Found: The ancient primate we can blame for genital herpes

The backstory

One night, three scientists from the University of Cambridge were discussing the evolution of the genital herpes virus. They knew from a scientific paper from 2014 that the genital herpes virus, HSV2, originally jumped from chimpanzees to humans about 3 million years ago. Dr. Charlotte Houldcroft and her two friends and collaborators decided to see if they could determine which hominin species originally caught genital herpes virus from the chimpanzees and then spread it to our ancient ancestors. 

The method

To find out which hominin species helped the genital herpes get into our human ancestors, Dr. Houldcroft and her collaborators gathered all the fossil records from the period when HSV2 jumped the species barrier. They also had to obtain climatic data from that time to figure out where the rainforests where the chimpanzees would have been living in Africa. When they modelled all this together with the viral genetics, they found their culprit. 

• Paper in the journal Virus Evolution
• Prevalence of Chlamydia trachomatis and herpes simplex virus type 2: Results from the 2009 to 2011 Canadian Health Measures Survey

The discovery

The most likely hominin species that picked up the virus from chimpanzees is a Plio-Pleistocene hominin Paranthropus boisei, also known as the 'Nutcracker Man.' It's called that because of its thick, chunky teeth and massive jaw. Dr. Houldcroft says the most likely scenario is that there was a violent clash between the chimpanzee and the P. boisei, which spread the HSV2 virus into it. Then the P. boisei would have likely passed on the virus to our ancient ancestors via Homo erectus.