Herpes – it’s truly the gift that keeps on giving. Everyone with it (hopefully) knows from where they got it, but what about mankind? How did herpes make its way to us, as a species, in the first place? Well, according to researchers at UCSB, we got it from chimpanzees. Simplex-1 infected us some six million years ago before we split genetically, while simplex-2 “jumped” from ancestral chimpanzees to our own ancestors about 1.6 million years ago.

“The results help us to better understand how these viruses evolved and found their way into humans,” said Joel O. Wertheim, PhD, assistant research scientist at the UC San Diego AntiViral Research Center and lead author of the study. “Animal disease reservoirs are extremely important for global public health. Understanding where our viruses come from will help guide us in preventing future viruses from making the jump into humans.”

The researchers compared the HSV-1 and HSV-2 gene sequences to the family tree of simplex viruses from eight monkey and ape host species. Using advanced models of molecular evolution, the scientists were able to more accurately estimate ancient viral divergence times.

Previous models did not account for natural selection over the course of viral evolution. The results indicated that humans have been infected with HSV-1 far longer than HSV-2.

As far as how exactly HSCV-2 “jumped” from ancient chimpanzees to ancient humans, it’s not clearly stated. One can probably make some inferences, though. Modern humans, having only existed for about 200,000 years, are more or less off the hook given the dating provided by the study.

“Comparing virus gene sequences gives us insight into viral pathogens that have been infecting us since before we were humans,” said Wertheim.