Where Do Lice Come From?
Sucking lice have been sucking primate blood for at least 25 million years.
So, where did we pick up these unwanted blood suckers in the first place? All signs point to a human–ape connection, and "connection" may mean something more tangible than an evolutionary link. Some studies suggest interaction between early Homo species and gorillas, and also between early Homo species and us.
The lice we carry around are sucking lice. That’s pretty self explanatory. Two subspecies we harbor, head lice and body lice, belong to the Pediculus genus (Pediculus humanus capitis and Pediculus humanus humanus, respectively). The other species we harbor (Pubic) is a member of the genus Phthirus. Our closest living relatives, the chimpanzees, harbor Pediculus, as well, while gorillas are home to another Phthirus species. In other words, we share a genus with each of them....
Here is a great article that digs deep into the history of lice:
Where Do Lice Come From