Evolution of Menopause

Science & Technology at Scientific American.com: Children Took a Toll in Pre-Industrial Societies, May Have Driven Evolution of Menopause -- The high costs of too many offspring may have shaped the psychology of women and could explain plunging modern-day birth rates

This one doesn't seem to add up to me. Evolution has always seemed relatively insensitive to lifespan. Lifespan varies widely between creatures of similar complexity. Take some very evolved squid that only live one year or turtles that live 300.

Consequently, menopause would not seem to be a huge advantage or disadvantage, especially given that until very recent times average lifespan was much less than 50 years.

It would also seem that beyond age two to four, the survival of offspring would seem uncorrelated to the survival of the mother, especially given humans have always seemed to live in larger social units.

I guess I would need to do some more research to see if we believe monkeys and other primates live long enough to reach an equivalent menopausal age to understand if this truly is a recent adaptation. Assuming the article is correct, then what would the selection pressure be?

Perhaps if children born after age 50 had a negative impact on the success of other offspring that could create an evolutionary advantage for those families who didn't birth children at that age?

Or perhaps if the survival of early matriarchal societies were improved by the presence of elder matriarchs, then those that were no longer child-bearing and thus lived longer would confer some advantage to the society?