Published January 20, 2014
In a study out this past summer, researchers sought to discover the reason behind menopause – i.e. why does menopause occur? The results suggest that it just may be that men prefer younger women. In a June 2013 study published in PLoS Computational Biology, researchers found that natural selection for a youthful mate has lowered the rate of reproduction for older women.
In a press release, Dr. Rama Singh, a researcher with the department of biology at McMaster University in Ontario, Canada, discussed the motivation for the study.
"Menopause is believed to be unique to humans, but no one has yet been able to offer a satisfactory explanation for why it occurs,” Singh said.
The original theories of menopause propose that it is a sort of “natural safeguard” against reproduction for women who will not live long enough to care for their children to adulthood. A similar concept dubbed, the “grandmother effect," suggests older women can no longer reproduce themselves in an effort to offer care for the younger generation's offspring, improving survival of future generations.
On average in the United States, most women reach menopause around the age of 51. Menopause is clinically defined as the cessation of the menstrual cycle for a consecutive period of 12 months, marking the end of fertility. Menopause is classically thought of as the end of sex and a struggle to maintain health – marking women with a sort of scarlet letter as they move away from their fertile years. However, studies have shown that most women experience improved sex lives after menopause, and through the pursuit of a healthy lifestyle, many women enjoy years and years of fruitful living.
More and more research is pouring out of laboratories to help physicians guide their patients through menopause and preserve quality of life. In previous years, women’s health was in question – cognitive decline and increased risk of cancer and heart disease were at play. Today, hormone and nutritional therapies are giving many women their quality of life back, in the midst of and after menopause. The most harrowing effect of menopause are the symptoms that accompany the condition: sleep disturbance, hot flashes, low energy, anxiety, depression and even a sense of loss.
But even with all the research about what to do about menopause, there are few fully understood reasons for why it occurs. To improve understanding, researchers created computational models based on computer simulations to determine how a man's preference could select for mutations that lead to the end of female reproductive abilities.
The "grandmother effect" was quickly disproven because natural selection chooses the most optimal traits, which includes being able to reproduce. The conclusion, or strongest hypothesis, to come out of the study was that menopause was an evolution – it evolved in women because they no longer needed the ability to reproduce beyond a certain age.
The study falls short in several facets, leaving it open to speculation and undercutting hope for a conclusive answer – at least at this point.
Dr. Maxwell Burton-Chellew, an evolutionary biologist from Oxford University who was not involved in the study, told one reporter, "The authors argue that the menopause exists in humans because males have a strong preference for younger females. However, this is probably the wrong way round. The human male preference for younger females is likely to be because older females are less fertile. The authors' paper offers no reason for why males prefer younger females – they just take it as a given, which is surprising."
Lynnette Leidy Sievert, a biological anthropologist and a professor at the University of Massachusetts, Amherst, was quick to offer her comments as well.
“The hypothetical model in the study showed that by the age of 50 or 60, half of the population was still alive, which is not true," Siever told one website. "By the age of 50, the skeletal evidence shows that only 10 percent of Neanderthals lived beyond 50.”
Sievert went on to point out that the study doesn’t really make any concrete hypotheses about why menopause occurs, “. . . 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. Sievert went on to discuss that fact that it all doesn’t really match up to why women lose their reproductive ability – leaving the question still unanswered.