For its “human edge” series, NPR looks at how slow and steady running won the race:
“Most animals are designed for speed, for power, not for endurance,” Lieberman explains, as we make a turn onto the bridge. “And we are a special species in having been selected for endurance, not speed.”
So we grew longer legs and lighter feet; the joints in the legs and pelvis got bigger to absorb a lot of impact; and we grew a bigger butt muscle.
Lieberman says these and other changes allowed us to run down and exhaust prey, like antelopes. He notes that “persistence hunters” in Africa have been known to do that. And the payoff would’ve been big for early humans: lots of high-calorie meat to feed a bigger brain.
Lieberman is creating a computer model of how we run — in contrast to how other primates might run:
“There are no humans out there with faces as large as Neanderthals,” he explains as he rummages through a cupboard, “so people wear weights in their mouths, which then changes the center of gravity of their head.”
Understanding head control is important. If you don’t keep your head still, you can’t focus your eyes. Lieberman says modern humans, unlike apes, have a special muscle that connects each arm to the neck and head. As you swing your arms, they become counterweights to stabilize your head.