Page "Hair" Paragraph 29

It was expected that dating the split of the ancestral human louse into two species, the head louse and the pubic louse, would date the loss of body hair in human ancestors.

However, it turned out that the human pubic louse does not descend from the ancestral human louse, but from the gorilla louse, diverging 3. 3 million years ago.

This suggests that humans had lost body hair ( but retained head hair ) and developed thick pubic hair prior to this date, were living in or close to the forest where gorillas lived, and acquired pubic lice from butchering gorillas or sleeping in their nests.