Stepfamilies and cultural transmission dynamics in Congo Basin hunter-gatherers

Generally high rates of adult mortality coupled with cultural approval of divorce/remarriage mean that alternatives to the nuclear-model of the family can be common in contemporary hunter-gatherer communities. While many studies of hunter-gatherer societies have emphasized the flexible, cooperative nature of childcare, research has not specifically considered how stepparents navigate their unique roles in the lives of their own or their partner’s children. Additionally, research has only just begun to investigate the ways in which cooperative caretaking interacts with the dynamics of cultural evolution in hunter-gatherer societies. For instance, vertical cultural transmission (i.e., learning from parents) has repeatedly been shown as important among hunter-gatherers. Yet, the implications of alternative family forms for the dynamics of cultural transmission are unclear. For instance, stepparents may enhance the spread and longevity of novel cultural traits by moving from a social role associated with oblique cultural transmission to one associated with vertical transmission from the perspective of their stepchildren. In this paper, we 1) present a mathematical model of cultural transmission under conditions where stepparenting is more or less common but stepparents can transmit culture like parents versus other adults (e.g., through vertical versus oblique cultural transmission), and then 2) present a preliminary survey of the frequency of alternative families from two BaYaka communities in northern the Republic of the Congo. Our modeling shows that remarriage and stepparenting can increase the frequency of a new cultural trait and its eventual mean frequency in a population. Validating the premise of the model, our data confirm that high rates of divorce, adult mortality, and remarriage mean that many BaYaka children in our sample live with stepparents. We then discuss how our model and the demographic data can be interpreted considering the ethnographic reality of the study communities and the region, and how this provides the potential for stepparenting to facilitate cultural adaptation. We conclude that the integration of data on family diversity and demography with cultural evolutionary modeling can further our understanding of cultural transmission in hunter-gatherer societies and beyond.