TORONTO – Are men the reason why women encounter menopause? It’s a controversial theory but an evolutionary geneticist at McMaster University suggests men are the reason why women go through this phase of hot flashes and night sweats — the female rite of passage into getting older.
In a new study, scientists at McMaster University say that menopause occurs because men are choosing younger women for mating, leaving older women’s reproductive uses on the back burner and eventually phased out. That’s when menopause occurs.
The scientist teaches human evolution and studies sex and reproduction in fruit flies in his laboratory.
“It occurred to me that it was such a simple thing: men change their choice from random mating to looking at younger women and choosing mates. For that, there’s evidence around the world of men looking for a younger wife or a younger daughter-in-law. That’s where the idea came from,” he said.
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Natural selection means that humans try to maintain the survival of their species by protecting fertility in women, especially when they’re most likely to reproduce – which is when they’re young, the study says.
It’s based on computer simulations that show male mating preferences. Over time, men compete for the younger women. Mutations in older women’s fertility are then fostered until, ultimately, they’re sterile.
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It’s counter to another idea, dubbed the “grandmother theory.” In that case, women evolve to be infertile so they can help protect and raise grandchildren. Menopause usually occurs in women in their 50s.
Singh suggests women should not be offended by his theory.
“They can blame men for the menopause. If nature had played the opposite game and older women mated preferentially with younger men, men would get the menopause,” Singh explained.
Even then, he says his theory opens the doors to the possibility of delaying menopause or eliminating it completely. With his findings in mind, Singh says doctors could look into what hormones or genes could be at play at the onset of menopause to help keep the condition away.
“It opens the possibility of doing research in science instead of sitting and waiting for it to happen and then treating the side effects,” Singh said.
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Other scientists aren’t sold on Singh’s idea.
“What he’s saying is that women’s biology is determined by men’s interest in them and I think for a lot of people that’s a difficult concept to agree with, in principal and from a physiological point of view,” Dr. Heather Shapiro told Global News.
She’s a reproductive endocrinologist at Mount Sinai Hospital and professor at the University of Toronto’s department of obstetrics and genecology.
“There’s been no reference of human beings in 2013 of any signals from outside an individual that affects their internal functioning,” Shapiro said.
She said Singh’s theory leaves her with some questions: if men are what keep women ovulating, would attractive women ovulate more or would less appealing women stop ovulating, even at a younger age?
Dr. Holly Thacker, Cleveland Clinic’s director for specialized women’s health, is skeptical.
“I think it’s a bunch of bunk,” she told Global News.
“I think the preference for some males to marry or mate with younger females is probably a manifestation of more matching maturity levels, with women being more mature sooner than males,” she said.
The optimal age for fertility in women is 24 but for men, it’s not as age-specific, Thacker said.
For now, Singh is seeing if menopause could exist in males – male fruit flies, at least.
He’s pairing older female fruit flies with younger males to see what happens to the older gentlemen.
He said he plans on carrying this out for several generations to see if the men then become infertile later on in life.
Singh’s complete findings were published Thursday in the journal PLoS Computational Biology.