Neanderthals may not have actually gone extinct, but may have been absorbed into modern human populations — one of the findings of a new study that suggests modern humans may make up between 2.5% and 3.7% of our DNA. Neanderthal genome.
“This study really highlights that what we thought was a separate Neanderthal lineage was actually more closely related to our ancestors.” Fernando VillaneaModern human and Neanderthal populations “shared a long history of exchange of individuals,” population geneticist David Schneider of the University of Colorado Boulder, who was not involved in the study, told Live Science.
Neanderthals are the closest extinct relatives of modern humans, and our lineage diverged about 500,000 years ago. More than a decade ago, scientists revealed that Neanderthals interbred with ancestors of modern humans who traveled out of Africa. Today, the genomes of modern human groups outside of Africa contain About 1% to 2% of Neanderthal DNA.
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But researchers know little about how modern human DNA ended up in the Neanderthal genome, largely because there are currently only three known complete, high-quality examples of Neanderthal genomes. Vindhija cave in CroatiaIt is believed to be between 50,000 and 65,000 years old. Chagyrskaya and Denisova They were discovered in a cave in Russia and date back approximately 80,000 and 50,000 years ago, respectively.
In comparison, scientists Hundreds of thousands of modern people Since the completion of the Human Genome Project in 2003.
“A great deal of research has focused on how interbreeding between Neanderthals and modern humans has affected our DNA and evolutionary history,” says the study’s lead author. Joshua Akey“But we don’t know much about how these encounters affected the Neanderthal genome,” said , a population geneticist at Princeton University in New Jersey, told Live Science.
In the new study, the scientists relied on the fact that both modern humans and Neanderthals typically have two versions of every gene, one inherited from their father and one inherited from their mother. Because the two groups were more different from each other than they were from other groups of the same species, mating between Neanderthals and humans would result in offspring that were more likely to have two different versions of each gene (a condition called heterozygosity) than non-interbred children.
The researchers compared the genomes of three Neanderthals with those of 2,000 modern humans and found that the Neanderthal genomes likely contained between 2.5% and 3.7% modern human DNA. One in 30 modern human parents have Neanderthal ancestry.
The team’s analysis suggests that modern human DNA entered the Neanderthal genome during at least two distinct mating events: 200,000 to 250,000 years ago, and again 100,000 to 120,000 years ago. Mating events could have occurred at other times as well, but such events may not have left detectable traces in the Neanderthal genome, Akey said.
a Recent, not yet peer-reviewed, studies It has been suggested that most of the Neanderthal DNA found in modern human genomes is the result of a single major interbreeding period that began about 47,000 years ago and lasted for around 6,800 years. Interbreeding that occurred at other times, such as earlier events that affected the Neanderthal genome, may not have left a detectable trace in our genome.
The skull was discovered Sukur and Qafzeh Caves in Israel Dating back about 100,000 years, roughly the same time as one of the major hybridization events identified in the study, the fossils appear to be those of modern humans, but retain relatively primitive features such as large eyebrows that may be “signs of genetic influx from Neanderthals.” Chris Stringer“It’s a very unique animal,” paleoanthropologist at the Natural History Museum in London, who was not involved in the study, told Live Science.
By analyzing the levels of genetic variation found in the three Neanderthal genomes, the new study also suggests that the long-term average Neanderthal population was about 20 percent smaller than previous estimates. “This doesn’t seem like a huge difference, but given that the Neanderthal population was already estimated to be quite small, the fact that it was even smaller is an important insight,” Akey said.
These new estimates of Neanderthal population size suggest that Neanderthals may have disappeared because they were “simply absorbed into the modern human population,” Akey said. “Repeated waves of modern human migration out of Africa eventually overwhelmed the ability of Neanderthals to persist as a distinct population, and they were eventually assimilated into the modern human gene pool.”
Akey said future research could explore the biological effects that modern human DNA may have had on Neanderthals, whether positive or negative.
The scientists published their findings in detail online in the journal Neuroscience on Thursday (July 11). Science.
