 The mitochondrial genome of the human species of body lice ( Pediculus humanus humanus ) , the head louse ( Pediculus humanus capitis ) and the pubic louse ( Phthirus pubis ) fragmented into a number of <unk> , at least seven million years ago . Analysis of mitochondrial DNA in human body and hair lice reveals that greater genetic diversity existed in African than in non @-@ African lice . Human lice can also shed light on human migratory patterns in pre @-@ history . The dominating theory of anthropologists regarding human migration is the Out of Africa Hypothesis . Genetic diversity accumulates over time , and mutations occur at a relatively constant rate . Because there is more genetic diversity in African lice , the lice and their human hosts must have existed in Africa before anywhere else . 
