The role of cultural group selection in explaining human cooperation is a hard case to prove.

We believe cultural group selection is an elegant theoretical framework to study the evolution of complex human behaviours, including large-scale cooperation. However, the empirical evidence on key theoretical issues - such as levels of within- and between-group variation and effects of intergroup competition - is so far patchy, with no clear case where all the relevant assumptions and predictions of cultural group selection are met, to the exclusion of other explanations.