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Sex differences

Keller, MC, Nesse, RM, Hofferth, S: The Trivers-Willard hypothesis of parental investment No effect in the contemporary United States Evolution and Human Behavior 22: 343-360, 2001.

A decade ago I went looking for the exact number of years by which men's lives were shorter than women's.  No luck, but I did find the WHO database with mortality rates by age, sex, country, and decade going back a century.  I finally figured out how to analyze it; the key is calculating the ratio of male mortality to female mortality. I thought that perhaps 120 men would die for every 100 women who died. When I did the math, I was astounded to discover that 300 men die for every 100 women who die in early adulthood. In work with Dan Kruger we outline the evolutionary reasons for this dramatic difference. It is not just accidents and violence, men have higher mortality from almost every cause. Even before puberty, 150 boys die for every 100 girls.  This is the most dramatic example of how selection shapes organisms to maximize reproductive success even at the expense of health, well being, and longevity.