Isn't there some evolutionary pressure, and it could be that it applies to primates in general and not just humans, for big-headedness? Like if big-headedness didn't help, then you could imagine two populations, A and B, where A has big heads and B doesn't. B loses fewer mothers during childbirth. Those mothers can then give birth more times, making B grow faster than A, so after enough time, we're all medium-head B-people. But somehow we ended up with me not being able to hold my head up in baby pictures. What gives?