Is There a Bigger Brain That Means You're More Intelligent?

The reason to change shape is when you walk upright, if you're a chimp, your body swings side to side. So we developed like gluteal muscles and other muscles that can cling to a specific shaped and sized pelvis so that we don't have to spend all that energy. And it's really strange to think that the decreasing in size of the birth canal actually was one of the factors that led to an increase in intelligence.