A new timeline of when Neanderthals and ancient humans interbred
The Neanderthal DNA found in modern human genomes has long raised questions about ancient interbreeding. New studies offer a timeline of when that occurred and when ancient humans left Africa.
Hidden in many people’s genetic codes is a mystery that has long intrigued scientists — a tiny slice of Neanderthal DNA that persists tens of thousands of years after the species vanished. Most non-African people can attribute around 1% to 2% of their DNA to Neanderthal ancestors.
But the details of that evolutionary history have remained unclear. How often did ancient humans and Neanderthals interbreed? Exactly when did that happen? Why did Neanderthals go extinct, and why did modern humans survive? What does that Neanderthal DNA do for us now?
Two research groups have separately analyzed collections of ancient genomes and come to the same conclusions about some of those core questions. Studies published in the journals Nature and Science on Thursday suggest that ancient humans and Neanderthals interbred during a limited period of time as the humans left Africa and migrated to new continents.
The wave of interbreeding took place roughly 43,500 to 50,500 years ago, according to the findings. Then, over the next 100 generations, most Neanderthal DNA got weeded out — but not all. Today, the DNA that remains is linked to traits like skin pigmentation, immune response and metabolism.
According to the new findings, the interbreeding event happened more recently than some previous estimates suggested, which in turn shifts and narrows the possible range of time when humans spread to places like present-day China and Australia.
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