 For example, one line of evidence from comparative ethnography looks at cooperative behavior, and reveals variation between groups even in the kinds of activities, relationships, and contexts that are governed by norms. Some groups “cooperate only in warfare and fishing, while others, just downstream, cooperate only in housebuilding and communal rituals” (Chudek, Zhao, &amp; Henrich 2013: 426). That behavioral variations like these can persist even in the face of the same ecological context (i.e., “just downstream”) suggests that they are due to differences in norms and other socially transmitted elements of culture, rather than responses more directly evoked by the physical environment (also see N. Henrich &amp; J. Henrich 2007).