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Modern humans have inherited genetic defenses against viral diseases such as hepatitis and Neanderthal flu when the two species crossed 50,000 years ago, according to a study.
Neanderthals mysteriously disappeared about 40,000 years ago, but before disappearing, they crossed paths with another human species that was just beginning to spread around the world.
As a result of these old discussions, many Europeans and modern Asians today host about two percent of Neanderthal DNA in their genome.
"Our research shows that a significant number of frequent Neanderthal DNA extracts have been adapted for a very good reason," said Dmitry Petrov, a professor at Stanford University in the United States. United.
"The Neanderthal genes have probably afforded us some protection against the viruses our ancestors encountered when they left Africa," Petrov said.
"It was much more logical for modern men to borrow genetic defenses already adapted to Neanderthals rather than wait for the development of their own adaptive mutations, which would have taken much longer," David said. Enard, a former postdoctoral fellow at Petrov's laboratory.
The results, published in the journal Cell, correspond to a model of "anti-poison" gene exchange between two species. In this scenario, Neanderthals bequeathed to modern humans not only infectious viruses, but also genetic tools to fight against invaders.
"Modern humans and Neanderthals are so closely related that it was not really a genetic barrier to prevent these viruses," said Enard, who is now an assistant professor at the University of California. University of Arizona.
"But this proximity also meant that Neanderthals could send us their protection against these viruses," said Enard.
In this study, scientists have shown that the genetic defenses that Neanderthals have passed on to us are against RNA viruses, which encode their genes with RNA, a molecule chemically similar to DNA.
Scientists have reached their conclusions after compiling a list of more than 4,500 genes in modern humans, known to interact one way or another with viruses.
Enard then checked his list against a sequenced Neanderthal DNA database and identified 152 fragments of these genes from modern humans, also present in Neanderthals.
Scientists have shown that in modern humans, the 152 genes inherited from Neanderthals interact with HIV, influenza A and Hepatitis C – All types of RNA viruses.
The researchers concluded that these genes helped our ancestors fight the old RNA viruses they had encountered while leaving Africa.
The Neanderthal genes that they have identified are present only in modern Europeans, suggesting that different viruses have influenced genetic exchanges between Neanderthals and the ancestors of today's Asians.
It is thought that miscegenation between Neanderthals and modern humans occurred several times and at several places in prehistory, and different viruses were probably involved in each case.
The results show that it is possible to analyze the genome of a species and find traces of old diseases that previously affected it, even when the viruses responsible for these diseases disappeared.
This technique would work particularly well for RNA viruses, whose RNA-based genomes are more fragile than their counterparts in DNA, Enard said.
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