Humans and chimpanzees might have one more thing in common: they both seem to have benefitted from sex with a closely related species.

During the last decade, geneticists have reported that our species interbred with ancient humans including the Neanderthals and Denisovans . They have also found tantalising signs that we benefitted from doing so, gaining DNA that may have boosted our immune systems or made us better able to survive at high altitude or in the frigid Arctic . …