Bruce Bower reports on Andrew Kitchen and colleagues’ work, establishing the divergence time of human head lice and body lice. The idea is that this divergence must have happened after the time when people started habitually wearing clothing.
An earlier analysis of mitochondrial DNA from the two modern types of lice indicated that body lice evolved from head lice only about 70,000 years ago. Because body lice thrive in the folds of clothing, they likely appeared not long after clothes were invented, many scientists believe.
Though well suited to gauging the timing of evolutionary events, mitochondrial DNA is a relatively small part of the genome. Kitchens team examined both mitochondrial and nuclear DNA samples from head and body lice, yielding the much older, and presumably more accurate, estimate of when body lice first evolved.
I’ll be interested to see this research when it is published. It’s a clever idea, but I’ve not yet been convinced that clothing is really the relevant ecological factor. Many tropical people have never worn clothes, more than a little strip around the waist. I wonder whether the reduction of body hair may have been more important, and if so, how long it took for the emergence and dispersal of a new louse species through the human population.
Plus, it’s sort of hard to believe people lived in Europe and northern China in the early Middle Pleistocene without any kind of clothing. Unless they had fur.