Some recent research indicates that chimpanzees, our closest genetic relatives, do not go through menopause as humans do. For female chimpanzees, reproductive capacity declines at the same pace as the rest of the body ages, and truly ends only with death. It’s not common for human females to have children much past the age of 40, but for chimps it happens more frequently, and there’s no prolonged period of healthy life after the reproductive system shuts down. Humans are rare or perhaps even unique in going through menopause and often having years of healthy post-reproductive life on the other side. This story from New Scientist has more information.
This ties in with a Live Science story from last year about male chimpanzees preferring older females to mate with, in contrast to human males, who tend to choose younger mates. Older female chimps are still in the running as far as having chldren, whereas female humans past a certain age are not. This is a key difference between chimp and human life patterns. (And think of how some deeply ingrained aspects of the human psyche and human culture would be different if female aging were not considered to be an anti-aphrodisiac.)
This story also brings up the perennially interesting (to 40-something females anyway) topic of life after menopause. If you’re a woman, even if you have no intention of having a child in the future, the onset of menopause can make you wonder what your role is, evolutionarily speaking. Why do human females live so long after they can no longer reproduce?
It’s hard saying for sure, but one hypothesis is that childbirth is (or used to be) dangerous enough that after a certain point it’s more genetically advantageous to stick around and raise your existing children and help raise your grandchildren than attempt to have more kids. A news story from Live Science from a few months ago talks about another possibility, perhaps working in tandem with the first. Men often choose younger women as mates, sometimes dramatically younger. When men in their 50s and 60s and 70s continue their own reproductive years by having children with a much younger woman, their children, boys and girls alike, can inherit whatever of their genetic endowment contributes to their longevity, lengthening the lifespan of the human species as a whole.
