Saturday, November 2, 2019

Toward a General Theory of Societal Collapse: A Biophysical Examination of Tainter’s Model of the Diminishing Returns of Complexity

Toward a General Theory of Societal Collapse: A Biophysical Examination of Tainter’s Model of the Diminishing Returns of Complexity. Jan 1. 2019. Bardi et al. via springer. or free PDF.

Abstract.

The collapse of large social systems, often referred to as “civilizations” or “empires,” is a well-known historical phenomenon, but its origins are the object of an unresolved debate. In this paper, we present a simple biophysical model which we link to the concept that societies collapse because of the “diminishing returns of complexity” proposed by Joseph Tainter.
 Our model is based on the description of a socio-economic system as a trophic chain of energy stocks which dissipate the energy potential of the available resources. The model produces various trajectories of decline, in some cases rapid enough that they can be defined as “collapses.” At the same time, we observe that the exploitation of the resource stock (“production”) has a strongly nonlinear relationship with the complexity of the system, assumed to be proportional to the size of the stock termed “bureaucracy.” These results provide support for Tainter’s hypothesis.

1. Introduction

The collapse of large social systems, also called “civilizations” or “empires,” is a well-known and highly studied subject. In many cases, the historical record does not provide quantitative data on these events, but in some cases it is possible to quantify the collapse phenomenon in terms, for instance, of the extent of the areas controlled by the central government as reported by Tageepera or of the output of the economic system as reported by Sverdrup and McCollen et al. In these studies, we can observe how collapses are often rapid in comparison to the build-up of the social and economic structures of a civilization. This behaviour is consistent with Diamond’s definition of collapse as, “a drastic decrease in human population size and or political / economic / social complexity, over a considerable area, for an extended time.”

Nevertheless, despite the number of studies in this area, there is little agreement on the causes of societal collapses and, in particular, on the possibility of a common mechanism causing them. Edward Gibbon was probably the first to attempt an interpretation of the fall of a large empire, the Roman one, attributing it mainly to the decline of the traditional values. Later authors explained the fall of Rome in widely different ways and Demandt (1984) lists about 210 different theories on this subject, probably an incomplete list. The same variety of interpretations affects the studies of the collapse of other societies in history, as described, for instance, by Tainter in 2008.

No consensus appears to exist in this field but, overall, we can divide the interpretations of collapses into two main subsets: theories based on several independent causes (concauses) and theories based on a single cause that generates a cascade of different effects. An example of the first approach – several independent concauses – is the study by E. H. Cline on the collapse of the Late Bronze Age Mediterranean Civilization. According to Cline, multiple negative effects occurred at the same time, including climate change, earthquakes, foreign invasions, and more. An extreme example of the multiplication of causes is the study Bury published in 1923 who argued that the collapse of the Roman Empire resulted from several contingent events all occurring at about the same time. Tainter comments stating that Bury considers that “The collapse was just bad luck”.

There are several examples of the second approach, single cause followed by a cascade of related events. One is Douglas Reynolds’ interpretation of the fall of the Soviet Union in 1991. Reynolds attributes it to mineral depletion and, specifically, to the cascade of negative effects generated by the growing costs of oil production which affected the whole Soviet economic system. Another single factor model of civilization collapse factor has been proposed by Joseph Tainter in his study “The Collapse of Complex Societies” and in later papers. Tainter identifies “diminishing returns,” a well-known concept in economics, as the general factor in the decline and fall of civilizations. The idea is that, as societies become larger, more complex control structures are needed to maintain the cohesion of society and solve the problems that appear along their path. These structures can be described in terms of governments, the nobility, armies, bureaucracy, and the like. According to Tainter, as these structures become larger, they become less efficient, to the point that the economic returns they provide are smaller than their cost. At this point, society becomes unable to cope with the challenges it faces and must decline, or even collapse. The contrast between single/multiple causes in the interpretation of the fall of societies highlights a general methodological problem. Not only data are often scarce on these historical phenomena, but their interpretation is often based on the author’s personal judgment of the relative importance of the events he studies. It goes without saying that the collapse of civilizations is not amenable to experimental studies but, even taking this point into account, one may ask how proposing a specific interpretation of the fall of – say – the Roman Empire can be justified. Here, we have several problems, including the fact that the very concept of “causation” is hard to approach in a quantitative manner.

Nevertheless, we can choose to rely on the basic scientific concept that the preferable interpretation of an event is not only one that’s compatible with the available data, but also which is of general validity – that is, can explain more than a single event of the same class. In this sense, Tainter’s interpretation of “diminishing returns of complexity” provides a general framework to interpret a large number of cases and it is, therefore, an interesting idea in view of understanding the general phenomenon of societal collapse. In the present study, we looked at Tainter’s ideas using the modern concept of “System Science.”

By using the modelling method known as “system dynamics” we developed a simple biophysical model describing the evolution of a society. The model includes the effects of overshoot and of diminishing returns in the exploitation of natural resources. It is not supposed to describe specific social systems but to provide a “mind-sized” model the main factors that cause collapse. We find that the complexity of the system assumed to be proportional to the size of a stock such as “bureaucracy” follows a trajectory that makes the model compatible with the one proposed by Tainter. That is, the system shows a hysteresis that makes its trajectory non-reversible: reducing the costs of bureaucracy doesn’t return society to the previous conditions of prosperity. ...

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