Group size is bounded by brainpower unless cultural solutions lift the limit

Evidence

Mutual cooperation has tremendous fitness benefits to individuals, but does not come for free. A considerable amount of brainpower is required to get along with one another, and the larger the number of social interactions one must track, the more cortical tissue one needs to navigate the ensuing complexity of the social world. Based on these considerations, the anthropologist Robin Dunbar conducted cross-species comparisons of brain size, and found that, among primates, the best predictor of neocortex volume relative to body size is group size. A wide range of intensely cooperative human behaviors begins to break down as groups get too large—unless additional cultural solutions are injected into the group dynamics. We see this in the smallest hunter-gatherer settlements, the earliest Neolithic farming villages, the basic unit of professional armies since Roman times, and in the breaking point of thriving religious movements. Limits to group size are demonstrated also in ethnographic work among the Arapesh, in remote parts of New Guinea, where villages routinely split once they exceed about 300 people (or 150 adults). The anthropologist Donald Tuzin reports on the historical emergence of an anomalous village of 1,500 people, and explains how additional cultural norms sustaining social organization, marriage, rituals, and morally involved supernatural agents converged to galvanize cooperation in a locale where this scale was previously unknown. — Norenzayan, Ara, Big gods - how religion transformed…, 413

Categorization

• XREF: Dunbar’s number here is used as causal mechanism: neocortex volume limits group size, so moralizing gods and rituals are cultural ‘injections’ that lift the limit — directly relevant to the fumi-e trampling logic where authorities break the very cultural glue enabling large-group solidarity.