There was an interesting article in the Guardian a couple of days ago about the biological reasons for menopause. I have not read the studies that this story is based on, so commenters with more knowledge of this stuff please feel free to correct anything that I have misconstrued.
Human females are one of three species currently known to undergo menopause at a relatively young age compared to average lifespan. The other two are pilot and killer whales. Female chimpanzees usually lose their fertility late in life as do other more closely related species to humans than killer whales. This leaves the reasons behind menopause wide open to speculation.
My preferred theory is the Grandmother theory: a woman in a subsistence environment has more chance of having her children survive into adulthood if she has older women to help her i.e. it takes a village to raise a child. Thus women surviving past their childbearing years has benefits beyond those inferred by fertility.
The other theory is that men have influenced human female biology by consistently choosing younger mates so that older women lost their fertility as it wasn’t being used. This theory neatly centres men in the evolutionary cycle. But it doesn’t explain why women still live so long after menopause when other species simply die. If older women are that useless surely we would just die off? I also like how this places human men as special snowflakes in evolutionary terms. In other species the male is a sperm donor and either buggers off soon after, is eaten, or dies. But not the human male, he decides the destiny of the human race.*
The theory of men influencing menopause makes a couple of assumptions that I find interesting. Firstly it assumes that menopausal women aren’t sexually attractive to anyone. Human sexuality is one of those fascinating things that I don’t think can be tied down to theories like this. I’m thinking that if you are a beta guy who wants a bed mate then an older woman is probably going to be a good option for you. Or you’re a bloke who is just looking to have a bit of fun with someone. It isn’t like all menopausal women immediately lose interest in sex or the ability to have sex. Effectively for the male selection theory to work all older women would have had to stop having any sex ever for menopause to become a evolutionary reality. I’m not sure that there would have been enough comely young women to ensure that every bloke who wanted a woman as a partner/shag/friend with benefits to ensure that outcome.
It also ignores the agency of women in choosing their partners. The common assumption is that blokes did all the choosing but do we know this to be absolute across all humans through time? Would young women necessarily choose older men? This theory seems to presuppose girls being married off to men to secure family alliances etc. Again, I’m not sure that this was going on for long enough to cause evolutionary change.
SotBO: yes this is tongue in cheek.