A comprehensive study of over 1,176 mammal and bird species reveals that sex differences in lifespan are deeply rooted in evolutionary biology rather than environmental factors alone. Female mammals live approximately 13% longer than males on average, while male birds typically outlive females by about 5%, a pattern that may partly reflect differences in sex chromosome systems between these groups. Mating strategies significantly influence these gaps: In polygamous species with intense male competition for mates, males die earlier, whereas in monogamous species, the lifespan difference narrows considerably.
Moreover, the research found that sex differences persist even in protected zoo environments; though, they are somewhat reduced compared to wild populations, suggesting both genetic and environmental factors contribute to longevity gaps. These findings indicate that the pattern of women outliving men in human populations has deep evolutionary roots unlikely to disappear entirely, as similar dynamics operate across many animal species.
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