FTA: Which step was more important in our evolution: bigger brains or bipedality?
Bipedality

Paleoanthropologist Carol Ward excavates at a field site. Courtesy of Carol Ward

Clearly, what is the most unusual, distinctive feature of humans today is our incredible and amazing brain. Our brains can do things that other animals on this planet have never even come close to doing. It gives us culture and language—and all those things that really make us distinctive today as a species. But the fossil record tells us that we began to walk upright on two feet maybe between 6 and 4 million years ago. Brains in early hominins really don’t start to get large until after 2 million years ago, so for the first two-thirds of human evolution, brain size change wasn’t really a major event.