Why do large-scale complex societies, within which >99% of humanity now lives, recurrently experience periods of social and political breakdown? This question is morbidly fascinating, especially since after we’ve entered the “Turbulent Twenties.” Books on collapse are now a cottage industry and there is a whole new science called collapsology. The classics, such as Joseph Tainter’s The Collapse of Complex Societies, enjoy enduring popularity. “Societal Collapse” has been surging on the GoogleBooks Ngram Viewer.
Tainter argued that as societies become more complex, they become more fragile and susceptible to collapse. More recently, this theory has received a name, “Complexity Overhang.”
A negative view of social complexity as a source of instability fits well with another current in political thought, anarchism, which sees the state as the source of all evil—oppression, violence, and legalized theft (aka taxation). In my view, political anarchism is complete bunk, as I’ve argued in these blog posts:
But returning to the question of the relationship between complexity and stability, I need to confess that until recently I also thought that “simple” societies—small-scale societies of farmers without deep social inequalities and no political organization beyond a local settlement (village)—were quite resilient/not susceptible to collapse. In such societies there is no state or nobles to rebel against and, in any case, what’s there to “collapse”?
Life in a simple society—prosperous, peaceful, and free of oppression? Source
But perhaps “collapse” is not such a useful way of thinking about societal dynamics — it is a problematic concept because it can mean so many things. This is why I am not a collapsologist—I prefer to work with well-defined concepts (which, ideally, are amenable to quantification). So let’s approach this question from the point of view of quantitative history.
The most basic property of a society is its size—how many people interact together and (hopefully) cooperate. Population numbers (or density – numbers divided by area) is, thus, a fundamental variable for cliodynamics. Previous work by my colleagues and me on state-level societies shows that waves of sociopolitical instability are often associated with substantial population declines—“population busts.” The current tabulation of past crises in CrisisDB (note: work in progress), indicates that in roughly half the cases sociopolitical crisis in “complex” societies results in a substantial population decline. What about pre-state, non-centralized societies?
There is a classic study by Ammerman and Cavalli-Sforza on the rate of spread of early farming in Europe, published in 1971. I studied it in graduate school because it was one of the first applications of the diffusion equation to population spread (population dynamics in space and time was my disciplinary specialty before I switched to quantitative history). These distinguished authors started with the observation that farming increases the “carrying capacity”—how many people can be supported per unit of land (e.g., a squared kilometer). A population of farmers, after spreading into a new area, would grow until it reached this carrying capacity and then stabilize at that level (with some fluctuations due to variable climate and other random factors). This dynamic process was captured by Ammerman and Cavalli-Sforza with the logistic equation.
But as archaeologists developed better methods for estimating past populations and accumulated lots more data, it turned out that this assumption was wrong. In several regions into which first European farmers spread (this is known as the LBK culture) we see, as expected, an initial population boom, resulting from a more productive economy. But instead of leveling off, the boom was abruptly followed by a bust.
Population densities of the early LBK in the lower Rhine basin. Figure 6 in Zimmermann, A., J. Hilpert, and K. P. Wendt. 2009. Estimations of Population Density for Selected Periods Between the Neolithic and AD 1800. Human Biology 81:357-380.
And the same pattern is observed not only in Europe, but also in other world regions.
Last week Daniel Kondor and I organized a workshop at the Complexity Science Hub in Vienna, in which we delved into this issue. While we know that population busts in early farming societies were a frequent occurrence, we don’t yet know whether such cycles were universal, or whether there were periods and places when population levels stabilized for long periods of time. For the list of participants and the questions that we discussed, see the CSH press release:
We also discussed the possible causes of population busts in prehistory. But that is a topic for another post.