Michael Gurven

University of California, Santa Barbara

 

Sex differences in mortality, health and well-being have been widely documented in populations worldwide. Explanations focus on differences in lifestyle, risk-taking, work patterns, biological frailty and healthcare access. Another explanation is that costs of reproduction unique to women contribute to differential rates of adult physical decline. An evolutionary life history framework predicts that energy invested in reproduction should trade-off against investments in maintenance and survival. Here we present sex differences in adult health and physical condition among the Tsimane, a Bolivian forager-horticulturalist population experiencing high natural fertility (TFR=9) and high mortality from infectious diseases. We test whether cumulative number of live births and the pace of reproduction predict variability in nutritional status and health using both cross-sectional and longitudinal data (2002-2012) from the Tsimane Health and Life History Project. While greater total reproduction exerts specific costs on women’s health (anemia, inflammation, cystocele), it bears only a minor impact on nutritional status (weight, BMI, body fat percentage). We discuss the role of self-selection in obscuring life history trade-offs, the role of resource buffering by kin networks, and situate our results within the larger literature on maternal depletion and costs of reproduction.