Neanderthals shared their viruses with Homo sapiens humans — but also passed on their genes for coping with these pathogens.
Modern Asian and European human genomes are made up of 2–3% Neanderthal DNA, a relic of prehistoric mating between the two hominin groups. To learn more about the genetic impact of this exchange, David Enard from the University of Arizona in Tucson and Dmitri Petrov at Stanford University in California looked for Neanderthal DNA in regions of the modern human genome that code for proteins that interact with viruses.
The researchers found that Neanderthal DNA was more common in these virus-fighting areas than elsewhere in the modern human genome. These sections of DNA also tended to be longer, and were found more frequently in modern humans, than other Neanderthal segments.
These results suggest that Neanderthal DNA in these genetic regions was advantageous, probably because it helped early Homo sapiens to fight off Neanderthal viruses. The authors say that studying DNA patterns in early hominins could illuminate the ancient epidemics that these populations faced.