If you have ever noticed that grandmothers often outnumber grandfathers at the seniors’ centre, you are seeing a long-running pattern. Across most societies and throughout history, women tend to live longer than men. Modern medicine and better living conditions have narrowed the gap in many places, but researchers suggest the difference is unlikely to vanish. The reasons run deep, shaped by biology, behaviour and how species raise their young.
A new global analysis led from the Max Planck Institute examined lifespan records for more than 1,100 mammal and bird species living in zoos. Zoos remove many external threats including predators, dangerous weather, and scarce food. Even in these protected settings, sex based lifespan gaps usually remained, which hints that something more than environment is at work.
One proposed piece of the puzzle is genetics, sometimes called the heterogametic sex hypothesis. In mammals, females carry two X chromosomes, while males carry one X and one Y. Having two Xs seems to offer a backup system, extra protection against harmful mutations, which may tilt longevity toward females. In birds, the chromosome system is flipped. Females are the heterogametic sex. Not surprisingly, many bird species show the opposite pattern, with males living longer on average. Biology sets the stage, but it is not the whole story.
Reproductive strategy matters too. In species where males compete hard for mates, the winners often carry traits that boost reproduction yet come at a cost. Larger bodies, brighter colours, horns or antlers and higher risk behaviour. Those investments can shorten lifespan. In contrast, monogamous species tend to show smaller sex gaps, less intense competition, and in many cases, longer-lived males. When the daily script is not about constant rivalry, bodies can spend more on repair, not just display.
Parental care also shapes the curve. In many mammals, including primates, females invest heavily in raising young. Living long enough to see offspring survive and become independent pays evolutionary dividends, so traits that support maternal longevity can be favoured over time. In birds, caregiving is more often shared, which helps explain the narrower or reversed gaps seen in many species.
What does any of this mean for humans? First, the sex gap in human longevity is not only social. It has biological roots. That said, the size of the gap is very much influenced by environment and behaviour. Public health, safer workplaces, vaccination, clean water, screening, and heart-healthy habits have already closed much of the historical distance between women and men, and appear to be able to keep closing it.
Second, focus on what you can control. For men, this research is not a sentence, it is a nudge. Prioritise prevention: blood pressure checks, diabetes screening, sleep, strength and balance, social connection, and timely medical care. For women, longer average lifespan brings its own planning questions: bone health, financial security, social networks that last and environments that support independence.
Finally, design matters. Homes and neighbourhoods that make healthy choices simpler: walkable routes, good lighting, zero-step entries, accessible bathrooms, supportive community hubs, help both sexes live not only longer, but better. Evolution may set some baselines. How we design our spaces and our day-to-day lives make a difference that matters.
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