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

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.

Most people alive today carry fragments of Neanderthal DNA in their genome. Now scientists are gaining a more intimate understanding of the ancient encounters that put it there.

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

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