Cooperative dynamics among hunter-gatherers: An experimental investigation of adaptive hypotheses

From small-scale food-sharing among hunter-gatherers to large-scale institutions in modern industrial societies, cooperation is central to human success. This thesis focuses on the former, exploring cooperative dynamics among the Agta, a Filipino hunter-gatherer population. I develop a novel experimental approach to exploring hunter-gatherer cooperative behaviour which simultaneously assesses the amount individuals cooperate and who they cooperate with. In contrast to much previous experimental literature, this non-anonymous design permits tests of specific theories for the evolution of cooperation, including: kin selection (cooperating with related individuals); reciprocity (cooperating with others who cooperate in return); and tolerated theft/demand sharing (taking from those with more resources), among other adaptive hypotheses. Using two experimental games – one exploring giving behaviour (donating resources to others) and another exploring demand sharing behaviour (taking resources from others) – I find that individuals from camps with a greater probability of repeated interactions give more to and take less from others. When individuals give to others it is directed towards kin and reciprocating partners, while when individuals take they do so from those with more resources, regardless of kinship or reciprocity. As predicted by theoretical models, this suggests that reciprocal transfers occur when interactions are repeated, while demand sharing occurs when repeated interactions are less likely. Differences in the frequency of repeated interactions may therefore explain some cross-cultural variation in forager food-sharing practices. This thesis also explores the effects of reputation on cooperative and interaction networks, finding that many aspects of forager social networks may reflect the trade of commodities in biological markets. Additionally, assessment of the ontogenetic roots of Agta cooperative behaviour suggests that 3 who children cooperate with, but not overall levels of cooperation, change over childhood in ways which are consistent with adaptive evolutionary hypotheses. These findings provide an insight into the evolutionary and ecological roots of hunter-gatherer cooperation