Men blamed for women's menopause
Researchers now suggest menopause happens because men prefer younger women.
Until now the theory has been menopause stops women from reproducing. McMaster scientists say the reason for menopause and infertility has actually been brought about by men.
Menopause evolved from mutations
Men prefer younger mates, a team of biologists have concluded, which means there isn't any need for older women to remain fertile; in turn driving women’s genes to mutate.
The researchers say other species reproduce throughout life, so they asked themselves why human females don’t have offspring throughout life.
The study, led by evolutionary biologist Rama Singh, used a computational model to come to the conclusion that men can be blamed for menopause.
The model suggested that women at one time reproduced throughout life, but with time, the odds of them being selected as mates declined.
What that means is older women have, over time, had fewer chances at reproducing. Enter menopause and harmful gene mutations which otherwise would not occur.
Singh says women would be reproducing throughout their entire life if it were not for men’s preference for younger women.
Menopause also brings a host of other health problems and is contrary to natural selection, Singh says.
"How do you evolve infertility? It is contrary to the whole notion of natural selection. Natural selection selects for fertility, for reproduction -- not for stopping it," he says.
He says if women had preferred young men, the situation would be reversed. Men would experience menopause and stop reproducing, rather than women. Perhaps we are seeing a trend, even now. Male menopause is real. Also, men's sperm counts and quality are mysteriously declining.
Most scientists believe menopause occurs so older women can help their children with child rearing, which improves survival of the family gene pool
The McMaster biologists say that theory doesn't hold water though, because grandparent and grandchildren only share one-quarter of their genes.
The finding suggests if women have babies later in life, then menopause could, theoretically, occur later. A more likely scenario Singh says is that fertility treatments will allow older women to reproduce.
The suggestion that men can be blamed for menopause is questionable. Unlike chimpanzees, human women have many years of quality life after ovulation stops.
Should we really compare human menopause to the life-long reproductive ability of female animals who die when they stop producing eggs? More studies might be needed before we really say men are to blame for the mystery of menopause.
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