Cross-cultural studies have revealed broad quantitative associations between subsistence practice and demographic parameters for preindustrial populations. One explanation is that variationin the availability of suitable weaning foods influenced the frequency and duration of breastfeeding and thus the length of interbirth intervals and the probability of child survival (the “weaning food availability” hypothesis). We examine the available data on weaning age variation in preindustrial populations and report results of a cross-cultural test of the predictions that weaning occurred earlier in agricultural and (...) pastoral populations because dairy and cereal production increased the availability of easily digestible, nutrientrich foods appropriate for weaning. We found that, contrary to predictions, supplementation with liquid foods other than breast milk was delayed in agricultural populations relative to less agriculturally dependent ones and complementary feeding with solid foods was delayed in pastoral populations relative to those less dependent on herding. Although the duration of breastfeeding was longer in populations dependent on hunting, there was no qualitative evidence that such populations lacked foods appropriate for weaning. The patterns observed suggest that the relationships between demography and subsistence observed among preindustrial societies cannot be explained by the “weaning food availability” hypothesis. We discuss the implications for understanding the mechanisms underlying prehistoric human demography, subsistence shifts, allocation to parenting and mating effort, and the evolutionary implications of tradeoffs between diet and disease. (shrink)

In this paper I use measures of childhood growth to assess from both an evolutionary theoretical and an applied public health perspective the impact of polygyny on maternal-child welfare among the Datoga pastoralists of Tanzania. I report that the growth and body composition of children varies in such a way as to suggest that polygyny is not generally beneficial to women in terms of offspring quality. Cross-sectional analysis of covariance by maternal marriage status revealed that children of first and second (...) wives in polygynous marriages grow relatively poorly, that this is correlated with maternal physical status, and that the pattern is not modified by household wealth. I discuss how the dynamics of sexual conflicts operating during the formation and maintenance of marriages may be important factors in the etiology of poor child growth in this population, leading to complex patterns of variation in anthropometric indicators of both women and children. The theoretical conclusion is that improved evolutionary models of polygyny should be designed to examine the potential for adaptive tradeoffs between the currencies of offspring quality and quantity for all types of parents in a polygynous population. The practical conclusion is that a better understanding of the relationships between marriage practices and health outcomes would assist in the development of culturally appropriate health and nutrition interventions. (shrink)