Humans are born as physiological fetuses to allow further growth of the skull. There is a natural limit to how early a child can be born, and therefore a natural limit on the size of heads. Human females have adapted wide hips to account mainly for the size of the brain, but there is a practical limit to that as well. The cesarean section will perhaps allow further increase in human intelligence.<p>If the hip-fat theory is correct, then other bodily fats should have a similar effect. I am guessing I could find data that suggests large-assed females actually have children with lower IQs, though I doubt I could get a grant for that.