Human cooperation is highly unusual. We live in large groups composed mostly of non-relatives. Evolutionists have proposed a number of explanations for this pattern, including cultural group selection and extensions of more general processes such as reciprocity, kin selection, and multi-level selection acting on genes. Evolutionary processes are consilient; they affect several different empirical domains, such as patterns of behavior and the proximal drivers of that behavior. In this target article, we sketch the evidence from five domains that bear on (...) the explanatory adequacy of cultural group selection and competing hypotheses to explain human cooperation. Does cultural transmission constitute an inheritance system that can evolve in a Darwinian fashion? Are the norms that underpin institutions among the cultural traits so transmitted? Do we observe sufficient variation at the level of groups of considerable size for group selection to be a plausible process? Do human groups compete, and do success and failure in competition depend upon cultural variation? Do we observe adaptations for cooperation in humans that most plausibly arose by cultural group selection? If the answer to one of these questions is “no,” then we must look to other hypotheses. We present evidence, including quantitative evidence, that the answer to all of the questions is “yes” and argue that we must take the cultural group selection hypothesis seriously. If culturally transmitted systems of rules that limit individual deviance organize cooperation in human societies, then it is not clear that any extant alternative to cultural group selection can be a complete explanation. (shrink)

Experiments are not models of cooperation; instead, they demonstrate the presence of the ethical and other-regarding predispositions that often motivate cooperation and the punishment of free-riders. Experimental behavior predicts subjects' cooperation in the field. Ethnographic studies in small-scale societies without formal coercive institutions demonstrate that disciplining defectors is both essential to cooperation and often costly to the punisher.

We examined the universality of the curse of knowledge by investigating it in a unique cross-cultural sample; a nomadic Nilo-Saharan pastoralist society in East Africa, the Turkana. Forty Turkana children were asked eight factual questions and asked to predict how widely-known those facts were among their peers. To test the effect of their knowledge, we taught children the answers to half of the questions, while the other half were unknown. Based on findings suggesting the bias’s universality, we predicted that children (...) would estimate that more of their peers would know the answers to the questions that were taught versus the unknown questions. We also predicted that with age children would become less biased by their knowledge. In contrast, we found that only Turkana males were biased by their knowledge when inferring their peers’ perspectives, and the bias did not change with age. We discuss the implications of these findings. (shrink)