Humans, Neanderthals 'interbred': research

5 Oct 2012, 1:00 pm   -   Source: AAP

Early humans probably interbred with Neanderthals relatively soon after migrating out of Africa, research suggests.

Early humans probably interbred with Neanderthals relatively soon after migrating out of Africa, research suggests.

The finding may explain why present-day Europeans have more Neanderthal DNA in their genetic make-up than Africans.

Neanderthals were already in Europe when the first members of our species, Homo sapiens, ventured out of their African homeland.

The two co-existed for many thousands of years before Neanderthals became extinct around 30,000 years ago.

Scientists now know that there is some Neanderthal DNA in all of us, but more in Europeans than in Africans.

How it got there has been a mystery. The simplest explanation is that the two human sub-species interbred.

Another is that Neanderthals and Homo sapiens had divided African ancestors. According to this theory, it was those modern humans more related to Neanderthals - and sharing more of their genes - that eventually left Africa.

Scientists measured the length of strands of DNA in Europeans to estimate the age of their Neanderthal genes.

The Neanderthal-related DNA would have shortened with each new generation.

The findings, published in the online journal Public Library of Science Genetics, suggest that Neanderthals and modern humans last exchanged genes between 37,000 and 86,000 years ago.

This was well after modern humans appeared outside Africa, but probably before they began to spread across Eurasia. It indicates that our direct ancestors really did interbreed with Neanderthals after leaving Africa.

The scientists, led by Dr Sriram Sankararaman, from Harvard Medical School in the US, said it was likely the sexual encounters took place in the Middle East.

They wrote: "Genetic analyses by themselves offer no indication of where gene flow may have occurred geographically. However, the date in conjunction with the archaeological evidence suggests that the two populations likely met somewhere in western Eurasia.

"An attractive hypothesis is the Middle East, where archaeological and fossil evidence indicate that modern humans appeared before 100,000 years ago."

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