When some of the first human migrants to Europe encountered Neanderthals, who had already lived there about 45,000 years ago, connections flourished.
Analysis of DNA found in human fossils from around that time—the oldest known human remains in Europe—suggests that interbreeding between Homo sapiens and Neanderthals, who were on the fast track to extinction, happened more often than often assumed, two new studies. offer.
Genetic evidence in new reports indicates for the first time that distinct human populations reached Europe shortly after 50,000 years ago. Neanderthals interbred with all the groups discovered so far, ensuring that some of their genes live on in our DNA today.
The remains of three individuals H. sapiens found in the Bacho Kiro cave in Bulgaria, yielded nuclear DNA containing approximately 3-4 percent Neanderthals, reported April 7 in Nature evolutionary geneticist Mateja Haidinjak from the Francis Crick Institute in London and his colleagues. The ancient DNA comes from a tooth and two bone fragments radiocarbon dated to between 43,000 and 46,000 years ago. Stone tools typical of Late Stone Age humans were found in the same deposit as the fossils.
“All of the Bacho Kiro had recent Neanderthal ancestors, only five to seven generations back in their family trees,” says Heidiniak.
Another piece of evidence for ancient interbreeding comes from an almost complete human skull found in 1950 in a cave in what is now the Czech Republic. About 2 percent of the genes in the DNA of this fossil, identified as female, also came from Neanderthals, evolutionary geneticist Kay Pruefer of the Max Planck Institute for Human History in Jena, Germany, and colleagues reported April 7 in Nature Ecology . & Evolution . Analysis of these DNA segments shows that she also lived about 45,000 years ago.
Fossils H. sapiens in Bulgaria and the Czech Republic are not the first to be found with fragments of Neanderthal DNA in their genomes, but they are likely the oldest. Long segments of Neanderthal DNA in an Eastern European woman, which in subsequent generations of humans broke up into shorter segments, suggest that she lived several hundred or several thousand years earlier than the 45,000-year-old Siberian man, who was previously reported to have 2 .3 percent of his genes with Neanderthals. This finding showed that interbreeding outside of Europe took place as early as 60,000 years ago. And a Romanian who lived about 40,000 years ago also had long stretches of Neanderthal DNA, indicating he was four to six generations from a Neanderthal relative.
Neanderthals died out about 40,000 years ago, although their genetic remnants survive—non-Africans today carry an average of nearly 2 percent Neanderthal DNA. Modern Africans have less Neanderthal genetic heritage.
Taken together, the new research suggests that some of the first people to arrive in Europe had a lasting impact on our DNA, while others hit a genetic dead end. Bacho Kiro’s people represent a newly identified population of ancient Europeans with genetic links to modern East Asians and Native Americans, but not to western Eurasians, Heidiniak’s group says. Like the ancient Romanian and Siberian men, the Czech woman did not contribute any genes to the H. sapiens who lived about 40,000 years ago.
“It is remarkable that the Bacho Quiro finds may represent a population that spread 45,000 years ago at least from Bulgaria to China,” says evolutionary geneticist Carles Lalueza-Fox of the Institute of Evolutionary Biology in Barcelona, who was not involved in any of the new research. investigation.
If H. sapiens and Neanderthals regularly interbred as the last population neared extinction, the relatively large number of incoming humans accumulated surprising amounts of DNA from smaller Neanderthal populations, Laluesa-Fox suspects. After 40,000 years ago, additional migrations into Europe of people with little or no Neanderthal roots further diluted Neanderthal DNA from the human gene pool, he says.
These people made characteristic stone and bone tools and served as the ancestors of modern Europeans, Haidinyak suggests. For example, DNA from a bone fragment of H. sapiens was recently found in Bacho-Kiro cave approximately 35,000 years old, has a different composition than the previous inhabitants of the cave. This individual contributed genes mainly to later populations in Europe and western Asia, Heidiniak says.