Mating with Neanderthals helped boost modern humans' ability to fight novel viruses in Europe and Asia, a new study contends.
Before vanishing about 40 000 years ago, Neanderthals interbred with modern humans who had migrated out of Africa. As a result, many modern Europeans and Asians have about 2% Neanderthal DNA in their genomes, the researchers explained.
The study was published online in the journal Cell.
Some bits of Neanderthal DNA are more common in modern humans than others, and scientists wondered if this was because those genes provided specific evolutionary advantages.
The new Stanford University study suggests that may be the case.
"Our research shows that a substantial number of frequently occurring Neanderthal DNA snippets were adaptive for a very cool reason," said researcher Dmitri Petrov, an evolutionary biologist at Stanford.
"Neanderthal genes likely gave us some protection against viruses that our ancestors encountered when they left Africa," Petrov said in a university news release.
When modern humans migrated out of Africa to Europe and Asia, they were exposed to new viruses. But Neanderthals had been living outside of Africa for hundreds of thousands of years, and their immune systems had evolved defences against those viruses, the study authors explained.
According to David Enard, a former postdoctoral fellow in Petrov's lab, "It made much more sense for modern humans to just borrow the already adapted genetic defences from Neanderthals rather than waiting for their own adaptive mutations to develop, which would have taken much more time."
The researchers found that the genetic defences that modern humans received from Neanderthals were against RNA viruses, which encode their genes with RNA, a molecule that's chemically similar to DNA.
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