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 (institutions) 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.
Of course, “non-relatives” is relative (no pun intended). In an ethnoracially homogeneous society, and focused on that society to the exclusion of the outside world. One can view cooperative social structures as being among “non-relatives” since, in that monoethnic background, non-family = non-relatives. However, in a demographically diverse state, or when considering the interactions of a monoethnic states with the rest of the world, genetic gradients become salient, and one can view the ethny among which group cooperation may work as a group of relatives. If “kin selection” is invoked as one explanation for large cooperative societies, then the genetic gradients that exist between groups at levels greater than that of between families must be considered. Further, as genes and culture exhibit bidirectional feedback, cultural group selection will, by its very nature if practiced by competing genetically distinct groups, will lead to genetic group selection (a form of kin selection) as a matter of course.
Also importantly, the concept of cultural group selection, particularly: “…culturally transmitted systems of rules (institutions) that limit individual deviance…” is a tool of social control to repress free-riding (the knee-jerk response of the mendacious who wish to poke holes in group selectionist theories, or even the EGI concept of Salter, which at its most fundamental is not dependent on group selection theory) – never mind my previous argument (made here at this blog) that inter-ethnic free-riding is always ignored by those who foam at the mouth about intra-ethnic free-riding, despite the fact that the inter-ethnic form is more damaging (due to the greater genetic distance between those riding and those being ridden) and also harder to control my social norms (it is easier to control the behavior of culturally similar people of your own group than bizarre aliens who are exploiting you).