Rule of 150 (Dunbar's Number)

Biological Parallel

Dunbar discovered that primate neocortex size predicts social group size with shocking precision: 150 is the cognitive limit for tracking relationships, obligations, and reputation across a network. Grooming time scales with group size—beyond 150, you'd need to spend more time maintaining relationships than foraging, creating an energetic impossibility. This isn't a cultural preference; it's a hard constraint where brain capacity and time budgets intersect, limiting stable coalition size across species from baboons to humans.