Community size: 50, 150, 500 — Mitigation of disruptive forces and the role of religion

The Hutterites split their communities once they are above ~150 because, in their experience, this is the limit at which community cohesion can be maintained without the need for formal laws and a police force to maintain discipline (Olsen, 1987). Forge (1972)) arrived at a similar conclusion from an analysis of settlement size and structure among New Guinea horticulturalists. He argued that, in these societies, 150 was a key threshold for community size because basic relationships of kinship and affinity were insufficient to maintain social cohesion when a community exceeded this size. It is perhaps relevant that, in natural fertility populations, the community of living descendants of a founding couple five generations back from the current offspring generation (grandparents’ grandparents, or about as far back as anyone currently alive will have known personally) is ~150, and that no culture has kinship terms that identify relationships beyond this limit (essentially second cousins) (Dàvid-Barrett and Dunbar, 2017, Dunbar, 1995). In effect, natural kinship classifications seem to be mapped onto the typical size of natural communities. The crucial implication of Forge’s observation is that, when community size exceeds ~500, the rising intensity of social and other stresses threaten community coherence and stability, and cohesion can only be maintained if some mechanism is available to suppress or mitigate these disruptive forces (Dunbar, 2012).

….

The contrast between religious and secular communes in both the US and kibbutz samples suggests that a religious framework might provide a mechanism that allows a larger group of people to be held together (in the US case, effectively quadrupling the community’s survival time compared to secular communities). One possible explanation is that a religious ideology somehow helps to keep a community better in tune with itself socially (Sosis & Ruffle, 2004). A moralizing ‘high god’ that acts as an all-seeing ‘police force’ (Purzycki et al., 2016) and religious obligations that foster self-control (Sosis and Ruffle, 2003, Ruffle and Sosis, 2007) may help to reinforce adherence to community rules. However, it may also be that a religious framework generates greater ‘bottom-up’ commitment to the ideals of the community, either by imposing high entry costs (what has to be given up to join) and/or on-going maintenance costs (e.g. attending religious rituals) or through personal ideological commitment (Near, 1997, Olsen, 1987, Sosis, 2000) such that individuals are more willing to tolerate the inevitable stresses of communal life.

From http://www.ehbonline.org/article/S1090-5138(17)30209-X/fulltext