The Perfect Runner

Millions of years ago, before we were hunters, we were hunted, preyed upon by stronger, faster animals. So, how did we survive the harsh environment of Africa's Great Rift Valley and evolve to dominate our world? Evolutionary biologists believe it has less to do with our brains than with our feet, legs, sweat glands, and hairless skin. Join us as we circle the globe and explore how two-and-a-half million years of evolution made us a super-specialized species, able to run greater distance, for longer periods, than anything else in nature.