Hominins lose their fur
Naked skin and millions of sweat glands make a primate the best long-distance cooler in the animal world.
- When
- —
- Duration
- 600 thousand years
- Known to
- ± 300 thousand years
- Era
- Early Pleistocene, Quaternary
Humans have roughly the same density of hair follicles as a chimpanzee but the hairs are vestigial, and we carry two to four million eccrine sweat glands — far more than any other primate. The combination allows sustained heat dumping that a panting quadruped cannot match. Dating the change relies on an indirect and rather elegant proxy: body lice, which live in clothing, diverged from head lice only much later, while the genetic split between human and chimpanzee lice sets a bound on when the fur went.