Humans are the world's best long-distance runners because of our unique ability to sweat.

Humans possess between 2 million and 4 million eccrine sweat glands distributed across nearly the entire body surface. This physiological trait is unique among primates and most mammals, who typically rely on panting or have sweat glands limited to their paw pads. Panting requires an animal to stop or slow down because it interferes with the heavy breathing needed for intense physical exertion.Anthropologist Louis Liebenberg and biologist Bramble and Lieberman from Harvard University have documented how this cooling system enabled 'persistence hunting.' This strategy involves tracking an ungulate like a kudu or zebra during the hottest part of the day for 2 to 5 hours. While the animal can sprint away, it eventually suffers from hyperthermia because it cannot shed heat fast enough while running.Evolutionary changes roughly 2 million years ago in Homo erectus, such as longer legs and the loss of body hair, further optimized this endurance. Research published in the journal 'Nature' suggests that these adaptations were critical for the transition to a meat-heavy diet. By maintaining a stable core temperature through evaporation, humans can sustain a steady trot that eventually pushes even the fastest four-legged sprinters to physiological collapse.