A friend in need is a friend indeed: Need-based sharing, rather than cooperative assortment, predicts experimental resource transfers among Agta hunter-gatherers

Bibliographic Collection: 
Publication Type: Journal Article
Authors: Smith, Daniel; Dyble, Mark; Major, Katie; Page, Abigail E.; Chaudhary, Nikhil; Salali, Gul Deniz; Thompson, James; Vinicius, Lucio; Migliano, Andrea Bamberg; Mace, Ruth
Year of Publication: 2019
Journal: Evolution and Human Behavior
Volume: 40
Issue: 1
Pagination: 82-89
Publication Language: eng
ISBN Number: 1090-5138
Keywords: Assortativity, cooperation, Experimental games, Hunter-gatherers, Need-based sharing, reciprocity

Despite much theorizing, the evolutionary reasons why humans cooperate extensively with unrelated individuals are still largely unknown. While reciprocity explains many instances of non-kin cooperation, much remains to be understood. A recent suite of models based upon ‘cooperative assortativity’ suggest that non-kin cooperation can evolve if individuals preferentially assort with certain cooperative phenotypes, such as helping those who help others. Here, we test these assortative hypotheses among the Agta, a population of Filipino hunter-gatherers, using an experimental resource allocation game in which individuals divide resources between themselves and camp-mates. Individuals preferentially shared with less cooperative individuals, arguing against cooperative assortativity as a mechanism sustaining resource transfers in this population. Rather, sharing was often based on the recipient's level of need, in addition to kin-based transfers and reciprocal sharing. Contrary to several recent theoretical accounts, in this real-world setting we find no evidence for cooperative assortativity influencing patterns of cooperation. These results may reflect the demands of living in a foraging ecology characterized by high resource stochasticity, necessitating need-based sharing as a system of long-term reciprocity to mitigate repeated subsistence shortfalls.

Short Title: Evolution and Human Behavior
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