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Paranthropus boisei
The species responsible for human genital herpes?
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Meet the hominin species that gave us genital herpes | University of Cambridge
One of the best pieces of evidence for common descent is the way the genetic relationships between our obligatory parasites and those of their related species, almost exactly maps onto the relationship between our genome and those of our own relatives.
I have previously written about how the evolution of our lice can be mapped onto our own evolution and divergence from the other apes.
Another parasite which, if anything, is even more obligatory that lice is the herpes virus, and like our lice there is not a close but not perfect match with our evolution. All primates are host to two versions of the herpes simplex virus, HSV1 which in humans causes cold sores and HSV2 which causes genital herpes in humans. The latter is normally regarded as a sexually transmitted disease.
Whereas we can make a direct link between two of our lice - the head louse (
Pediculus humanus capitis) and the body louse (
Pediculus humanus humanus) - and the body lice of chimpanzees (
Pediculus schaeffi), there is no such clear link with the pubic louse and an immediate ancestor. We can see how our body louse became our head louse when we lost our body hair and it had nowhere else to go and how it then diverged into two subspecies when we started wearing clothes to become our body louse as well. However, the closest relative of our pubic louse (
Phthirus pubis) is the gorilla body louse (
Phthirus gorillae)! Somewhere in our evolution, the gorilla louse jumped the species barrier, otherwise it, or as descendent, would be present on chimpanzees too. The degree of divergence is enough to show that this wasn't a recent event, but somewhere, after we diverged from the chimpanzees, one of our ancestors got close enough to a gorilla to catch pubic lice from it!