At the physics school of Les Houches, in March 2018, Gregoire Chambaz of the University of Lausanne gave a talk on the phenomenon of "collapse caused by diminishing returns of complexity." (The image above is not from Les Houches but from a meeting in Lausanne last year).
In itself, it is already interesting that a meeting of physicists gives space to the idea of societal collapse, but the school of Les Houches was one of the rare cases of a truly interdisciplinary meeting. The result was a wide variety of approaches, including the talk by Gregoire Chambaz who approached the problem examining the concept of "diminishing returns of complexity" proposed by Joseph Tainter already in 1988. You can find a summary (in French) of Chambaz's work at this link.
If you are a reader of this blog, you probably know Tainter's graphic to explain his concept. Here it is.
The idea is that, as societies become larger, they must develop more and more complex control systems in order to manage the whole system. These control systems may be in the form of bureaucracy, an imperial court, the army, the church, the legal system, and more. And, as these systems become larger, they become unwieldy, rigid, and unmanageable. The effort needed to increase their size is not matched by the benefit they provide. According to Tainter, this is the ultimate reason for the collapse of large societies.
As a model, Tainter's one has proved to be hugely popular and surely it is a "mind sized model," easy to understand and providing an immediate grasp of the evolution of the system. The problem is that Tainter's model has no evident basis in physics. There is no precise explanation of what would cause the behavior that Tainter proposes, not it is possible to measure concepts such as "the benefits of complexity." It is only a qualitative model.
Can we model this kind of collapse using physics? Perhaps. In principle, there could be two reasons why the system stops improving its performance as it grows in size. One could be an effect of entropy. If you work in a large organization, you understand how, over time, it becomes a tangle of contradictory rules and of people and offices which seem to exist only to prevent any work being done (OK, I have in mind the University of Florence, but I am sure it is not the only case in the world). But how to quantify this effect?
Then, the reason for this behavior could be another one. Maybe it is not an intrinsic property of a large system to lose efficiency as it grows, but an effect of the slow decline of the net energy that it uses. That would explain many things and I put together a tentative dynamic model a few years ago which seemed to work. We are working on improving it taking into account the dynamics of the Seneca Effect. It is a work we are doing together with my coworkers Sara and Ilaria, but it will take a little time before we publish it.
Overall, the impression I have is that we are starting to develop an extremely rich field of studies, that of critical phenomena in complex networks. Tainter gave us a first indication of the way to go, but there is much, much more to do before we can say we have a solid theory explaining the periodical collapse of civilizations we observe in history. But we keep going.
