A network model of the appearance of biologically irresolvable conflict in prehistoric hunter-gatherer groups
Erick Pérez and Tom Froese
According to Gamble et al. (2014), human groups consist of multiple layers of relationships that build up to create ever-larger communities. They propose the following group sizes: 5, 15, 50, 150, 500, and 1500, which in the case of hunter-gatherers refer to intimate groups, foraging groups, bands, communities, mega-bands, and tribes, respectively. A key problem is to explain the maintenance of cooperation in these different groups. Gamble et al. claim that modern humans biologically evolved to cooperate within groups of maximally 150 individuals (also known as Dunbar’s number), such that the appearance of larger group sizes during the early Neolithic period led to constraints that required the emergence of new cultural mechanisms of conflict mediation. Examples include religion, hierarchy, and warfare, with the latter two finding support in detailed agent-based simulations (Turchin et al., 2013). We chose a more abstract approach to investigate this problem by employing the REDS model, an energy-constrained spatial social network model first introduced by Antonioni et al. (2014). The REDS model comprises four components (Reach, Energy, Distance, and Synergy), and the generated topologies have key features of real social networks: high clustering, positive degree correlation, and the presence of community structure. We created REDS networks according to the six group sizes specified by Gamble et al. and ran a standard Hopfield network model on their topology to determine their capacity for global conflict resolution via local interactions. We report that networks with more than 150 nodes are no longer capable of spontaneously giving rise to global conflict resolution via local interactions alone. In addition, following related work by Froese et al. (2014), we consider how the emergence of large-scale group rituals could have helped to overcome this problem while otherwise keeping the original heterarchical network structure intact.
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Froese, T., Gershenson, C., & Manzanilla, L. R. (2014). Can government be self-organized? A mathematical model of the collective social organization of ancient Teotihuacan, Central Mexico. PLoS ONE, 9(10), e109966. doi: 10.1371/journal.pone.0109966
Gamble, C., Gowlett, J., & Dunbar, R. (2014). Thinking Big: How the Evolution of Social Life Shaped the Human Mind. London: Thames & Hudson Ltd.
Turchin, P., Currie, T. E., Turner, E. A. L., & Gavrilets, S. (2013). War, space, and the evolution of Old World complex societies. Proceedings of the National Academy of Sciences of the USA, 110(41), 16384-16389.