In order to find evidence of ancient diseases that once affected our species, researchers at Stanford University combed through the human genome, zooming in on 4,500 genes in modern humans that are known to interact in some way with viruses, which the researchers compared against a database of sequenced Neanderthal DNA.
Now they have found that some parts of Neanderthal DNA appear in modern humans, including Europeans and Asians. Interbreeding has left many Europeans and Asians with 2%Neanderthal DNA. There, they identified 152 fragments of the modern humans genes were also found in Neanderthals.
"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 David Enard, an evolutionary biologist, now at the University of Arizona. Humans also became exposed to new Eurasian viruses for the first time - viruses that Neanderthals had built up defenses against. When they arrived, they met up with Neanderthals who, along with their own ancestors, had been adapting to that geographic area for hundreds of thousands of years. Luckily, the Neanderthals' immune systems evolved genetic defenses against these viruses that were also passed on to humans, according to a study reported in Cell.
Researchers think their findings - published this week in the journal Cell - could inform investigations of ancient epidemics. However, this interbreeding between ancient humans and Neanderthals offered us immunity against ancient viral epidemics.
"It is anything but a stretch to envision that when present-day people got together with Neanderthals, they contaminated each other with pathogens that originated from their particular surroundings", David Enard, a colleague educator in nature and developmental science at the University of Arizona, said in a news discharge.
For a very long time anthropologists, evolutionists have claimed that Neanderthals and Homo sapiens existed in parallel, without mixing, and if they had sexual contact, it could not produce fertile offspring capable of reproduction.
To test their hypothesis, the scientists have compiled a list of more than 4500 genes in modern humans that are associated with virus protection. "We trust that protection from particular RNA infections given by these Neanderthal groupings was likely a major piece of the objective behind their specific advantages".
Recently, British researchers have concluded that Neanderthals had a highly developed medicine, which helped them to survive severe injuries.
This technique would work especially well for RNA viruses, whose RNA-based genomes are more frail than their DNA counterparts, Enard said.
"You can think of these genetic adaptations like footprints from long-extinct dinosaurs preserved in fossilized mud. Our method is similarly indirect: Because we know which genes interact with which viruses, we can infer the types of viruses responsible for ancient disease outbreaks".