No Tarzans Here: Earliest Humans Quickly Lost Their Ape-Like Climbing Abilities

When the earliest human ancestors left the trees and struck out to make a new life for themselves on the ground, there was no going back, a new study suggests. Researchers examined the ankle bones of those early people and compared them to those of chimpanzees, and say that by 4 million years ago the proto-humans were no longer adapted for skillful tree climbing.