Modeling The Egalitarian Revolution

I mentioned the drawn out process of me trying to download this new paper, “Dynamics of Alliance Formation and the Egalitarian Revolution,” the other day. I’ve read it and although I found it to be a difficult and theoretically dense paper, I believe you should also read the open access piece if you have any interest in understanding how culture evolved and the possible mechanisms of egalitarian behavior early on in human evolutionary history. The paper’s first author is Sergey Gavrilets, a theoretical evolutionary biologist from the University of Tennessee, Knoxville. The other co-authors are also from the same institution.

You may know Gavrilets’ other piece on cultural evolution, the 2006 paper in which he and Aaron Vose built a mathematical model to test out the social brain hypothesis — creating situations where genes control brains which invent and learn strategies that are then used by individuals to gain advantage in competition for mates. He’s continued researching the evolution of social behavior, and in his most recent piece he and his team tackle the dynamics of coalition formation.

The observation that Gavrilets et al. make is that while our closest living evolutionary cousins form alliances and cooperate in groups, their social systems are extremely hierarchical. The most glaring example can be seen in a gorilla troop where a dominant silverback presides over a few adolescent males and a harem of females. The group dynamic is fluid throughout life history, but each member of the system ultimately plays a role in the dominance hierarchy.

But early human societies, such as the quintessential hunter-gatherer society, is generalized as being egalitarian. Prior to the agricultural revolution, hunting and gathering is thought to have been the only subsistence strategy deployed by early human cultures. Studying modern day hunter gatherers, ethnographers have noted that such societies distribute dominance much more equally and thus tend to be non hierarchical. Leaders are comparatively weaker than their subordinates which reverses the pyramid of power.

So why was there such a big behavioral shift during our evolutionary history? We may never know for sure. There are ideas floating around that all seem to suggest the lack of food and realization that cooperation, rather than competition, was more beneficial for overall survival. When food sources became more dependable, as seen after the Neolithic and the dawn of agriculture and pastoralism, is when we’ve seen a return to a traditional hierarchy.

Gavrilets and team created a complex model which ultimately relied on probability to solve problems. They simulated alliance formation among a group of individuals who had different fighting abilities. Their system distinguished between conflicts that existed only between pairs of individuals and conflicts that were composed of more than two individuals. In situations that conflicts existed solely between two individuals, a very structured hierarchy emerged, favoring the ones best able to fight for their interests. In situations that composed of more than two individuals, there was interference or a balance of power, where the hierarchy was biased towards one result over another.

With an increase of group size, Gavrilets et al. were able to see an increase in dyadic conflicts. When members of a group were aware of other conflicts, of which they were not directly related, there was also an increase of dyadic conflicts. Naturally, larger coalitions have a higher probability of winning a conflict and a positive outcome increased affinity between members of the coalition.

Again, this was a rather hard paper to read, and I’ve left out a lot of details. I’m a bit unclear about what was rewarded to drive forward the model, i.e. what were they fighting for? Some of you may write off models as being controversial and reductionist. You’re right. For starters, it is difficult to interpret methods and the data doesn’t seem like it factors in the interactions of so many different variables — some come from evolutionary, ecological, behavioral, and social factors and all acting simultaneously. It is also awkward to evaluate relevant time-scales, aside from generation turnover, and to figure out possible evolutionary dynamics.

But the model did show that the tendency towards egalitarianism is rapid — it consistently happened in the course of several generations. Under situations where all members of a group were a part of one alliance, where not all members were equal, they still remained united. But alliances weren’t permanent. They would phase and out of intensity. Outsiders were also a crucial part of keeping the dynamic alive.

Gavrilets and crew suggest that egalitarianism came along with changes in mating systems and influenced by primate mother-daughter bonding. They also noted that the emergence of language most definitely facilitates the formation of alliances. One last thing, the authors sent out a warning against considering modern day humans under such constraints, because when we join alliances, our decisions are strongly affected by how much we perceive to get out of the alliance versus the costs and risks of being a part of the alliance, which are factors not included in the model.

All aside, this model is informative but it is by no means the way human social behavior evolved. I’ve already outlined some of the caveats to modeling. To further supplement, there are exceptions to the rule that all hunter gatherer societies are/were egalitarian. Non-egalitarian hunter gatherer systems, such as the Haida, have been well documented by ethnographers. I also remember one of my anthropology professors telling me her accounts of living with outcasted Dassenach people. They were forced out of the pastoral lifestyle and into a hunting for crocodiles and fish one. But, they still retained the social structure despite the shift in subsistence.

    Sergey Gavrilets, Edgar A. Duenez-Guzman, Michael D. Vose, Erik I. Svensson (2008). Dynamics of Alliance Formation and the Egalitarian Revolution PLoS ONE, 3 (10) DOI: 10.1371/journal.pone.0003293

2 thoughts on “Modeling The Egalitarian Revolution

  1. Reminds me of “Demonic Males”, which I reviewed here. Wrangham attributes the social difference between gorillas and our closer relatives, the chimpanzees, to their feeding patterns. He also thinks humans diverged from chimpanzees because we were forced to feed on roots rather than fruit. His focus is more on gender-egalitarianism, a metric by which the first world ranks higher than hunter gatherers.

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