When did humans start wearing clothes, and what did lice have to do with it?

Nobody knows the exact year, but the best guesses run from about 40,000 years ago to, in the most daring estimates, 3 million. What makes the question answerable at all is an unlikely witness: the human body louse. Clothes rot much faster than stone, bone or metal, so the earliest garments left no trace, and what we know about them is inferred. Lice offer a different kind of clue.

Human body lice cannot survive outside clothing; away from it they die within a few hours. Most of their eggs are secured in clothing. That means the body louse could only have become its own kind of louse once people were wearing something it could live in. Geneticists estimated when the body louse split from the head louse and found a date between 40,000 and 170,000 years ago. Reading it backwards, clothes were already in use by then.

The method has a catch. Later work found that body and head lice are almost genetically identical; they look the same and will interbreed in the lab, and the difference is probably a regulatory response to environmental signals rather than a deep genetic divide. The louse clock is therefore a hint, not a stopwatch. Direct evidence is welcome: in 2021 scientists reported signs of clothes being made 120,000 years ago in Morocco, and a needle at least 50,000 years old turned up in Siberia's Denisova Cave, made by Denisovans.

Today clothing is a feature of every known human society, and it does far more than keep us warm: it also expresses status, identity and personal style.