My husband is in school for anthropology, and he mentioned this the other day. He had learned about a theory that the increasing size of humans' skulls should have curbed the population growth, due to many babies not being able to be born vaginally (resulting in death of baby and mom, I assume). Yet, when we developed the c-section method, we were able to overcome this, and population continues to increase. Does this make sense? My husband explained it much more eloquently Interesting stuff, though.