Detecting ancient epidemics in present human genomes
Modern humans migrated out of Africa about 60,000 years ago. As they started colonizing the new environments of Eurasia, they found that they were not the first humans to have ventured out of Africa. Neanderthals had preceded them and colonized the cold prehistoric Eurasia hundreds of thousands of years before. Modern humans and Neanderthals then not only came in contact with each other, but also interbred with each other. This interbreeding, however, hid an invisible poison: Neanderthal viruses that rapidly infected modern humans. At the same time however, Neanderthals gave us the antidote as a gift: genes from their genome that gave us resistance against their own viruses. Remarkably, these Neanderthal genes are still present is specific modern human populations to this day, and make it possible to identify which viruses Neanderthals infected modern humans with when they interbred. In other words, evolutionary genomicists have opened a new window on long-gone and forgotten epidemics.