The transition from egalitarianism to leadership and despotism

Powers ST, Lehmann L. 2014 An evolutionary model explaining the Neolithic transition from egalitarianism to leadership and despotism. Proc. R. Soc. B281: 20141349. http://dx.doi.org/10.1098/rspb.2014.1349

Abstract

The Neolithic was marked by a transition from small and relatively egalitarian groups to much larger groups with increased stratification. But, the dynamics of this remain poorly understood. It is hard to see how despotism can arise without coercion, yet coercion could not easily have occurred in an egalitarian setting. Using a quantitative model of evolution in a patch-structured population, we demonstrate that the interaction between demographic and ecological factors can overcome this conundrum. We model the coevolution of individual preferences for hierarchy alongside the degree of despotism of leaders, and the dispersal preferences of followers. We show that voluntary leadership without coercion can evolve in small groups, when leaders help to solve coordination problems related to resource production. An example is coordinating construction of an irrigation system. Our model predicts that the transition to larger despotic groups will then occur when: (i) surplus resources lead to demographic expansion of groups, removing the viability of an acephalous niche in the same area and so locking individuals into hierarchy; (ii) high dispersal costs limit followers' ability to escape a despot.* Empirical evidence suggests that these conditions were probably met, for the first time, during the subsistence intensification of the Neolithic.

1. Introduction

Understanding how leadership and dominance behaviours in humans have changed over evolutionary time is relevant to both biology and the social sciences. What drove the transition from largely egalitarian hunter–gatherer groups, where leadership was facultative and dominance attenuated [1], to the hereditary and more despotic forms of leadership that arose during the Neolithic [2,3]?

On the one hand, ‘coercive’ (or ‘agency’) theories have focused on the development of inequality that was made possible with the origin of food storage and agriculture, allowing dominant individuals to build up resource surpluses that could be used to consolidate their power [4–6]. On the other hand, ‘functional’ (or ‘integrative’) theories have addressed the benefits that leaders provide to other group members. In particular, as human group size increased during the Neolithic [7,8], the resulting scalar stress [9] would have necessitated increased hierarchy in order to solve various coordination and collective action problems [10–16]. Leadership could have been favoured to solve problems, including the coordinated harvesting of marine resources [17–19], the construction of irrigation systems [20–23] and defensive warfare [24,25].

But when considered alone as competing theories, both coercive and functional models struggle to explain the transition to despotism seen during the Neolithic. Purely coercive theories cannot explain why individuals would initially choose to follow a despot [16,26]. Boehm [1] presents evidence suggesting that present-day hunter–gatherers actively form coalitions to suppress would-be dominants, and argues that prehistoric hunter–gatherers did likewise. Moreover, the advent of projectile weapons is likely to have made such coalitions particularly effective [27], tipping the balance of power away from an individual dominant. Thus, the question is, why would individuals not continue to prevent despotic behaviour? But if individuals are unconstrained in their choice of leader, then it is difficult to see how despotism could develop.

Several authors have argued that an adequate model of the origin of increased social stratification must incorporate both functional and coercive aspects [15,22,28]. There is evidence that aspiring leaders drove the development of technology that increased subsistence intensification and raised population carrying capacity [17,22]. For example, construction of irrigation systems would have allowed more land to be used for agriculture, providing an incentive for individuals to follow the leader. This fits with functional theories. On the other hand, the surplus resources that this provided could then be appropriated by leaders to further their own ends and consolidate their power. This is particularly the case given that irrigation farmers would be tied to the system, making dispersal away from a despot difficult. Spencer [22] developed a verbal model of this for the case of irrigation systems in prehispanic Mexico, and warfare in prehispanic Venezuela. However, the feedbacks between population size, functional aspects of leadership and the development of despotism remain poorly understood and are difficult to capture with verbal models.

Here, we present an evolutionary model of the dynamics of the transition from small-scale egalitarian to larger-scale hierarchical groups, which integrates both functional and coercive aspects of leadership. We use a demographically explicit model of a patch-structured population, in which surplus resources translate into increased reproductive output for those who receive them, as has been common throughout human history [29,30]. Unlike previous work, this allows us to capture the ecological and demographic interactions between subsistence intensification, dispersal costs and the evolution of despotic behaviour.

For informal commentary, see Sid Perkins, The benefits of inequality, Science, August 5, 2014:

When the researchers let the model run over several generations, they found that, in general, groups made up of leaders and followers were able to produce or gather more resources than those made up of egalitarian-minded individuals. That, in turn, enabled the hierarchical group to grow more quickly and to better eke out a living. According to the model, groups made up of leaders and followers eventually grew to about twice the size of societies solely composed of egalitarians. And even when leaders skimmed a large portion of a group’s resulting surplus for themselves and their families, their followers received, on average, more resources than they would have if they’d been part of a leaderless band, Powers and Lehmann report online today in the Proceedings of the Royal Society B. [Above]

To see how this might have worked in the real world, consider nascent agricultural societies, Powers says. In such groups, widespread cooperation is necessary for large endeavors such as planting and harvesting crops and for building irrigation systems. Having leaders to organize such projects and followers to carry them out may have been a more efficient form of social organization than true egalitarianism. Followers may have been willing to exchange a bit of control over their lives for access to a society-wide increase in resources, Powers says.

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* On the second point, see my post, Reading The Human Swarm 1: Hunter-Gatherers and the Plant Trap:

And here’s something I think is very important, 137-8:

As it would turn out, giving up hunting and gathering was no advance in quality of life. After the advent of farming, people grew smaller, weaker, and more sickly as they struggled to nurture and harvest crops–conditions that wouldn’t be reversed until the invention of the plow and harnessed oxen.

This is something not appreciated widely enough. For all except the ruling elite, the agricultural life style was a step back in terms of material life, something David Hays discussed in his book, The Evolution of Technology Through Four Cognitive Ranks (1995) – I’ve excerpted the relevant passage at this link, which includes thumbnail estimates of per capita energy expenditure, work hours, and material welfare. Moffett continues on, 138:

Taking to cultivation at all but the smallest scale of simple gardening had another drawback that no early farmer could have predicted: it could ensnare a society in a plant trap. A trap, because the option of going back to hunting and gathering full time faded away once an expanding society committed to agriculture. [...] Yet once a society grew to a huge population, or was packed in tight with other agricultural societies, the numbers of people would be too great to be supported by native foods and starvation would be guaranteed.

Plant trap: I'm wondering if the USA got into a similar situation after WWII. We'd geared up war production to fight the war and then kept it going through Korea and the rest of the fifties leaving us with the military-industrial complex Eisenhower warned about. Now, with military production dispersed through all 50 states our economy is become (all but permanently) stuck in war mode.