Baby humans are premature, fetal apes

My dad calls the first few months of a baby's life "the necessary larval stage". I've heard other people refer to it as "the fourth trimester". Basically, newborn human babies are pretty useless, as far as baby animals go. This is especially true in comparison to baby apes, who come out of the womb at a much higher level of development. Scientific American has an excerpt from an upcoming book by Chip Walter that talks about this fact and its connection to two key moments in human evolution — the development of bigger brains (and thus, bigger heads) and walking upright (which has the side effect of creating a narrower birth canal).