Perhaps because groupishness comes so easily to humans, clear operational definitions of the phenomena and justifications for the claim that it is deep‐seated are lacking in much of the literature. Furthermore, the assertion of human groupishness glosses over several important questions including which behaviors, which social boundaries, and which evolutionary processes make us groupish. In this paper I use an evolutionary lens, and cross‐species and cross‐cultural comparative examples to clarify the bases on which such a claim of particular human groupishness (...) can be made. Specifically, if humans are particularly groupish, it is because we produce culturally‐structured social landscapes. This means the cognitive science of groupishness must incorporate the social science of the cultural evolution of group boundaries. (shrink)