This paper investigates the impact of kin on child survival in a matrilineal society in Malawi. Women usually live in close proximity to their matrilineal kin in this agricultural community, allowing opportunities for helping behavior between matrilineal relatives. However, there is little evidence that matrilineal kin are beneficial to children. On the contrary, child mortality rates appear to be higher in the presence of maternal grandmothers and maternal aunts. These effects are modified by the sex of child and resource ownership: (...) female children and children in households where women, rather than men, own land suffer higher mortality rates in the presence of maternal kin. These modifiers suggest the detrimental effects of matrilineal kin may result from competition between such kin for resources. There are some positive effects of kin on child survival: the presence of elder siblings of both sexes is correlated with higher survival rates, and there is some weak evidence that paternal grandmothers may be beneficial to a child’s survival chances. There is little evidence that any male kin, whether matrilineal or patrilineal, and including fathers, affect child mortality rates. This study highlights the importance of taking social and ecological context into account when investigating relationships between kin. (shrink)

Modern industrialized populations lack the strong positive correlations between wealth and reproductive success that characterize most traditional societies. While modernization has brought about substantial increases in personal wealth, fertility in many developed countries has plummeted to the lowest levels in recorded human history. These phenomena contradict evolutionary and economic models of the family that assume increasing wealth reduces resource competition between offspring, favoring high fertility norms. Here, we review the hypothesis that cultural modernization may in fact establish unusually intense reproductive (...) trade-offs in wealthy relative to impoverished strata, favoring low fertility. We test this premise with British longitudinal data (the Avon Longitudinal Study of Parents and Children), exploring maternal self-perceptions of economic hardship in relation to increasing family size and actual socioeconomic status. Low-income and low-education-level mothers perceived the greatest economic costs associated with raising two versus one offspring. However, for all further increases to family size, reproduction appears most expensive for relatively wealthy and well-educated mothers. We discuss our results and review current literature on the long-term consequences of resource dilution in modern families. (shrink)

Weight- (WAZ), height- (HAZ), and BMI-for-age (BMIZ) are frequently used to assess malnutrition among children. These measures represent different categories of risk and are usually hypothesized to be affected by distinct factors, despite their inherent relatedness. Life history theory suggests weight should be sacrificed before height, indicating a demonstrable relationship among them. Here we evaluate impact of family composition and household economics on these measures of nutritional status and explore the role of WAZ as a factor in HAZ. Anthropometrics, family (...) demographics, and measures of household economy were collected from Sidama agropastoralist children in a peri-urban village in southwestern Ethiopia (n = 157; 79 girls). Just over half of the sample (50.9%) had z-scores of − 2SD or below on at least one measure, indicating an elevated risk of morbidity/mortality; 30% were at or below − 2SD on two or more measures. We used hierarchical linear regression with random intercept analysis to model WAZ and HAZ. Siblings and crop sales significantly decrease WAZ while electricity, agriculture, and polygyny improve z-scores; however, an interaction between polygyny and siblings indicates negative effects of siblings in polygynous families and positive effects in nonpolygynous ones (adj. R2 = 66.5%). For HAZ, agriculture and electricity are positively associated with z-scores whereas siblings have a negative effect; the interaction term again indicates that effects of siblings vary in polygynous and nonpolygynous families (adj. R2 = 74.2%). A mediation model exploring the role of weight in height outcomes suggests not only that WAZ has direct effects on HAZ but also that effects of electricity and agriculture on HAZ are partially mediated by WAZ. Our findings indicate that WAZ and HAZ are primarily affected by shared variables, but effects of siblings vary by polygyny status. Long-term outcomes (HAZ) among Sidama children would likely benefit from interventions focused on stabilizing WAZ across family members. (shrink)