Wednesday, July 05, 2017

Earlier date for African interbreeding

Carl Zimmer reports in the NY Times:
In a study published Tuesday in Nature Communications, Dr. Krause and his colleagues report that Africans did indeed walk out — over 270,000 years ago.

Based on newly discovered DNA in fossils, the researchers conclude that a wave of early Homo sapiens, or close relatives of our species, made their way from Africa to Europe. There, they interbred with Neanderthals. ...

The new study raises a host of tantalizing implications about human history.

It is not possible to know just how many times these early Africans interbred with Neanderthals. But somewhere in prehistory, at least one female human from Africa must have carried the child of a male Neanderthal.

“Now you have this hybrid child, which is probably pretty unusual-looking,” Dr. Siepel said. “One way or another, this hybrid individual was absorbed into Neanderthal society.”
Not only that, but such hybrids are the ancestors of all modern non-Africans.

All of this calls into question the conventional wisdom that Neanderthals were some sort of non-human species. Neanderthals and Africans (at the time) were just two races of humans that occasionally interbred. This research implies they interbred 270k years ago, and other work implies interbreeding 50k years ago. Maybe Denisovans were another race. These races were as modern and as human as the others. More African DNA has survived than Neanderthal, but the DNA differences are not well understood.

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