Denisovan-Neanderthal Link — Immune Boost?

Did sex with Neanderthals and Denisovans shape our immune systems? The jury’s still out


Neanderthals may be extinct, but they live on inside us. Last year, two landmark studies from Svante Paabo and David Reich showed that everyone outside of Africa can trace 1-4 percent of their genomes to Neanderthal ancestors. On top of that, people from the Pacific Islands of Melanesia owe 5-7 percent of their genomes to another group of extinct humans – the Denisovans, known only from a finger bone and a tooth. These ancient groups stand among our ancestors, their legacy embedded in our DNA.

Paabo and Reich’s studies clearly showed that early modern humans must have bred with other ancient groups as they left Africa and swept around the world. But while they proved that Neanderthal and Denisovan genes are still around, they said little about what these genes are doing. Are they random stowaways or did they bestow important adaptations?

When I spoke to Reich about this earlier this year, he was starting to sift through the data. “To a first approximation, they are random,” he said. “It’s possible that modern humans could have used the Neanderthal or Denisovan material to adapt to their environment, but we don’t have evidence for that.” However, palaeontologist Chris Stringer offered an intriguing suggestion: “If Denisovans were in South-East Asia long-term, they would have evolved immunities and defences to some of the diseases there, like different forms of malaria. That’s something modern humans could have picked up that would’ve been useful.”

He might have been right. Laurent Abi-Rached from Stanford University has just published a new study suggesting that our immune system owes a debt to our ancestors’ trysts with Neanderthals and Denisovans.

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