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Genomics: close encounters of the first kind

Ancestors of Eastern Neanderthals from the Altai Mountains of Siberia and modern humans may have met and interbred much earlier than previously thought, reports a paper published in Nature. It has been shown that Neanderthals contributed genetic material to modern humans outside Africa around 47,000 to 65,000 years ago. The new study suggests that there may also have been gene flow in the opposite direction, from modern humans to Neanderthals from Siberia, some 100,000 years ago.

Sergi Castellano and colleagues analysed the genomes of a Neanderthal and a Denisovan (an extinct human species) from the Altai Mountains, as well as two present-day human genomes. They also studied detailed sequence data from chromosome 21 of two further Neanderthals: one from Spain and one from Croatia. They find evidence of gene flow from a population that diverged early from other modern humans in Africa to the ancestors of Neanderthals from Altai around 100,000 years ago. By contrast, they did not detect such a genetic contribution in the Denisovan or the European Neanderthals.

The authors speculate that this modern human population could have met and interbred with Neanderthals in the Levant, where modern humans and Neanderthals are thought to have been present as early as 120,000 years ago, or possibly in Southern Arabia and the area around the Persian Gulf, where modern humans may also have settled early.