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 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.

Some Neanderthal populations lived in complete isolation for tens of thousands of years, separated from others with no genetic exchange. One such group, represented by an individual named “Thorin,” was discovered at the Grotte Mandrin site in France.

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