Why is it that almost everywhere on the planet women outlive men? And how come that’s been true for centuries, at least in Europe, even though childbirth used to be a really risky proposition? These questions grabbed me while I was researching an article on life expectancy for SCF.
As far back as the 1500s, the average woman lived longer than the average man, and men couldn’t quite believe it. They complained that it was unnatural because men were stronger and should survive longer. Puzzled 18th-century French physicians observed that it “went against nature” for women to outlast men.
So why do we? Theories abound. Hormone fanciers give estrogen credit for women’s longevity and blame testosterone for male vulnerability. Others point out that a woman’s metabolism is slower than a man’s, which isn’t good if you’re trying to lose weight, but it could conceivably mean you’ll age more slowly. Then again, women menstruate and that’s apparently a good thing because it gives the heart an especially vigorous workout once a month. (Who knew?)
Women and men are different physically and mentally, and presumably some constellation of those differences provides women with a few extra years to whoop it up. A more basic question is why did evolution program women to have longer lives to begin with.
The theories of evolutionary biologists often have a kind of me-Tarzan, you-Jane quality. One argument is that men shorten their lives by taking risks, and that they have to do this to compete for mates; those who are successful supposedly pass on their risk-taking genes.
A complementary theory holds that evolution programmed women to be risk averse because they’re caregivers: with children to raise, we can’t afford to take the chances that men do, and therefore we live longer.
If it’s all about risk, it would seem that men could extend their lives by taking better care of themselves. Evolutionary biologist Nigel Barber, PhD, sourly notes that, “Boring and safe is the point.” If men want to live as long as women, he blogged for Psychology Today, they have to live like women.
To support the caregiver hypothesis, Barber cites the owl monkey of Central America and northern South America. In most species, females outlive males—sperm whales by a good 30 years—but male owl monkeys live longer than females. Barber suggests evolution is rewarding them for providing most of the child care: they turn infants over to their mothers only at feeding time.
Interesting, but not conclusive. I like another hypothesis better: that evolution favors long lives for women because grandmas are so useful. In the article “What Is Old Age For?,” reprinted on this website, geriatrician William H. Thomas, MD, suggests that since way back in time, children have been more likely to survive in families with a grandmother in residence. Through the offspring they help raise, these relatively long-lived women pass on their excellent genes.
Finally—to shift from evolutionary biology to something equally basic—some scientists give chromosomes credit for women’s greater longevity. Women have two X chromosomes. Men have an X plus a Y. In effect, women have a spare X, which may be able to compensate when a gene on the first chromosome misbehaves, threatening the life of the woman.
In addition, the Y chromosome appears to be in trouble. Geneticists say it has shrunk over the past 300 million years and has accumulated so many mutations that it has only a small number of active genes left. Brian Sykes, a genetics professor at Oxford University, warns that at this rate there won’t be any more men in 125,000 years. At that point, as New York Times columnist Maureen Dowd put it, “the male chromosome could go the way of the dial-up connection.”
Flora Davis has written scores of magazine articles and is the author of five nonfiction books, including the award-winning Moving the Mountain: The Women’s Movement in America Since 1960 (1991, 1999). She currently lives in a retirement community and continues to work as a writer.
