Human lice likely co-evolved with people. Our primate relatives harbor their own species of lice. Recent evidence is suggestive that body (clothing) lice evolved from head lice. The timing of this change is quite controversial. Whereas certain experts argue that the divergence occurred many thousands of years ago, others believe that this split was far more recent. Yet other experts claim that head lice and body lice are the same species, but this fails to explain the dramatic differences in the physiology, ecology, epidemiology and public health significance that are characteristic of these two kinds of lice.
Female human head louse, Pediculus humanus capitis.
Photo by Gilles San Martin (Flickr: Female human head louse) [CC-BY-SA-2.0], via Wikimedia Commons