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People are innately prepared to act as members of tribes, but culture tells us how to recognize who belongs to our tribes, what schedules of aid, praise, and punishment are due to tribal fellows, and how the tribe is to deal with other tribes — allies, enemies, and clients. […] Contemporary human societies differ drastically from the societies in which our social instincts evolved. Pleistocene hunter-gatherer societies were likely comparatively small, egalitarian, and lacking in powerful institutionalized leadership. […] To evolve largescale, complex social systems, cultural evolutionary processes, driven by cultural group selection, takes advantage of whatever support these instincts offer. […] cultural evolution must cope with a psychology evolved for life in quite different sorts of societies. Appropriate larger scale institutions must regulate the constant pressure from smaller-groups (coalitions, cabals, cliques), to subvert the large-group favoring rules. To do this cultural evolution often makes use of “work arounds” — mobilizing tribal instincts for new purposes. For example, large national and international (e.g. great religions) institutions develop ideologies of symbolically marked inclusion that often fairly successfully engage the tribal instincts on a much larger scale. Military and religious organizations (e.g., Catholic Church), for example, dress recruits in identical clothing (and haircuts) loaded with symbolic markings, and then subdivide them into small groups with whom they eat and engage in long-term repeated interaction. Such work-arounds are often awkward compromises […] Complex societies are, in effect, grand natural social-psychological experiments that stringently test the limits of our innate dispositions to cooperate.
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Robert Boyd, Peter J. Richerson (The Origin and Evolution of Cultures (Evolution and Cognition))