We knew it all along: Men are to blame
Researchers conclude that what causes menopause is – wait for it – men.
Finally, the truth is out: menopause in women is really all the fault of men, a team led by McMaster University biologist Rama Singh has concluded.
Professor Singh, an evolutionary geneticist, backed by computer models developed by colleagues Jonathan Stone and Richard Morton, has determined that menopause is actually an unintended outcome of natural selection.
Over time, human males have shown a preference for younger women in selecting mates, stacking the Darwinian deck against continued fertility in older women, the researchers have found.
“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,” says Singh, whose research specialties include the evolution of human diversity.
Far from menopause preventing older women from continuing to reproduce, say the researchers, it is the lack of reproduction that has given rise to menopause, which is believed to be unique to humans. The prevailing “grandmother theory” holds that women have evolved to become infertile after a certain age to allow them to assist with rearing grandchildren, thus improving the survival of kin. Singh says that does not add up, because natural selection selects for fertility and for reproduction.
The new theory holds that, over time, competition among men of all ages for younger mates has left older females with much less chance of reproducing. Because the forces of natural selection protect fertility in women while they are most likely to reproduce, the development of menopause merely recognised that fertility did not serve any ongoing purpose beyond a certain age. If women had historically been the ones to select younger mates, the situation would have been reversed, with men losing fertility.
Menopause brings not only lost fertility, but also an increased risk of illness and death that arises with hormonal changes that occur with menopause. These could, ultimately, be reversed.
Source: McMaster University