It is now well established that as modern humans migrated out of Africa, we mated with the Neanderthals already present in the Middle East and shared a few of our genes. But it wasn’t only our genes that we shared. We also managed to leave a few, shall we say, more unsavory parting gifts, in the form of sexually transmitted infections.
Most sexually active people around the world will at some point be infected by the human papilloma virus, and some will be repeatedly infected. There are over 100 different types of HPV, most of which are benign and relatively harmless, but there are at least a dozen strains of the virus that have been linked to more serious conditions, such as cervical and oral cancers.
The two main culprits for this are HPV16 and HPV18, which together cause the vast majority of HPV-induced cancers. It now seems that we may have been swapping HPV16 with Neanderthals when we started interbreeding tens of thousands of years ago. Research, published in the journal Molecular Biology and Evolution, has managed to trace the ancestry and timing of the HPV16 family tree in more detail than ever before, and what they found was fascinating.
It seems that the virus was already infecting our humanoid ancestors before we split into the separate linages that gave rise to modern humans on one side, and Neanderthals and Denisovan on the other. The HPV16 then appears to have evolved in sync with these two branches of our own family tree, the two strains themselves diverging to form the A variant that infected Neanderthals, and the B/C/D variant that infected modern humans.
That is until the two human species met between 60,000 and 100,000 years ago when modern humans started their epic journey around the globe. At this point, it appears that humans became infected with the HPV16 A variant, and then took it with them as they migrated. This fits almost perfectly with the fact that while the HPV16 A variant is almost non-existent in sub-Saharan Africa, as the modern human ancestors from these regions didn’t do the dirty with Neanderthals, the diversity of HPV is at its greatest within East Asia, where both species are well known to have been mating with each other.
“Oncogenic [tumor causing] viruses are very ancient. The history of humans is also the history of the viruses we carry and we inherit,” explains Ignacio Bravo, who co-authored the paper. “Our work suggests that some aggressive oncogenic viruses were transmitted by sexual contact from archaic to modern humans.” So it seems that we may all be a little closer to the Neanderthals then we thought before.