Even in the throes of a hot flash, I've never really given much thought to the evolutionary purpose of menopause, but it seems that scientists are as mystified by it as they have been about the female orgasm.I didn't know this, but other than humans, two species of whale are the only other animals whose females undergo menopause. Weird, right? A recent study  at UC Berkeley reinforces a theory that the key to menopause lies with grandmothers. Historically, childbirth was the number one killer of women. By undergoing menopause, older women were spared that particular cause of death, but were also around to help their daughters with childbirth and newborn childcare, and without producing more children of their own to compete for food and resources. Not only were their daughters more likely to live, but also their grandchildren, which provided a double whammy of insurance that their genes would be passed down to future generations.