Long ago, Neanderthals and humans interbred. But among Neanderthals, their human blood came mostly from their female ancestors, and a new genetic study finds this was likely due to their mating preferences.

When ancient humans interbred, new research shows that the pairings were predominantly male Neanderthals and female Homo sapiens.

Neanderthal males had a tendency to mate with human females, new research suggests.

Geneticists have found an interesting pattern in how early humans and Neanderthals interbred—and it wasn't balanced.

Geneticists have a better understanding of how prehistoric pairings unfolded, with new research suggesting they were mostly between male Neanderthals and female humans.

By now, it’s firmly established that modern humans and their Neanderthal relatives met and mated as our ancestors expanded out of Africa, resulting in a substantial amount of Neanderthal DNA scattered throughout our genome. Less widely recognized is that some of the Neanderthal genomes we’ve seen have pieces of modern human DNA as well.

Learn how sex-biased interbreeding between Neanderthals and modern humans explains why Neanderthal DNA is largely missing from the X chromosome.