Of everything I learned in pursuing my Master of Science in Gerontology, one of my favorite topics was the scientific background behind why women live longer than men. Women live longer than men not because they have a slower progression of aging, but because they are more robust.
There are several theories as to why women have longer lifespans: estrogen somehow protects females at a cellular level, females have a more robust immune system, heterogametic sex hypothesis, reduction in the activity of growth hormone, and oxidative stress hypothesis. For this discussion, let's explore the heterogametic sex hypothesis. (Austad, 2006)
The second X chromosome provides women with compensatory alleles, contributing to longer lifespans. Men are exposed to additional risk as they have only one copy of more than 1,000 genes that appear in the X chromosome, but not the Y. Two copies of the gene allow for women to activate the stronger options, while inactivating the less superior gene. Additionally, an advantage may be provided as approximately 17 percent of the genes on the "inactivated" X chromosome are at least partially active. (Austad, 2006)
This "asymmetrical inheritance of sex chromosomes" enables women to maximize their fitness, pointing to the sex being more robust than males. (Maklakov & Lummaa, 2013) And who says women are the fairer sex?!
Sources:
Why women live longer than men: Sex differences in longevity, Austad, Gender Medicine, 2006
Evolution of sex differences in lifespan and aging: Causes and constraints, BioEssays, 2013
Photo source: Unsplash, Museums Victoria
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