How Neanderthals went extinct while humans survived is one of the biggest questions in our species' history. Researchers have long wondered if our closest extinct relatives might have succumbed to viral infections that plague modern humans today.

That thinly evidenced theory, first proposed in 2010, has become a little more plausible with the discovery of ancient DNA from three viruses found in 50,000-year-old Neanderthal bones, unearthed at Chagyrskaya cave in Russia.

Previously, researchers suggested that infectious diseases could have contributed to the Neanderthals' demise based on signs in viral and bacterial genomes of when those pathogens first infected humans – long enough ago that humans could have carried pathogens from Africa and passed them on to Neanderthals in Europe.

Otherwise, researchers have used mathematical models to simulate the spread of diseases between Homo sapiens and Neanderthals (H. neanderthalensis), and their differing immunity.