Foot Bone Puts Giant Leap for Mankind at 3.2 Million Years Ago

A prehistoric foot bone found in Ethiopia shows that human ancestors took a giant step forward in their evolution as much as 3.2 million years ago, U.S. researchers say.

The fossil is a fourth metatarsal, one of the long bones in the foot that connect to the toes, according to a report in the journal Science. The bone, found 11 years ago, indicates the foot had an arch, providing evidence that the species walked on two feet, instead of swinging from the trees like chimpanzees. Apes don’t have permanent arches on their feet, which gives the feet more flexibility than humans’ and makes it easier to climb tree trunks.