Study Reveals Male Neanderthals Bred Mainly with Female Humans

A new genetic study reveals that interbreeding between Neanderthals and early modern humans primarily involved pairings between male Neanderthals and female Homo sapiens, shedding light on the social dynamics of these ancient encounters across Europe, Asia, and the Middle East tens of thousands of years ago.

The research, published Thursday in the journal Science by scientists at the University of Pennsylvania, analyzed ancient Neanderthal genomes alongside modern human DNA. It found a striking pattern in the X chromosome, one of the two sex chromosomes. Most people today, excluding those from sub-Saharan African populations whose ancestors did not encounter Neanderthals, carry 1 to 4 percent Neanderthal DNA throughout their genome. However, this ancestry is notably scarce on the human X chromosome, which geneticists describe as an "archaic desert."

To investigate, researchers compared Neanderthal DNA from three ancient female samples with genomes from present-day African women, who lack Neanderthal ancestry, providing a clear baseline for identifying Homo sapiens contributions. The analysis revealed an excess of human DNA on Neanderthal X chromosomes, the opposite of the...