Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Monday, December 7, 2015

The fall of the Mediterranean society during the bronze age: why we still don't understand civilization collapse

Eric Cline  wrote an excellent book on the end of the Bronze Age in the Mediterranean region but, unfortunately, it doesn't arrive to a definite conclusion about the reasons of the collapse. Cline suggests that "several stressors" worked together to ensure the demise of this civilization. But this is very disappointing, to say the least. It is like a murder mystery where, at the end, we are told that the killer of Miss Scarlett could have been Professor Plum, Mrs. Peacock, Mrs. White, Reverend Green, or Colonel Mustard but, really, it seems that all of them simultaneously stabbed her.

Imagine a team of archaeologists living three thousand years in the future. They work at digging out the remains of an ancient civilization on the Eastern shore of the Mediterranean Sea, a region that its ancient inhabitants called "Syria." They find clear evidence that the Syrian civilization collapsed in correspondence of a series of disasters: a severe drought, a civil war, the destruction of cities by fire, foreign invaders, a reduction in population, and more. The evidence for these events is clear, but what exactly caused them? Our future archaeologists are baffled; they suspect that there is a single reason for this coalescence of disasters, but they can't find proof of what it could have been. One of them proposes that it had to do with the fact the ancient Syrians were extracting something from underground and using it as a source of energy. But, without reliable data on the production trends, they cannot prove that oil depletion was the basic cause of the Syrian collapse.

Something similar is happening today to the archaeologists who try to understand the reasons of the collapse of the Mediterranean civilization of the end of the second millennium BCE; the end of the Bronze Age. We have archaeological evidence of a brilliant and thriving civilization: palaces, works of art, commerce, metallurgy, and more. But we have also evidence that this civilization met a violent end: there are traces of fires destroying palaces and cities, there is evidence of droughts and famine, and some of the people living in the region, the Hittites for instance, disappeared forever from history. But what caused the collapse? That's a very difficult question.

Eric Cline's book, titled "1177 BC" shines some light on the history of the Bronze Age civilization and its demise. As a book, it is well done and it summarizes very well the result of nearly two hundred years of archaeological studies. It is a fascinating story of a time that strikes our imagination as a refined and sophisticated world; not an empire, but a loose federation of peoples. Sometimes they were engaged at warring with each other, but more often in commerce and in cultural exchanges. We can't imagine that such a sophisticated civilization would collapse so fast; possibly in just a few decades. And yet, it did.

So, what caused the collapse? Cline's book is good evidence of how difficult it is to understand these phenomena. A whole chapter, the last one, is dedicated to explore the reasons for the collapse, but it doesn't arrive to any definitive conclusion. As it is almost always the case when discussing societal collapse, we see different proposed reasons piling up: some experts favor external causes: invasions, droughts, earthquakes, volcanoes, or similar. Others seek for internal causes: rebellions, institutional decline, political struggle, and more. And some, including Cline himself, favor a combination of several causes. He writes:

"There probably was not a single driving force or trigger, but rather a number of different stressors, each of which forced the people to react in different ways to accommodate the changing situation(s).... a series of stressors rather than a single driver is therefore advantageous in explaining the collapse at the end of the Late Bronze Age."

Unfortunately, this is far from being satisfactory. Suppose that I were to tell you "I am suffering of a number of different stressors, including fever, throat ache, sneezing, coughing, pain at the joints, and more." Then, you would look at me, perplexed, and say,"you mean you have a flu, right?" Yes, of course, all these different "stressors" result from a single cause: a viral infection. Just like a flu is a common illness in humans, collapse is such a common feature in human societies that we can hardly imagine that it could be caused by a fortuitous combinations of stressors, all acting in the same direction.

In examining this issue, a basic point is that societies are complex systems, and need to be understood as such. Unfortunately, the knowledge about complex system has not yet permeated the study of societal collapse, as it is amply demonstrated by the discussion in the last chapter of Cline's book. Several authors have apparently tried to explain the collapse of the Bronze Age society in terms of what they call "complexity theory". But I am afraid they didn't understand the theory very well.

Just as an example, in Cline's book we read a sentence taken from the work of Ken Dark who says ""The more complex a system is, the more liable it is to collapse." Now, this is simply wrong if it is applied to human organizations as complex systems, such a companies, or civilizations. And you don't need to be an expert in complex systems to note that large and very complex systems tend to be more resilient than small ones. Compare, for instance, IBM with the large number of small upstart companies in information technologies that appear and quickly disappear. So, you just can't invoke "complexity" as a mumbo-jumbo to explain everything, as, indeed, Cline correctly notes in the book.

A lot of confusion in this area has arisen from the variability of the definition of "complex system;" there is not just one kind of complex system, there are several (and that is something you would expect since they are, indeed, complex!). One kind of complex system that has had a lot of success in the popular imagination is the "sandpile", proposed by Bak, Tang, and Wissental, a model that shows a series of small and large collapses. The problem is that the sandpile model is valid for some systems, but not for others. It works nicely for those systems which have only simple, short term interactions: the financial system, for instance. But it doesn't work at all for systems which base their complexity on stabilizing feedbacks: civilizations, for instance. The difference should be clear: the financial system was never built with the idea that it should be stable. The opposite is true for a civilization or a large company, both have plenty of feedbacks designed to keep them stable or, if you prefer "resilient". Large organizations are often more resilient than small ones simply because they can afford more stabilization feedbacks.

Then, what can bring down a feedback-stabilized complex system? The answer is "a forcing that is strong enough." The term "forcing" is used in the study of system dynamics and it can be seen as having the same meaning of the "stressor" employed by Cline in his discussion. A forcing is an external factor that forces the system to adapt by changing some of its parameters. If the forcing is really strong, the adaptation can take the shape of a fast and disastrous reduction in complexity; it is what we call "collapse".

So, it is starting to appear clear that civilizations tend to collapse because they lose access to the resources that created them and allowed them to exist; often as the result of overexploitation. Over and over, civilizations have been brought down by soil erosion and the loss of agricultural productivity. Then, some civilizations have collapsed because of the depletion of the mineral resources that had created them, an example is the collapse of the modern Syrian state that I was describing at the beginning of this post. Another example is the collapse of the Roman Empire, It showed a lot of symptoms that we could call "stressors:" rebellions, corruption, wars, invasions, depopulation, and more. But they all originated from a single cause: the depletion of the gold mines of Spain which deprived the Imperial government of its fundamental control system: gold and silver coinage.

At this point, we can conclude that, most likely, there never were a combination of parallel stressors that brought down the Bronze Age Civilization. Rather, there was some basic factor that generated the various catastrophes that we observe today in the archaeological record. The problem is that we don't know what this forcing was. There are elements showing that climatic change played a role, but we lack sufficient evidence to be sure that it was "the" cause of the collapse.

So, perhaps it was mineral depletion that brought down this civilization? Maybe, and we can note how the defining term for this age is "bronze" and in order to have bronze you need to alloy copper with tin. And we know that there was plenty of copper available from mines in the Mediterranean region, but no tin; it had to be transported from a long and probably precarious supply route from the region we call Serbia today, or maybe from the Caucasus. If the people of the Bronze Age used bronze as currency, then their commercial network would have been badly disrupted by an interruption of the supply of tin. So, they might have been destroyed by the equivalent of a financial crisis.

Even though we cannot arrive to a definitive conclusion, the story of the Bronze Age civilization is part of the fascination we feel for the subject of civilization collapse. It is a fascination that derives from the fact that we may be seeing our "Western" civilization starting right now its final phase of collapse, after having badly depleted its sources of energy and generated the disastrous disruption of the ecosystem that we call "climate change." In our case, unlike for civilizations lost long ago, we have all the data we need to understand what happening. But we still don't understand collapse.


  1. Hi Ugo I love your work, Please don't take this the wrong way but perhaps we are over thinking this collapse thing. We know from nature that many if not all biological organisms are capable of, given the right circumstances (an energy subsidy) going through a bloom overshoot and crash process. It is possible to interoperate the collapse of many complex societies through this lens. If you look at complexicity as a problems solving strategy to solve the problem of human numbers reaching the capicity of the habitat to support that density then all that it takes to produce collapse is for deminishing returns to operate for a period of time. If we look at the civilizations of south America to see this in operation. What is also clear from these societies is that agricultural productivity need only drop a small fraction and it will undermine the capacity of complicity to support society as it is formulated.
    I have thought for some time that we attribute far to much to human agency as it could be argued that all of what we think of as civilization and indeed our obsession with thing such as resource depletion, technology, terrorism etc may well be nothing more than noise in the system.

  2. It is true, things change all the time, and when they change very fast, sometimes we use the term collapse. But the real thing is change and maybe the various collapses are just noise superimposed to a slow movement in some direction. Difficult to say where we are going, though....

  3. As I see it our real problem is too much success. Homo sapiens have used technology to delay the negative feedbacks that should have operated on human numbers and consumption habits. Humans are biological organisms so we can only delay these feedbacks not overcome them. It seems to me and others that the consequences of success are now immanent. It also appears to me that the overshoot is so large and so long delayed that the reversion to the mean could be large enough and fast enough to threaten the continuation of our species. That being said we cannot know the future and feedbacks such as climate change may not reach a runaway phase. Keep up the good work.

  4. Remains of Indus valley civilization also show a well organized and sophisticated network of cities, that collapsed rapidly for no single reason.

  5. Joseph Tainter based his book precisely on the increasing complexity of societies that lead eventually to their collapse due to diminishing returns. Instead of self stabilising feedback as you suggest, I suppose negative feedback operated instead such that more complexity resulted from increasing scale.

    As for ancient Rome, I have also read that the depletion of timber/wood in the Mediterranean was the ultimate cause, as it was the key source of energy at the time, another of which was slave labor of course.

  6. Oops I meant positive feedback, which works to keep increasing complexity.

  7. Again an interesting post!
    The depleted gold mine thing, though, I don't get: isn't currency meant to circulate, in other words, if the gold mass circulating diminishes, which seems to have been the case in Rome, where has it gone?
    Also, concerning the single cause of collapse: There is this saying, that one dog can have lice as well as fleas. Or this other saying that many dogs are the hares death.
    Also this leads to an interesting excursus into philosophy: what do we call "cause" of an event, given, that the case history is often complex? We ask for the most interesting aspect of the case history and call it "cause". If two people have differing notions of "interesting", they may name different "causes" for an event. So the very concept of "cause" has to be used with some caution.
    A widely acknowledged sort of an interesting aspect is, when the lines of causality have a common knot. In your flue example, this is the flue. But this is not always the case. A man kills another while beeing drunk. What is the cause? The alcohol? The early childhood? The genes? The fact, that the victim missed the bus and was not supposed to be there in the first place? Or the uncaused individual (in the literal meaning 'not divisible') responsability of the slayer?
    The credit crunch. What was cause? Too much money in the markets and no more high yield lo risk investment opportunities? Dumbness? A system of false incentives? Greed? The genes again? Lax regulation? Short memory of financial stakeholders?

    1. if the gold mass circulating diminishes, which seems to have been the case in Rome, where has it gone?

      There were several major precious metal sinks:

      1) The ground and the sea bottom (some fraction of all coinage gets buried/lost for various reasons, if that was not the case, archaeologists' lives would be much more difficult)

      2) Asia. The Roman empire was huge but it still did not produce everything the Romans wanted within the empire itself, it imported all sorts of luxury goods from the Arabian peninsula, India and China. That had to be paid for somehow.

      A third significant sink developed when it became a practice to buy off the barbarians on the northern border in order to placate them.

      So gradually the empire was being drained of precious metals because the outflow exceeded internal production and there was no significant inflow once the conquests ended.

      Regarding causes -- this is the core of the debate. One view is that if you have a huge and very complex system, it can have many "stabilizing" feedbacks but still be highly vulnerable to a long list of disturbances because it needs a very long list of inputs to keep going. So it eventually collapses, and many people end up arguing which exactly disturbance (or combination of) brought it down. We can call people who do that "proximal cause" seekers, but if we follow the line of thinking that focuses on the size and complexity of the system, the proximal reasons don't really matter that much (eventually some limiting factor will kick in), the ultimate cause for the collapse is size and complexity.

    2. Exactly this, Georgi. Most of the Roman gold ended in China, and part of it was buried underground; incidentally originated the myth of dragons hoarding it

  8. Ugo, I don't understand the motivation behind insisting that there should be a single cause (forcing, stressor, etc.) behind a civilization's collapse. Your attribution of the fall of the Roman Empire to the depletion of mines in Spain is a good example. Another scholar, John Perlin, has compellingly argued that the main cause was timber depletion:

    If you haven't read his book, I highly recommend it!

    I think you unnecessarily weaken your argument by insisting that a single factor is more important than others. Even if I have the flu virus, maybe my immune system is able to repel it one time but not another? Maybe I got my vaccination this year and someone else didn't? There's always a multitude of things at play.

    Lastly, pertaining to your discussion about Syria (in the post linked to), Norway is a good example of a country that prepared for depletion. So there is no inevitability to it. The Norwegians will run out of oil and gas as one of the richest countries in Europe with a gigantic fund for future generations.

    Greetings from an American in Germany

    1. Of course the matter is complicated and there is plenty of space for different interpretations. I didn't know of Perlin's book; thanks for the link, I'll be sure to look at it. Anyway, you may be interested in a comment that I published on the "" site, that I report here


      Well, thanks for these comments. I think they add consistency to my statement that most of us are ill-equipped to understand the collapse of complex systems. Maybe it is because in our evolutionary history we didn't need to think in systems; it was easier to think in terms of single causes and single effects (like: "I shoot arrow into mammoth - mammoth dies")

      But maybe it is because I didn't explain myself clearly enough. Let me try again. First, what I am NOT saying:

      single cause ----> single effect

      What I AM saying is

      single cause ----> cascade of effects

      So, I am NOT saying what some people have been criticizing: that I want to think in linear terms and see collapse as something simple (shoot arrow into mammoth.....). Not at all. Complex systems behave in a complex manner and a single stressor always generates a cascade of complex effects. But you should not confuse the external stressor with the internal feeback effects.

      So, think a little of the human body, which is a complex system dominated by feedbacks. When you die (collapse) you normally die for a single reason: infection, stroke, cancer, bumping your head into something hard, whatever. You don't read in medical statements that the poor guy died of "a combination of cancer and stroke while at the same time falling from the third floor" Might even happen, but it is not the normal reason why people die.

      Perhaps the best example is AIDS. It is generated by the HIV virus, but nobody dies because of the HIV virus, people die because of opportunistic infections resulting from the HIV virus. It is always the same thing: one main stressor (HIV) and a cascade of resulting effects.

      Or so I think.

    2. And, BTW, collapse is never inevitable. It is if one makes the wrong choices, that's the difference between Syria and Norway. And I still hope that we can avoid OUR collapse - but it seems that we are also doing all the wrong choices

  9. I don't know if we will ever have a total understanding of civilisational 'collapse'. And, in the end, or, at least for those that come out the other side of a 'collpase', does it really matter? Is it due to declining marginal returns as Tainter argues, environmental degradation as Jarid Diamond tends to focus upon, self-serving social institutions as Carroll Quigley blamed, or as Arnold Toynbee argued militarism, nationalism, and the tyranny of a despotic minority?
    Will it even be a sudden 'collapse' or slow decline as James Howard Kunstler and John Michael Greer suggest?
    We have certainly appeared to have shot past a sustainable carrying capacity for the planet and as the primary resources we have used to build our complex, global civilisation fade from existence the shift to a less complex living arrangement seem inevitable (and may be speeding up with each and every attempt to intervene and prolong the 'party'). The best one can hope for at this point, I think, is to be living in an area that has a good supply of fresh water, fertile soil, and reasonable security.

  10. Has there been a positive effect of the bronze age collapse? As I read here ( - the old world needed some hundred years to create the greek system of connected city-states, of polis'. And this created more or less the basis of modern thinking. It was a gigantic framework for experiments with political (the very word comes from there) constitutions, art, and thaughts and produced outstanding thinkers and ideas.



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)