Curious Parents

Menopause Might Be The End Of Reproduction, But It's The Just The Start Of Wisdom

Grandma can tell you the names of all the flowers in your yard, show you how to make the world's best mashed potatoes, and will definitely let you know if that person you're dating is bad news. What would you do without her? It turns out that grandmotherly wisdom isn't just nice to have; our species may not have survived without it.

How Is Menopause A Thing?

Menopause has long been a sticking point for evolutionary biologists. Humans and whales are the only species that keep living for decades after they stop being able to reproduce, and that leaves researchers scratching their heads: if evolution is all about creating more offspring, how could menopause possibly be a benefit?

Up until now, researchers have generally championed one of three hypotheses:

  • The maternal hypothesis: because giving birth gets more dangerous the older a woman gets, this theory says that menopause evolved to avoid the risk of either mother or baby dying in childbirth.
  • The grandmother hypothesis: because bigger, stronger individuals can gather more food, but it takes humans a long time to grow big and strong, menopause evolved so that big, strong grandmothers could spend more time feeding and caring for their smaller, weaker grandchildren.
  • The embodied capital model: because gathering food takes skill and smarts, something you only get over years of experience, menopause evolved so that smart, skillful grandmothers could spend more time feeding and caring for their naive, inexperienced grandchildren.

The last two hypotheses focus on an important detail of evolution: it's not just about how many offspring you produce, but whether they live to produce offspring of their own. In that way, a grandmother who ensures the survival of her family could be a big evolutionary benefit to the species.

To Grandmother's Thesis Defense We Go

So which one is correct? Drumroll please...the embodied capital model! That's according to a 2017 study in PLOS Computational Biology that used a computer model to simulate the evolution of reproduction under various conditions. The researchers pointed out that the maternal hypothesis is weak because it doesn't give a benefit, just a risk, and doesn't explain why women live so long after menopause. In contrast, their model showed that when women live longer after menopause, their children are more fertile and their grandchildren are more likely to survive.

Why not the grandmother hypothesis? They found that skill, not strength, was the driving force behind the evolution of menopause. They referenced a 2010 study in the Annals of the New York Academy of Sciences, which showed that while humans are at their physical peak around age 20, they're at their peak productivity, foraging wise, between 40 and 50. The human body gets old long before the brain does, so strength fails while smarts carry on. So listen to grandma. She's why you're alive.

Why Do Humans Have Menopause?

Written by Ashley Hamer August 7, 2017

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