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"What we're saying is that menopause will occur if there is a preferential mating with younger women and older women are not reproducing," he said Thursday from Hamilton.

Researchers at McMaster University believe that over tens of thousands of years, a lack of reproduction among older women has given rise to menopause as an unintended result of evolutionary natural selection.

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"This theory says if women were Nike Flyknit Junior reproducing all along, and there were no preference against older women, women would be reproducing like men are for their whole lives."

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research into ways to prevent menopause, which would lengthen a woman's reproductive life while also helping to maintain better health as she ages.

Singh, however, doesn't believe the grandmother theory holds up from an evolutionary perspective.

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Kristen Hawkes, an anthropologist at the University of Utah in Salt Lake City, is among the leading proponents of the grandmother theory.

Using computer modelling, the researchers found that over time, competition among men of all ages for younger mates left older females with much less chance of reproducing.

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Besides ending reproduction, menopause also affects a woman's health as hormonal changes increase the risk for such conditions as cardiovascular disease and osteoporosis, said Singh.

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Women go into menopause because men want younger mates

"The preference men have for young partners is a striking contrast with other primates," Hawkes said by email, noting that it's been well documented that male chimpanzees prefer older females as mates.

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TORONTO Theories abound as to why women go into menopause, but the latest hypothesis being put forward suggests it may be men or specifically their preference for younger mates that has led to women's loss of fertility at a certain age.

And over time, an accumulation of such mutations harmful to female fertility ended up producing a menopausal period that became part of the overall human female genome, the hypothesis suggests.

"That's just like all the mutations that affect our aging white hair, weak muscles, this and that. These are mutations which affect fertility."

Any genetic mutations that caused an end to fertility later in life would be passed down from generation to generation, he said.

infertile after a certain age to allow them to assist with rearing grandchildren, thus helping to promote survival of their children's offspring.

"My guess about that has been it's a consequence of our life history something selection would favour after not before our grandmothering life history evolved . when women continue to be healthy and competent beyond their fertility."

"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 said.

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Singh said women would have had children when they were younger from 15 to Nike Air Max Flyknit Womens 2015

The researchers' hypothesis runs counter to prevailing theories about menopause, including the widely held "grandmother theory."

He hopes the new theory might spawn Flyknit Racer Vivid Purple

30, based on the computer model.

That theory suggests that women evolved to become Flyknit Air Max Womens 2015

Other primates, such as chimpanzees, do not live as long as humans, but females of the species have a loss of fertility, or parturition, at similar ages to their human counterparts, she said. Female chimps rarely live beyond their child bearing years, usually dying in their 30s or sometimes their 40s.

"It's a very simple theory. What it does is it demystifies menopause. . It becomes a simple age related disease, if you can call it that," said Singh.

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