Across 1,176 species, women live longer: a genetic shield explains the longevity gap
A sweeping new analysis of lifespan across 1,176 species – mammals and birds kept in zoos worldwide – points to a genetic explanation for why women often outlive men. In mammals, females tend to live about 13 percent longer than their male counterparts, a pattern that holds across roughly three-quarters of species studied. In birds, however, the pattern shifts: a sizable fraction of species shows males living longer than females. The study has been hailed as the most comprehensive cross-species test to date, offering support for the idea that differences in sex chromosomes play a protective role for females, independent of culture, country, or century. The key idea is simple in theory: having two X chromosomes provides a biological backup that can shield against harmful mutations, a redundancy men lack because they carry only one X chromosome and a Y that carries a different genetic load. Yet researchers emphasize that chromosomes don’t tell the whole story; physiology, behavior, life history, and mating systems all shape how long a species’ members live.