We also know that Neandertals lived in Eurasia from 230,000 until about 30,000 years ago. Where they came from or why they disappeared remains an open question. And we know that anatomically modern humans first appear in Africa at least 200,000 years ago. Some of them made their way to Asia and Europe sometime in the last 100,000 years.
So when did modern human/Neandertal interbreeding last occur? Did it occur deep in our past, before modern humans and Neandertal ancestors left Africa? Or did it occur after both left Africa, sometime—in other words—within the past 100,000 years?
A new study claims to find evidence that the interbreeding occurred out of Africa. Researchers argue that on the basis careful analysis of the shared DNA, the most recent interbreeding occurred sometime between 37,000 and 86,000 years ago.
Caption: Reconstruction of a Neandertal, 2006, by Stefan Scheer, from Stefanie Krull, Neanderthal Museum Picture Library, Mettmann, Germany
If so, it is pretty strong evidence that the interbreeding occurred after anatomically modern human left Africa. This may have occurred in the Middle East, researchers point out, but probably not just at the beginning of the modern human migration out of Africa. The most recent interbreeding, they conclude, occurs well after this 100,000 date, suggesting ”a more recent period, possibly when modern humans carrying Upper Paleolithic technologies expanded out of Africa.”
In that case, the conceptual challenge posed by the modern human/Neandertal interbreedng remains clearly in front of us. What is the human species? Were Neandertals human? And what are we to make of our new insight into modern human diversity. All puzzling questions, to put it mildly.
The article, "The Date of Interbreeding between Neandertals and Modern Humans," is published in the current issue of PLOS Genetics, where it is available free to the public.
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