One theory of human evolution states that our ancestors began eating meat about 2 million years ago, whose caloric and fat density allowed the enlargement and development of their brains.
Hominids didn’t begin using stones and sticks for hunting until about 200,000 years ago. So between 2.3 million and 200,000 years ago, our original strategy was to run game animals to death in order to feast upon them. Sweating was the key factor in the ability to run long distances to wear out quarry without overheating. Game animals, who cannot sweat, become overheated over time and are at risk of damaging themselves or dying if they don’t stop to catch their breath, allowing early hunters to catch and dispatch them. Animals that do not walk upright cannot fully extend their diaphragms to take deep breaths until they stop running.
Some tribal peoples still take part in persistence hunting and there is evidence that the strategy was utilized all over the world in the distant past. This helps us to understand why several aspects of human development — walking upright, hairless skin, sweating, and the ability to run long distances — appear to have evolved simultaneously.
Via Big Think