If you weren't already blaming the man in your life for those pesky hot flashes, now's the time to start—and you can thank McMaster University researchers for the pleasure. A study by evolutionary geneticists at the Canadian school concludes men's partiality for younger mates made fertility futile in older women, and that gave rise to menopause. Highlights, per Discovery News and the BBC:
- A popular previous theory: the "grandmother effect," in which women were believed to have evolved to lose fertility at an age when they might not live to care for a child. So, menopause created an inability to reproduce.
- The new theory: It happened the other way around: A lack of reproduction spurred menopause. The team reached this theory of "preferential mating," using computer modeling. Says the study head, "There is evidence in human history; there was always a preference for younger women."
- The detractors: An evolutionary biologist tells the BBC it's actually the opposite: "I think it makes more sense to see the human male preference for younger females largely as an evolved response to the menopause."
- Fascinating fact: Menopause is very, very rare in the animal kingdom.
- Interesting side note: The study head adds that the trend toward later childbirth could delay when women go through menopause (in the UK, the average is at age 52). "The social system is changing ... with the possibility of menopausal age being delayed."