Older woman
Older women became infertile because they no longer needed to reproduce (wiki commons)

Men are responsible for the menopause because of their preference for younger women, a biologist has claimed.

McMaster University's Rama Singh, along with colleagues Jonathan Stone and Richard Morton, said the menopause was an unintended outcome of natural selection and that it could, technically, be reversed to allow women to reproduce until they die.

Singh says that older women stopped being able to reproduce because there was no need for them to do so. Infertility in women accelerated because of "preferential mating" on the part of men, he said.

The researchers explained that if women were the ones who had been selecting younger mates, men would have become infertile in later life.

Humans are believed to be the only animal where the female stops being able to reproduce. Most animals are able to reproduce until death.

One theory is that women have evolved to become infertile so they can help with bringing up grandchildren and therefore improve family survival.

Singh, however, disagrees: "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."

Disease risk after menopause

The researchers said that over time competition among men to get a younger mate meant women had far less chance of reproducing.

Natural selection was only concerned with the survival of the species through fitness, explaining why the risk of disease increases in post-menopause women, Singh said. They have a higher risk of ovarian and uterine cancer, coronary heart disease and osteoporosis.

"If women were reproducing all along, and there were no preference against older women, women would be reproducing like men are for their whole lives," added Singh.