Living Neanderthal Descendents Have Ancient Sex to Thank for Their Existence

Neanderthals passed down an extremely important trait.

In the last 100,000 years, Homo sapiens and Homo neanderthalensis interbred twice. While our ancient cousins went extinct about 40,000 years ago, fragments of their DNA live on today as a result of those trysts: Most people of European and Asian descent have approximately 2 percent Neanderthal DNA. In 2018, scientists discovered just how important this DNA is — without it, many of our ancestors would have perished long before our family lines could begin.

Scientists reported in the October issue of Cell that Neanderthals passed on life-saving genetic adaptations to their Homo sapien-Neanderthal offspring. Interbreeding, co-author and University of Arizona professor David Endard, Ph.D. explained to Inverse, gave modern humans a “fast-track route for adaptation” against the new viruses they encountered during the migration to Eurasia. Instead of “reinventing the genetic wheel,” we borrowed it from Neanderthals.

This story is #11 on Inverse’s 25 Most Surprising Human Discoveries Made in 2018.

Importantly, Neanderthals lived in Eurasia for hundreds of thousands of years before encountering Homo sapiens. During that time they encountered new pathogens, many died from them, and the survivors slowly evolved to have genomes that contained adaptive mutations. These enabled their descendants to fight off dangerous viruses and — when those descendants later mated with anatomically modern humans — they continued that beneficial chain of inheritance.

Neanderthal traits
Neanderthal DNA influences particular traits in humans. 

“Neanderthal genetic material was like a protective antidote because Neanderthals had likely been infected for a long time by the same viruses that were now harmful to modern humans,” Enard explained. “This long exposure means that Neanderthals had plenty of time to adapt against these viruses before modern humans showed up.”

Neanderthal inherited genes today don’t protect humans from viruses in modern day. But the scientists know that they once did, thanks to the 152 DNA fragments that are present in the genomes of both living Europeans and sequenced Neanderthals, and which interact with modern day RNA viruses like HIV, influenza A, and hepatitis C. The team reasons that these Neanderthal genes were conserved because they once helped our ancestors fight off ancient RNA viruses.

In turn, many living humans have Neanderthals to thank for their very existence. This study also reminds us that, as Enard puts it, “the evolution against viruses is an arms race” — and we’re lucky that today we can be protected from viruses from shots, instead of relying on a serendipitous combination of sex and death.

As 2018 winds down, Inverse is highlighting 25 surprising things we learned about humans this year. These stories told us weird stuff about our bodies and brains, uncovered insights into our social lives, and illuminated why we’re such complicated, wonderful, and weird animals. This story was #11. Read the original story here.