Neanderthals evidently gave humans a precious “gift” that allowed them to survive horrible viruses and diseases. A new study suggests that when they interbred, the more adapted Neanderthals passed to humans both the viruses and the DNA tools to fight them.

Neanderthals’ And Humans’ Interbreeding

It is so far known that Neanderthals and humans interbred at least twice in a period of 100,000 years, but some snippets of Neanderthal DNA remain in some members of the modern human population than in others. In fact, many modern Asians and Europeans carry about 2 percent of Neanderthal DNA.

Neanderthals mysteriously vanished about 40,000 years ago, and when the species first interbred with humans, they had already been outside of Africa for thousands of years, whereas the humans had only left Africa for a significantly shorter time. This means that the Neanderthals’ immune systems were already much more accustomed to the viruses and diseases in Europe and Asia compared to the humans who were still much more vulnerable at the time.

According to researchers of a new study published in the journal Cell, those frequently occurring snippets of Neanderthal DNA may have been very useful for human adaptation when it comes to protecting our ancestors against viruses.

'Poison-Antidote' Model

After compiling a list of over 4,500 modern human genes that interact with viruses, researchers identified 152 fragments of genes that were also present in Neanderthals. These genes are the ones that interact with RNA viruses such as HIV, influenza A, and hepatitis C, suggesting that the genes that humans inherited from Neanderthals helped the ancient humans to fight off the viruses that the Neanderthals were already accustomed to.

In a "poison-antidote" model of gene swapping between the two species, the Neanderthals passed on to the humans both the viruses as well as the right tools to fight them with.

“It made much more sense for modern humans to just borrow the already adapted genetic defenses from Neanderthals rather than waiting for their own adaptive mutations to develop, which would have taken much more time,” said study co-author David Enard.

Neanderthal DNA In Europeans

What’s interesting about the researchers’ find is that the Neanderthal DNA-based adaptation was evidently especially strong among modern-day Europeans, suggesting that the genetic swapping between Neanderthals and modern-day Asians likely involved different viruses. It makes sense, according to researchers, as the interbreeding between humans and Neanderthals occurred at different times and in different places, thereby possibly involving different viruses each time they interbred.

Apart from shedding light on the gene swapping between humans and Neanderthals, the researchers’ study also showed how ancient diseases and epidemics can be detected through studying a species’ genome even if the virus or disease is already long gone.

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