Modelling group formation in small scale societies

Summary

Several human activities require an optimal number of individuals to maximise their utility, often leading to the coexistence of positive and negative frequency dependence. This generates unstable equilibria, as group close to the optimal size will be invaded by joiners who will increase their fitness by becoming new members, leading either beneficial or detrimental effects to the incumbent members. If a group is optimally sized, incumbent member will experience a decline in fitness, while joiners will increase its fitness by joining the group. This leads to an Evolutionary Stable Strategy (ESS) where group sizes are greater than the optimal size in the case of ideal free individuals.

This outcome will be different if the acceptance of a new member can be blocked by the receiving group. The group members will face a volunteer's dilemma, as any cost of rejecting incoming individuals will be benefited by the entire group. This paper examines the role of this ESS in group formation dynamics. The decision-making process of individuals is explored, focusing on situations where members of a group can choose to reject new members for a given cost. Different scenarios are considered, including individual and shared costs, and macro scale implications are discussed.

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This Resource is Part of the Following Collections

• Society for American Archaeology 80th Annual Meeting, San Francisco, CA (2015)   •
• SimulPast -- Simulating the Past to Understand Human Behaviour

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