Around 2% of modern humans carry Neanderthal DNA, meaning we know early humans got super intimate with our now-extinct relatives. According to new research, when Neanderthals and humans did hit it off, it seems they favored a particular sex combination over another.
In a paper published today in Science, evolutionary geneticists at the University of Pennsylvania report an excess of modern human ancestry on the Neanderthals’ X chromosome compared to other parts of their genome. That excess was probably due to sex-based mating, specifically between human women and Neanderthal men, according to the new study.