Scientists have long known that humans outside of Africa owe 2 to 3 percent to their Neanderthal genome ancestors. But now, using the oldest modern human DNA ever analyzed, two studies have found that ancestor. the only rise of the crossover which happened between 45,000 and 49,000 years ago.
Neanderthals (Homo neanderthalensis) and modern humans (Wise man) They were encountered many times over tens of thousands of years: modern human DNA is found in Neanderthals who lived more than 200,000 years agoand some human populations he mixed more with Neanderthals until the last species became extinct 39,000 years ago. But not all of these interactions have left a shared imprint on all non-African populations today. This is the moment he left an almost global genetic fingerprint It happened in a few thousand years, between the Neanderthals who settled in Europe and the humans who had just arrived in their land.
“We believe that the peak of this interaction was 47,000 years ago, which also gives us a rough estimate Out-of-Africa migration could happen,” says Leonardo Iasi, a postdoctoral researcher in evolutionary genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and lead author of one of the studies published Thursday. science. He is also the co-author of the other work that was published in nature.
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Multiple waves of humans left Africa, where Homo The genus originally evolved over thousands of years and established populations in the Middle East and Europe. There, they encountered and sometimes bred Neanderthals, descendants of a human ancestor who had left Africa hundreds of thousands of years earlier. The last common ancestor of Neanderthals and modern humans is unknown, but this species probably lived between 650,000 and 500,000 years ago. Researchers still can’t say for sure where Neanderthal-human admixture did happen, but two new studies significantly narrow the “when” question.
in the year nature study, biochemist Johannes Krause, archaeogeneticist Kay Prüfer and PhD candidate Arev Sümer, all at the Max Planck Institute for Evolutionary Anthropology, and their colleagues sequenced the genomes of six individuals found in Ranis, Germany, and the Zlatý kůň site in the Czech Republic. These people, who lived between 49,000 and 42,000 years ago, contained some of the oldest modern human genomes that have been sequenced. According to Sümer, they also included the oldest family of modern humans. The Ranis people were a mother and her young daughter, as well as another female member of the same extended family. Even more surprisingly, the Zlatý kůň person—a single female known from the bones in her skull—was a distant relative of this Ranis family.
These related populations, probably only 300 members spread across Central Europe, shared 2.9 percent Neanderthal ancestry. By looking at the length of the Neanderthal gene segments in these human genomes, the researchers were able to measure when Neanderthal ancestors entered. (Longer segments are more recent additions because genetic recombination hasn’t had a chance to mix. Shorter segments come from a more distant admixture event.) Scientists put these Central Europeans about 80 generations removed, or between 1,500 and 1,000. years, from ancestors who mixed with Neanderthals.
in the year science In the study, the researchers analyzed a larger dataset of 59 ancient human genomes from 45,000 to 2,200 years ago, as well as the genomes of a diverse group of 275 present-day humans. “We were also interested in estimating the time of Neanderthal ancestry and whether that happened over a short period of time or over a long period of time,” says Priya Moorjani, a population geneticist at the University of California, Berkeley, along with Benjamin. Peter, from the Max Planck Institute for Evolutionary Anthropology, was the lead author of the paper. (Peter is also a co-author of the book nature paper.)
Like Krause’s group, Moorjani and his colleagues found evidence for a single pulse of Neanderthal genetics in the human genome between about 50,500 and 43,500 years ago. The scientists also saw evidence of natural selection in these genes: after about 100 generations, the human genome looked much like it does today, with segments containing many Neanderthal genes and segments containing very few. For example, the modern X chromosome contains few Neanderthal genes.
This genetic change is fascinating, says Joshua Akey, a Princeton University genomicist who was not involved in the new research, because it points to places in the human genome where Neanderthal genes could enhance survival and reproduction and be permanently embedded or damaged. and disappeared. “They’re all naturally fascinated by what makes us different from other types of humans that have existed,” Akey says. “And if there are genetic substrates that define differences, these are the places in the genome where they live.”
Furthermore, the researchers found that the inhabitants of Ranis and Zlatý kůň, although they were connected to the non-African population that spread around the world, did not leave behind any descendants. “There are multiple lineages that we’ve identified now that didn’t contribute to modern humans,” says Krause, “which also tells us that the human story isn’t just a success story. We went extinct too.”
Moreover, these findings raise new questions about the dispersal of modern humans and how humans gradually replaced Neanderthals as the dominant species in Europe, says Isabelle Crevecoeur, a paleoanthropologist at the French National Center for Scientific Research (CNRS) and the University of Bordeaux. France, which did not participate in the new studies. “The big challenge for us now, as paleoanthropologists or prehistorians, is really trying to match genetic results with cultural or archaeological data, and trying to make sense of it,” he says.
