Sex differences in mortality rates are shaped by reproductive strategies and population characteristics

Researchers have known about sex differences in longevity for at least 250 years. There are multiple levels of mechanisms which contribute to this disparity, an ultimate explanation follows from reproductive patterns. Women provide greater investment in offspring and have greater constraints on reproductive potential, so men compete for reproductive access to women. In humans, male competition includes competition for social status and resource control, which are related to male reproductive success. Sex differences in human mortality rates are greatest in young adulthood, when males are reaching sexual maturity. This mortality is mainly from behavioral causes, such as accidents, homicides, and suicides. Rates of behaviorally mediated internal causes of death, as well as sex differences in mortality rates, are greater in mid to late adulthood. We predicted that there will be higher degrees of excess male mortality (above that for females) where there is a greater degree of male competition. In areas where there is high potential or actual variability and skew in male resource holding or status, comparatively more risky male behavioral strategies will lead to greater male mortality rates and more excess male mortality. We demonstrate that the population sex ratio, the degree of economic inequality, and the degree of polygyny are all related to sex differences in mortality rates. Changes in socioeconomic conditions within countries, such as the rapid transition to market economies in Eastern Europe in the 1990s, have also affected sex differences in mortality rates.