Why do women live longer than men? Explained by evolution

• Mammals vs birds: Of the 1,176 species analysed, female mammals lived on average 13% longer than males. In contrast, among birds, males lived about five percent longer than females.
• Mating strategies are important: In species where competition for mates is intense – as it is for most mammals – males tend to die at a younger age. In species that form monogamous pairs, such as many birds, males often outlive females.
• Zoo comparisons: The gap between the age of males and females is larger in wild populations than in zoo environments. This pattern suggests that genetic factors and external conditions influence how long each species lives.

In almost every country and in every historical era, women tend to live longer than men. While medical advances and improving living standards have narrowed this gap in some places, the new findings suggest that the difference is deeply rooted in evolution and is unlikely to disappear. Similar patterns appear in many animal species, suggesting that the roots of longevity go far beyond modern life.

A team of scientists led by the Max Planck Institute for Evolutionary Anthropology in Leipzig, in collaboration with 15 collaborators around the world, has conducted the largest and most detailed analysis ever of lifespan differences between male and female mammals and birds. Their findings provide new insight into one of biology’s most enduring questions: Why do the sexes age at different rates?

Longevity: a matter of chromosomes?

In most mammalian species, females live longer – for example, female baboons and gorillas often outlive males. But this pattern is reflected in other groups. In many birds, reptiles and insects, males have longer lifespans. One possible explanation, known as the heterogametic sex hypothesis, links these differences to sex chromosomes. Female mammals have two X chromosomes, while males have one X and one Y (making them heterogametic sexes). Having a pair of X chromosomes may protect females from harmful mutations and extend their lives. In birds, the system is reversed: females are the heterogametic sex.

Using data from more than 1,176 species of mammals and birds in zoos around the world, the researchers noticed a stark contradiction that supports this hypothesis. In most mammals (72 percent), females lived longer, on average twelve percent. In most bird species (68%), males were the longest-living sex, averaging 5% longer. However, this pattern was far from universal. “Some species showed the opposite of the expected pattern,” explained lead author Joanna Stark. “For example, in many birds of prey, females are larger and longer-lived than males. So sex chromosomes can only be part of the story.”

How mating and parenting shape longevity

In addition to genetics, reproductive strategies also play a role. Through sexual selection, males in particular develop conspicuous characteristics such as colorful plumage, arms, or large body size, which increases reproductive success but can shorten lifespan. The new study supports this assumption: in polygynous mammals with strong competition, males generally die earlier than females. On the other hand, many birds are monogamous, which means there is less competitive pressure and males often live longer. In general, differences were smaller in monogamous species, while polygyny and pronounced size differences were associated with a more pronounced advantage for females.

Parental care also plays a role. The researchers found evidence that the sex that invests more in raising offspring — in mammals, often females — tends to live longer. In long-lived species such as primates, this is likely a selective advantage: females live until their offspring become independent or sexually mature.

Zoo life reduces age gaps—but doesn’t erase them

There is a long-standing idea that environmental pressures, such as predators, disease, and extreme weather, lead to differences in the lifespan of males and females. To test this, scientists turned to zoo collections, where these risks are minimal. Even in these safe conditions, age gaps persisted. Comparing zoo and wild data showed that although differences were smaller in captivity, they rarely disappeared completely. This pattern reflects the human experience: better health care and living conditions may reduce the gap between men and women, but they do not eliminate it.

Together, the results suggest that age differences between males and females are deeply rooted in evolution. It is shaped by sexual selection, parental care, and genetic factors associated with sex determination. The environment affects the size of these gaps, but it cannot completely eliminate them. These gender discrepancies are not simply a product of circumstance, they are woven into our evolutionary past and are likely to persist into the future.