Evolution may explain why women live longer than men

Now we have a better idea of ​​why women live longer than men, on average, thanks to the most comprehensive analysis of differences in life between men and women and birds.

A The average global life expectancy is about 74 years for women and 68 years For men. There are various ideas to explain why Women tend to live longer than menIncluding the assumption that young men are more likely to die in accidents or conflicts, and that women are better protected from potentially harmful mutations in chromosomes that determine the sexes than men, but the picture is far from completed.

Search for tips from other animals, Johanna Stark at the Institute of Evolutionary Anthropology Max Planck In Leipzig, Germany and its colleagues analyzed data on the life expectancy of 1176 species – 528 mammals and 648 birds – in zoos, as well as in wild populations.

They found that in 72 percent of species of mammals, women live longer than men, an average of 12 or 13 percent. But in birds, men, as a rule, experience women in 68 percent species, surviving an average of 5 percent.

Researchers say that this trend confirms the idea that sex chromosomes explain some differences in life.

In mammals, having two copies X chromosome It makes a separate genetically female, while men have two different sexual chromosomes, X and Y. Theoretically, women are better protected from harmful mutations in sexual chromosomes, because the second copy of the X -chromosome acts as a backup copy.

Birds have a floor determination system – on the contrary: women have two different sex chromosomes called Z and W, while men have two Z chromosome. Thus, various trends in the expected life expectancy of mammals and birds confirm the idea that sex with different chromosomes – heterogametic sex – bears durability.

“But what was very interesting is that we found exceptions,” says a team member Fernando KolcheroAlso at the Institute of Evolutionary Anthropology, Max -Plane. “And with these exceptions, our idea was to check other evolutionary hypotheses about why these sexual differences occur.”

Digging into the data, the team found that mating systems seem to play a role. Polygamous mammals, where there is strong competition for comrades, such as Babuins, Gorillas and Chimpanzees, men usually die earlier than women.

“From -competition for the possibilities of mating, people – usually men – will invest in signs preferred by sexual selection, such as a large body size, decorative feathers or horns,” says he says Nicole Riddle At the University of Alabams in Birmingham. “These features are expensive for production, and usually there are other expenses related to competition for the possibilities of mating, for example, through fighting with other men.”

These factors will mean that a person has fewer resources available for investing in his own long -term survival, she says.

It also applies to birds with polygamous mating systems. “In general, this can also explain why the male advantage of birds is much lower than in women -mushrooms,” says Pau Karazo At the University of Valencia in Spain.

He says that mammals, both a genetic factor and Sexual selection The features work in the same direction in a reduction in the life of men, while in birds the pressure can balance each other, because men often participate in strong sexual selection, but women bear the cost of heterogeneity.

Stark and her colleagues also found that sex, which puts more importance in increasing offspring, has a tendency to live longer. In mammals, these are often women. In long -lived species, such as people or other primates, this is probably evolutionarily beneficial, because it helps women to survive until their offspring becomes sexually mature themselves.

However, there were exceptions. “Birds of prey are opposite to everything that we find in other species,” says Stark. “Women are larger, and often women are much more engaged in the protection of the territory, but still women live longer.” Why a mystery, she says.

According to Karazo, the differences between the floors between the floors are smaller in the population of the zoo than in wild populations, probably because life in captivity minimizes the pressure in the environment, such as battles, predation and illness. According to him, this control over the environment may also be why the differences in life between the sexes in people are reduced, although they can never leave completely.

“There are still some very very encoded differences – physiological differences and genetic differences – between men and women,” says Kolchero. “Who knows where the medical sciences will lead us, but in general we do not expect these differences to completely disappear.”

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