Delayed reciprocity in sharing networks of Batek hunter-gatherers in Peninsular Malaysia

Sharing and generalized reciprocity have long been thought to have played an important role in human evolution. As such, patterns of sharing interactions in hunter-gatherers have received a great deal of interest from anthropologists seeking to understand how and why sharing occurs in small-scale societies that engage in the widespread exchange of food resources, child care, and information. In this study we apply social network analysis to a historical economic dataset collected in the 1970’s on Batek hunter-gatherers in Peninsular Malaysia. To understand both the endogenous and exogenous factors underlying the exchange of food resources, we analyzed the structure of Batek sharing networks through time using pooled temporal exponential family random graph models. Our analysis reveals a strong effect of delayed reciprocity, in addition to relatedness, marriage ties, and transitivity, on the structure of Batek food sharing networks. Further, we found that the cumulative degree distribution of sharing networks was “scale-free,” suggesting that these networks are structurally similar to many other real world networks that demonstrate the small-world property. Our results suggest an important role for delayed reciprocity in structuring Batek sharing networks and demonstrate the utility of placing hunter-gatherer sharing networks in the context of real-world networks more generally.