A University of Utah study showing how lice evolved with the people they infested reveals that a now-extinct species of early human came into direct contact with our species about 25,000 years ago and spread the parasites to our ancestors. The study found modern humans have two genetically distinct types of head lice. One type is found worldwide and evolved on the ancestors of our species, Homo sapiens. The second type is found only in the Americas, evolved on another early human species (possibly Homo erectus) and jumped to Homo sapiens during fights, sex, sharing of clothes or perhaps cannibalism.
