A new study traces the possible origin of some human papillomavirus 16 (HPV16) lineages, some of which are oncogenic, to Neanderthals or Denisovans, Vox reports.
Researchers from the Catalan Institute of Oncology analyzed the genetic diversity of existing HPV16 strains, and compared the phylogeography of HPV16 and modern humans to find that codivergence with modern humans only accounts for a third or less of the virus' current distribution, as they report in Molecular Biology and Evolution. Instead, they hypothesized that some HPV16 viruses evolved with another archaic human population and then later infected the ancestors of modern humans.
In particular, their analyses indicated that an ancestral HPV16 virus infected the common ancestor of Homo sapiens and Homo neanderthalensis about 500,000 years ago and when the host lineages diverged, so did the viral HPV16 lineages. But when a group of modern humans migrated out of Africa and encountered Neanderthals, they also encountered and became infected with the Neanderthal lineage of HPV16. That lineage then spread throughout modern human populations in Eurasia and the Americas to become dominant. The Catalan team further notes that the interaction between the viral and host genotypes could account for the differences in cancer risk that HPV16 poses.
"The results mean that humans have been living with this STD for a long time," Vox adds. "And it's a notable chapter in our human history."