Reportedly, "virtually every female creature on Earth remains reproductive until the day she dies," yet human females experience menopause. According to Canadian researchers, menopause is "an unintended outcome of natural selection" and "men's sexual preferences might be to blame."
According to computer models set up by Rama Singh, Richard Morton, and Jonathan Stone of McMaster University in Hamilton, Ontario, competition among men of all ages for younger women left older females with a diminished chance of reproducing. Over time, natural selection protects fertility in women but only when they are most likely to reproduce. The researchers? simulations showed that male mating preference for younger females resulted in the accumulation of deleterious mutations that negatively impacted fertility among older females. The net result: the advent of menopause in the human species.
To run the simulation, the researchers relied on two primary assumptions. First, that there was a shift of male preference toward younger females. And second, that there are female-specific mutations with detrimental effects on fertility in older women (e.g. hormonal changes, oocyte depletion and ultimate loss, ovulation cessation, menstruation termination, and so on).
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