Field of Science

The Origins of Inequality
Inequality is a national conversation topic now, thanks largely to the efforts of Occupy Wall Street and the broader Occupy movement. Fundamental questions are being asked, such as "Must inequality necessarily be a part of human society?", "Are we genetically disposed toward hierarchy or egalitarianism?", and "What would a global egalitarian human society look like?"

We can gain a bit of perspective on these questions by looking at the evolutionary history of humans and our primate relatives:
  • Our two closest animal relatives are chimpanzees and bonobos. Chimpanzee society is characterized by a strict hierarchy of males, with frequent aggressive conflicts between them to maintain or challenge dominance order. In bonobo society, on the other hand, hierarchies are weak, and conflict resolution is peaceful, often involving sex play.
  • Baboon societies in the wild are also characterized by a strict dominance hierarchy, in which higher-ranking males regularly harass lower-ranking ones and commandeer their food or resting spots. There is one notable exception, however. In 1982, all of the dominant males in a baboon tribe observed by Robert Saplosky were suddenly wiped out by a tuberculosis outbreak, leaving only the lower-ranking males. There followed a marked shift in the culture of the troop: hierarchy remained, but those at the top were much less likely to harass lower-ranking males or steal their food. Moreover, this more relaxed culture was observed in the same tribe two decades later, even after all the males present during the original shift had died or migrated to other tribes (Saplosky and Share 2004).
  • Modern hunter-gatherer societies, the closest analogue we know of to our distant ancestors, are uniformly characterized by a strong egalitarian ethos, in which resources are shared and those who attempt to hoard them are ostracized (Boehm 2001). On the other hand, the transition to agriculture lead to the advent of unequal social classes, with the lower classes often suffering from malnutrition (Diamond 1987).

From left to right: Chimpanzee, Bonobo, Olive Baboon.  Source: Primate Info Net

Taken together, these examples suggest that humans aren't inevitably predisposed to either hierarchy or egalitarianism. Rather, we are capable of either mode of society. These examples also suggest that, like the baboons, we might be able to shift from one mode to the other in the wake of a destabilizing catastrophe.

A mathematician, economist, or theoretical biologist would call this an example of multiple equilibria. The situation might be depicted like this:

That is, there are two stable configurations of society (really, much more than two, but we're simplifying here): hierarchical and egalitarian. Each equilibrium is stabilized by different mechanisms. In hierarchical societies, those at the top have enough power to squelch any attempt at overthrowing the hierarchy. In egalitarian societies, those who attempt to selfishly amass resources or power are ostracized by the rest of the group. Christopher Boehm discovered these mechanisms for egalitarianim in his survey of modern hunter-gatherer societies
I discovered that their egalitarian political arrangements were quite deliberate. They believed devoutly in maintaining political parity among adults. This belief was so strong that males who turned into selfish bullies, or even tried to boss others around for reasons useful to the group, were treated brutally, as moral deviants. (Boehm 2007)
Because of these mechanisms, the two extreme ends of this spectrum are quite stable. Escaping them is very difficult without a demographic catastrophe like the tuberculosis outbreak in baboons, a major technological shift like the development of agriculture, or a "starting over" opportunity like the colonization of a new continent.

The middle regions of this spectrum, however, are less stable. In these regions, some individuals wield a disproportionate share of power, but not enough to completely suppress the interests of the less-powered classes (the 99%). This leads to persistent power struggles between these classes, in which the balance could ultimately be tipped in either direction.

The United States has always been an unequal society, but the checks and balances of democracy have thus far kept it from sliding into despotic hierarchy. The balance of power has fluctuated throughout our history, with periods of robber baron-style capitalism alternating with progressivist movements. I'm worried, however, that we're currently sliding toward self-reinforcing inequality, as the moneyed elite increase their influence over politics, which leads to policies that make them richer, which gives them even greater influence over politics, and so on.

This multiple equilibria model tells us that we may have only a limited window of opportunity to correct this slide. If an equilibrium of extreme inequality is reached, only an enormous catastrophe would be able to undo it.

Sapolsky, R. and Share, L. (2004). A Pacific Culture among Wild Baboons: Its Emergence and Transmission PLoS Biology, 2 (4) DOI: 10.1371/journal.pbio.0020106


  1. I believe that this position is highly possible, this is a small-part of human behavior.

  2. nice analysis. what your saying seems to be consistent with the history showing that big catastrophes or crises are needed to spur major policy changes in a progressive direction (great depression, 60s unrest), and without them, we more naturally veer in a hierarchical, conservative direction.

  3. That's true, Jesse, though our current great recession seems to be an odd exception so far.

  4. The Sapolsky paper only shows reduced aggression in a population in which aggressive males died at a higher frequency. The hierarchical structure and its stability did NOT change. This paper only shows that aggression has genetic components. Aggression is not the same as dominance. On the other hand, there is absolutely no evidence to claim that modern hunter-gatherers are the closest analogs to our distant ancestors. The absence of evidence for hierarchy in our distant ancestors is not evidence for the absence of hierarchy.


    This is correct. I tried to make this distinction in my description of his research, though I suppose I'm implicitly conflating the two ideas in the way I'm juxtaposing them.

    This paper only shows that aggression has genetic components.

    Well, this is certainly not what Saplosky and Share claim that their research shows. Rather, they claim that their observations are evidence that these behaviors are transmitted culturally, not just genetically. New males who later joined the group learned and adopted these less aggressive manners.


    Can you suggest a closer living analogue?


    Sure, but direct evidence either way is hard to come by, so we have to look at analogues or indirect clues.

  6. Well I think that having a big crisis might be a necessary but not sufficient condition for progressive change. So although every major progressive moment was facilitated by crisis, it wouldn't follow that every crisis facilitates a major progressive moment. Indeed, conservatives' can use crises for their own benefit too -- per Naomi Klein's book, The Shock Doctrine.

  7. As for this other issue, evolutionary psychology is a bitch for just that reason: we don't have fossils of the brains of our ancestors, so we have to use circumstantial evidence to create the most plausible "Just So" stories we can.

  8. With regard to baboons "transmitting" norms of a less violent hierarchy memetically, isn't it possible that such expression of less violent tendencies is the result of the surviving baboons of the outbreak producing and secreting less pheromones and behavioral hormones, thereby being less likely to incite increased production in newer members? It is well known that, among chimps at least, Alpha male position reflects the highest levels of both hormones and pheromones that trigger aggression in himself and his subordinates, in that sense constituting a highly dynamic group organism with the alpha male as its locus, only producing as much as is needed to maintain his position in a feedback loop "arms race" of chemical production/aggression. So, potentially, the baboons just need the right circumstances, and the currently peaceful members will up their production, and trigger increased aggression for themselves and subsequent generations. This sort of supports what you are suggesting in a roundabout way, only more biologically situated.


  10. CT--Yes, that makes sense as a possible explanation. I would still call it a form of cultural evolution, but through chemical cues rather than observation and imitation. I hadn't thought of this before.


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