For generations, it’s been known that women outlive men. Across nearly every country, women can expect to live several years longer — a pattern often linked to healthier habits and more attention to wellbeing. But new research suggests the explanation may reach far deeper, stretching back to the roots of evolution itself.
A large-scale study published in Science Advances has found that humans aren’t unique in this longevity gap. In fact, female mammals across species tend to live longer than males, while in birds, the reverse is true.
Researchers analysed life expectancy data from 528 mammal and 648 bird species living in zoos and compared them with populations in the wild.
The results were striking. In 72% of mammal species, females lived on average 12% longer than males. Among birds, males lived longer in 68% of species by roughly 5%. These consistent patterns suggest that sex-linked survival differences are not just environmental — they are biological.
Part of the answer lies in our chromosomes. In mammals, females have two X chromosomes, which may help buffer against harmful genetic mutations. Males, with only one X and one Y, lack that backup. In birds, the situation is reversed: females have two different sex chromosomes (Z and W), giving males — with two Zs — a protective advantage.
Yet genetics only tells part of the story. The researchers found that behaviour and mating systems also play a key role. The longevity gap was narrowest in monogamous species, while in those where males compete for multiple partners — and often grow larger to do so — males died significantly earlier. The more intense the competition, the shorter the male lifespan.
Interestingly, these differences persisted even in zoo environments, where animals are protected from predators and food is abundant. That suggests the roots of the survival gap lie not in external threats, but in evolutionary trade-offs shaped by reproduction, mating strategies, and genetic design.
Even our closest relatives, chimpanzees and gorillas, show a stronger female survival advantage than humans — reinforcing the idea that this pattern is ancient, not modern.
So while better healthcare and lifestyles can extend lives on both sides, biology may ensure that, on average, women — and female mammals everywhere — continue to outlive their male counterparts.
06.10.2025.
