Human aging and menopause

Published on March 29, 2011 Updated on April 30, 2017   45 min

Other Talks in the Series: Evolution and Medicine

I'm Kristen Hawkes. I'm an evolutionary anthropologist at the University of Utah. And my topic is "Human Aging and Menopause". I'm an evolutionary anthropologist and so that means that I think in terms of natural selection as the key to explaining why things vary in the living world. And if you think about natural selection, aging initially looks like quite a riddle. But, of course, we're not the only ones that age. Aging is a thing about living organisms. And so evolutionary biology has given us some crucial tools. Hence, thinking about how we live in a finite world, all organisms do, it means that there are always tradeoffs. And because there are tradeoffs, aging senescence is a necessary result from natural selection.
More is spent on maintenance and repair means less can be spent on current reproduction. And so the tradeoff between those two things provides this wonderful leverage for explaining variation. This figure shows that tradeoff between what's put into somatic maintenance and repair on the one hand, and what's put into current reproduction. And if those parallel lines represented lines of equal lifetime fitness, the expectation is that selection would adjust that tradeoff to hit the line of highest lifetime fitness. And it turns out to be a very powerful toolkit for explaining some of the variation in rates of aging across the living world. How much goes into maintenance and repair depends on, first of all, what the chances are of surviving to older ages. If the chances are very low, if mortality is very high, then that kind of investment won't payoff. And so when mortality is low, it does. And it also matters what the reproductive payoff is if you do survived to those ages.