cousin of DNA carries instructions for making proteins and can give a snapshot of which genes are active.

The strongest association identified was with specific versions of SMC1B, a gene for a key protein that helps hold the two halves of chromosomes together. Another significant association was drawn to C14orf39, which helps mediate important interactions between chromosomes as cells divide.

The study provides insight into aneuploidy's relationship to a process called "crossover recombination," in which chromosomes exchange chunks of DNA during the formation of an egg or sperm cell. McCoy's team observed that crossover count — the number of DNA exchanges that happen during this process — was lower in aneuploid embryos. That supported previous findings that linked errors in crossover recombination, which can cause issues with chromosome separation during cell division, to a greater likelihood of aneuploidy.

But the study also uncovered something new about this relationship: The genetic variants tied to aneuploidy risk are also involved in crossover recombination. "The same machinery that's influencing recombination is the machinery that's influencing risk of producing these aneuploidies," McCoy said.

"This helps us understand how all of these traits are tied together," said Shai Carmi, a professor of computational and statistical genetics at the Hebrew University of Jerusalem who was not involved in the research. "What are the risk factors that make some women have more aneuploidy and, therefore, lower fertility?"

Even for those not experiencing infertility, pregnancy loss is incredibly common.

"About 10% to 20% of clinically recognized pregnancies end in miscarriage," McCoy said. "But we actually think that about half of all conceptions are lost before birth, many of them very early on in development."

In uncovering the shared genetic basis underlying both crossover recombination and aneuploidy, this study underscores the fact that crossovers play an essential role in ensuring that the correct number of chromosomes end up in a given egg, so that an eventual pregnancy is viable.

Because each genetic variant tied to aneuploidy can explain only a small part of an individual's overall risk, it's too early for these findings to be applied to actual patients. Still, "that doesn't mean that it's not possible, in the future, to get better predictions of people's risk," McCoy said. "And this provides one clue as to what we should be looking for."

These findings could also serve as a starting point for further research aimed at developing therapies and diagnostics to help reduce pregnancy loss. That said, McCoy also thinks simply knowing more about the mechanisms behind pregnancy loss is meaningful in itself.

"I personally think that the value of this study is more fundamental," he said. "It's helping us understand who we are as humans."

"Ghost lineages" may sound paranormal, but the term is rooted in real science that genetic studies have revealed only relatively recently.

So what is a ghost lineage?

A ghost lineage is an extinct population that has left no fossils but whose traces can still be detected in the genomes of many living things, including humans and other primates. University of Wisconsin-Madison palaeoanthropologist John Hawks defines them as "ancient groups that became extinct, but not before contributing some of their own genes to other populations that survived."

In animals generally, not just in humans, finding ghost lineages has "mostly been by accident," Love Dalén, an evolutionary geneticist at Stockholm University who studies extinct animals, told Live Science. "Our goals have been to study the evolution of mammoths, bovids and lemmings, and finding these ghost lineages was quite unexpected."

In their analyses of ancient DNA recovered from the frozen fossils of key ice age animals that are now extinct — including mammoths, Pleistocene yaks and certain types of lemmings — Dalén and colleagues have detected several ancient populations that were revealed only by genetics.

These ghost lineages indicate that genetic diversity — the range of inherited traits within a population — was greater during the last ice age than it is now. "This is definitely a pattern we see in Arctic species that are alive today," Dalén said. "Nearly all of them had much higher genetic diversity in the past, and to me this illustrates how important past climate change has been in shaping present-day biodiversity."

But ghost lineages are too important to leave to chance findings. "It becomes more and more clear that we need to use an ancient DNA approach to fully quantify past changes in biodiversity," Dalén said.

Human "ghosts"

Genetic ghosts in human evolution are especially interesting to scientists because they reveal a much more complex story of human evolution than many experts supposed.

The ghost lineages detected in the genomes of modern humans and our extinct relatives have revolutionized the study of millions of years of human evolution.

Most scientists once thought human evolution had progressed at a steady pace through known stages, culminating in the emergence of Homo sapiens in Africa about 300,000 years ago and its eventual replacement of all other forms of humans, with some limited interbreeding.

But genetic analyses over the past two decades have revealed traces of several human ghost lineages in the ancestry of people today and in the ancient DNA recovered from fossils. These human ghost lineages are echoes of archaic groups that existed for hundreds of thousands or even millions of years but that left no known fossils.

"Our discipline has gone from a simplified, straightforward linear model of evolution to a 'bushier' model in describing the last 7 million years," Michael Petraglia, a paleoanthropologist at Griffith University in Australia, told Live Science in an email.

The human evolutionary "tree" grew ever larger and less well defined — turning into a "braided stream" of ancient groups — as more ghost lineages were identified, he said, and it is still growing.

When newfound fossils match "ghost genetics," lineages become "de-ghosted," and de-ghosting human ghost lineages is an important area of research. "With the application of DNA, it has become clear that gaps in our evolution existed, suggesting the presence of ghost populations for which the fossil record was not clearly present," Petraglia said.

"Superarchaic" ancestors

Scientists have seen traces of human ghost lineages in the genomes of some modern-day human populations in parts of West Africa, Asia and Oceania, and Petraglia said paleoanthropological research has focused on a group of "superarchaic" hominins known only from their genes.

This ancient human ghost lineage separated from our own family tree of modern humans, Neanderthals and Denisovans between about 2 million and 1.8 million years ago — roughly when Homo erectus was the dominant species in Africa.

There are no fossils from the superarchaic ghost lineage, so scientists have only inferred its existence from the presence of ghost genes in their analyses of Neanderthal, Denisovan and H. sapiens genomes.

But the picture is complicated because of the confusion created by interbreeding. "Genetic work suggests that the ancestors of Denisovans, Neanderthals and Homo sapiens met and interbred a number of times," Petraglia said. "This has set off debate as to finding the last common ancestor and understanding the line of descendants."

There is genetic evidence that the Denisovans interbred with the superarchaic lineage in at least two distinct interbreeding events, resulting in a relatively high number of "ghost" genes from the superarchaic human lineage in the genomes of Denisovans and those of modern humans with Denisovan ancestry.

"These are exciting times in human evolutionary studies, and there is growing support that hominin evolution was much more complex than imagined before, including multiple interbreeding events that make us what we are today," Petraglia said.

Human evolution quiz: What do you know about Homo sapiens?

On a cold day in February, an Augustinian friar described his experiments breeding garden-variety plants — and gave rise to the field of modern genetics.

Gregor Mendel was an Austrian priest who had spent eight years cultivating and crossbreeding more than 28,000 pea plants (Pisum sativum) in the garden of Monastery of St. Thomas in Brno (formerly known as Brünn), painstakingly recording details of the plants' progeny.

Mendel was actively discouraged from pursuing his research. His bishop giggled whenever Mendel told of his scientific experiments, according to a letter his abbot Cyril Napp wrote to him in 1859.

"He asked if I though [sic] it seemly for a man of your intellectual attainments to be plodding in a pea patch, prying into the germinal proclivities of peas. He suggested that pea propagation was a subject less worthy of your curiosity than, say, the writings of the Church Fathers or the Doctrine of Grace. My dear Brother Mendel, as sympathetic as I am to your researches [sic], we can ill afford to have the monastery made the laughingstock of the diocese."

But Mendel was undeterred from his research — not because of a deep-seated interest in plants, but because he wanted to reveal the principles of inheritance.

He had chosen to study the plants of this unassuming legume for a number of reasons. First, pea plants reproduced quickly and well in both pots and in the ground, according to an 1866 monograph he wrote about his research. Second, they seemed to have clear traits they passed along to their offspring — such as pink, white or red flowers — and the hybrids were perfectly fertile.

Finally, "accidental impregnation by foreign pollen, if it occurred during the experiments and were not recognized, would lead to entirely erroneous conclusions," he wrote.

He identified several distinct traits to track — such as the color of the peas and their pods, the positions of the flowers, and the lengths of the stems — and then crossbred those with differing characteristics. Then, he let each distinct type of plant "self-breed" for two years, showing that the traits continued to be passed along to offspring.

Next, he crossbred those plants and crossbred the resulting hybrids. He painstakingly tallied all of the ways traits were inherited, denoting different traits from each parent with simple labels like Aa, Bb and Cc.

By analyzing the mathematical patterns in each subsequent generation, he deduced the basic principles of inheritance. First, he noted that some traits were transmitted in discrete units, or "particles" — if you cross a green-pea plant with a yellow-pea plant, you get either green or yellow offspring, not yellowish-green ones.

He also concluded that some traits were inherited in a "dominant" pattern. For instance, if plants bred for generations to have only smooth seeds were bred with those that had wrinkly seeds, the offspring would always have smooth seeds.

When Mendel crossbred hybrids, he noticed something strange: Most of the plants would look smooth, but about a quarter would look wrinkled. He deduced that the wrinkly trait was instead passed on in a "recessive" manner and that the trait actually came from the grandfather plant's generation.

Mendel wasn't content to study one "particle" at a time. He also crossbred plants that were hybrids for two different traits and learned that each trait was transmitted separately, which is now known as the principle of segregation.

Mendel's work wasn't recognized in his lifetime. And although Mendel is often known as the "father of genetics," the term "genetics" was not coined until the early 1900s, when English biologist William Bateson rediscovered Mendel's forgotten work and realized its overarching significance.

Soon after, some argued Mendel's data was "too good to be true," and that he must have fabricated his results. A 2020 study put that idea to rest, showing that given the seeds available then, what Mendel knew, and how seeds were classified then, his results were in fact what you'd expect.

Decades later, research would reveal that inheritance isn't as simple as Mendel's pea plants would suggest — some genes are inherited in a sex-linked manner, and other traits have incomplete "penetrance," meaning they don't always manifest the same way. And in early 2026 research revealed that some disease-causing genes we believed were dominant don't operate like we thought, which may challenge some of the fundamental tenets of Mendelian inheritance.

Around 90% of people are infected with Epstein-Barr virus at some point in their lifetimes. For most of them, the virus causes a mild, transient illness or no symptoms at all. But for a subset of people, Epstein-Barr can eventually contribute to chronic illnesses, such as lupus and multiple sclerosis, or to the development of cancer.

Now, new research uncovers 22 human genes that might make an Epstein-Barr infection more likely to turn into a chronic condition.

Researchers can't yet definitively say whether these genes directly make Epstein-Barr more dangerous, or whether they are part of an underlying immune suppression that allows the virus to persist at higher levels in the body than usual. But the new study should provide a jumping-off point, said Jill Hollenbach, a professor of neurology at the University of California, San Francisco, who was not involved in the study.

"My lab is already looking into the results and thinking about what we can learn from this and what other avenues of research it suggests," Hollenbach told Live Science. Hollenbach wrote a commentary of the new study accompanying its Jan. 18 publication in the journal Nature.

Nearly two dozen genes

Epstein-Barr virus can cause mononucleosis, better known as mono, a temporary illness notable for producing extreme fatigue. But even once the symptoms of mono disappear, the virus lies latent in the body, mostly in the immune system's B cells, which remember and defend against specific germs.

For most people, this latent Epstein-Barr virus causes no problems. But in other people, the virus persists at a higher, more active level. In these cases, it can raise the risk of certain nasopharyngeal cancers and lymphomas, and may fuel autoimmune disorders such as multiple sclerosis. Chronic, active Epstein-Barr has also been linked to heart and lung disease.

To understand why only some people seem to experience these chronic effects, Ryan Dhindsa at the Baylor College of Medicine and colleagues turned to an underexplored source of information: human DNA biobanks. These biobanks collect full gene sequencing data and health records for hundreds of thousands of individuals. In sequencing the human genome, they also happen to scoop up the DNA of any viruses that happen to be in residence inside cells.

"Typically, when we're analyzing human genome sequence data we ignore the reads that don't map back to a human reference genome. We just kind of throw them away," Dhindsa told Live Science. "Here, we decided maybe we could go through those reads that we normally throw away and see if we could recover viral DNA."

By combing through tossed-aside Epstein-Barr sequences from 750,000 people in the UK Biobank and the U.S. National Institutes of Health's All of Us biobank, the researchers were able to identify individuals — about 11% of the total — who had very high levels of Epstein-Barr DNA. They found that these high levels of viral DNA were associated with health conditions previously linked to Epstein-Barr, including diseases of the spleen and Hodgkin lymphoma.

The presence of viral DNA was also associated with conditions thought to be linked to Epstein-Barr, although less definitively: rheumatoid arthritis, chronic obstructive pulmonary disease (COPD), and lupus. Other associations in the data reinforce even less well-studied connections, including links between Epstein Barr and heart disease, kidney failure, stroke and depressive episodes.

In addition, the researchers found 22 genes tied to a higher likelihood that someone would be in the 11% of people with chronic Epstein-Barr. Many of these genes were in a region of the genome called the human leukocyte antigen (HLA) locus, which is known to code for the immune cells that present antigens — immune-response-triggering foreign molecules — to other immune cells.

"It seems like these variants changed the way an individual's immune response actually presents Epstein-Barr virus to the immune system," Dhindsa said, possibly making it harder for the body to suppress viral replication. That said, the data has only shown a link between these genes and persistent infection — more research is needed to prove cause-and-effect.

In people with high levels of Epstein-Barr, the researchers also saw variations in genes that regulate the immune system. One, the SLAMF7 gene, typically encodes for a cell-surface protein that helps the immune system's natural killer cells attack tumors. Another, called CTLA4, encodes for a receptor on T cells that helps keep the immune system from attacking the body.

"They found some really interesting results," Hollenbach said.

She and her team are now interested in looking deeper at the mechanisms that link the genetic variation to the immune response to Epstein-Barr. Meanwhile, Dhindsa and his colleagues are interested in using biobank data to search for other viruses that have long-term impacts on human health. Some examples are the cancer-causing viruses Merkel cell polyomavirus and human T-cell lymphotropic virus type 1.

The researchers are also eager to expand their methods to more diverse global datasets of human genes. While the All of Us dataset includes participants from a variety of backgrounds, the U.K. Biobank is predominantly made up of people of European ancestry.

"We need to be able to look at genetic differences across more representative samples in future work," he said.

The spotted lanternfly has spread across the United States with unrelenting speed — and now we have a clue as to why: living in cities seems to have helped these invasive insects evolve to be more resistant to stresses.

"Cities may act as evolutionary incubators that help an invasive species to better deal with pressures like heat and pesticides, which then helps them to better adapt to new environments," lead author Fallon (Fang) Meng, a biologist at New York University, told Live Science.

The spotted lanternfly (Lycorma delicatula) is a planthopper that uses its long mouthparts to suck sap from plants. The insect is native to China, but has spread through South Korea, Japan and to the U.S., where it was first detected in Pennsylvania in 2014, but is now seen in 19 states in the eastern U.S.

Its preferred host plant is the tree of heaven (Ailanthus altissima), which is also an invasive species — but it is able to sup on a wide range of plants, including economically valuable ones like grapevines, hops, maples, fruit trees and hardwood trees.

Spotted lanternflies can weaken plants, and as they feed, they also excrete a sticky, sugary fluid that promotes the growth of sooty mold. What's more, when bees decide to forage on this sugary waste rather than visiting flowers it gives the honey they produce a smoky aroma and a lingering aftertaste, although this honey is still safe to eat.

All this adds up to a potentially huge financial impact. For example, a 2019 study estimated that in Pennsylvania alone, if uncontrolled, the insect's effects could cost $324 million annually.

Lanternfly genetics

To get a better handle on how the lanternflies have adapted so well to life in the United States, researchers sequenced the genomes of lanternflies from urban and rural areas in Shanghai, China, and from New York City, Connecticut and New Jersey. The study was published Wednesday (Feb. 4) in the journal Proceedings of the Royal Society B: Biological Sciences.

In the lanternfly populations in China, they found clear genetic differences between those in the urban and rural areas. "Even though they're just 30 kilometers [19 miles] away, they have very strong population differentiation," Meng said.

This is probably because although lanternflies can fly, they need to feed continuously, so they stick close to the host trees on which they depend. This means it is easy for populations to stay separate, Meng added.

This separation means the urban lanternflies in Shanghai evolved genetic tolerance to stresses that the rural ones didn't, adapting them to the hotter conditions of cities, and boosting their ability to detoxify and metabolize toxins and pesticides.

In the U.S., however, the lanternflies were genetically similar across all locations, even though some were sourced from locations 124 miles (200 kilometers) apart. The same genes that evolved for city living were further adapted in U.S. populations, according to the study.

Using demographic modeling on the genomic data to reconstruct the recent history of the lanternflies, researchers revealed three genetic bottlenecks, when populations were established from a limited pool of insects. One was more than 170 years ago, when Shanghai underwent rapid urbanization. The second aligned with when lanternflies moved from China to South Korea in 2004, and the third was in 2014 when the insects arrived in Pennsylvania — probably hitchhiking on goods shipped from overseas.

Adapting to China's cities may have primed the lanternfly to tolerate other hot, polluted environments, Meng said. "We should study invasive species and urbanization as interconnected parts of a whole. Those two major aspects are too often studied in isolation, but their effects actually can compound in synergistic and surprising ways."

The ability to handle a wider range of toxins might be helping spotted lanternflies spread in the U.S., said Zach Ladin, an ecologist at the University of Delaware, who wasn't involved in the study.

The relatively high densities of tree of heaven give spotted lanternflies a foothold in many cities, he told Live Science, "but some of those genes that they found that are related to overcoming toxic chemical exposure could really help them switch hosts and take advantage of other plants."

Ladin added that the new genetic information could help people slow or contain the spread of spotted lanternflies. "From a chemical control perspective, now we have some genes to target which could be important in making sure we're not just driving resistance to certain chemicals," he said.

Saltwater crocodiles used to occupy a massive range that stretched across the Indian Ocean to the Seychelles, new DNA research confirms.

The now-extinct population of crocodiles in the Seychelles, an archipelago in the western Indian Ocean, was not a group of Nile crocodiles (Crocodylus niloticus), nor was it a separate species. Instead, it was likely the westernmost population of saltwater crocodiles (Crocodylus porosus), which today live in India, Southeast Asia, Australia and islands across the Western Pacific, researchers reported Jan. 28 in the journal Royal Society Open Science.

"The founders of the Seychelles population must have drifted at least 3,000 kilometers [1,864 miles] across the Indian Ocean to reach the remote archipelago, perhaps even much further," study co-author Frank Glaw, a reptile expert at the Bavarian State Collections of Natural History, said in a statement.

The Seychelles used to be home to a large population of crocodiles, according to expedition notes from more than 250 years ago. But when human settlers arrived in the late 18th century, they wiped out all of the crocodiles on the islands. The remains of a few specimens were kept in museums in the Seychelles, London and Paris.

Initially, Western scientists thought the Seychelles crocodiles were part of a population of Nile crocodiles that had migrated from Africa. But in 1994, researchers reclassified the preserved remains as saltwater crocodiles based on their physical traits.

In the new study, a different team of scientists confirmed that conclusion using genetic material. They collected mitochondrial DNA from the skulls and teeth of several older museum specimens of various crocodile species and then compared that DNA with tissue samples from modern museum specimens and living crocodiles.

The genetic markers of the Seychelles crocodiles matched closely with those of the saltwater crocodiles, the team found. That suggests that saltwater crocodiles' range stretched over 7,500 miles (12,000 km) from east to west before the Seychelles population was exterminated.

"The genetic patterns suggest that saltwater crocodile populations remained connected over long periods and across great distances, pointing to the high mobility of this species," study co-author Stefanie Agne, an evolutionary biologist at the University of Potsdam in Germany, said in the statement.

To spread as far west as the Seychelles, C. porosus would have had to cross thousands of miles of ocean. But the crocodiles are adapted to life at sea, sporting special salt glands on their tongues that let them expel excess salt. That adaptation could have helped the animals spread widely across the Indo-Pacific region and limited further speciation, the researchers wrote in the study.

But future work could still uncover differences among groups of saltwater crocodiles. Mitochondrial DNA is inherited only from the mother, and it might not capture subtle genetic differences driven by male crocodiles. Future studies using DNA from the nuclei of crocodile cells could help unpack any regional differences among populations, the researchers wrote.

A group of people living in the far southern reaches of Greece's Peloponnesian Peninsula have been genetically isolated for over a millennium and can trace their roots back to the Bronze Age, an analysis of their DNA reveals.

A new genetic study shows that this group, known as the Deep Maniot Greeks, are paternally descended from ancient Greeks and Byzantine-era Romans. Long-term genetic isolation and strict patriarchal clans likely contributed to the unique genetics of the Deep Maniot Greeks over the past 1,400 years, according to the study authors.

The Mani Peninsula is the middle of three peninsulas that extend south from mainland Greece. In ancient times, the area was part of the Laconia region, which was dominated by the city-state Sparta in the seventh century B.C. Much of the Greek Peloponnese region experienced demographic upheaval as Slavic peoples invaded in the sixth century A.D. However, the Mani Peninsula was spared, and the Deep Maniots who lived in the far southern part of the peninsula became geographically and culturally isolated from the rest of Greece.

In a study published Wednesday (Feb. 4) in the journal Communications Biology, researchers analyzed the DNA of more than 100 living Deep Maniots and discovered that they represent a "genetic island" due to long-standing isolation.

"Our results show that historical isolation left a clear genetic signature," study lead author Leonidas-Romanos Davranoglou, a zoologist at the Oxford University Museum of Natural History, said in a statement. "Deep Maniots preserve a snapshot of the genetic landscape of southern Greece before the demographic upheavals of the early Middle Ages."

During Europe's Migration Period (circa A.D. 300 to 700), which is sometimes called the "Barbarian Invasions," various groups of people — including Germanic tribes, the Visigoths, the Huns and early Slavs — moved throughout the continent. This resulted in numerous waves of migration, only some of which were historically documented. Ancient DNA research has begun to tease out these Migration Period population waves.

But these Migration Period movements did not seem to affect the Deep Maniots, according to historical, linguistic and archaeological evidence. So Davranoglou and colleagues turned to DNA analysis of modern Maniots to investigate why.

The researchers looked at genetic markers on the Y chromosomes (which are passed down from father to son) of 102 people with Deep Maniot ancestry on their paternal side, as well as mitochondrial DNA (passed down from mother to child) sequence data from 50 people with maternal Deep Maniot ancestry.

The DNA analysis revealed that Deep Maniots have an extremely high frequency of a rare paternal lineage that originated in the Caucasus region around 28,000 years ago, the researchers wrote in the study. And when compared with the DNA of present-day mainland Greeks, the DNA of Deep Maniots lacked evidence of common lineages that came from Germanic and Slavic peoples during the Migration Period.

Taken together, these results suggest that genetic drift (a reduction in genetic variation due to a small population size) played an important role in shaping the paternal lineage of Deep Maniots, the researchers wrote, forming a kind of "genetic island." This island of paternal ancestry is rooted in the ancient Balkans and West Asia and is strongly linked to Bronze Age, Iron Age and Roman-period Greek-speaking populations, they noted.

Analysis of the maternal Deep Maniot lineages through mitochondrial DNA revealed a more complex genetic picture, however. The researchers identified 30 distinct maternal lineages in their population sample of 50 Deep Maniots. Most of those lineages have connections to Bronze Age and Iron Age people from Western Eurasia, but several appear to be Deep Maniot-specific, showing no close matches to other present-day European populations.

"These patterns are consistent with a strongly patriarchal society, in which male lineages remained locally rooted, while a small number of women from outside communities were integrated," study co-author Alexandros Heraclides, an epidemiologist at European University Cyprus, said in the statement.

Both the paternal and maternal DNA markers also show evidence of a founder effect, which happens when a new population is established by a very small subset of a larger population. The new population includes only the genes of its small number of founders and, over time, becomes distinct from the larger population.

The genes of present-day Deep Maniots reveal that there was a founder effect among their paternal ancestors around A.D. 380 to 670. As a result, over 50% of Maniot men today descend from a single male ancestor from the seventh century. There was also a founder effect among their maternal ancestors around 540 to 866, the team found, suggesting the number of both maternal and paternal lineages shrank around the same time.

The DNA study suggests that the Deep Maniot population "represents a snapshot of the genetic landscape of the Greek-speaking world prior to the demographic turmoil of the Migration Period," the researchers wrote.

"Many oral traditions of shared descent, some dating back hundreds of years, are now verified through genetics," study co-author and independent researcher Athanasios Kofinakos said in the statement.

Around 50% of a person's lifespan is determined by genetics, a new study suggests, more than doubling previous estimates of the heritability of longevity.

The new research, published Jan. 29 in the journal Science, used a carefully designed mathematical model to reach this conclusion. With the model, the team behind the work could account for external causes of death, such as accidents or infections, eliminating these environmental factors from their heritability estimates.

The heritability of different human traits is usually determined using twin studies, which enable scientists to compare individuals who share either nearly 100% or 50% of their DNA. Identical, or "monozygotic," twins share nearly all of their DNA, while fraternal, or "dizygotic," twins share only 50%.

The researchers looked at the correlation of lifespan and genetics in individual sets of twins, and then compared how well those metrics matched across many sets of twins. "If a trait is very genetically determined, then the correlation in the monozygotic twins will be much higher than the correlation in the dizygotic twins," said study co-author Joris Deelen, a geneticist at Leiden University in the Netherlands.

Previous estimates from such studies have placed the heritability of human lifespan between just 6% and 25%, which suggested genetics have a limited influence on how long people live. Those estimates are substantially lower than those for other complex human traits, such as psychiatric disorders, or the heritability of life span observed in other mammals, which are both typically placed at around 50%.

However, observations of long-lived families and the genetic risk associated with age-related diseases, such as heart disease, suggested to Deelen and colleagues that longevity likely has a far larger genetic contribution than scientists once thought.

A different way of looking at lifespan

The difficulty lies in separating drivers of death with strong genetic components — such as the risk of age-related diseases or the speed of physical decline — from external factors, such as accidents and infections. Deelen did note that the divide between these genetic and external factors is not always clear cut; but in the case of infections, for instance, they focused on diseases that are generally very treatable, such as scarlet fever.

"Previously, when we studied lifespan and predictors, we tended to use all-cause mortality, where we're just looking at what age people died and not really considering what the causes are — cause of death is often missing [from those records]," said Luke Pilling, a geneticist at the University of Exeter in the U.K. who wasn't involved in the work.

Deelen's team — which included geneticists, physicians and statisticians — designed a model to mathematically account for these extrinsic contributors, even for cases when the causes of death were not available. The team fed data from twin cohorts in Sweden, Denmark and the U.S. into the model, and each returned an estimated lifespan heritability of around 50%. The datasets collectively included people born between 1870 and 1935.

"They also looked at this study of Swedish twins born between 1900 and 1935, and that allowed them to do a really interesting analysis, stratified by decade," Pilling added. "Because the twins born in 1900 experienced a very different exposure to infection to the twins born in the 1930s, extrinsic mortality was decreasing over that period."

Classical estimates of lifespan heritability would likely show an increase in heritability over that time frame, as genetic factors began to dominate the calculations. That would support the idea that environmental causes of death had influenced previous estimates. In contrast, the new model gives a consistent estimate for heritability, independent of those external factors.

Like all models, though, the new approach has limitations. "The best scenario would be to have a cohort where you know the actual cause of death and can classify it directly as intrinsic or extrinsic so you don't need to model it in," Deelen said. "But that data just doesn't exist."

In addition, the model has so far been tested primarily on people of Northern European descent, owing to a similar lack of data from elsewhere.

"It's a big question," Deelen said. "Is this heritability something specific for Nordic countries, or is it similar in other parts of the world?"

Modern recordkeeping may enable scientists to determine the answer in the future. But for now, what could these results mean for medicine?

Understanding the genetic markers that influence how long people live — and how long they remain healthy during that lifespan — has important consequences for the future of geriatric medicine, Pilling said, particularly as more and more countries deal with aging populations.

"If we understand the biological mechanisms that cause people to live longer and healthier, we can perhaps design interventions to promote those pathways and to promote health span — the period of life spent in good health," Pilling said. "I will certainly be using this in my research."

Crucially, though, the 50% heritability estimate neither guarantees you a long life or dooms you to a short one, Deelen said.

"What it shows is that you have a certain propensity to become long-lived which is in your genes, and the rest is based on what you do and where you live," he clarified. "Environment is still super important, and people should try to optimize their lifestyle as much as they can."

Genetic variants believed to cause blindness in nearly everyone who carries them actually lead to vision loss less than 30% of the time, new research finds.

The study challenges the concept of Mendelian diseases, or diseases and disorders attributed to a single genetic mutation. The idea is that Mendelian diseases — such as the neurological disease Huntington's and the bleeding disorder hemophilia — are passed down in predictable ways in families, and if a given person carries a disease-causing mutation, they will have it.

These diseases stand in contrast to those caused by multiple genes and environmental factors, which makes their occurence harder to predict in family lines.

"What we suggest is that there is overlap there," senior study author Dr. Eric Pierce, director of the Ocular Genomics Institute at Mass Eye and Ear and an ophthalmologist at Harvard Medical School, told Live Science. In other words, many diseases thought to have simple, Mendelian causes might be a lot more complex than previously thought.

And this doesn't only apply to inherited blindness. Similar results have been found for other genes once thought to be strongly linked to health conditions. A 2023 study on ovarian insufficiency, a condition that causes infertility and early menopause, found that 99.9% of supposedly disease-causing variants were actually present in healthy women. And certain kinds of inherited diabetes also have more complex genetics than previously believed, according to 2022 research.

"We're in an era of discovering a lot more about the complexity of our genomes," said Anna Murray, a geneticist at the University of Exeter who led the ovarian insufficiency research.

Simple or complex?

Pierce and his colleagues focused on inherited retinal disorders (IRDs), a group of diseases that cause significant vision loss, sometimes as early as age 10 but certainly by age 40, said study co-author Dr. Elizabeth Rossin, a vitreoretinal surgeon and scientist in Mass Eye and Ear’s Retina Service and a Harvard ophthalmologist. Researchers have teased out the genetic roots of these diseases by doing genetic testing on affected patients and their families.

But that method can lead to a problem called ascertainment bias, Pierce said. True, you'll learn that some genetic variants are associated with the disease. But because you're studying only people with the disease and their relatives, you don't get a clear notion of how many people have the same gene variants and don't go blind.

To widen their view, the researchers used data from two large biobanks that contain genetic sequencing data from people, as well as their medical diagnoses and demographic information. One, the All of Us biobank, is a program run by the National Institutes of Health and included nearly 318,000 individuals with both genetic and electronic health record data at the time of the study. The other, the UK Biobank, is comparatively less diverse but contains data from 500,000 individuals, including about 100,000 with images of their retinas submitted to the database.

The researchers picked the 167 genetic variants thought to have the strongest causal link to IRDs and searched for them in the All of Us database. They then used the health record data to see if the people with the variants had vision loss. To their surprise, depending on which diagnostic codes they used, only 9.4% to 28.1% of people with the variants had any indication of a retinal disorder or vision problems.

"You would expect, given what we know about these diseases, that nearly 100% of the people would have blindness," Rossin told Live Science. "But it was far fewer than that."

To validate their findings, the researchers turned to the UK Biobank, this time using the included retinal imagery to seek out evidence of IRDs themselves. They found that only between 16.1% and 27.9% carriers of the gene variants had indications of possible retinal disease.

People who were older who carried these retinal disease genes weren't any likelier to have gone blind. And there was no other evidence that their results were because they were catching people who might later lose their vision. Instead, Pierce says, it seems that the complexity of these presumed Mendelian diseases has been underestimated.

"The mutation we used to think caused disease 100% of the time doesn't exist in isolation," he said. Instead, people carry tens or hundreds of thousands of other genes, some of which may protect against retinal disease, he added.

New avenues for treatment

In theory, those protective gene variants could lead to ways to treat these retinal disorders.

"It's going to take a lot of data in order to find these types of low-effect variants," Pierce said. "There are likely many of them, each contributing a little bit to the protection against disease."

There are good reasons to study the genes of patients with particular disorders, Murray said. For instance, finding genes associated with a condition — even if they don't always cause it — can help researchers pinpoint the biology underlying the disease. In ovarian insufficiency, these kinds of patient-centered studies have shown that genes associated with DNA repair are important for the disorder. But such studies should still be taken with a grain of salt.

"It is only now that we have the ability to look at the granular detail of the genetic sequence in hundreds of thousands of people," she said. To learn more, these databases need to become more diverse, she added. And at the same time, she added, biomedical researchers need better lab models of diseases in which to test certain gene mutations and their effects.

"There are likely some [diseases] where it really is a one-to-one correspondence," Pierce said. "But my prediction would be [that] the majority of these disorders are going to share this new complexity."

The new findings appeared Jan. 8 in the American Journal of Human Genetics.

Editor's note: This story was updated on Jan. 16, 2026, to add mention of Dr. Eric Pierce's and Dr. Elizabeth Rossin's affiliations with Mass Eye and Ear, where the work was conducted.

A stretch of DNA in the mouse genome left by ancient viral infections is crucial for early development in the womb, new research shows.

According to the study, published in December in the journal Science Advances, this viral DNA switches on genes that give cells in early-stage mouse embryos the potential to become almost any cell type in the body. The viral DNA — known as MERVL — itself gets activated by a protein called the "Dux transcription factor," which binds to the sequence and essentially kick-starts the embryo's development.

Although it's important in the womb, if Dux stays activated too long, it kills cells. The human version of Dux, called DUX4, causes a progressive muscle-wasting disorder when quirks in its genetic code cause it to be active for too long in muscle cells. That inherited disease, called facioscapulohumeral muscular dystrophy (FSHD), currently has no cure.

The new study not only unravels the roles of MERVL and Dux in the womb but also teases apart these harmful effects that can appear later in life. It's an "important piece of work," said Sherif Khodeer, a postdoctoral research fellow who focuses on stem cell and developmental biology at the university KU Leuven but was not involved in the study.

A powerful gene-editing tool

Researchers at the Medical Research Council Laboratory of Medical Sciences in England used a gene-editing tool called CRISPR activation (CRISPRa) to untangle the close relationship between Dux and MERVL. Unlike traditional CRISPR, which cuts DNA to change its code, CRISPRa boosts the activity of specific genes without changing the underlying DNA sequence.

The team used CRISPRa to switch on either Dux or MERVL in mouse embryonic stem cells. This enabled the researchers to examine how each factor influenced early embryonic development.

When the researchers switched on only MERVL, the stem cells showed "totipotency," or the ability to become any cell type — an important feature of the very earliest embryos. But the cells were missing key traits, the researchers found. This suggests that, while MERVL plays an important role in early mouse embryo development, Dux is also required.

Turning on Dux alone, on the other hand, produced cells that looked much more like natural early embryonic cells. So, the researchers think Dux activates the genes necessary for the embryo's development, independently of MERVL.

Because Dux and MERVL are so closely linked during the earliest stages of embryonic development, scientists previously suspected that MERVL might also contribute to Dux's harmful effects later in life. But the new study suggests this isn't the case.

The researchers tested how Dux causes cell damage by looking at its effects in stem cells with and without a gene called NOXA, which is known to be involved in cell death triggered by various stressors. They found that Dux turns on this NOXA gene, which produces a protein that triggers cell death. When the team removed NOXA, Dux caused much less harm. That showed that NOXA is responsible for the toxicity, not MERVL.

A potential therapeutic target

NOXA was already known to be elevated in FSHD, the human muscle-wasting disease. It's possible that developing a drug to inhibit NOXA could prevent cell death in the condition, thereby helping to improve the survival of muscle cells, the study authors think.

"Facioscapulohumeral muscular dystrophy is a complex disease," senior study author Michelle Percharde, head of the chromatin and development group at the Medical Research Council Laboratory of Medical Sciences , said in a statement.

"Even though all cells of a patient have the genetic changes that cause it, only a subset of cells activate DUX4," she explained. "Understanding what triggers DUX4 activation just in muscle cells, as well as how this compares to activation in early development, are key questions we hope to explore in future research."

It would be "valuable to compare" how mouse Dux and human DUX4 function, Khodeer said, adding that future studies should also explore precisely how MERVL controls nearby genes and when and how MERVL is switched off during mouse embryo development.

Crucially, Khodeer pointed out that MERVL is not present in the human genome. But scientists suspect that certain parts of the human genome could be equivalent to MERVL. As in mice, these stretches of DNA are leftover from ancient viral infections.

Khodeer said the new results raise several questions. For example, do early human embryos develop via the same mechanisms seen in mice? And which bits of ancient viral DNA in humans might play roles similar to MERVL at this early stage of development? "Answering these questions could clarify species-specific differences in early developmental regulation," he told Live Science in an email.

Scientists say they may have extracted Leonardo da Vinci's DNA from a Renaissance-era drawing for the very first time.

The trace DNA, embedded in a red chalk sketch called the "Holy Child" that some claim was made by da Vinci, shows similarities with genetic material recovered from a letter penned in the 1400s by Frosino di ser Giovanni da Vinci, a cousin of Leonardo da Vinci's grandfather, Antonio da Vinci.

Specifically, the drawing and the letter contain Y chromosome sequences that match those of a haplogroup, or genetic lineage, with a common ancestor in Tuscany, where Leonardo da Vinci was born. The researchers published their findings Tuesday (Jan. 6) to the preprint database bioRxiv, so they have not yet been peer reviewed.

Because Y chromosome sequences are passed down almost unchanged from father to son, the recovery of these sequences is "a great starting point" for researchers who want to piece together Leonardo da Vinci's DNA, Charlie Lee, a geneticist who leads the Jackson Laboratory for Genomic Medicine in Connecticut who was not involved in the study, told Science.

However, some experts don't think Leonardo da Vinci drew "Holy Child" himself, believing instead that one of his students made the sketch.

As a result, "it's a flip of a coin" whether the DNA from the drawing is da Vinci's, said Lee. The genetic material could belong to a student or to any number of curators with Tuscan roots who handled the drawing over the years, Science reported.

Researchers want to reconstruct da Vinci's DNA to help authenticate some of his art. Some experts also suggest the Italian polymath's genetic material could reveal biological reasons for his exceptional artistic and other abilities, such as better-than-normal vision.

However, there are many hurdles in the way. For one, da Vinci's tomb in France was partially destroyed during the French Revolution, and his remains lost, or at least mixed with others, during a move to a new supposed burial site at the Chapel of Saint-Hubert in Ambroise.

Yet although this grave may contain bones rich in the Renaissance polymath’s DNA, researchers are not granted access to sequence genetic material from the tomb until a reliable comparison sample is found elsewhere.

This has left scientists with few options but to try to extract DNA from da Vinci's artworks. This poses challenges as some pieces are off limits and others — such as "Study of the Front Legs of a Horse" — have no traces of human DNA. "Holy Child" is the only drawing attributed to Leonardo da Vinci that has yielded human DNA to date; however, its authorship is debated.

Another problem is that da Vinci's mother, Caterina di Meo Lippi, is buried in an unknown location. Caterina was a teenage servant when she gave birth to Leonardo. If found, her remains could provide a match with the "Holy Child" drawing for mitochondrial DNA, a type of DNA that is passed on from mother to child and typically found in bigger quantities on objects than DNA from chromosomes is.

Scientists have also been denied access to da Vinci's father's tomb in Florence, where they may have been able to find Y chromosome DNA to match with "Holy Child." And da Vinci himself doesn't have any known direct descendants, because he never married or had children.

One remaining option is to find other male da Vinci relatives to compare the Y chromosome sequences from "Holy Child" with. Researchers are currently analyzing three bones recovered from a family vault in Italy where Leonardo's grandfather Antonio da Vinci is buried, and are also sampling DNA from known living descendants. The teams are also sequencing DNA from a lock of hair that was excavated in 1863 in Ambroise and that may have come from Leonardo da Vinci's beard, Science reported.

Finally, researchers are searching for letters and other documents written by male relatives that may have preserved their author's DNA. The letter from Frosino di ser Giovanni da Vinci is one such artifact. For the new study, scientists compared DNA from the letter with around 90,000 known markers that separate Y chromosome sequences into lineages called haplogroups. The Y chromosome DNA in the letter and the "Holy Child" sketch belonged to the haplogroup E1b1b, which Leonardo da Vinci and his extended family may have belonged to.

Scientists extracted DNA from the drawing by gently swabbing it. This method could help authenticate all kinds of artworks whose origins are uncertain, experts told Science.

Overall, the preprint "is a great paper" that uses "cutting-edge stuff" to draw its conclusions, S. Blair Hedges, a professor and evolutionary biologist at Temple University in Pennsylvania who was not involved in the study, told Science.

The study authors are now working on the various leads available to them. Aside from the lock of hair — if it really is Leonardo da Vinci's — and direct evidence from the polymath's tomb, the most likely source of DNA is from manuscripts and drawings that we know da Vinci penned himself, the researchers said.

The scientists hope their paper will help convince officials and archivists to let them swab more of Leonardo da Vinci's works. For example, a 72-page notebook of observations known as the "Codex Leicester" has a fingerprint that is almost certainly da Vinci's, making it a good candidate, Domenico Laurenza, an art historian at the University of Cagliari who was not involved in the study, told Science.

Archaeologists in Hungary have discovered the 1,100-year-old burials of three elite male warriors, and a DNA analysis has revealed that the men were related.

The warriors' burials hold weapons, including a saber and a bow with a quiver of arrows, as well as dozens of coins. A DNA analysis indicates that one of the warriors might be the father or brother of a teenage warrior in one of the other burials and that all three warriors were related along their paternal lines.

Located near the village of Akasztó, about 57 miles (92 kilometers) southeast of Budapest, the burials were discovered by volunteers from the Katona József Museum's community archaeology program and were excavated by a team of volunteers and professionals led by Wilhelm Gábor, the head of the museum's archaeology department.

All three men were buried in the 920s or 930s, the archaeological team told Live Science in an email. In total, the three burials yielded 81 coins. Most are from northern Italy and date to the reign of Berengar (888 to 924), a king who ruled parts of Italy and was a great-grandson of Charlemagne. At that time, the Hungarians had formed a kingdom in Hungary, and warriors from the kingdom were involved in military campaigns in northern Italy. It's possible that the warriors in the burials obtained the coins during those campaigns, the archaeologists said.

One of the warriors was 17 to 18 years old when he died and had a belt that was partly decorated with gilded silver. On his right side was a leather pouch, known as a sabretache, that was decorated with a silver plate.

"On his left hand he wore a gold ring with blue glass stones," and his "legs were adorned with ornate silver bracelets and anklets," the archaeologists wrote. Several small, gold plates were found on his body — possibly the remains of clothing or his death shroud, the team suggested. He was also buried with a horse harness that had straps decorated with gilded silver.

Another burial contained a warrior who died at the slightly younger age of 15 to 16. He was buried with a quiver that contained seven arrows and a bow. The "stiff arched ends and handle of his bow were covered with decorative antler plates," the archaeological team wrote.

The third burial held a warrior who died between the ages of 30 and 35. It contained a saber, archery equipment, a horse harness, a silver bracelet, and a belt decorated with coins, the archaeologists said. A DNA analysis revealed that this individual was likely the father or brother of the youngest warrior and that all three warriors were related.

The team also looked at the ratios of isotopes, or elements with varying numbers of neutrons in their nuclei, in the warriors' remains. This analysis showed that the three warriors had diets rich in animal protein.

From the archaeological finds, "it can be stated that an elite warrior group, presumably members of a military leadership, were buried here," the archaeologists wrote. Research is underway to learn more about the warriors' identities. It's not clear how they died.

The group had traveled for thousands of miles, crossing Africa and the Middle East until finally reaching the dimly lit forests of the new continent. They were long-vanished members of our modern human tribe, and among the first Homo sapiens to enter Europe.

There, these people would likely have encountered their distant cousins: Neanderthals.

These small bands of modern-human relatives had hooded brows, large heads and squat bodies, and they had spent epochs acclimating to Europe's colder climate. At several points across millennia, these two forms of humanity would meet, mingle and mate.

Tens of thousands of years later, these ancient encounters have left traces in the genetic code of billions of humans alive today. The lingering genes affect us in ways large and small, from our appearance to our risk of disease.

"In some places in our genome, we're more Neanderthal than we are human," Joshua Akey, a professor of integrative genomics at Princeton University, told Live Science.

These were our closest human relatives, and this is their legacy.

The first encounter

By 75,000 years ago, but possibly up to 250,000 years ago, the ancestors of most modern Eurasians first ventured out of Africa and into Eurasia. Here, modern humans came face-to-face with Neanderthals, who last shared a common ancestor with modern humans hundreds of thousands of years earlier and had been living in these continents ever since. On multiple occasions over the millennia, the groups interbred.

Related: Could Neanderthals talk?

At first, modern humans inherited whole chromosomes from Neanderthals, Sriram Sankararaman, a professor of computer science, human genetics and computational medicine at UCLA, told Live Science. However, from generation to generation, via a process known as genetic recombination, these stretches of DNA were broken up and shuffled around.

Neanderthal DNA was generally "deleterious" to modern humans, meaning it was rapidly weeded out of modern humans' DNA through evolution. This resulted in "deserts of Neanderthal DNA," or large regions of the modern human genome lacking it, Sankararaman said. For instance, scientists think the Y chromosome in males doesn't contain any Neanderthal genes. It may be that genes on the Neanderthal Y were incompatible with other human genes or they may have been randomly lost via a process known as genetic drift.

In people who inherited Neanderthal DNA, the X-chromosome also contains a lot less Neanderthal ancestry than other, non-sex chromosomes carry. This is probably because any harmful or nonfunctional mutations on the X chromosome will be expressed in males, because they lack a matching, functional copy of the gene to compensate. That likely created strong evolutionary pressure to remove such harmful Neanderthal genes from the modern human X, Emilia Huerta-Sanchez, an associate professor of ecology, evolution, and organismal biology at Brown University, told Live Science.

But some Neanderthal DNA helped modern humans survive and reproduce, and thus it has lingered in our genomes. Nowadays, Neanderthal DNA occupies, on average, 2% of the genomes of people outside Africa. However, the frequency of Neanderthal DNA that codes for beneficial traits may be as high as 80% in some regions of the genome, Akey said.

Our physical appearance

For many people, the legacy of Neanderthals is apparent in a highly visible feature: skin color.

A Neanderthal gene variant on chromosome 9 that influences skin color is carried by 70% of Europeans today. Another Neanderthal gene variant, found in most East Asians, regulates keratinocytes, which protect the skin against ultraviolet radiation via a dark pigment called melanin.

Neanderthal gene variants are also associated with a greater risk of sunburn in modern humans. Likewise, around 66% of Europeans carry a Neanderthal allele linked to a heightened risk of childhood sunburn and poor tanning ability.

Neanderthals had spent millennia at higher latitudes with less direct sun exposure, which is needed for vitamin D production. Therefore, changes to hair and skin biology may have allowed modern humans to quickly capitalize on lower levels of sunlight while still producing enough vitamin D to be healthy, John Capra, an evolutionary geneticist at Vanderbilt University, told Live Science.

"One of the cool things about interbreeding is that instead of waiting for new beneficial mutations to arise, which is a really slow process, you introduce a ton of genetic variation at once," essentially fast-tracking evolution, Huerta-Sanchez said.

Related: What's the difference between Neanderthals and Homo sapiens?

In addition, our ancestors had to adapt to colder Eurasian weather. To do so, they may have acquired Neanderthal genes that affected face shape. In a 2023 study, scientists discovered that modern humans inherited tall-nose genes from Neanderthals. A taller nose may have allowed more cold air to be heated to body temperature in the nose before reaching the lungs, suggested Kaustubh Adhikari, co-senior study author and a statistical geneticist at University College London.

The clock that makes our cells tick

Neanderthal DNA also may have helped H. sapiens adjust to the bigger differences in day and night length at northern latitudes.

Lingering Neanderthal genes affect our circadian clock, which regulates internal processes such as body temperature and metabolism. For instance, some early risers can thank Neanderthals for their circadian clock genes, Capra and colleagues found.

This may have helped our ancestors adapt to shorter winter days farther from the equator, Capra said.

"It seems like it's not that being a morning person is what matters," Capra said. "It's that that's a signal of how essentially flexible your clock is and how able it is to adapt to the variation in light-dark cycles with seasons," he said.

Our internal defenses

Many of the strongly retained Neanderthal genes are tied to immune function.

By the time H. sapiens arrived in Europe, Neanderthals had already spent hundreds of thousands of years fighting infections specific to Eurasia. By mating with Neanderthals, modern humans got an instant infusion of those infection-fighting genes.

"Those pieces of Neanderthal DNA, especially the immune ones, that were already adapted against pathogens that Neanderthals had been living with for a long time started to rise in frequency under natural selection in modern human populations," David Enard, an assistant professor of ecology and evolutionary biology at the University of Arizona, told Live Science.

While many of the ancestral pathogens that sickened ancient humans are lost to time, some of the Neanderthal genes that helped fight them off still work against modern pathogens. For example, a 2018 study by Enard and a colleague revealed that modern humans inherited Neanderthal DNA that helped them combat RNA viruses, a group that today includes the flu (influenza), HIV and hepatitis C.

Related: 10 unexpected ways Neanderthal DNA affects our health

The darker side of Neanderthal DNA

Some of the Neanderthal genes that once helped our ancestors may be harmful in the modern world.

For the most part, Neanderthal genes are not strongly expressed in the brain, which hints that they were strongly selected against during evolution. Neanderthal genes have been linked to mood disorders such as depression and to brain signaling pathways that make people more likely to become addicted to nicotine.

And even the immune boost from Neanderthals may have a downside. In 2016, scientists discovered that Neanderthal genes that prime the immune system to fight pathogens may also predispose people to allergic diseases. In addition, Neanderthal genes have been tied to a higher risk of developing autoimmune diseases, such as Graves' disease, caused by an overactive thyroid; and rheumatoid arthritis, which inflames the joints and even "Viking disease," in which one or more fingers become bent or frozen.

One Neanderthal gene variant may have made us more likely to have a severe case of COVID-19. That variant, found on chromosome 3, is found in half of South Asians and one-sixth of Europeans. But even there, the picture is complicated, as other Neanderthal genes, carried by up to half of people in Eurasia and the Americas, are associated with a reduced risk of severe COVID-19.

"Unfortunately, there are no diseases we can really say, or even traits in general, we can say, 'Oh, you can blame your Neanderthal DNA for that,'" Capra said.

That's especially true for some of the biggest health ailments, such as heart disease and cancer, where dozens or hundreds of genes, along with myriad environmental factors, affect your risk of disease.

What lies ahead

So how long will the traces of these long-lost humans linger in our genomes? Over hundreds of thousands of years, some of these Neanderthal fragments will gradually be eliminated from our genomes. Others will become firmly embedded, Akey said.

In the meantime, there's still much more to learn about how Neanderthals left their mark on us.

"Being able to leverage new genomic technology like CRISPR and gene editing is going to play an important role in understanding the actual underlying biology of how Neanderthal sequences contribute to human traits and diseases," Akey said.

Deciphering what these genes actually do could aid the development of treatments for certain conditions, he said.

And the gene flow wasn't one-way; scientists are also trying to determine how modern-human DNA may have influenced Neanderthals and are applying artificial intelligence (AI) methods to ancient genomes to create a more detailed picture of what our long-lost cousins were like.

Figuring out the role of Neanderthal DNA in our genomes does more than help us understand our health. These bits of DNA can provide clues as to what makes us unique, Sankararaman said.

"Neanderthal DNA entered our genomes at an important time in our history," Sankararaman said, when our ancestors were moving into new environments.

"By looking at the fate of these bits of DNA," he said, "we can hope to understand what were the functionally important regions in our genome over this period of time."

Editor's Note: This story was originally published in March 2024.

Neanderthals have fascinated scientists since they were first discovered in the 19th century. Their long heads and low brow ridges initially convinced experts that Neanderthals were some kind of evolutionary wrong turn that ended up in European caves.

It took more than a century for researchers to prove that Neanderthals were actually quite intelligent and that they interbred with modern humans (Homo sapiens). The number of discoveries related to Neanderthals' biology and culture has skyrocketed in recent years — and 2025 was a noteworthy year. While we learned that Neanderthals had biological features that were strikingly different from modern humans', this year's discoveries also showed that some aspects of their behavior and culture were similar to ours.

Here are 10 major Neanderthal findings from 2025 — and what they teach us about our own evolution.

1. Neanderthals were the first to make fire.

The hottest — but also somewhat controversial — Neanderthal discovery of the year was that the first humans to make and control fire were Neanderthals living in England more than 400,000 years ago.

In December, researchers announced that they had found reddened clay and heat-shattered flint hand axes at an archaeological site in Suffolk. But the smoking gun was the discovery of tiny flakes of pyrite, a mineral that produces sparks when struck against flint.

Experts have debated for decades whether early human ancestors deliberately made fire or whether they opportunistically used wildfires that sprang up. The combination of flakes of pyrite and charred soil and tools points to Neanderthals' purposeful creation of fire.

The discovery, however, does not tell us whether Neanderthals invented this technology or they learned it from even earlier ancestors, such as Homo erectus. Regardless, the fire evidence shows that Neanderthals were smart enough to figure out how to survive in cold and dark European climates.

2. Neanderthals cannibalized women and children.

Around 45,000 years ago — very close to when Neanderthals disappeared forever — six members of a Neanderthal group were cannibalized, according to a study published in November. Their remains were discovered in the Goyet cave system in Belgium with butchery marks similar to those on animal bones.

This isn't the first time archaeologists have found evidence of cannibalism in Neanderthals. But it is the best evidence experts have to suggest one group — probably Neanderthals but possibly modern humans — deliberately targeted the women and children of another group, perhaps as a way to eliminate the group's reproductive potential.

3. A Neanderthal left the world's oldest fingerprint.

A curious-looking rock found in Spain contains the world's oldest known fingerprint, and it was probably made by a Neanderthal using ocher 43,000 years ago, researchers announced in May.

The team investigating the rock, which is the size of a large potato, thinks that it has face-like features and that the red dot may be a nose. If they're correct, it would mean Neanderthals were creating symbolic art, which could settle a decades-long debate in paleoanthropology.

Not all experts agree that the rock is an early version of Mr. Potato Head, but they do think the fingerprint and its characteristic whorl pattern represent a clear example of Neanderthals' use of red ocher pigment.

4. Neanderthals may have used "crayons."

Scientists in Crimea found three pointy chunks of red and yellow ocher that Neanderthals may have used as early "crayons" 100,000 years ago, according to research published in November.

The hunks of mineral appear to have been repeatedly sharpened, which suggested to the researchers that the ocher was used for culturally meaningful purposes rather than in practical tasks, such as tanning hides.

Although ocher has been found at other Neanderthal sites, not all experts are convinced of the crayon interpretation. Instead, they suggest Neanderthals may have scraped powder from the ocher chunks for another purpose, such as to leave a fingerprint.

5. Neanderthals were low-energy.

In July, researchers discovered that a key Neanderthal gene variant that is still found in some humans today could be detrimental to athletic performance because it limits the body's ability to produce energy during intense exercise.

Researchers found that the Neanderthal version of an enzyme called AMPD1 was different from the one in most modern humans. The Neanderthal enzyme variant allowed adenosine monophosphate (AMP) to build up in their muscles rather than being quickly removed. This AMP buildup is problematic because it makes it harder to produce adenosine triphosphate (ATP), a molecule that the body uses to store energy.

Modern humans who carry the Neanderthal variant of the gene have a lower probability of achieving elite athletic status, the researchers found. But while the Neanderthal variant may have affected their muscle metabolism slightly, it may not have contributed to their extinction.

6. Neanderthals were more susceptible to lead poisoning compared with humans.

In a study published in October, researchers examined 51 teeth from H. sapiens, Neanderthals and other ancestors for evidence of lead exposure. Lead occurs naturally in our environment, but it is known to be toxic at high levels, causing damage to the brain and other organs. Researchers discovered that human ancestors were affected by episodic lead exposure for nearly 2 million years — and that human brains may have evolved some protection against lead poisoning.

Humans living today have a unique version of a gene called NOVA1 that is important for brain development and language skills. The gene also appears to confer greater resistance to lead than other versions of the gene do, such as the one in our Neanderthal cousins.

Therefore, researchers propose, the modern-human version of NOVA1 may have given us a slight advantage over Neanderthals and may have contributed to the demise of the Neanderthals.

7. Neanderthals had a "fat factory" in Germany.

Neanderthals primarily ate meat (and maggots), which put them at risk of developing protein poisoning, a lethal condition that results from eating too much protein and too few fats and carbohydrates.

But in July, researchers announced their discovery of a "fat factory" that Neanderthals may have used to stave off this condition 125,000 years ago. Their survey of nearly 200 animal bones revealed that Neanderthals smashed the bones to get at the marrow inside, which they boiled to extract the fat.

Fat is high in calories, and Neanderthals may have saved it to eat during food shortages. This innovative food-collection method is similar to what some ancient modern-human foraging groups did, suggesting that, in at least one way, Neanderthals were similar to us.

8. Neanderthals lacked a key DNA-synthesizing gene.

In August, researchers investigating the enzyme adenylosuccinate lyase (ADSL) found that the version in Neanderthals was more active than the one in humans. ADSL helps synthesize purine, which is one of the fundamental building blocks of DNA, and an ADSL deficiency is known to result in intellectual disability in modern humans. So researchers modified mice to have a modern-human-like ADSL gene and found that they were better at completing a task to get water.

But even though ADSL deficiency can cause intellectual and behavioral problems in modern-day people, it's not yet clear whether the Neanderthal variant impaired them.

9. Our cousins suffered a population bottleneck.

Even before Neanderthals disappeared forever, their numbers were dwindling because of a population bottleneck, according to research published in February.

Scientists looked at the tiny inner-ear bones of Neanderthals from various time periods and noticed that, around 110,000 years ago, there was an abrupt decline in the diversity of bone shapes. This decline suggests a bottleneck event, when a species undergoes a sudden reduction in variation due to factors such as genocide or climate change.

While the ear bones alone didn't cause the Neanderthals' downfall, the bottleneck may have been the beginning of the end.

10. Neanderthals' blood may have doomed them.

Biologically, Neanderthals had distinct blood variants that separated them from modern humans — and two of those variants we learned about this year may have hastened our ancient cousins' extinction.

In January, researchers discovered that Neanderthals had a rare blood type that may have been fatal to their offspring when they mated with Denisovans or early H. sapiens.

Neanderthals carried a variation of the blood antigen Rh, which gives the positive and negative signs to blood types. Before modern medical interventions, if someone who was Rh-negative was pregnant with a fetus that was Rh-positive, it caused a miscarriage or stillbirth. The researchers found that, if a Neanderthal female mated with a H. sapiens or Denisovan male, there would have been a high risk of anemia, brain damage and infant death. And that might have spelled the end of the line for Neanderthals.

Another study published in October suggested that a fatal red blood cell incompatibility between Neanderthals and humans also contributed to our ancient cousins' extinction. Researchers focused on the PIEZO1 gene that affects oxygen transportation in red blood cells. Neanderthals' version of this gene essentially let their blood cells trap oxygen efficiently, while the modern-human version more efficiently released oxygen to tissues. When maternal oxygen isn't passed on to the fetus, it can restrict the growth of the fetus or lead to miscarriage. So, if a hybrid Neanderthal-human mother mated with a modern-human father or with a hybrid Neanderthal-human father, their offspring would be more likely to die than the offspring of non-hybrids.

Although Neanderthals' extinction likely did not hinge on any one specific gene variant, the new research into red blood cells and maternal-fetal incompatibility is providing key insight into the demise of our archaic cousins around 35,000 years ago.

Neanderthal quiz: How much do you know about our closest relatives?

An excavation in Italy has unearthed the oldest and first known evidence of father-daughter incest in the archaeological record, a new genetic study reveals.

The team found genetic clues of this incest in the remains of a teenage boy who was buried in a Bronze Age cemetery in south Italy.

The cave site of Grotta della Monaca in Calabria — the "toe" of Italy — was used as a burial ground between 1780 and 1380 B.C. Archaeologists analyzed the DNA of the 23 people buried there in order to understand the genetic background of the group, but they did not anticipate finding such "extreme parental consanguinity."

In a study published Monday (Dec. 15) in the journal Communications Biology, a team of researchers outlined their genetic findings from prehistoric Grotta della Monaca.

Even though the skeletons were fragmented and mixed up, the researchers were able to identify the genetic sex for 10 females and eight males. They also found a variety of mitochondrial and Y-chromosome DNA haplotypes — genetic information that is passed along by a parent — which indicated that the group included a mixture of people from different backgrounds.

While investigating genetic relationships within the burial site, researchers found two cases of first-degree relatives, meaning parents and their offspring.

On the surface, this finding is not particularly noteworthy, as many cultures bury their dead with biological kin. Indeed, genetic analysis revealed that a mother and her daughter were buried near one another at Grotta della Monaca.

But the case of an adult male and a pre-adolescent male buried in the Grotta della Monaca cave was different. The researchers measured runs of homozygosity (ROH) segments in their DNA. ROH refers to chunks of similar genetic material that get passed down from parent to offspring. Typically, when humans mate outside their biological family, they mix their genes and end up with low ROH. A higher ROH, on the other hand, correlates with inbreeding.

Most of the people buried at Grotta della Monaca had ROH numbers that suggested their parents were distantly related — perhaps in the last six to 10 generations, the researchers wrote. But the pre-adolescent male had "the highest sum of long ROH segments ever reported in ancient genomic datasets to date."

Further investigation yielded "indisputable evidence that the young male was the offspring of a first-degree incestuous union," the researchers wrote, unambiguously showing that he was the son of an adult male buried at the site and his own daughter. The researchers did not, however, find the skeletal remains of the boy's mother.

Humans tend to avoid incestuous unions, perhaps due to biological instinct or to cultural taboos. But incest has been documented by archaeologists. For example, the Altai Neanderthal's genes suggested her parents were half-siblings. Brother-sister marriages occurred among royal families in ancient Egypt, and a Stone Age man found in Ireland also had parents who were likely brother and sister.

But those sibling examples are considered second-degree unions, whereas parent-child unions are first-degree — and tend to carry a higher probability of genetic disorders in offspring. The researchers investigated the teenager's genes to determine if he had any rare genetic disorders, but they did not find any.

The discovery that a father and daughter produced a son is "an exceptionally rare and remarkable finding," the researchers wrote, as well as "the earliest identified in the archaeological record."

It is currently unclear why people at Grotta della Monaca engaged in this unusual behavior. The community wasn't particularly small and did not appear to have a hierarchical or royal inheritance system where close-kin marriages would help consolidate wealth and power.

"The reproductive union between parent and offspring observed in our study may reflect a socially sanctioned behaviour," the researchers wrote. That may explain why the father was the only adult male buried in a cemetery otherwise full of the graves of women and kids.

But whether the union was acceptable to everyone, a one-off event, or the result of coercion or violence may never be known.

"This exceptional case may indicate culturally specific behaviours in this small community, but its significance ultimately remains uncertain," study co-author Alissa Mittnik, an archaeogeneticist at the Max Planck Institute for Evolutionary Anthropology in Germany, said in a statement.

Human skeleton quiz: What do you know about the bones in your body?

Temperature stress may be driving genetic mutations in polar bears in southern Greenland, a new study reports.

The species is struggling in the face of a changing global climate. Global sea ice levels dropped to a record low in February, and the warming planet is pushing up sea levels. These changes threaten polar bears, which live and hunt on the shrinking ice sheets.

But a group of polar bears (Ursus maritimus) in southern Greenland may be evolving to cope with their challenging environment. Researchers have found a link between changes in polar bear DNA and rising temperatures.

The study, published Dec. 12 in the journal Mobile DNA, "shows, for the first time, that a unique group of polar bears in the warmest part of Greenland are using 'jumping genes' to rapidly rewrite their own DNA, which might be a desperate survival mechanism against melting sea ice," lead author Alice Godden, a senior research associate at the University of Anglia in the U.K., said in a statement.

Jumping genes, also known as transposons or transposable elements, are pieces of DNA that move from one location on the genome to another. Depending on where they insert themselves into the organism's genetic code, transposons can change how other genes are expressed. More than one-third of the polar bear genome is made up of transposable elements, while in plants it can be as much as 70%. By contrast, transposons make up about 45% of the human genome.

Transposons appear to be helping polar bears adapt to climate change, the authors of the new study argue.

A 2022 study published in journal Science described an isolated population of polar bears in southern Greenland that was less reliant on sea ice. The group split from a community of bears in northern Greenland about 200 years ago, and their DNA was different from that of bears in the North. The new research builds on these earlier findings.

The researchers analyzed the DNA of 17 adult polar bears in Greenland — 12 from the cooler northeast and five from the group in the warmer southeast. They compared transposon activity in the two populations, and then linked that with climate data.

In the Southeastern population, there were changes to genes linked to heat stress, aging, and metabolism, as well as fat processing, which is important when food is scarce. According to the study, this suggests the bears "might be adjusting to their warmer conditions."

"By comparing these bears' active genes to local climate data, we found that rising temperatures appear to be driving a dramatic increase in the activity of jumping genes within the southeastern Greenland bears' DNA," Godden said. "Essentially this means that different groups of bears are having different sections of their DNA changed at different rates, and this activity seems linked to their specific environment and climate."

Despite the bears' potential ability to adapt to warmer climates and less ice, Godden warned that climate change remains a real threat to polar bears.

"We cannot be complacent; this offers some hope but does not mean that polar bears are at any less risk of extinction," she said. "We still need to be doing everything we can to reduce global carbon emissions and slow temperature increases."

The largest genetic analysis of psychiatric disorders to date shows that most relevant genetic variants are linked to multiple mental health conditions rather than just one.

The study found that 14 psychiatric disorders can be classified into five major groups, depending on the genetic variants associated with them. For instance, the findings group together anorexia nervosa, obsessive-compulsive disorder (OCD) and Tourette's syndrome according to their shared genetic profile.

The findings, published Dec. 10 in the journal Nature, suggest that disorders within the same group may stem from shared biological mechanisms. An understanding of these common pathways could help scientists develop treatments that work across multiple mental health conditions, the team said.

Chunyu Liu, a professor of psychiatry and behavioral sciences at SUNY Upstate Medical University who was not involved in the study, said the findings make sense based on existing research.

"Even before seeing the results, this is generally expected," Liu told Live Science in an email. "The shared genetics between schizophrenia and bipolar disorder pointed us in this direction [as a field]."

He agrees with the study authors' conclusion that shared genetics point to shared biological mechanisms. However, Liu noted that the study does not explain why clinical symptoms vary so widely between these disorders, even when the underlying genetics overlap.

"It is an important paper, but still a small step toward understanding the disorders," he said.

Genes aren't the whole story

The study showed that many of the genetic variants linked to psychiatric disorders are also linked to other traits, including intelligence; sleep problems like insomnia; personality; social behaviors like aggression; and socioeconomic status.

"Not all of these links are negative," Abdel Abdellaoui, a geneticist at the University of Amsterdam who was not involved in the study, wrote in a commentary article for Nature. For example, the genetic overlap between schizophrenia and bipolar disorder is also associated with traits that can support academic success, such as creativity and persistence.

This nuance matters because embryos used for in vitro fertilization (IVF) are sometimes screened for psychiatric risk factors, which are measured via the embryo's genetics. Parents-to-be then have the option to select embryos with lower "risk scores" for psychiatric disorders. But this choice isn't necessarily clear-cut, Abdellaoui argued. Carrying certain genetic traits doesn't guarantee a disorder will emerge, and the same genes can influence positive traits, such as creativity or resilience, he noted.

Abdellaoui said psychiatric disorders often appear at the extreme ends of a natural range of genetic variation, especially when combined with certain life experiences. In other words, a person can have a genetic predisposition for a given disorder but not ultimately develop it unless they encounter certain adverse events, whether trauma or environmental hazards.

"This should reframe mental illness not as defective biology, but as the unfortunate intersection of natural variation and environmental stress," he said.

The five groupings

To study which genetic variants are unique to each disorder and which are shared across disorders, Andrew Grotzinger, an assistant professor at the Institute for Behavior Genetics at the University of Colorado Boulder and his colleagues analyzed genetic information from more than 1 million people who primarily had European ancestry.

Disorders that share many genetic variants were dubbed "genetically correlated." Using these correlations, the scientists found that the 14 disorders fell into five genomic factors:

Five genomic factors

• Compulsive: Anorexia, OCD, Tourette's
• Neurodevelopmental: Autism, ADHD
• Internalizing: Depression, PTSD, anxiety
• Substance use: Alcohol, cannabis, nicotine and opioid dependence
• Schizophrenia-bipolar

Each genetic factor showed a unique biological pattern, in terms of how the associated genes behave in the brain. For example, genes linked to the schizophrenia-bipolar factor are strongly active in excitatory neurons, which push other neurons to activate, and in brain areas involved in interpreting reality.

Genes linked to the internalizing factor are associated with glia, the brain's support cells. Glia serve as immune protection and maintain connections between neurons, among other roles. This implies that these disorders may relate more to these support cells than to neurons, Abdellaoui said.

The substance-use factor included gene variants that encode the enzyme responsible for breaking down alcohol, and others that encode the receptors that respond to nicotine.

Liu cautioned that these genetic links to psychological disorders should be interpreted carefully. "Genes or biological pathways statistically associated with a disorder should not be interpreted as causal without additional evidence supporting a direct mechanistic role," he said. In short, correlation does not imply causation.

"There are multiple alternative explanations for why a gene is associated with a disorder," he said, "or why two disorders exhibit overlapping genetic signals."

This article is for informational purposes only and is not meant to offer medical advice.

Cephalopod evolution has long had a missing chapter in its story: how did squid-like ancestors give rise to today's octopuses? The answer, it turns out, was floating in the deep sea all along.

With its glowing ghostly eyes, eight arms like its octopus cousins and a dark ruby coloring to match, the elusive vampire squid (Vampyroteuthis infernalis) has finally revealed its genetic secrets.

In a study published Nov. 27 in the journal iScience, researchers sequenced the genome of Vampyrotheuthis and discovered its chromosomes still resemble those of squids and cuttlefish — despite belonging to the octopus order. This discovery hints at what the common ancestor of modern squids and octopuses may have looked like at the genetic level 300 million years ago when octopus and squid evolutionarily diverged. The researchers described the vampire squid as a "living fossil."

On the cephalopod evolutionary tree, the vampire squid belongs to the group that includes octopuses, but underwent a "very ancient split" from the rest of the clade, study lead author Oleg Simakov, a researcher at the Department of Neuroscience and Developmental Biology in the University of Vienna, Austria, told Live Science in an email.

After acquiring a tissue sample from a vampire squid collected as bycatch in the West Pacific Ocean from a research cruise, the researchers used a genetic analysis platform called PacBio to sequence the DNA of the sample. Unfortunately, there were no other vampire squid samples to compare it to, due to their rarity. Using PacBio, the researchers compared the vampire squid's genome to that of other cephalopods like the Argonaut (Argonauta hians), the common octopus (Octopus vulgaris) and the curled octopus (Eledone cirrhosa).

The findings revealed the vampire squid has an 11 billion-base-pair-long genome, almost four times the size of the human genome — and the largest cephalopod genome sequenced to date.

While modern octopuses have DNA that consistently gets reshuffled, resulting in some chromosomal mixing, the researchers found that the vampire squid's genome kept much of its ancestral, squid-like chromosomal arrangement. Essentially, it's an octopod that genetically looks like an ancient squid.

The vampire squid has had a long history of being misunderstood. When it was initially discovered in 1903, it was thought to be a cirrate octopus due to its unique webbing between its arms. In the 1950s however, scientists reclassified it as its own group, belonging to neither octopus nor squid but in the order Vampyromorphida, so named because it looks like it's wearing a vampire-like cloak.

The finding is welcome news for cephalopod scientists as it is "nice to have resolved" why vampire squids retain much of their ancestral, squid-like traits, said Bruce Robison, senior scientist at the Monterey Bay Aquarium Research Institute (MBARI) who was not involved in the research.

Part of what makes the fully sequenced genome so valuable is how hard it is to study vampire squids, mainly "because they live in a habitat that is difficult to access, they are solitary, rare, and do not survive well in captivity," Robison said. "Some people think that we can just dive into deep water, and find one whenever we like, which is definitely not the case."

He added that the findings "reinforce the notion held by some of us that vamps would be the key to the puzzle. They are interesting to study because they are such cool animals, and because they just look like they are hiding secrets."

Most modern dog breeds have small amounts of wolf ancestry from long after dogs were domesticated, according to a new study.

The wolf DNA isn't left over from when dogs and wolves diverged; instead, it most likely came from interbreeding in the past few thousand years. That wolfish influence may be linked to certain characteristics, such as size and personality traits, in different dog breeds, researchers reported Nov. 24 in the journal PNAS.

"Dogs are our buddies, but apparently wolves have been a big part of shaping them into the companions we know and love today," study co-author Logan Kistler, curator of archaeobotany and archaeogenomics at the Smithsonian National Museum of Natural History in Washington, D.C., said in a statement.

Wolves and dogs genetically split more than 20,000 years ago. Since then, there has been some gene flow between dogs and wolves, thanks to their genetic compatibility. To measure the extent of intermixing and its effects on both animals, researchers studied the previously published genomes of nearly 2,700 dogs and wolves from the Late Pleistocene (the last ice age) to the present. This group included 146 ancient dogs and wolves, 1,872 modern dogs and about 300 "village dogs" that lived around humans but weren't pets.

At least 264 modern dog breeds have wolf ancestry passed on from mating that occurred an average of 900 dog generations ago, which equates to about 2,600 years ago — long after dogs became domesticated at least 20,000 years ago, the team found. The most wolfish dogs had up to 40% wolf ancestry in their genomes, but most had between zero and 5% wolf ancestry.

"Prior to this study, the leading science seemed to suggest that in order for a dog to be a dog, there can't be very much wolf DNA present, if any," study co-author Audrey Lin, an evolutionary biologist at the American Museum of Natural History in New York City, said in the statement. "But we found if you look very closely in modern dog genomes, wolf is there. This suggests that dog genomes can "tolerate" wolf DNA up to an unknown level and still remain the dogs we know and love."

Czechoslovakian and Saarloos wolfdogs had the highest degree of wolf ancestry, which is perhaps unsurprising, since they were intentionally bred by crossing domestic dogs with wolves in the 20th century. Larger dogs and certain working breeds — such as Arctic sled dogs, hunting dogs and certain guardian dog breeds from west and Central Asia, such as Anatolian shepherds — tended to have higher levels of wolf ancestry.

But plenty of breeds didn't fit these patterns. Some large guardian dogs, such as bullmastiffs and Saint Bernards, didn't have any detectable wolf ancestry. And some smaller dogs had small amounts of wolfish DNA. For instance, 0.2% of the Chihuahua's genome can be traced back to wolves, the team found.

"This completely makes sense to anyone who owns a Chihuahua," Lin said in the statement. "And what we've found is that this is the norm — most dogs are a little bit wolfy."

Meanwhile, every tested "village dog" had wolf DNA in its genome, the scientists found. And the reason why might be related to their survival. "The stretches of wolf DNA we found in village dog genomes contained genes related to olfactory receptors," Lin and Kistler wrote in The Conversation. "We imagine that olfactory abilities influenced by wolf genes may have helped these free-living dogs survive in harsh, volatile environments."

Some personality traits that kennel clubs use to describe certain breeds also tracked with the amount of wolfish influence. Breeds with lower wolf ancestry were frequently described as "friendly," "easy to train" or "lively," while breeds with more wolf DNA were pegged as "suspicious of strangers," "independent" and "dignified." It's not yet clear if wolf genes are directly responsible for these traits.