Natural Variation in the Sex Gap in Life Expectancy

Women outlive men in all countries of the world and for decades women’s life expectancy has increased more rapidly then that of males. Factors contributing to these observations are believed to be associated with the external environment and internal biological factors. It has been hypothesized that females withstand harsh environments better then males in terms of survival, partly explaining their higher life expectancy. If this hypothesis is true and females survive environmental stressors better then males then large sex differences in life expectancies could reflect the action of these environmental factors whereas small differences would reflect a lower action of the factors and approach the ‘natural’ biological level. Here we examine variability in sex differences in life expectancy in 47 historical and contemporary human populations to address our hypothesis: large sex differences in life expectancies reflect large variation in mortality across age and thus indicate larger influence from environmental factors.