Sex differences in mortality rates stem from a complex set of genetic, physiological, psychological, and social causes whose interconnections are best understood in an integrative evolutionary framework. We predicted that the transition from centrally planned to market economies in Eastern Europe inflated the discrepancy between male and female mortality rates, because economic uncertainty and increasing variation and skew in social status and resources should increase risky male behavior and the impact of stress on physiological susceptibility to internal causes of death. We computed the ratio of the male mortality rate to the female mortality rate separately for 14 Eastern European countries and for the combined population of 12 Western European countries in the pre-transition (1985-1989), transition (1990-1994), and post-transition (1995-1999) periods. We found that the Male to Female Mortality Ratio (M:F MR) for 14 Eastern European nations increased during the years of economic transition, most prominently during early adulthood. Larger sex differences in mortality rates occurred in both young adulthood, reflecting a shift towards riskier behavioral strategies, and middle adulthood, indicating greater physiological susceptibility to stress. For 12 of the 14 Eastern European nations, the increase was substantially larger than the slight increase in the overall Western European M:F MR. The impact of the transition on the magnitude of mortality discrepancy across countries varies considerably and likely reflects conditions particular to each country. These findings illustrate how traits shaped by natural selection interact with environmental conditions to influence male psychology and ultimately mortality patterns.
Kruger, D.J., & Nesse, R. M. (2006). An evolutionary life-history framework for understanding sex differences in human mortality rates. Human Nature, 17, 74-97.
Sex differences in mortality rates stem from genetic, physiological, behavioral, and social causes that are best understood when integrated in an evolutionary life history framework. This paper investigates the Male-to-Female Mortality Ratio (M:F MR) from external and internal causes and across contexts to illustrate how sex differences shaped by sexual selection interact with the environment to yield a pattern with some consistency, but also with expected variations due to socioeconomic and other factors.
Kruger, D.J., & Nesse, R. M. (2006). Understanding sex differences in Croatian mortality with an evolutionary framework. Psihologijske teme /Psychological Topics, 15, 351-364. Invited, peer reviewed article for the special issue on Evolutionary Psychology.
Being male is the strongest demographic predictor of early mortality in Croatia. For every woman who dies between the ages of 15 and 34, three men die. Between the ages of 15 and 54, men are four times as likely as women to die from behavioral causes of death, such as accidents, homicides, and suicides. A causal explanation for sex differences in mortality must be based on an understanding of how sex differences were shaped by natural selection, and how those differences interact with environmental factors to create observed patterns and variations. In brief, males have been selected for riskier behavioral and physiological strategies than women, because of the greater variance and skew in male reproductive success. This paper examines the sex difference in Croatian mortality in three parts. First, we quantify the Croatian Male to Female Mortality Ratio (M:F MR) for 9 major causes of death across age group to provide a richer understanding of the sex difference in mortality from a life history framework. Second, we compare the Croatian M:F MR from behavioral, internal, and all causes with that of the available world population to demonstrate how Croatian mortality can be understood as part of a universal pattern that is influenced by unique environmental context. Third, we investigate how the War of Independence in 1991-1995 affected mortality patterns though its impact on behavioral strategies and the physical embodiment of distress.
This paper extends the evolutionary understanding of sex differences in mortality rates by quantifying and graphically examining the overall Male to Female Mortality Ratio (M:F MR) for 11 specific leading causes of death across age groups in the USA, over the course of the lifespan in 20 different countries, and across the past 70 years in 5 countries. The resulting quantitative descriptions of rates, trends, and the relative contributions of various proximate causes of death to the M:F MR provide an initial exploration of the risks associated with being male. This analysis also illustrates how sex differences shaped by sexual selection interact in complex ways with multiple aspects of culture and environment to yield a pattern that has some consistency across decades and societies, but also has variations arising from differences among cohorts and cultures. The results confirmed our expectations of higher mortality rates for men than for women, especially in early adulthood, where three men died for every woman who died. For external causes the ratios were even higher. Historical mortality data reflect an epidemiological transition in which discrepancies between male and female mortality rates increase as general mortality rates fall. Cross-national variation in the modern M:F MR further suggests a universal pattern that is influenced by cultural and environmental context. Being male is now the single largest demographic risk factor for early mortality in developed countries.