Most mammals share a pattern of a period of high dependency, followed by a period of pre-reproductive independence, and then adulthood. Primates share these aspects of the mammalian pattern. Yet primates have a growth spurt that is not seen in most mammals. Why?

The obstetric dilemma:

Homo was standing up, pelvis shape changing, skull size increasing.
So give birth about 3 months earlier!

Life History Theory:

You win if you maximize your own reproduction. (across individual life spans.)
So older mothers should invest more (deer and kidney fat index).
Short inter-birth interval is useful.

Problems with life history theory?

late growth spurt in humans (vs other primates) and late reproductive maturity
smallest family sizes seen in the most prosperous societies
family size in developing world
why have grandparents?

Questions: which animals have a growth spurt?

What do we mean by growth spurt?
How do you know the age or brain size of a skeleton?

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