Ancient Neanderthal and Denisovan Viruses Discovered in Modern Human DNA

Could ancient viruses impact us even today? It turns out that they can. Scientists have discovered ancient viruses from Neaderthals in modern human DNA, revealing further insight into the similarities between Neanderthals and humans.

Around eight percent of human DNA is made up of endogenous retroviruses (ERVs), which are DNA sequences made from viruses which pass from generations to generation. This is part of the 90 percent of our DNA with no known function that's sometimes called "junk" DNA.

"I wouldn't write it off as 'junk' just because we don't know what it does yet," said Gkikas Magiorkinis, one of the researchers, in a news release. "Under certain circumstances, two 'junk' viruses can combine to cause disease--we've seen this many times in animals already ERVs have been shown to cause cancer when activated by bacteria in mice with weakened immune systems."

In this latest study, the researchers compared genetic data from fossils of Neanderthals and another group of human ancestors called Denisovans to data from modern-day cancer patients. In the end, they found evidence of Neanderthal and Denisovan viruses in the modern human DNA. This suggested that the viruses originated in our common ancestors more than half a million years ago.

Currently, the scientists are looking to further investigate these ancient viruses, which belong to the HML2 family of viruses, for possible links with cancer and HIV. More specifically, they're looking at whether these ancient viruses affect a person's risk of developing diseases such as cancer.

"Using modern DNA sequencing of 300 patients, we should be able to see how widespread these viruses are in the modern population," said Robert Belshaw, one of the researchers, in a news release. "We would expect viruses with no negative effects to have spread throughout most of the modern population, as there would be no evolutionary pressure against it. If we find that these viruses are less common than expected, this may indicate that the viruses have been inactivated by chance or that they increase mortality, for example through increased cancer risk."

The findings are important for better understanding the role that these viruses play in modern health. In addition, they show a bit more about our ancient past.

The findings are published in the journal Current Biology.