Recent studies have helped explain why women outlive men by so much. It shows that, on average, women are expected to live longer than men around the world. The study, published in the journal Science Advances, explores the genetic and evolutionary reasons for these inequalities.
The study, led by Johanna Stärk, explores the heterogametic sex hypothesis, which posits that differences in sex chromosomes significantly influence lifespan. Females are XX, meaning they have two copies of the X chromosome. In contrast, males have one X and one Y chromosome, thus making them the heterogametic sex. This unusual chromosomal structure may provide females with a genetic advantage. It also offers them a hope to escape from disruptive mutations, which otherwise would reduce their lifespan.
Research indicates that females outlive males in 72% of mammal species. In fact, on average, they get to live an average of 12% longer. In a surprising departure from most other species, male birds typically have a longevity advantage over females. This is true about 68% of the time, though the age difference is often only about 5%. The data was based on more than 1,176 different species of birds and mammals kept in zoos across the world. This large dataset further supports the soundness of the heterogametic sex hypothesis.
This study sheds new light on the molecular mechanisms underlying proneness to sex differences in the aging process. Certainly, having two X chromosomes does provide some level of safeguard for females. This genetic buffering might help to account for the female longevity advantage often seen, where females live longer than males.
The same research recognizes that how organisms reproduce is a central factor in explaining those differences. While some species exhibit the expected patterns of longevity, others display unexpected results where males outlive females or vice versa. This complexity underscores the importance of continued research to better understand the nuances of lifespan variation between species.
The discoveries further inform a decades-long biological mystery as to why women seem to always outlive men. In this study, the researchers are linking genomic data with reproductive strategies. Their mission is to expose how these elements intersect and shape our longevity.