Man seems an unlikely survivor of the primal world. We don’t have claws like Dinofelis, deadly teeth like Sabertooth, thick skin like early rhinos, or the huge size of a mammoth. How did we escape becoming the favorite snack to all these better-equipped predators?
One way is we learned to run. Not the sprint of a gazelle who can take off and flee at an outrageous pace. Like her, many Pliocene animals relied on quickness and speed to escape predators or catch prey. Few had resources beyond that initial sprint.
We weren’t as swift as our four-legged competitors, but when the gazelle quickly tired and had to stop to regenerate, we kept running. In fact, even then, we could run great distances which enabled us to chase down prey when they tired and overheated.
We learned to pace ourselves for long-distance running. Paleoanthropologists noted that by 2 million years ago, our genus Homo already had long slender legs and short(er) arms. These are traits that serve the runner. Long legs for a better stride with an Achilles’ tendon that anchors the calf muscles to the heel and stores and releases energy during running–unnecessary for ordinary walking. Shorter arms because we no longer headed for trees as the first means of escape.
By then, we had developed millions of pores for sweating, lost much of the hair and fur that keep the heat of exercise in our bodies, and evolved a cooling system in our heads to keep that most vulnerable of parts from overheating. There was even a snazzy ligament attached to the base of the skull to keep our heads steady as we ran.
Most important is our gluteus maximus–the muscle of the buttocks. Chimps don’t have the powerful, pronounced one that we do, the physical attribute that stabilizes the trunk as we lean forward to run.
Before 2 million years ago–during Australopithecus’ time–none of these traits were prominent. Maybe that’s why they disappeared and Homo lives on.