Men blamed for early menopause
Study says wooing young girls can lead to their premature loss of fertility
Men who behave like Michael Douglas, Rod Stewart and Ronnie Wood are to blame for women ending their reproductive life early, according to a new theory.
All three celebrities are famous for wooing partners much younger than themselves.
And it is the male preference for young mates that has led to menopause, researchers said.
Through the forces of natural selection, men have unwittingly stacked the Darwinian deck of cards against older women remaining fertile, it is claimed.
“In a sense it is like ageing, but it is different because it is an all-or-nothing process that has been accelerated because of preferential mating,” evolutionary biologist Professor Rama Singh, from McMaster University in Canada, said.
The average woman hits the menopause at 51, but for some the “change” can come in their 40s. But quite why human women become infertile in middle age is an unsolved mystery.
Only two other species, pilot and killer whales, experience a menopause in a similar way to humans. Female chimpanzees, our closest animal cousins, only stop being fertile near the end of their lives, typically around the age of 45.
The new theory turns the conventional view that menopause prevents older women from continuing to reproduce on its head.
Instead, it holds that lack of reproduction has given rise to menopause.
Another idea called the “grandmother theory” suggests women evolved to become infertile after a certain age to free them up to assist with rearing grandchildren. This in turn improves the survival of kin, and so is an example of positive selection.
Singh, whose theory is published in the online journal Public Library of Science Computational Biology, said the menopause did not emerge to benefit the species, but simply because fertility served no purpose beyond a certain age.
Natural selection, which favours the survival of the fittest, protected fertility in women while they were most likely to reproduce.
Inherited genetic mutations that cause infertility at younger ages are weeded out, because young women carrying them cannot have babies.
But the same reproductive check is not there to quell the accumulation of mutations interfering with fertility in middle age.
Over many generations this has led to menopause, the theory states.
If women had a history of choosing younger “toy boy” mates, the situation would be reversed, with men losing their fertility in their 50s, Singh maintains.
But British expert Maxwell Burton-Chellew, an evolutionary biologist from Oxford University, strongly rejects the hypothesis. He pointed to the evolution of sterile worker bees as proof that natural selection can favour infertility.