A new study indicates that some 50,000 years ago, Neanderthals were infected with three types of viruses still affecting human beings today. The scientists identified traces of adenovirus, herpesvirus, and human papillomavirus in DNA from two Neanderthal male skeletons found in the Altai mountains in Russia. These viral pieces could finally be the remains of the oldest known human viruses.
The findings also raise questions about whether infectious diseases played a role in the eventual extinction of Neanderthals, our closest ancient human relatives. Neanderthals lived from 400,000 years up until 40,000 years ago before they vanished, and while their extinction hasn’t been formally explained, several possible factors are thought to be at play including competition with modern humans, climate changes, and transfer of diseases.
“This DNA contains a mixture of various sources, including from the Neanderthal, plus bacteria, fungi, and viruses that may have infected them,” says Marcelo Briones, an author of the study and a genome researcher at Brazil’s Federal University of São Paulo. “The degree of viral genome changes matches the age of the Neanderthal bones, showing they are not modern contaminants.”
These results do not prove that virulent viruses were what tipped the scales for Neanderthal extinction, but they do show that such ancestors could be infected by diseases still affecting humans today. Between 1-4% of DNA in modern non-Africans originates from Neanderthals because of ancient interbreeding.
“We show evidence that viral diseases could have crossed species boundaries and circulated between archaic and modern humans,” Briones said. “This could have facilitated the exposure of Neanderthal populations to pathogens carrying deleterious genes that were circulating in modern humans.”