Scientists have found out: why women live longer than men

Despite medical advances and improved living conditions, the gap in life expectancy between the sexes persists. A new international study led by the Max Planck Institute for Evolutionary Anthropology (Germany) answers the question of why this phenomenon is so persistent.

Scientists analysed data on more than 1,176 species of mammals and birds collected from zoos around the world. The findings are published in the journal Science Advances and show that differences in longevity between the sexes is a deeply rooted evolutionary phenomenon.

One possible answer has to do with genetics. According to the "heterogametic sex" hypothesis, in mammals, females have two X chromosomes, while males have one X and one Y. The presence of two X chromosomes provides "insurance" against harmful mutations and gives females an evolutionary advantage.

In birds, the situation is the opposite: females have a different set of sex chromosomes (ZW), while males have the same (ZZ). Therefore, it is male birds that are more likely to live longer. On average in mammals, females live 12 per cent longer, while in birds, a 5 per cent advantage in longevity is more often seen in males.

However, the study also showed exceptions: for example, in birds of prey, females are not only larger than males, but also live longer. This means that chromosomes explain only part of the pattern.

Beyond genetics, reproductive strategy plays a key role. In polygamous mammalian species, males have to compete for females by developing a large body, weapons or striking appearance. These traits help win the competition for mates but shorten lifespan.

In many birds, monogamy prevails, where there is less competition, so males live longer. Scientists have shown that differences in longevity are minimal in monogamous species and most marked in species with strong sexual competition.

Parental care proved to be an important factor. The sex that is more invested in raising offspring is more likely to live longer. In mammals, these are mostly females: their survival increases the chances of their offspring surviving to adulthood. In primates, including humans, this strategy is cemented as an evolutionary advantage.

To test the role of the environment, the scientists compared data on animals in the wild and in zoos. Even in sheltered housing, the gap between the sexes persisted, albeit smaller.

This confirms that differences in longevity have deep biological roots and do not depend only on external factors.

The authors conclude that the gap in life expectancy between men and women is the result not only of living conditions, but also of evolutionary processes. Genetics, sexual selection and parental care shape this phenomenon, which will not disappear even with further medical progress.