Here’s an awesome question:
Could you please write a post about the evolutionary basis of menopause?
The evolution of human reproduction is LIKE WOAH complex, not least because a human hasn’t really been “reproductively successful” until she’s become a GRANDPARENT. See, if we can manage to get pregnant in the first place and then give birth without dying, we have 15(ish) years of childrearing – including up to five years of breastfeeding – before that offspring is mature enough to reproduce themselves. Given that the evolutionary point of this endeavor is to move our genes into the “next generation,” we’ve only accomplished that if we can produce offspring AND KEEP THEM ALIVE AND HEALTHY for 15 FREAKIN’ YEARS.
The technical term for this is “parental investment.”
So there’s this one hypothesis – the grandmother hypothesis – that suggests human developed menopause so that we would stop reproducing as the quality of our eggs diminished (or maybe the diminishment of egg quality was selected for as part of menopause? Egg expiration dates are a thing, since all our eggs are made all at once, while we’re still in the womb ourselves), and allocate our time and energy to maintaining the wellbeing of our existing offpsring.
And of our offsprings’ offspring.
Not only, the hypothesis runs, do we have PARENTAL investment, we also have GRANDPARENTAL investment. That’s how resources intensive human offspring are: they have a real advantage when more than one generation of kin is supporting them.
And so that’s what menopause is for – in theory. It’s part of what our long lifespans are for (if we make it to reproductive age ourselves, which maybe a little over half of us did (PDF).)
And basically everyone should just go read this blog post from Kate Clancy. Read the whole rest of her blog, Context and Variation, while you’re there. It’s amazing. I assign her blog posts as readings in my class.