I think that's definitely a part of it. Our monkey brains process that there is danger, and (naively) find ways to amliorate it in peer groups. We associate in-

I think that's definitely a part of it. Our monkey brains process that there is danger, and (naively) find ways to amliorate it in peer groups. We associate in-groups with safety and out-groups with dangers, and both infinitely large and infinitesimally small in (or out) groups would require the brain to do the much bigger work of individual threat analysis. Delegated decision-making.