Scientists may have solved a mystery regarding the origins of Neanderthals

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A new analysis of ancient genomes deepens scientists’ understanding of Neanderthal DNA carried by human groups in Europe and Asia — genetic traces that may have medical significance today.

The findings, published Wednesday in the journal Science Advances, trace the genetic legacy An ancient relative of our species, Homo sapiens, more precisely, thanks to a critical mass of invaluable data, according to the researchers.

Most humans alive today can trace a very small percentage of their DNA back to Neanderthals — the result of prehistoric sexual encounters between our ancestors and now-extinct Stone Age hominins, before the latter disappeared about 40,000 years ago.

However, Neanderthal DNA is slightly more abundant in the genomes of East Asians.

This discrepancy has long puzzled scientists because Neanderthal remains have been found widely throughout Europe and the Middle East but not to the east of the Altai Mountains in Central Asia.

“What is puzzling is that the region where we did not find any Neanderthal remains has more Neanderthal DNA,” said study co-author Mathias Korat, a senior lecturer in genetics and evolution at the University of Geneva.

On average, Neanderthal DNA represents about 2% of the genetic makeup of people in Eurasia, while in East Asia it can be as high as 4%, Korat said.

Korat and his colleagues at the University of Geneva found an explanation for this discrepancy by analyzing the distribution of Neanderthal DNA in human genomes over the past 40,000 years.

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“We are starting to obtain enough data to more accurately characterize the percentage of DNA of Neanderthal ancestry in the Sapiens genome at certain periods of prehistory,” Korat explained.

The researchers found that over time, the distribution of Neanderthal DNA did not always look like it does now.

The study team extracted information from A Database More than 4,000 ancient genomes from across Europe and Asia have been collected by a team led by Dr. David Reich, professor of genetics and human evolutionary biology at Harvard Medical School in Boston.

For samples older than 20,000 years, the researchers found that the genomes of Stone Age Homo sapiens, who lived as hunter-gatherers in Europe after the extinction of Neanderthals, contained a slightly higher percentage of Neanderthal DNA than those who lived in Asia.

The study team thus concluded that the current pattern of a higher proportion of Neanderthal ancestry in Asian populations compared to those in Europe must have evolved at a later stage, most likely during the transitional period to the Neolithic when agriculture began to replace hunting and gathering as a means of subsistence. . Life about 10,000 to 5,000 years ago.

At this time, the first farmers from Anatolia, in what is now western Turkey and the Aegean Sea, began to mix with the hunter-gatherers of western and northern Europe. This resulted in a decline in the proportion of Neanderthal DNA in European genomes during this period.

“The thing is that they had fewer Neanderthal ancestors, so they diluted (the Neanderthal lineage) in the European population,” Korat said.

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He said it was unclear how this shift occurred in Asia due to the relative lack of information. The study included 1,517 samples from Europe compared to 1,108 samples from Asia, an area four times larger.

Tony Capra, associate professor of epidemiology and biostatistics at the Paccard Institute for Computational Health Sciences at the University of California, San Francisco, said the research was “an example of an exciting and very promising strategy for integrating analysis of ancient human DNA from different geographic regions.” Loci with modern genomes to connect evolutionary dots across time and space. He did not participate in the research.

Some genetic traces left by encounters with Neanderthals could make a difference in the health of modern humans. For example, Neanderthal DNA may play a small role in influencing the course of COVID-19 infection, according to a September 2020 study.

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