The Grandmother Hypothesis Could Explain Why Women Live So Long

The grandmother hypothesis states that women live well past menopause so that they can help raise successive generations of children. (Credit: Goran Bogicevic/Shutterstock) From an evolutionary perspective, the point of life is to procreate and pass on genes. That’s why most animals keep reproducing until their deathbeds. Yet in humans, females tend to live for decades after they're no longer fertile. All around the world, women experience menopause at around age 50 and routinely continue living into their 70s or 80s. Few other primates ever live long enough to make it through menopause. The rare individuals that do are usually zoo captives, who survive just several years more. Looking out across the entire animal kingdom, the only species known to have substantial numbers of females living past reproduction are four types of whales (killer, beluga, short-finned pilot and narwhal) and one insect, the aphid, Quadrartus yoshinomiyai. So it’s weird that women (as well as whales and aphids) live beyond menopause. As a woman, I’m pleased. But as an anthropologist, I’m puzzled — and I’m not alone. Researchers have long vexed over this evolutionary anomaly. One compelling explanation is that women live past menopause to help raise their grandchildren. According to this “grandmother hypothesis,” ceasing reproduction around age 50 allows older women to devote care and resources to their children’s children. In this way, grandmas still ensure the survival of their genes — those genes are just two generations down the family tree. This is considered a better strategy than older women attempting childbirth, which becomes riskier with age. The idea is certainly appealing, but is it supported by evidence?