Roughly 8 million years ago, some apes stood up and started human evolution.

Okay, that’s not really what happened. But it is a fair characterization of the way scientists identify the oldest fossils likely to be human ancestors. Upright walking apes mark the start of the study of human evolution in many texts and classes.

That’s because bipedalism, or two-legged locomotion, was the first major evolutionary change in human ancestors, which is evident from bones. Other distinguishing fe