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Scientists have compiled the largest database of ancient DNA based on the bones and teeth of nearly 5,000 people who lived across Western Europe and parts of Central Asia from 34,000 years ago to the middle ages.
Analysis of this unique and detailed pool of ancient genetic information suggests that genes that may have increased the risk of neurodegenerative diseases such as multiple sclerosis and Alzheimer’s in Europeans may have been identified by hunter-gatherers. -protecting prehistoric gatherers or Bronze Age herders from harmful pathogens.
The ambitious five-year project involving a team of 175 international experts combined previously known ancient genomes with newly sequenced DNA from hundreds of skeletal specimens obtained from museums and other institutions across Europe. Together these data constitute the largest ancient gene bank in the world, according to the scientists involved in the project.
Researchers were able to use the database to trace the spread of genes — and diseases — over time as populations migrated and interbreeded, showing how specific and dramatic changes in the environment, such as the a shift from a hunter-gatherer lifestyle to farming, in a certain genetic favor. vary.
By comparing the ancient DNA with modern samples, the researchers gained a new biological understanding of debilitating disorders and physical characteristics today. The initial results of the project were published in four papers in the scientific journal Nature on Wednesday.
“What’s great about this data set is that now we can see what happened in the past, we can actually see what genetic variants changed frequency in the past due to natural selection . And that allows us to give us this really detailed picture,” Rasmus Nielsen, a professor of integrative biology and genetics at the University of California, Berkeley, who helped spearhead the project, said at a news briefing this week.
As Bronze Age shepherds are linked to MS
One of the main findings from the first batch of research, based on more than 1,600 genomes in the database, involved multiple sclerosis, often called MS, a lifelong autoimmune disease of the nervous system that affects 2.5 an estimated million people worldwide. It is a complex condition shaped by multiple environmental and genetic factors with many possible symptoms, including problems with vision, arm or leg movement, sensation, and balance.
Northern Europeans are among the people most at risk of the disease, the study noted, but the reasons are little understood.
Researchers used the database to investigate the genetic basis of multiple sclerosis. They found that the genetic risk of the condition is correlated with the percentage of ancestry from a group of ancient herders who introduced domesticated animals to Europe around 5,000 years ago.
These nomadic herders of cattle and sheep, known as the Yamnaya, came from the Pontic steppe, which stretches from southeastern Europe to Kazakhstan. They are thought to have been the first horse riders, making them very mobile.
When they moved back to Europe, they brought specific genetic variants that the researchers believe evolved to protect the nomads from pathogens carried by domesticated animals, the study found.
These genetic variants may have subsequently been beneficial to European populations as they transitioned from hunting and gathering to farming.
And because the Yamnaya migrated primarily into northern Europe, the team concluded that the increased proportion of pastoral ancestry in present-day northern Europe may be partly responsible for the disease’s higher prevalence there.
“We were all surprised by these results. They provide a major step forward in our understanding of the evolution of MS and other autoimmune diseases,” William Barrie, a postdoctoral researcher in Cambridge University’s Department of Zoology and co-author of one of the papers, said in a statement. “Showing the impact of our ancestors’ lifestyles on today’s disease risk shows how much we inherit ancient immune systems in a modern world.”
Today, the protective benefits of these genetic variants are no longer so useful, said coauthor Astrid Iversen, professor of virology and immunology at the University of Oxford.
“We now live a very different life to that of our ancestors in terms of hygiene, diet, and medical treatment options and this combined with our evolutionary history means that we may be more susceptible to certain diseases than our ancestors were. ancestors, including autoimmune diseases such as MS. ,” Iversen said in a statement.
Alzheimer’s Link
Researchers also mapped the origin of a genetic variant, APOE ε4, which is known to increase the risk of Alzheimer’s disease. The gene was linked to populations of early hunter-gatherers who once lived in prehistoric Europe, one of the four studies found.
“DNA from hunter-gatherers is present at higher levels in Northeast Europe, meaning the region has an elevated genetic risk of developing Alzheimer’s disease,” Barrie said.
Similarly, ancient genetic knowledge sheds light on the evolutionary history of traits such as height and lactose tolerance.
In a commentary accompanying the research, Samira Asgari, assistant professor of genetics and genomic sciences at the Icahn School of Medicine at Mount Sinai in New York, said it was essential to expand these types of studies outside of Europe to other regions to ” give them a better understanding. how differences in population history may have contributed to the risk of autoimmune diseases such as multiple sclerosis.”
“Although human biology is shared, each population has a unique history and focusing on one population limits opportunities for discoveries that may yield insights that advance medicine,” wrote Asgari, who was not involved with the four study.
The new database provides the “most comprehensive views of a region’s genetic history to date,” said Tony Capra, associate professor of epidemiology and biostatistics at the Bakar Institute for Computational Health Sciences at the University of California, San Francisco.
“This allowed the authors to fill in missing data in our understanding of who lived, where and when as well as how natural selection shaped the characteristics of modern individuals,” he said.
However, Capra cautioned that “there is seldom a simple answer as to why one population might have a genetic variant over another.”
“The evolutionary history of our species contributes a lot to our health and traits today,” Capra, who was not involved in the research, said via email.
“However, now and then, the environment modifies all these genetic effects. And for most traits, including MS, the genetic effects are the result of multiple genetic variants,” he said. “Ultimately, we cannot say that MS originated from Bronze Age populations, but the movements and environments of these populations contribute to differences in MS risk today.”
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