Did Men's Yen for Younger Women Cause Menopause?
Study found bias may have sidelined older women sexually, prompted changes that led to infertility
WebMD News Archive
The scientists found that the development of menopause seems to have done nothing to improve the chances of human survival over time, but rather occurred because women of a certain age weren't finding mates, and thus reproductive ability was unnecessary for them.
Yet Singh pointed out that if women long ago had been the ones choosing younger mates, older men would have been the ones losing their fertility, not women.
The process of natural selection favors the most fit, so women who are most likely to reproduce are protected, explained Singh. Natural selection is the gradual, non-random process through which biological traits become either more or less common, due to the way reproduction occurs, Singh explained.
The researchers used computational models and computer simulations to show how male mating preference for younger females could increase the number of mutations that stopped women's reproductive ability, creating menopause.
Singh said his research suggests that it might be possible for women who delay childbearing to also postpone menopause, allowing them to have a longer window in which to conceive. "We might be able to extend the time period in which you can have children, rather than rush it," he said.
Lynnette Leidy Sievert, a biological anthropologist and a professor at the University of Massachusetts, Amherst, raised questions about the study.
"The study showed that by the age of 50 or 60, 50 percent of the population was still living, but that just doesn't match what we know about human evolution," she said. "By the age of 50, the skeletal evidence shows that only 10 percent of Neanderthals lived beyond 50. Our own homo sapiens [humans] had about 17 percent living past the age of 40."
Sievert, a member of the board of trustees of the North American Menopause Society, also questioned whether the concept of men mating with younger women fully explains menopause.
"Because it's a human and mammalian pattern for men to die younger [than women], you have a younger female with an older male who is going to die," she explained. "I get mixed up about how that pulls a woman's lifespan across menopause."
Singh said he's planning to do more simulations based on a Canadian long-term study of aging that is following 50,000 men and women. He is interested in learning more about the relationship between menopause, reproduction and genetic markers. "I really want to see if you can do something to delay menopause," he explained.