Parathropus boisei was a heavyset human-like species that walked on two legs with a smallish brain and dish-like face.
It likely contracted the virus after eating infected ancestral chimpanzees, and then passed the pathogen onto us when hunted by Homo erectus for food.
Close contact between P. boisei and our ancestor Homo erectus would have been fairly common around sources of water, such as Kenya’s Lake Turkana, the researchers found.
This provided the opportunity for the genital herpes virus to shift onto our bloodline.
‘Once this virus gains entry to a species it stays, easily transferred from mother to baby, as well as through blood, saliva and sex,’ said study coauthor Dr Charlotte Houldcroft, from the University of Cambridge.
‘The genital herpes virus would have crept across Africa the way it creeps down nerve endings in our sex organs – slowly but surely.’
Somewhere between three and 1.4 million years ago, genital herpes jumped the species barrier from African apes into human ancestors.
Scientists have previously speculated that the virus made the leap via an intermediate hominin species unrelated to humans.
Now, a team of scientists from Cambridge and Oxford Brookes universities have found that Parathropus boisei is to blame.