" One of the most important adaptations for human running is our unique ability to cool by sweating instead of panting, thanks to millions of sweat glands combined with a lack of fur. Most mammals have sweat glands on just their palms, but apes and Old World monkeys have some sweat glands elsewhere on their bodies, and at some point in human evolution we exuberantly augmented the number of the glands to between 5 and 10 million. "

― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease