It’s a big claim, and one that is bound to generate little enthusiasm among scientists and positive distrust among historians. For the first group, history is the quintessential mine field, where contingency and human agency rule the day, unlike the tidy behavior of subatomic particles, always the same under easily imposed identical conditions. As for historians, this will be seen as yet another arrogant attempt by a scientist to colonize their field and push aside the humanities (despite Turchin’s claim of potential unification of science and the humanities).
Turchin complains that there are more than 200 explanations proposed for the collapse of the Roman empire, a situation he finds “as risible as if, in physics, phlogiston theory and thermodynamics coexisted on equal terms.” Hmm, but then again, there are hundreds of different types of string theory, and none of them is, at the moment, empirically testable... Nonetheless, Turchin goes on to explain that there are, in fact, regularities, in human history. For instance, with two of his colleagues, Turchin found a statistically significant trend (statistics applied to history!) across various societies, according to which “the number of instability events per decade is always several times higher when the population was declining then when it was increasing.” This result was obtained by studying societies and time periods as different as the Roman Empire and eight Chinese dynasties.
Of course, this is not the first attempt to inject some science into the study of history. Most famously, another biologist, Jared Diamond, has provided us with empirically-based theories of the rise and fall of civilizations in his books, Guns, Germs and Steel and Collapse. Biologists are particularly well positioned for this sort of cross-disciplinary work because biology itself is largely historical in nature, especially evolutionary biology (Diamond’s specialty) and ecology (Turchin’s).
While I am sympathetic to the idea of moving history from a purely narrative-based discipline to one that relies on some degree of data collection, pattern analysis, and most importantly empirical hypothesis testing, I also find that scientists seem to chronically underestimate the problems posed by historicity in their own discipline, let alone in history itself. Diamond’s scenarios are very compelling, but they are far from the only explanation of why the Fertile Crescent, for instance, gave us so many early advances in civilization while meso-America lagged behind. This is not very different from the continuing debate, say, among paleontologists about why the dinosaurs went extinct: pretty much everyone agrees that the impact of an extraterrestrial body had something to do with it, but it is also clear that the dinosaurs had been in decline for millions of years before, and we may never know exactly why.
Turchin’s own example in the Nature article is really confined to uncovering a pattern, not testing an explanation. Pattern discovery is of course crucial, but Turchin himself admits that “the connection between population dynamics and instability is indirect, mediated by the long-term effects of population growth on social structures,” going on to list a good number of interacting causes that may underlie the pattern he uncovered. But how is one going to test a multi-causal, multi-level hypothesis with a chronic paucity of comparable data? Again, the situation is similar to the discussions among paleontologists about what causes mass extinctions, where people disagree even on the number of such events during earth’s history, and where the number of occurrences is barely sufficient to reach statistical significance as a pattern, let alone to provide enough discriminatory power among complex causal hypotheses.
Nonetheless, the proof is in the pudding, so to speak, so I wish Turchin and his cliodynamics much luck, and I will follow with interest whatever else he, Diamond and colleagues may turn up over the next few years. Now, is there any historian out there who would like to tell us why this is so wrongheaded as not to be worth even trying?