Exercise Physiology - Human Evolution

Human Evolution

Humans are specifically adapted to engage in prolonged strenuous muscular activity (such as efficient long distance bipedal running). This capacity for endurance running evolved to allow the running down of game animals by persistent slow but constant chase over many hours.

Central to the success of this is the ability of the human body, unlike that of the animals they hunt, to effectively remove muscle heat waste. In most animals, this is stored by allowing a temporary increase in body temperature. This allows them to escape from animals that quickly speed after them for a short duration (the way nearly all predators catch their prey). Humans unlike other animals that catch prey remove heat with a specialized thermoregulation based on sweat evaporation. One gram of sweat can remove 2,598 J of heat energy. Another mechanism is increased skin blood flow during exercise that allows for greater convective heat loss that is aided by the upright posture. This skin based cooling has involved humans in acquiring an increased number of sweat glands, combined with a lack of body fur that would otherwise stop air circulation and efficient evaporation. Because humans can remove exercise heat, they can avoid the fatigue from heat exhaustion that affects animals chased in persistence hunting, and so eventually catch them when they fatigue from heat exhaustion due to being forced to move constantly.