I’ve just read five of Peter Turchin’s books: Historical Dynamics (2003), War & Peace & War (2006), Secular Cycles (2009), Ultra Society (2015), and Ages of Discord (2016). Four of them in the last week. I did this because I love careful big picture thinking, and Turchin is one of the few who does this now on the big question of historical cycles of conflict and empire. While historians today tend to dislike this sort of analysis, Turchin defies them, in part because he’s officially a biologist. I bow to honor his just defiance and careful efforts.

Turchin’s main story is a modest variation on related farmer-era historical cycle stories, such as by Jack Goldstone in 1991, & Ibn Khaldun in 1377 (!):

Different groups have different degrees of cooperation .. cohesiveness and solidarity. .. Groups with high [cohesion] arise on .. frontier .. area where an imperial boundary coincides with a fault line between two [ethnic] communities .. places where between group competition is very intense. .. Only groups possessing high levels of [cohesion] can construct large empires. ..

Stability and internal peace bring prosperity, and prosperity causes population increase .. leads to overpopulation, .. causes lower wages, higher land rents, and falling per capital incomes. At first, low wages and high rents bring unparalleled wealth to the upper class, but as their numbers and appetites grow, they also begin to suffer from falling incomes. Declining standards of life breed discontent and strife. The elites turn to the state for employment and additional income and drive up its expenditures at the same time that the tax revenue declines. .. When the state’s finances collapse, it loses the control of the army and police. Freed from all restraints, strife among the elites escalates into civili war, while the discontent among the poor explodes into popular rebellions.

The collapse of order brings .. famine, war, pestilence, and death. .. Population declines and wages increase, while rents decline. .. Fortunes of the upper classes hit bottom. .. Civil wars thin the ranks of the elites. .. Intra-elite competition subsides, allowing the restoration of order. Stability and internal peace bring prosperity, and another cycle begins. (pp.5-8 W&P&W)

Turchin (& coauthor Nefedov) collect much data to show that this is a robust farmer-era pattern, even if there are many deviations. For example, in Europe, 33 of 43 frontier situations gave rise to big empires, yet only 4 of 57 of non-frontier situations did (p.84 HD). “Secular cycles” vary in duration from one to four centuries; Western Europe saw 8 cycles in 22 centuries, while China saw 8 cycles in 21 centuries (p.306,311 SC). During the low instability part of each cycle, instability shows a rough “alternating generations” 50 year cycle of conflict.

I’ll grant that Turchin seems to have documented a reasonably broad pattern, containing most of his claimed elements. Yes, empires tend to start from frontier groups with high cohesion, and core cohesion changes slowly. First there’s war success and a growing area and population, and bigger cities. Eventually can come crowding and falling wages. Inequality also grows, with more richer elites, and this is quite robust, continuing even after wages fall.

While the amount of external war doesn’t change over the cycle, success in war falls. Many signs of social cohesion decline, and eventually there’s more elite infighting, with crime, duels, misspending state revenue, mistreatment of subordinates, and eventually civil war. Big wars can cut population, and also elite numbers and wealth. Eventually war abates and cohesion rises, though not to as high as when the empire started. A new cycle may begin; empires go through 1-3 cycles before being displaced by another empire.

Just as science fiction is often (usually?) an allegory about issues today, I suspect that historians who blame a particular fault for the fall of the Roman Empire tend to pick faults that they also want to warn against in their own era. Similarly, my main complain about Turchin is that he attributes falling cohesion mainly to increased inequality – an “overproduction” of elites who face “increased competition”. Yes, inequality is much talked about among elites today, but the (less-forager-like) ancients were less focused on it.

As Scheidel said in The Great Leveler, inequality doesn’t seem to cause civil wars, and civil wars tend to increase inequality during and after the war (p.203). External wars reduce inequality for losers and increase it for winners, without changing it much overall. It is only big mass mobilization wars of the 1900s that seem to clearly cause big falls in inequality.

In biology, over multiple generations organisms slowly accumulate genetic mutations, which reduce their fitness. But this degradation is countered by the fact that nature and mates select for better organisms, which have fewer mutations. Similarly, it seems to me that the most straightforward account of the secular cycle is to say since empire founders are selected out of a strong competition for very high cohesion, we should expect cohesion to “regress to the mean” as an empire evolves.

That is, in order to predict most of the observed elite misdeeds later in the secular cycle, all we need to assume is a random walk in cohesion that tends to fall back to typical levels. Yes, we might want to include other effects in our model. For example, civil war may allow a bit more selection for subgroups with more cohesion, and humans may have a psychological inclination to cohere more during and after a big war. But mostly we should just expect cohesion to decline from its initial extreme value, and that’s all a simple model needs.

Yes, Turchin claims that we know more about what causes cohesion declines. But while he goes to great effort to show that the data fit his story on which events happen in what order during cycles, I didn’t see him offering evidence to support his claim that inequality causes less cohesion. He just repeatedly gives examples where inequality happened, and then instability happened, as if that proves that the one caused the other.

We already have good reasons to expect new empires to start with a small area, population, and inequality. And this by itself is enough to predict growing population, which eventually crowds to cut wages, and increasing inequality, which should happen consistently in a very wide range of situations. I don’t see a need for, or data support for, the additional hypothesis that inequality cuts cohesion. We may of course discover more things that influence cohesion, and if so we can add them to our basic secular cycle model. But we don’t need such additions to predict most of the cycle features that Turchin describes.

In his latest book, Turchin points out many U.S. signs today of rising inequality and declining social cohesion, and at the end asks “Will we be capable of taking collective action to avoid the worst of the impending democratic -structural crisis? I hope so.” But I worry that his focus on inequality leads people to think they need to fight harder to cut inequality. In contrast, what we mostly need is just to fight less. The main way that inequality threatens to destroy us is that we are tempted to fight over it. Instead, let us try more to see ourselves as an “us” contrasted with a “them”, an us that needs to stick together, in part via chilling and compromising, especially regarding divisive topics like inequality.