Most mammals don’t go through menopause, a process that shuts down a female’s ability to menstruate or have children. It’s something of a mystery why human women do.
In many species, there seems to be a clear biological advantage in being able to reproduce for as long as possible. Even in chimpanzees, our closest relatives, females can continue to bear young into old age — and chimp males may even prefer an older, more experienced female.
In the new study, Canadian researcher Rama Singh and her colleagues focused on the role of male choice in setting up the situation that allowed menopause to evolve. McMaster University evolutionary biologist Singh said:
“Our first assumption is that mating in humans is not random with respect to age, which means men of all ages prefer to mate with younger women. If mating is with younger women, any deleterious mutations which affect women’s reproduction later in life will accumulate because they are not being acted on by natural selection.”
Uh oh. As a result, men cause menopause unintentionally simply by repeatedly selecting younger women for their mates.
The researchers tested the idea by creating a computer simulation that started with both men and women being able to reproduce for their entire adult life. Over time, the model agreed that if men consistently select younger women to carry their babies, the older women will eventually lose the ability to reproduce in later life.
After an estimated 50,000 to 100,000 years of the men choosing younger women, the mutation that caused menopause was universal in the female population.
However, several critics think the study has reversed cause and effect. University of Utah anthropologist Kristen Hawkes told Fox News:
“As human life spans increased, women might have had many healthy years after fertility. As a result, men grew to prefer younger women because older women couldn’t reproduce.”
What do you think? Is the new study just another example of backwards logic? Or is it pretty decent evidence that men caused menopause?
[photo by Rob Bayer via Shutterstock]