On the analysis of risk-sensitive foraging: a comment on Codding et al

Biological constraints and socioecological influences on women's pursuit of risk and the sexual division of labour

Evolutionary treatments of women's work and the sexual division of labour derive from sexual selection theory and focus on an observed cross-cultural trend: tasks performed by women tend to be more compatible with childcare and produce less economic risk than tasks performed by men. Evolutionary models emphasize biological sex differences and opportunity costs to understand this pattern of behaviour, yet deviations remain poorly understood. We examine variation in women's work among Shodagor fisher-traders in Bangladesh with the goal of explaining such deviations related to women's work. First, we demonstrate that women's trading produces higher variance returns than men's work - a pattern not previously quantified. Next, we test predictions from the economy of scale model to understand the socioecological circumstances associated with trading. We suggest that relaxing model assumptions around biological constraints may elucidate key circumstances under which members of one gender should systematically engage in work that is incompatible with childcare and/or produces higher levels of economic risk. Results indicate that biological sex differences are insufficient to explain gendered patterns of behaviour but removal of childcare constraints and comparative advantages related to opportunity costs can explain adherence to and deviation from trends in women's work and the division of labour.

Family ties: the multilevel effects of households and kinship on the networks of individuals

Among social mammals, humans uniquely organize themselves into communities of households that are centred around enduring, predominantly monogamous unions of men and women. As a consequence of this social organization, individuals maintain social relationships both within and across households, and potentially there is conflict among household members about which social ties to prioritize or de-emphasize. Extending the logic of structural balance theory, I predict that there will be considerable overlap in the social networks of individual household members, resulting in a pattern of group-level reciprocity. To test this prediction, I advance the Group-Structured Social Relations Model, a generalized linear mixed model that tests for group-level effects in the inter-household social networks of individuals. The empirical data stem from social support interviews conducted in a community of indigenous Nicaraguan horticulturalists, and model results show high group-level reciprocity among households. Although support networks are organized around kinship, covariates that test predictions of kin selection models do not receive strong support, potentially because most kin-directed altruism occurs within households, not between households. In addition, the models show that households with high genetic relatedness in part from children born to adulterous relationships are less likely to assist each other.