A related link was posted in this comm not too long ago.. It tries to address why female chimps would live past reproductive age, to begin with.

The catch here is that adult male chimps stay in the clan of their parents, while the female ones migrate to other clans. And this creates an asymmetry between old vs. newer adult females in the same clan:

• from the PoV of an older female, the children of younger females are likely also the children of her sons, thus her relatives/grandchildren.
• from the PoV of a newer female, the children of the older females are not relatives.

In situations where food is short, it’s advantageous for the clan to have less children: every new child spreads the food resources thinner, and puts at risk the lives of the other children. But that pressure to stop having children only affects the older female, because it puts at risk the lives of her grandchildren; for the newer females it’s more like “why would I stop having children? For the sake of my in-laws? Screw them!”.

Evolution solved this through menopause; you got the older females still alive, gathering resources, and taking care of the children of the clan, but they aren’t bearing new children.