Some people today might think hairless lower regions are sexy but apparently our ancestors thought the more the merrier, the bushier the better, a plush, hairy genital region was a major turn-on.
Why humans alone have pubic hair
15:15 27 February 2009
Being Human
Andy Coghlan, reporter
Robin Weiss, a virologist at University College London, had an intimate revelation in the shower recently.
Public hair, he decided, developed as a sexual ornament. It became bushy and prominent after our ancestors split from non-human primates, he says, when we lost most of our other body hair. As it disappeared, human pubic hair acquired a new role as a prominent sexual ornament, a visual signal of sexual maturity and possibly a reservoir for sexual pheromones.
The bushier and coarser it became, according to Weiss's theory, the more attractive you were.His theory, published in the Journal of Biology (DOI: 10.1186/jbiol114) is not backed by new scientific data but is essentially a new interpretation of results published in 2007, on how the
"crab" lice that infect pubic hair in humans are related to those that now live on the fur of gorillas.
Our ancestors and those of gorillas went their separate evolutionary ways at least 7 million years ago. But the lice that infect gorillas and modern humans didn't become different species until much later - around 3.3 million years ago, as revealed through research in 2007 by
David Reed of the University of Florida Natural History Museum in Gainesville.
So why didn't the lice become different species 7 million years ago, when we and gorillas followed separate evolutionary paths?
Reed's investigations of lice DNA led him to conclude that the ancestors of lice which now live on gorillas (
Pthirus gorillae) originally died out in our own ancestors. But the gorilla lice crossed back into the human lineage about 3.3 million years ago, then evolved into today's pubic lice (
Pthirus pubis).
Reed argued that the lice returned to us through physical contact, perhaps when human ancestors slept in vacated gorilla nests or came into contact with the gorilla lice while handling gorilla meat.
Weiss agrees, but thinks we re-acquired the pubic lice because our pubic region had been evolving, starting off as smooth vestigial fur but eventually becoming coarse and bushy enough for the gorilla lice to grip on to. Essentially, the coarser hair gave the gorilla lice a reason to return to the human lineage. Weiss thinks this happened after we lost most of our other body hair, and that the bushiness and coarseness evolved as an advertisement of sexual maturity in our otherwise naked forbears.
To back up his case Weiss visited zoos to peer at the groins of our closest relatives. He noticed that in other great apes, hair in the pubic region was if anything much finer and shorter than elsewhere on the body - the opposite of the human situation. It supported his argument that human pubic hair is different and probably unique, both in its evolution and in its physical appearance and purpose.
Weiss admits that the theory is pure speculation. However, the good news, he says, is that the days of crabs may themselves be numbered because of an increasing fashion for shaving off pubic hair.
"Thus there may be a health benefit to this emerging sexual lifestyle," he writes.
