But this oversimplified view of human evolution is not quite right ... this stronger-legged species had evolved in such a way that its legs were capable of supporting its upper body weight.

And yet, its humerus (an arm bone) is quite human-like. Characteristics of its tibia (a lower leg bone) indicate that A. anamensis walked on two feet. This species includes "Lucy," the 3.2 million ...

This includes Lucy, a 3.2-million-year-old human ancestor discovered in Ethiopia ... But she also walked on two legs, like modern humans. Receive a weekly dose of discovery in your inbox!