Civilizational Collapse (Part 2)

Last time I told you a story of the American Southwest, starting with the arrival of small bands of hunters around 10,000 BC. I focused on the Anasazi, or ‘ancient Pueblo people’, and I led up to the Late Basketmaker III Era, from 500 to 750 AD.

The big invention during this time was the bow and arrow. Before then, large animals were killed by darts thrown from slings, which required a lot more skill and luck. But even more important was the continuing growth of agriculture: the cultivation of corn, beans and squash. This was fueled a period of dramatic population growth.

But this was just the start!

The Pueblo I and II Eras

The Pueblo I Era began around 750 AD. At this time people started living in ‘pueblos’: houses with flat roofs held up by wooden poles. Towns became bigger, holding up to 600 people. But these towns typically lasted only 30 years or so. It seems people needed to move when conditions changed.

Starting around 800 AD, the ancient Pueblo people started building ‘great houses’: multi-storied buildings with high ceilings, rooms much larger than those in domestic dwellings, and elaborate subterranean rooms called ‘kivas’. And around 900 AD, people started building houses with stone roofs. We call this the start of the Pueblo II Era.

The center of these developments was the Chaco Canyon area in New Mexico:

Chaco Canyon is 125 kilometers east of Canyon de Chelly.
Unfortunately, I didn’t see it on my trip—I wanted to, but we didn’t have time.

By 950 AD, there were pueblos on every ridge and hilltop of the Chaco Canyon area. Due to the high population density and unpredictable rainfall, this area could no longer provide enough meat to sustain the needs of the local population. Apparently they couldn’t get enough fat, salt and minerals from a purely vegan diet—a shortcoming we have now overcome!

Yet the population continued to grow until 1000 AD. In his book Anasazi America, David Stuart wrote:

Millions of us buy mutual funds, believing the risk is spread among millions of investors and a large “basket” of fund stocks. Millions divert a portion of each hard-earned paycheck to purchase such funds for retirement. “Get in! Get in!” hawk the TV ads. “The market is going up. Historically, it always goes up in the long haul. The average rate of return this century is 9 percent per year!” Every one of us who does that is a Californian at heart, believing in growth, risk, power. It works—until an episode of too-rapid expansion in the market, combined with brutal business competition, threatens to undo it.

That is about what it was like, economically, at Chaco Canyon in the year 1000—rapid agricultural expansion, no more land to be gotten, and deepening competition. Don’t think of it as “romantic” or “primitive”. Think of it as just like 1999 in the United States, when the Dow Jones Industrial Average hit 11,000 and 30 million investors held their breath to see what would happen next.

The Chaco phenomenon

In 1020 the rainfall became more predictable. There wasn’t more rain, it was simply less erratic. This was good for the ancient Pueblo people. At this point the ‘Chaco phenomenon’ began: an amazing flowering of civilization.

We see this in places like Pueblo Bonito, the largest great house in Chaco Canyon:

Pueblo Bonito was founded in the 800s. But starting in 1020 it grew immensely, and it kept growing until 1120. By this time it had 700 rooms, nearly half devoted to grain storage. It also had 33 kivas, which are the round structures you see here.

But Pueblo Bonito is just one of a dozen great houses built in Chaco Canyon by 1120. About 215 thousand ponderosa pine trees were cut down in this building spree! Stuart estimates that building these houses took over 2 million man-hours of work. They also built about 650 kilometers of roads! Most of these connect one great house to another… but some mysteriously seem to go to ‘nowhere’.

By 1080, however, the summer rainfall had started to decline. And by 1090 there were serious summer drought lasting for five years. We know this sort of thing from tree rings: there are enough ponderosa logs and the like that archaeologists have built up a detailed year-by-year record.

Thanks to overpopulation and these droughts, Chaco Canyon civilization was in serious trouble at this point, but it charged ahead:

Part of Chacoan society were already in deep trouble after AD 1050 as health and living conditions progressively eroded in the southern districts’ open farming communities. The small farmers in the south had first created reliable surpluses to be stored in the great houses. Ultimately, it was the increasingly terrible conditions of those farmers, the people who grew the corn, that had made Chacoan society so fatally vulnerable. They simply got back too little from their efforts to carry on.


Still, the great-house dwellers didn’t merely sit on their hands. As some farms failed, they used farm labor to expand roads, rituals, and great houses. This prehistoric version of a Keynesian growth model apparently alleviated enough of the stresses and strains to sustain growth through the 1070s. Then came the waning rainfall of the 1080s, followed by drought in the 1090s.

Circumstances in farming communities worsened quickly and dramatically with this drought; the very survival of many was at stake. The great-house elites at Chaco Canyon apparently responded with even more roads, rituals, and great houses. This was actually a period of great-house and road infrastructure “in-fill”, both in and near established open communities. In a few years, the rains returned. This could not help but powerfully reinforce the elites’ now well-established, formulaic response to problems.

But roads, rituals, and great houses simply did not do enough for the hungry farmers who produced corn and pottery. As the eleventh century drew to a close, even though the rains had come again, they walked away, further eroding the surpluses that had fueled the system. Imagine it: the elites must have believe the situation was saved, even as more farmers gave up in despair. Inexplicably, they never “exported” the modest irrigation system that had caught and diverted midsummer runoff from the mesa tops at Chaco Canyon and made local fields more productive. Instead, once again the elites responded with the sacred formula—more roads, more rituals, more great houses.

So, Stuart argues that the last of the Chaco Canyon building projects were “the desperate economic reactions of a fragile and frightened society”.

Regardless of whether this is true, we know that starting around 1100 AD, many of the ancient Pueblo people left the Chaco Canyon area. Many moved upland, to places with more rain and snow. Instead of great houses, many returned to building the simpler pit houses of old.

Tribes descending from the ancient Pueblo people still have myths about the decline of the Chaco civilization. While such tales should be taken with a huge grain of salt, these are too fascinating not to repeat. Here are two quotes:

In our history we talk of things that occurred a long time ago, of people who had enormous amounts of power, spiritual power and power over people. I think that those kinds of people lived here in Chaco…. Here at Chaco there were very powerful people who had a lot of spiritual power, and these people probably used their power in ways that caused things to change, and that may have been one of the reasons why the migrations were set to start again, because these these people were causing changes that were never meant to occur.

My response to the canyon was that some sensibility other than my Pueblo ancestors had worked on the Chaco great houses. There were the familiar elements such as the nansipu (the symbolic opening into the underworld), kivas, plazas and earth materials, but they were overlain by a strictness and precision of design that was unfamiliar…. It was clear that the purpose of these great villages was not to restate their oneness with the earth but to show the power and specialness of humans… a desire to control human and natural resources… These were men who embraced a social-political-religious hierarchy and envisioned control and power over places, resources and people.

These quotes are from an excellent book on the changing techniques and theories of archaeologists of the American Southwest:

• Stephen H. Lekson, A History of the Ancient Southwest, School for Advanced Research, Santa Fe, New Mexico, 2008.

What these quotes show, I think, is that the sensibility of current-day Pueblo people is very different from that of the people who built the great houses of Chaco Canyon. According to David Stuart, the Chaco civilization was a ‘powerful’ culture, while their descendants became an ‘efficient’ culture:

… a powerful society (or organism) captures more energy and expends (metabolizes) it more rapidly than an efficient one. Such societies tend to be structurally more complex, more wasteful of energy, more competitive, and faster paced than an efficient one. Think of modern urban America as powerful, and you will get the picture. In contrast, an efficient society “metabolizes” its energy more slowly, and so it is structurally less complex, less wasteful, less competitive, and slower. Think of Amish farmers in Pennsylvania or contemporary Pueblo farms in the American Southwest.

In competitive terms, the powerful society has an enormous short-term advantage over the efficient one if enough energy is naturally available to “feed” it, or if its technology and trade can bring in energy rapidly enough to sustain it. But when energy (food, fuel and resources) becomes scarce, or when trade and technology fail, an efficient society is advantageous because it simpler, less wasteful structure is more easily sustained in times of scarcity.

The Pueblo III Era, and collapse


By 1150 AD, some of the ancient Pueblo people began building cliff dwellings at higher elevations—like Mesa Verde in Colorado, shown above. This marks the start of the Pueblo III Era. But this era lasted a short time. By 1280, Mesa Verde was deserted!

Some of the ruins in Canyon de Chelly also date to the Pueblo III Era. For example, the White House Ruins were built around 1200. Here are some of my pictures of this marvelous place. Click to enlarge:

But again, they were deserted by the end of the Pueblo III Era.

Why did the ancient Pueblo people move to cliff dwellings? And why did they move out so soon?

Nobody is sure. Cliff dwellings are easy to defend against attack. Built into the south face of a cliff, they catch the sun in winter to stay warm—it gets cold here in winter!—but they stay cool when the sun is straight overhead in summer. These are good reasons to build cliff dwellings. But these reasons don’t explain why cliff dwellings were so popular from 1150 to 1280, and then were abandoned!

One important factor seems to be this: there was a series of severe droughts starting around 1275. There were also raids from other tribes: speakers of Na-Dené languages, who eventually became the current-day Navajo inhabitants of this area.

But drought alone may be unable to explain what happened. There have been some fascinating attempts to model the collapse of the Anasazi culture. One is called the Artificial Anasazi Project. It used ‘agent-based modeling’ to study what the ancient Pueblo people did in Long House Valley, Arizona, from 200 to 1300. The Villages Project, a collaboration of Washington State University and the Crow Canyon Archaeological Center, focused on the region near Mesa Verde.

Quoting Stephen Lekson’s book:

Both projects mirrored actual settlement patterns from 800 to 1250 with admirable accuracy. Problems rose, however, with the abandonments of the regions, in both cases after 1250. There were unexplained exceptions, misfits between the models and reality.

Those misfits were not minor. Neither model predicted complete abandonment. Yet it happened. That’s perplexing. In the Scientific American summary of the Long House Valley model, Kohler, Gummerman, and Reynolds write, “We can only conclude that sociopolitical, ideological or environmental factors not included in our model must have contributed to the total depopulation of the valley.” Similar conundrums best the Villages Project: “None of our simulations terminated with a population decline as dramatic as what actually happened in the Mesa Verde region in the late 1200.”

These simulation projects look interesting! Of course they leave out many factors, but that’s okay: it suggests that one of those factors could be important in understanding the collapse.

For more info, click on the links. Also try this short review by the author of a famous book on why civilizations collapse:

• Jared Diamond, Life with the artificial Anasazi, Nature 419 (2002), 567–569.

From this article, here are the simulated versus ‘actual’ populations of the ancient Pueblo people in Long House Valley, Arizona, from 800 to 1350 AD:

The so-called ‘actual’ population is estimated using the number of house sites that were active at a given time, assuming five people per house.

This graph gives a shocking and dramatic ending to our tale! Lets hope our current-day tale doesn’t end so abruptly, because in abrupt transitions much gets lost. But of course the ancient Pueblo people didn’t disappear. They didn’t all die. They became an ‘efficient’ society: they learned to make do with diminished resources.

16 Responses to Civilizational Collapse (Part 2)

  1. Super post!

    En bref, plus ça change, plus c’est la même chose.

  2. The shocking and dramatic end! They were probably chased off by cannibals:

    • Karl Reinhard, A Coprological View of Ancestral Pueblo Cannibalism, American Scientist 94 (2006)

    (Perhaps unappetizing, but fascinating read. To add insult, one cannibal defecated in the victims’ fire place, leaving a coprolith for modern analysis…)

  3. Peter Morgan says:

    Do we know from the archaeology whether there was illness?

    • John Baez says:

      I haven’t heard that, and I imagine I would have if people had noticed something ilke this.

      After all, I did read—and mentioned in Part 1—that in earlier times skeletal remains showed increased osteoporosis due to a low-mineral diet (too much corn, not enough green vegetables or meat), and bone damage due to overwork.

      But I guess not all diseases can be read off from skeletal remains!

  4. Jeff Posey says:

    Great round-up of Anasazi history, evidence, and interpretation, John. Every synthesis I see makes me think and see things a little differently, a little more deeply. I’ve been hiking their stomping grounds for a couple decades, and sometimes just standing there you get a chill or a shudder, and you know, you just know, something happened there. You just don’t know what. Most of the evidence has washed away. Only a scintillating scatter of hard remnants. Thanks for putting this together. I’m glad I found it.

    • John Baez says:

      Glad you liked this post! I’m jealous of you… I didn’t make it all the way to Chaco Canyon this time. On the day were going to go, it started snowing… and the next day was Christmas, and we realized the park would probably be closed. I was really bummed out. I’ll have to try again. And I want to see Mesa Verde, too.

      You might like the whole book Anasazi America, where I got most of my information. It’s well written.

  5. Ruggero says:

    If you are interested I took some poor man’s 3D pictures of the Mesa Verde park. Since most of the places are visible from across the canyons, I took a pictures, then walked laterally for about 30 meters, then took a second picture.
    This gives the idea that the position of the pictures is much closer, standing up in the air. Of course this kind of parallax trick has his (flattening etc. limits) but it’s not too bad and the results aren’t terrible.

  6. Last week, I talked a bit about a side-trip I took to Fallingwater with Barb. I thought I’d follow that up with a trip the two of us took a few years ago to Mesa Verde.

  7. Mark Blevins says:


    Recently stumbled on Azimuth. Great. Thanks.

    Enjoyed these posts especially as I live in this neck of the woods.
    You may have read this:

    … if not, you might enjoy it. J. Tainter examines Roman, Lowland Maya and Chacoan societal collapse. Concludes that ‘diminishing marginal returns on complexity’ are root cause, if I read him right. Might bear on our current situation, and some of your themes…


  8. nad says:

    Quote from the above quote by Stuart:

    Think of Amish farmers in Pennsylvania…


    But when energy (food, fuel and resources) becomes scarce, or when trade and technology fail, an efficient society is advantageous because it simpler, less wasteful structure is more easily sustained in times of scarcity.

    and a quote from Wikipedia:

    As of 2000, over 165,000 Old Order Amish live in the United States and about 1,500 live in Canada.[5] A 2008 study suggested their numbers have increased to 227,000,[6] and in 2010 a study suggested their population had grown by 10 percent in the past two years to 249,000, with increasing movement to the West.[7]

    If the Amish have that strong (?) population growth as the Wikipedia article suggests then amongst others I find a question which arises here is here: how “more easily sustained would the amish live on one and the same confined territory.”

    • Reminds me of the Syrian population explosion… The good Amish would soon get unsustainable. Then, having reached systemic boundaries, a little eco shock like some drought would suffice to engender rapid collapse. Suigenocide by overpopulation: Basic ecology combined with bloody human nature. This age old scenario should be called the “Syria scenario”. When will they ever learn?

      • nad says:

        I think what’s needed here is a more detailed assessment of land and resource need sorted with respect to human activities, which is in particular including land need for energy generation etc. That is the high growth rate for the amish is probably partially due to religious customs but given their low tech standard probably also needed. That is amongst others agriculture without many machines is quite labour intensive. Machines however also need energy. They are partially fed by crops, just as humans (biofuel) but they can also “eat” fossil fuels which seem to be eventually more energy intensive. So those machines need also either land (solar energy (regarding solar energy harvesting from space still as futuristic)) or “stored solar energy” (i.e. fossil fuels) or other stored resources (like nuclear). Moreover the Amish appear to be at least somewhat protected by the US surroundings, things would look even less good if they would need to defend their territory.

        As said I am missing out a trustworthy and really detailed but conscise assessment and thus tried to gather this information myself (see e.g. here, here, newer information might still be somewhat scattered like here, here etc.). The current (sofar unpublished) written up version is a bit more detailed and restructured. But I am also still in the stage of assessing, which activities should be accounted for as relevant and how those are connected with human nature. In that game plot Utopia I thought that this could at least partially be assessed within a game-like setting, but since quite a while I also kept trying to sort that out a bit myself. Currently this appears to me necessary for conciseness.

        But gathering all this it is not really something I super-like to do but which I only do because it seems (at least to me) urgently needed and secondly it is quite a task, which is hardly to be handled by one person as a “free-time” task. In particular the work at this “gathering” exceeded already what I could really afford as “free-time task” given my pension expectations (and partially also of what I like to do). I am thus thinking about whether I should make that into a book in order to get some chance of reimbursement for this work.

        There are though problems with this “book” concept. One is that some of the data is partially rather fast outdated, so it would be better to include the possibility of (to be paid ?) updates (ebook portal?). Another problem might be that not too many people like to hear about limitations, so the readership might be considerably lower than for pure entertainment, regardless how entertaining you write such a book. The fact that I am german and the “german inclination towards austerity” is globally already seen with critical eyes and the fact that my grandfather did a somewhat similar “accounting job” for the Nazis will eventually make me even less appealing as an author for such a thing….that is I already see the sentence: “german Nazi-granddaughter wants to tell us what to eat and how to live!” in front of me.

        But there are even more mundane problems, like since I am not an official journalist, I am not eligible to Künstlersozialkasse and thus any not-profitable enough effort could leed to bad debts due to a not very well adapted social insurance fee policy. Yes it’s crazy but working mommy might cost the family well a couple of thousand Euros.

        So even if one would make that “book” let’s say into an Azimuth Kickstarter project, I might not be able to “risk” an imbursement.

        • Martin Gisser says:

          Your grandfather story sounds quite interesting. Maybe there actually is an Ansatz for a book? (Beyond Vorwärtsverteidigung. If there is some similarity to your project. Actually what you tell smells a bit like you’re on a similar Holzweg.)

          (I haven’t read/followed much Azimuth for quite some time, for I was trapped in heavy brain work (pondering and extending millions of lines of undocumented legacy Java code). Now that ugly job is gone, I’m free again, and will hopefully never return wasting my brain for money and time. Looking for a job as farm hand instead. Yes, as another pillar of my Rentenversicherung.)

          It looks/smells you’re a bit too much into quantifying things.

          But our life support system is nonlinear (incl. lots of circular causality on diverse time scales) so numbers are not very helpful when the system is stretched to its boundaries. Add to that “natural” fluctuations of parameters (like it happened in Syria and will happen to the hypothetically non-emigratory Amish) and things will get totally unpredictable. A different Ansatz is needed here: Qualitative understanding, something like .
          Here’s a paradigmatic example of that thinking: (I’m typing on a stupid Android netbook without < > on the keyboard).

          Alas human nature wants numbers, not qualitative wisdom, and greed then wants to stretch the numbers to the limits. Alas we are beyond the limits now, using 1.5 planets/year… ==> What is desperately needed is change in behaviour and attitude toward Earth and survival, not just a change in parameters. As I said in the “Google gave up” thread: The most economic thing is to kill ourselves. Shall we do that? Or better give up economic metaphysics, the failed pseudo rationality?

          Reminds me of the old Einstein quote: “We cannot solve our problems with the same thinking we used when we created them.”

  9. Part 1: the rise of the ancient Puebloan civilization in the American Southwest from 10,000 BC to 750 AD.

    Part 2: the rise and collapse of ancient Puebloan civilization from 750 AD to 1350 AD.

    Part 3: a simplified model of civilizational collapse.

    Part 4: the collapse of Greek science and the resulting loss of knowledge.

  10. Bill Connelly says:

    Just a quick note of thanks. That was a superb read!

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