By mining electronic medical records, scientists show the lasting legacy of prehistoric sex on modern humans’ health.
Modern humans originated in Africa, and started spreading around the world about 60,000 years ago. As they entered Asia and Europe, they encountered other groups of ancient humans that had already settled in these regions, such as Neanderthals. And sometimes, when these groups met, they had sex.
We know about these prehistoric liaisons because they left permanent marks on our genome. Even though Neanderthals are now extinct, every living person outside of Africa can trace between 1 and 5 percent of our DNA back to them. (I am 2.6 percent Neanderthal, if you were wondering, which pales in comparison to my colleague James Fallows at 5 percent.)
This lasting legacy was revealed in 2010 when the complete Neanderthal genome was published. Since then, researchers have been trying to figure out what, if anything, the Neanderthal sequences are doing in our own genome. Are they just passive hitchhikers, or did they bestow important adaptations on early humans? And are they affecting the health of modern ones?