Kangaroos jump, ostriches stride, and apes support themselves on their hands. But a Homo sapien is the only species that can walk elegantly on two feet the whole time. This function goes hand in hand with the development of a larger brain.
AT THE REAR
Nothing would work were it not for our behinds. The three muscles in this group - gluteus maximus, medius and minimus - are an evolutionary stroke of genius. They stabilize the center of the body and allow us to stand up straight - and to run and run.
ON THE INSIDE
During a marathon, a runner produces and uses 165 pounds of adenosine triphosphate, a kind of internal biodiesel. The energy expended is the equivalent to 2 pounds of TNT.
Humans get natural benefits from running. If the body has to produce a peak performance beyond the pain barrier, it releases endogenous opioids, which are addictive.
ON THE OUTSIDE
Any number of animals would beat us in a sprint. But in terms of stamina, we’re out there on our own. We have no fur, but 3 million sweat glands keep us cool over long distances. And which body part has the most sweat glands? The soles of the feet.