• Neanderthal DNA in Africans suggest back-migration to Africa from present-day Europe

    Sandipan Talukdar

    February 4, 2020

    Image Courtesy: Natural History Museum.uk

    Ten years before, research had showed that today’s Europeans, Asians and their descendants have Neanderthal DNA in them. Further, it has been made clear that the Neanderthal DNA entered these populations through a process of interbreeding of modern humans and the Neanderthals. Modern humans migrated out of Africa and on their way they met with the Neanderthals in the areas which are Europe and Asia today.

    Also, for these ten years, scientists had believed that the Neanderthal DNA is present only in modern day Europeans and Asians, but not amongst Africans. But this narrative has been overturned by the findings of a new study published in Cell, which found an unexpectedly high amount of Neanderthal DNA across African population. This finding is suggestive of the fact that the presence of Neanderthal DNA in African population is due to back-migration of modern humans from Europe and Asia to Africa, over almost 20,000 years ago.

    Joshua Akey, an evolution biologist from Princeton University, teamed up along with othersto decipher how Neanderthal DNA is linked to the African population. The team compared the genome of a Neanderthal, vestiges of which was found in the Altai mountain region of Siberia, with 2,504 modern genomes from the "1, 000 genome project" which includes five African sub populations. The Neanderthal genome was sequenced in 2013.

    The analysis of their results showed that, on average, African populations have significantly more Neanderthal DNA than was previously thought. The African populations have 17 megabases, amounting to 0.3% of their DNA acquired from Neanderthal. Their research also give hints that some Neanderthal genes may have undergone natural selection after they entered Africans’ genomes. These genes include those that boost immune function and protect against UV radiation.

    The analysis also showed that the African population acquired these genomes from the Europeans who back migrated to Africa some 20,000 years back. These Europeans who already had Neanderthal DNA interbred with the African population and in the process, the Africans acquired the Neanderthal genomes. 

    The new study could also hint towards an answer to another head scratcher, that is why East Asians have 20% more Neanderthal genes than Europeans? It is Europe where the Neanderthal remains are mainly found, so naturally Europeans should have largest amount of Neanderthal DNA than any other populations, which, apparently is not the case.

    The new study points to an explanation: Researchers previously assumed that Neanderthal sequences shared by Europeans and Africans were modern and subtracted them out. After correcting for that bias, the new study found similar amounts of Neanderthal DNA in Europeans and Asians—51 and 55 Mb (Megabase), respectively. 

    Anthropologist Michael Petraglia from the Max Planck Institute for the Science of Human History, is quoted to have said, “That gene flow with Neanderthals exists in all modern humans, inside and outside of Africa, is a novel and elegant finding.”

    First published in Newsclick

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