Neanderthal Genes Hint at Much Earlier Human Migration From Africa - The New York Times - 0 views
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From DNA recovered from the bones, researchers deduced that modern humans interbred with Neanderthals some 60,000 years ago, after leaving Africa.
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Using a new method to analyze DNA, however, a team of scientists has found evidence that significantly reshapes that narrative.
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Their study, published on Thursday in the journal Cell, concludes that a wave of modern humans departed Africa far earlier than had been known: some 200,000 years ago.
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The scientists also found evidence that people living somewhere in western Eurasia moved back to Africa and interbred with people whose ancestors never left. The new study suggests that all Africans have a substantially greater amount of Neanderthal DNA than earlier estimates.
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The research offers a view of human history “almost as a spider web of interactions, rather than a tree with distinct branches.”
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These people interbred with Neanderthals, the new study suggests. As a result, Neanderthals were already carrying genes from modern humans when the next big migration from Africa occurred, about 140,000 years later.
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The Neanderthal lineage left the continent; the fossils of what we describe as Neanderthals range from 200,000 years to 40,000 years in age, and are found in Europe, the Near East and Siberia.
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The human genome is detailed in units called base pairs, about 3 billion such pairs in total. The scientis
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ts found that Europeans on average had 51 million base pairs that matched Neanderthal DNA, and East Asians had 55 million.Dr. Akey’s previous research had indicated that East Asians carried far more Neanderthal ancestry than did Europeans.Africans on average had 17 million base pairs that matched Neanderthal DNA — far higher than predicted by the original models describing how humans and Neanderthals interbred.
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They concluded that a group of modern humans expanded out of Africa perhaps 200,000 years ago and interbred with Neanderthals. Those modern humans then disappeared. But Neanderthals who lived after that disappearance inherited some modern human DNA.
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sitation over the analysis of African DNA, Dr. Reich said the new findings do make a strong case that modern humans departed Africa much earlier than thought
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It’s possible that humans and Neanderthals interbred at other times, and not just 200,000 years ago and again 60,000 years ago. But Dr. Akey said that these two migrations accounted for the vast majority of mixed DNA in the genomes of living humans and Neanderthal fossils.
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In recent years, Dr. Reich and other researchers have found evidence that ancient people from the Near East moved back into Africa in the past few thousand years and spread their DNA to many African populations.