Neanderthals and humans interbred much earlier than thought

New research carried out by the Max Planck Institute for Evolutionary Anthropology reveals that modern humans and Neanderthals may have interbred much earlier than previous estimates, up to 100,000 years ago. This study challenges the central idea that modern humans migrated from Africa 60,000 years ago.

While it is known that modern humans carry around 4% of Neanderthal DNA in their genomes, this study suggests that gene flow may have occurred in the opposite direction too and Neanderthal genomes contain a proportion of modern human DNA.
50,000 year old DNA from four samples was analysed: a Neanderthal and Denisovan from Siberia, and two European Neanderthals. This DNA was compared to 500 DNA samples from modern Africans.

Neanderthals and Denisovans are more closely related to each other than either of them are to modern humans, so it was expected that their genomes would have more in common with each other too. However the research found that the Siberian Neanderthal genome was more similar to that of modern Africans than to either European group. In particular, the human FOXP2 gene, which is involved in language development, was found in the Neanderthal genome. The length of human DNA sequences found in Neanderthal genomes allowed researchers to calculate how long ago the interbreeding event occurred.

It is currently thought that modern humans bred with Neanderthal populations after modern humans migrated from Africa, and mated with the Neanderthals who had already settled further north in Europe and Asia. These Neanderthals had evolved to cope with cooler temperatures, different diseases and a lack of sunlight.

These findings open up new doors for the study of human evolution, and the search is now on for traces of human ancestors around the world in the time before 60,000 years ago.

Photo: New Scientist