Sarah Mathew
School of Human Evolution and Social Change
Arizona State University


Thursday 18 February
6.00 pm (reception at 5.30 pm)

Friday 19 February
10.00 am

Ahmadieh Family Lecture Hall (FHI Garage) Bay 4 Smith Warehouse

Readings for the workshop:

Punishment_sustains_large-scale_cooperation-(Mathew_and_Boyd) Human_cooperation_and_norm_enforcement-(Mathew_et_al)

Human cooperation is an evolutionary puzzle because unlike other species we cooperate extensively
with genetically unrelated and unfamiliar individuals. To understand how this unique form of
prosociality evolved, it is necessary to investigate how cooperation is maintained in societies without
formal centralized institutions. I will present findings from the Turkana, a politically uncentralized
pastoral society in East Africa, which show that: 1) the Turkana maintain costly large-scale cooperation
in warfare through informal sanctions against free riders; 2) Turkana norms regulating warfare benefit
the cultural group, not smaller social units; 3) Turkana norms regulating moralistic punishment help
solve the second-order free rider problem and promote group-beneficial punitive behavior. I will discuss
how these findings are consistent with the idea that cultural group selection played an important role in
the evolution of human cooperation.
About our guest speaker:
Sarah Mathew studies the evolution of human ultra-sociality and the role of culture in enabling it. She is
especially interested in how humans evolved the capacity to cooperate with millions of genetically
unrelated individuals, and how this links to the origins of moral sentiments, prosocial behavior, norms,
and large-scale warfare. To address these issues, she combines formal modeling of the evolution of
cooperation with fieldwork among the Turkana (an egalitarian pastoral society in East Africa who
cooperate with hundreds of other Turkana who are neither kin nor close friends). Through systematic
empirical studies in this unique ethnographic context, her research project aims to provide a detailed
understanding of the mechanisms underpinning cooperation and its moral origins

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