Why do women live longer than men? Scientists say evolution may offer clues

Women across the globe can expect to live longer than men, a longevity gap that has been attributed to women often having healthier diets and lifestyles and paying better attention to their health.

A new study offers another explanation: evolution.

The lifespan gap isn’t unique to humans, with female mammals often living longer than males and male birds generally living longer than females, according to the research published in Science Advances.

The findings suggest women could continue outliving men regardless of advancements in medical care and living conditions.

The study followed 1,176 species, including chimpanzees, rodents, moose, and many types of birds in both the wild and zoos, in what the researchers said is the most comprehensive analysis to date.

In 72 per cent of mammal species, females lived an average of 12 per cent longer than males, the study found. Meanwhile, males lived longer in 68 per cent of bird species, by an average of five per cent.

Differences in sex chromosomes could help explain the lifespan gap, the researchers said. In mammals, females have two X chromosomes and males have one X and one Y chromosome, potentially giving females an advantage by protecting them from “harmful” genetic mutations.

Meanwhile, in birds, females have two different chromosomes and males have two pairs of the same chromosome, seeming to give males a survival advantage.

However, “some species showed the opposite of the expected pattern,” Johanna Stärk, who researches evolution at the Max Planck Institute in Germany, said in a statement.

“For example, in many birds of prey, females are both larger and longer-lived than males. So sex chromosomes can only be part of the story,” added Stärk, the study’s lead author.

The researchers believe that a combination of genetic differences, sexual selection strategies, parental involvement, and environment shapes longevity differences between males and females across species – including in humans.

Overall, the lifespan gap was smallest in monogamous species, while males tended to die much earlier in species where they tend to have multiple mates at a time and have more pronounced size differences, the study found.

While the gap was biggest in the wild, it persisted even in zoos, where conditions are less harsh.

The female advantage is more common in chimpanzees and gorillas than in humans – which suggests it is “rooted in evolutionary processes,” the researchers said

“At least in terms of sex differences in survival, our species is not unique,” they added.