Why do Tibetans have a genetic adaptation that allows them to survive in the low-oxygen environments of the Tibetan Plateau? An international team of researchers led by the University of California, Berkeley have found that Tibetans acquired the gene by interbreeding with Denisovans, an extinct human ancestor. Study leader Rasmus Nielsen explains.

"There was almost a complete match between the DNA sequence we found in Tibetans and the DNA sequence that was found in Denisovans. We could show that the DNA must have come from Denisovans into modern humans and like what allowed Tibetans to have this physiological adaptation and allowed them to settle and live on the Tibetan Plateau."

This is what’s called adaptive integration, or the process of getting DNA from one species to another.

"So, that’s what we think is going on in this case. And to us, as evolutionary biologists, the reason why this is particularly interesting is because it might point to the fact that adaptive integration might have been more important in human evolution than people have previously thought."