Scientists may have unraveled the mystery of the origins of Neanderthals

New analysis of ancient genomes deepens scientists’ understanding of Neanderthal DNA, with genes identified in human populations in Europe and Asia.

According to the researchers, the discovery, published in the journal Science Advances, tracks the genetic heritage of our species’ archaic relatives, Homo sapiens, with greater precision thanks to invaluable data.

Most living humans may share a very small percentage of their DNA with 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 common in the genomes of East Asian populations.

This discrepancy has long puzzled scientists, since Neanderthal remains have been found widely throughout Europe and the Middle East, but no further east than the Altai Mountains in Central Asia.

“And what’s puzzling is that in an area where we’ve never found Neanderthal remains, there’s more Neanderthal DNA,” said study co-author Mathias Karrath, a senior lecturer in the department of genetics and evolution at the University of Geneva.

On average, Neanderthal DNA makes up about 2% of the genetic makeup of people in Eurasia, while in East Asia the share can be as high as 4%, Karrath said.

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

“We are starting to have enough data to better and more accurately describe the percentage of DNA of Neanderthal origin in the sapiens genome at certain periods of prehistory,” Karratt explained.

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

The research team pulled information from a database of more than 4,000 ancient genomes from across Europe and Asia, compiled by a team led by Dr. David Reich, professor of human genetics and evolutionary biology at Harvard Medical School in Boston.

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

Thus, the research team concluded that the current pattern of higher percentages of Neanderthal ancestry in Asian populations compared to populations in Europe must have arisen at a later stage, most likely during the Neolithic transition, when farming began to replace hunting and gathering as a way of life approximately 10,000–5,000 years ago.

At this point, the first farmers from Anatolia, in what is now western Turkey and the Aegean Sea, began to mingle with the existing hunter-gatherers in Western and Northern Europe. This resulted in a decrease in the proportion of Neanderthal DNA observed in European genomes during this period.

“The point is that they had less Neanderthal ancestry, so they diluted (the Neanderthal ancestry) into the European population,” Karratt said.

Some genes may influence the health of modern people. For example, according to a September 2020 study, Neanderthal DNA may play a small role in the course of Covid-19 infection.