At some point in our distant past, humans gained the habit of wearing clothing rather than walking around naked. Certainly, clothing became essential once humans left Africa for colder climates. But how long ago did this occur? David Reed of the University of Florida and his colleagues used a novel method for answering that question: they studied lice.
Lice that make their living on human bodies currently come in three flavors: head lice, body or clothing lice, and pubic lice. This was not always so. Before humans lost their body hair, there was only one type of human louse that was free to roam from head to toe. Without body hair, the desert of bare skin confined lice to specific regions, namely the head and pubic area. Lice finding themselves stranded in these regions evolved apart from each other. Later, when humans began to wear clothing, head lice found a new way to make a living by hiding in the folds and creases of clothing. From these safe havens, they could venture forth to make a meal on the hairless regions of the human form. As with the pubic lice, body lice diverged from head lice until they became the two independent species they are today.
Reed and his team used genetic analysis to determine when head lice and body lice diverged, and came up with a range of 83,000 to 170,000 years ago. Therefore, humans began wearing clothing during approximately the same time period. This corresponds well to some of the known human migrations out of Africa.
One final note: this method looked at modern head and body lice to determine when the two species diverged. In other words, it could only answer the question of when modern humans began to wear clothing. We don’t have any head or body lice from Neanderthals, although they were known to be living in cold climates far earlier than modern humans. Extinct human species may well have taken to wearing clothing many thousands of years before modern humans did.