" Most animals in the tropics, including carnivores, rest sensibly in the shade during the middle of the day. Since bipedal hominins cannot sprint very fast, the ability to walk long distances during the day without overheating was probably a critical adaptation for early hunter-gatherers in Africa, allowing them to forage when carnivores were least likely to kill them. The "

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