Equality, hierarchy, oligarchy: Model-driven investigation of the evolutionary origins of social organization
Social hierarchy is a pervasive element of modern societies, yet almost absent before the advent of agriculture during the Neolithic transition. Despite evidence supporting hierarchy as a product of evolution, it is hard to explain the mechanisms which drove this evolution. For instance, the evolution of followers appears as a paradox because followers receive fewer resources than leaders. A theory from political science called the “iron law of oligarchy” proposes that the key to the Neolithic transition lies in the role of leaders in collective decision-making. First, leaders would emerge in response to an increase in group size because leaders facilitate coordination. Then, leaders would use their newly acquired influence to bias opinions and group decisions to impose inequality that benefits themselves. This theory has the benefit of explaining the origin of both beneficial and despotic sides of leaders. Yet, its investigation has been limited because of the lack of a formal description of (i) how individuals change with time and (ii) how individuals take collective decisions. Thus, we propose the evolutionary iron law of oligarchy, which reinterprets the iron law in evolutionary terms. We reduce leaders and followers to their capacity to influence and we claim that describing the evolution of this trait under the environmental changes observed at the Neolithic transition is sufficient to explain the emergence of helpful and despotic leaders. To investigate this claim, we build individual-centred models simulating consensus formation — how individuals take collective decisions — and evolutionary dynamics — how individuals change with time. On one hand, our results show that the evolutionary iron law of oligarchy is a viable scenario, which can unify previous theories explaining either the beneficial or despotic side of leaders. On the other hand, we developed a mechanistic model of the iron law of oligarchy which can apply across a range of scenarios, and which show under which condition the iron law of oligarchy would apply.
References
2020
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From disorganized equality to efficient hierarchy: how group size drives the evolution of hierarchy in human societies
Proceedings of the Royal Society B: Biological Sciences, Jun 2020
A manifest trend is that larger and more productive human groups shift from distributed to centralized decision-making. Voluntary theories propose that human groups shift to hierarchy to limit scalar stress, i.e. the increase in cost of organization as a group grows. Yet, this hypothesis lacks a mechanistic model to investigate the organizational advantage of hierarchy and its role on its evolution. To fill this gap, we describe social organization by the distribution of individuals’ capacity to influence others. We then integrate this formalization into models of social dynamics and evolutionary dynamics. First, our results demonstrate that hierarchy strongly reduces scalar stress, and that this benefit can emerge solely because leaders and followers differ in their capacity to influence others. Second, the model demonstrates that this benefit can be sufficient to drive the evolution of leader and follower behaviours and ultimately, the transition from small egalitarian to large hierarchical groups.
2019
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Being a leader or being the leader: The evolution of institutionalised hierarchy
In , Jul 2019
Abstract. Human social hierarchy has the unique characteristic of existing in two forms. Firstly, as an informal hierarchy where leaders and followers are implicitly defined by their personal characteristics, and secondly, as an institutional hierarchy where leaders and followers are explicitly appointed by group decision. Although both forms can reduce the time spent in organising collective tasks, institutional hierarchy imposes additional costs. It is therefore natural to question why it emerges at all. The key difference lies in the fact that institutions can create hierarchy with only a single leader, which is unlikely to occur in unregulated informal hierarchy. To investigate if this difference can affect group decision-making and explain the evolution of institutional hierarchy, we first build an opinion-formation model that simulates group decision making. We show that in comparison to informal hierarchy, a single-leader hierarchy reduces (i) the time a group spends to reach consensus, (ii) the variation in consensus time, and (iii) the rate of increase in consensus time as group size increases. We then use this model to simulate the cost of organising a collective action which produces resources, and integrate this into an evolutionary model where individuals can choose between informal or institutional hierarchy. Our results demonstrate that groups evolve preferences towards institutional hierarchy, despite the cost of creating an institution, as it provides a greater organisational advantage which is less affected by group size and inequality.
2018
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Can justice be fair when it is blind? How social network structures can promote or prevent the evolution of despotism
In , Jul 2018