As a side note, humans have evolved to be quite possibly the best long distance runners in the entire animal kingdom due to adaptions we have at chasing prey on the African Savanna. Given enough distance, a well trained endurance runner can out run a dog, a horse, any large predator, or any migratory animal that lives on land. We cool ourselves, supply glycogen to our slow twitch muscle fibers, and run at slow speeds more efficiently than just about any other animal. Almost all of our physical characteristics are adapted to running long distances and cooling ourselves as we do so. As sprinters though, we are quite mediocre.