People are living longer, but research shows women have a higher average life expectancy than men. This is not something that’s exclusive to the human world, as even mammalian lifespans usually favour females, who tend to live 12% longer than males—with some exceptions. In some species, such as birds, insects, and reptiles, males outlive females. And now researchers know why… (Picture: Getty)
Genetics could be one reason why women live longer than men, as it is thought that having two X chromosomes could protect them from major genetic mutations that heterogametic males do not have as much of a defense against. But this reverses in birds. To try and solve the puzzle, an international team of researchers examined over 1,000 animal species to track down which evolutionary traits were common amongst species where one sex tends to outlast the other (Picture: Getty)
It seems that child rearing and sexual selection is the reason why women live longer than men in humans. The study found that one sex of a species may drain their potential lifespan by using too many resources to develop and maintain traits that give them an edge in attracting mates. In some animals, lifespan can be reduced by the stresses of gestation, giving birth or laying eggs, and caring for offspring. However, this does not seem to affect human females (Picture: Getty)
The team looked at zoo animals since they are not exposed to the added pressures of predators, illness, injury, or starvation. They wrote: ‘Species often live considerably longer in zoos than in the wild, and abundant resources and managed reproduction in zoos may lower individual survival costs associated with growth and reproduction. For example, the influence of sexual size dimorphism on male survival tends to be lower, and the individual cost of producing offspring appears to have no effect on female survival in zoo settings’ (Picture: Getty)
In zoos, female mammals lived 16% longer than male mammals, while male birds lived 6% longer than female birds. However, in the wild, those differences in lifespan shifted significantly as male birds lived an average of five times longer than the females, and female mammals lived 1.5 times longer than male mammals on average. Males of polygamous species of mammals often experience intense competition for a mate, so larger body size and weapons like sharp teeth and claws could give them an advantage but could use up enough energy and other body resources to shorten their lifespans (Picture: Getty)
Lead author Dr Johanna Staerk said: ‘Our findings may help explain why differences in [average life expectancy] between men and women are so consistent across time and cultures. Specifically, female-biased [average lifespan] appears to be common to chimpanzees and gorillas, suggesting that longer life expectancies for females are a characteristic long embedded in our evolutionary history’ (Picture: Getty)
So, the caregiving sex often lives longer, and this seems to be true for primates. For example, young chimps can remain with their mothers for up to 10 years, which means the longer the mother lives, the longer she can care for her offspring. So from evolution’s point of view, being a lifelong partner and a good parent is the key to males having a longer life (Picture: Getty)
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