Civilizational Collapse (Part 1)

A few weeks ago I visited Canyon de Chelly, which is home to some amazing cliff dwellings. I took a bunch of photos, like this picture of the so-called ‘First Ruin’. You can see them and read about my adventures starting here:

• John Baez, Diary, 21 December 2012.

Here I’d like to talk about what happened to the civilization that built these cliff dwellings! It’s a fascinating tale full of mystery… and it’s full of lessons for the problems we face today, involving climate change, agriculture, energy production, and advances in technology.

First let me set the stage! Canyon de Chelly is in the Navajo Nation, a huge region with its own laws and government, not exactly part of the United States, located at the corners of Arizona, New Mexico, and Utah:

The hole in the middle is the Hopi Reservation. The Hopi are descended from,the people who built the cliff dwellings in Canyon de Chelly. Those people are often called the Anasazi, but these days the favored term is ancient Pueblo peoples.

The Hopi speak a Uto-Aztecan language, and so presumably did the Anasazi. Uto-Aztecan speakers were spread out like this shortly before the Europeans invaded:

with a bunch more down in what’s now Mexico. The Navajo are part of a different group, the Na-Dené language group:

So, the Navajo aren’t a big part of the story in this fascinating book:

• David E. Stuart, Anasazi America, U. of New Mexico Press, Albuquerque, New Mexico, 2000.

Let me summarize this story here!

After the ice

The last Ice Age, called the Wisconsin glaciation, began around 70,000 BC. The glaciers reached their maximum extent about 18,000 BC, with ice sheets down to what are now the Great Lakes. In places the ice was over 1.6 kilometers thick!

Then it started warming up. By 16,000 BC people started cultivating plants and herding animals. Around 12,000 BC, before the land bridge connecting Siberia and Canada melted, people from the so-called Clovis culture came to the Americas.

It seems likely that other people got to America earlier, moving down the Pacific coast before the inland glaciers melted. But even if the Clovis culture didn’t get there first, their arrival was a big deal. They be traced by their distinctive and elegant spear tips, called Clovis points:

After they arrived, the Clovis people broke into several local cultures, roughly around the time of the Younger Dryas cold spell beginning around 10,800 BC. By 10,000 BC, small bands of hunters roamed the Southwest, first hunting mammoths, huge bison, camels, horses and elk, and later—perhaps because they killed off the really big animals—the more familiar bison, deer, elk and antelopes we see today.

For about 5000 years the population of current-day New Mexico probably fluctuated between 2 and 6 thousand people—a density of just one person per 50 to 150 square kilometers! Changes in culture and climate were slow.

The Altithermal

Around 5,000 BC, the climate near Canyon de Chelly began to warm up, dry out, and become more strongly seasonal. This epoch is called the ‘Altithermal’. The lush grasslands that once supported huge herds of bison began to disappear in New Mexico, and those bison moved north. By 4,000 BC, the area near Canyon de Chelly became very hot, with summers often reaching 45°C, and sometimes 57° at the ground’s surface.

The people in this area responded in an interesting way: by focusing much more on gathering, and less on hunting. We know this from their improved tools for processing plants, especially yucca roots. The yucca is now the state flower of New Mexico. Here’s a picture taken by Stan Shebs:

David Stuart writes:

At first this might seem an unlikely response to unremitting heat and aridity. One could argue that the deteriorating climate might first have forced people to reduce their numbers by restricting sex, marriage, and child-bearing so that survivors would have enough game. That might well have been the short-term solution [….] When once-plentiful game becomes scarce, hunter-gatherers typically become extremely conservative about sex and reproduction. […] But by early Archaic times, the change in focus to plant resources—undoubtedly by necessity—had actually produced a marginally growing population in the San Juan Basin and its margins in spite of climatic adversity.


Ecologically, these Archaic hunters and gatherers had moved one entire link down the food chain, thereby eliminating the approximately 90-percent loss in food value that occurs when one feeds on an animal that is a plant-eater.


This is sound ecological behavior—they could not have found a better basic strategy even if they had the advantage of a contemporary university education. Do I attribute this to their genius? No. It is simply that those who stubbornly clung to the traditional big game hunting of their Paleo-Indian ancestors could not prosper, so they left fewer descendents. Those more willing to experiment, or more desperate, fared better, so their behavior eventually became traditional among their more numerous descendents.

The San Jose Period

By 3,000 BC the Altithermal was ending, big game was returning to the Southwest, yet the people retained their new-found agricultural skills. They also developed a new kind of dart for hunting, the ‘San Jose point’. So, this epoch is called the ‘San Jose period’. Populations rose to maybe about 15 to 30 thousand people in New Mexico, a vast increase over the earlier level of 2-6 thousand. But still, that’s just one person per 10 or 20 square kilometers!

The population increased until around 2,000 BC. At this point population pressures became acute… but two lucky things happened. First, the weather got wetter. Second, corn was introduced from Mexico. The first varieties had very small cobs, but gradually they were improved.

The wet weather lasted until around 500 BC. And at just about this time, beans were introduced, also from Mexico.

Their addition was critical. Corn alone is a costly food to metabolize. Its proteins are incomplete and hard to synthesize. Beans contain large amounts of lysine, the amino acid missing from corn and squash. In reasonable balance, corn, beans and squash together provide complimentary amino acids and form the basis of a nearly complete diet. This diet lacks only the salt, fat and mineral nutrients found in most meats to be healthy and complete.

By 500 BC, nearly all the elements for accelerating cultural and economic changes were finally in place—a fairly complete diet that could, if rainfall cooperated, largely replace the traditional foraging one; several additional, modestly larger-cobbed varieties of corn that not only prospered under varying growing conditions but also provided a bigger harvest; a population large enough to invest the labor necessary to plant and harvest; nearly 10 centuries of increasing familiarity with cultigens; and enhanced food-processing and storage techniques. Lacking were compelling reasons to transform an Archaic society accustomed to earning a living with approximately 500 hours of labor a year into one willing to invest the 1,000 to 2,000 yours coming to contemporary hand-tool horticulturalists.

Nature then stepped in with one persuasive, though not compelling, reason for people to make the shift.

Namely, droughts! Precipitation became very erratic for about 500 years. People responded in various ways. Some went back to the old foraging techniques. Others improved their agricultural skills, developing better breeds of corn, and tricks for storing water. The latter are the ones whose populations grew.

The Basketmakers

This led to the Basketmaker culture, where people started living in dugout ‘pit houses’ in small villages. More precisely, the Late Basketmaker II Era lasted from about 50 AD to 500 AD. New technologies included the baskets that gave this culture its name:

Pottery entered the scene around 300 AD. Have you ever thought about how important this is? Before pots, people had to cook corn and beans by putting rocks in fires and then transferring them to holes containing water!

Now, porridge and stews could be put to boil in a pot set directly into a central fire pit. The amount of heat lost and fuel used in the old cooking process—an endless cycle of collecting, heating, transferring, removing and replacing hot stones just to boil a few quarts of water—had always been enormous. By comparison, cooking with pots became quick, easy, and far more efficient. In a world more densely populated, firewood had to be gathered from greater distances. Now, less of it was needed. And there was newer fuel to supplement it—dried corncobs.

Not all the changes were good. Most adult skeletons from this period show damage from long periods spend stooping—either using a stone hoe to tend garden plots, or grinding corn while kneeling. And as they ate more corn and beans and fewer other vegetables, mineral deficiencies became common. Extreme osteoporosis afflicted many of these people: we find skulls that are porous, and broken bones. It reminds me a little of the plague of obesity, with its many side-affects, afflicting modern Americans as we move to a culture where most people work sitting down.

On the other hand, there was a massive growth in population. The number of pit-house villages grew nine-fold from 200 AD to 700 AD!

It must have been an exciting time. In only some 25 generations, these folks had transformed themselves from forager and hunters with a small economic sideline in corn, beans and squash into semisedentary villagers who farmed and kept up their foraging to fill in the economic gaps.

But this was just the beginning. By 1020, the ancient Pueblo people would begin to build housing complexes that would remain the biggest in North America until the 1880s! This happened in Chaco Canyon, 125 kilometers east of Canyon de Chelly.

Next time I’ll tell you the story of how that happened, and how later, around 1200, these people left Chaco Canyon and started to build cliff dwellings.

For now, I’ll leave you with some pictures I took of the most famous cliff dwelling in Canyon de Chelly: the ‘White House Ruins’. Click to enlarge:

18 Responses to Civilizational Collapse (Part 1)

  1. Admirable consensed history. Alas they didn’t reach the stage of metals as I recall.

  2. Arrow says:

    I wonder who they blamed for climate change back then.

  3. John Baez says:

    Over on Google+, Justen Robinson wrote:

    I’ve visited many of the pueblo ruins in Arizona that are open to the public (or at least accessible). They are pretty fascinating places. One of the things I find most interesting about them is how they took advantage of the unique geological features of the area to help them survive in the challenging climate of the southwest (which was no easy task even before the area dried up). The cliff dwellings are amazing, but so are the hilltop dwellings in the Verde Valley area.

    There are these tiny fertile strips along the sides of the rivers, but they flood seasonally during the monsoons. So the ruins are all on the tops of these buttes and cliffs overlooking the valleys. Or at least the ones that didn’t get washed away are up there; I’m no expert and don’t know how they originally arranged themselves.

    It’s a pretty stark contrast with how modern Arizonans live, essentially in ignorance and denial of the local environment’s inability to support them thanks to massive engineering projects that bring water, power and air conditioning into the desert. Other than the faddish “southwestern” style houses, they’re mostly living in homes designed for temperate plains and forests, if they were designed to an environment at all. Technology does through brute force what earlier inhabitants did through clever observation and judicious use of resources.

    I replied:

    Nice comments! In Part 2, I’ll get to how the Chaco Canyon civilization overreached itself, perhaps a bit like how people are doing now in Arizona—though of course with less technology. They prospered for a while but seem to have reached an unstable point where new construction projects were always required to keep their society going, while life for farmers slowly worsened. And then, eventually, they collapsed!

    So, they weren’t always acting in an ecologically sound way. But after the collapse of 1280 they learned more about sustainability.

  4. Frederik De Roo says:

    On the one-but-the-last picture, is that some artistic figure (man, lizard) carved in the rocks?

    • John Baez says:

      Yes, it’s a petroglyph. I didn’t think to ask what it represents. There are a bunch more in the ‘Kokopelli Ruin’ in Canyon de Chelly:

      Kokopelli is the hunch-backed flute player here. He’s an important character in current-day Hopi mythology, but he goes back to their early ancestors, the ancient Pueblo peoples who built the cliff dwellings here. He’s a fertility god, who carries unborn children on his back — and his music brings in the spring. The wiggly line is a snake: a symbol of earth and fertility.

  5. Yummy writeup! I also enjoyed the winter pictures of your diary – been at some of the same places during a hot summer – amazing (hitherto unimaginable for me) to see the snow…

    One glitch perhaps: Beringia never was glaciated. Wikipedia has a nice animation.

    Apropos petroglyphs: There’s a swastika (with one leg missing?) above Antelope House. I knew it is a very old and widespread symbol (from Finnland to India), but never heard it was also used by ancient Americans. Did the Clovis people bring it across Beringia, or is it just an independently emerged “archetype”? The Anasazi were quite ingenious ornament artists.

    • John Baez says:

      I’m glad you liked this! I love travelling through Arizona in winter: in the summer it’s really hot and there are tons of tourists.

      I didn’t mean to imply Beringia was glaciated. I said:

      It seems likely that other people got to America earlier, moving down the Pacific coast before the inland glaciers melted.

      What I meant here is that many experts believe the Clovis people moved south through a corridor between two glaciated regions in North America: the Cordilleran Ice Sheet and the Laurentide Ice Sheet.

      But some experts now believe that other people moved down along the Pacific coast, perhaps with the help of boats, before the inland glaciers melted enough to form this corridor!

  6. Aaron F. says:

    Wow… I thought talking to medievalists was humbling, but looking down on ten thousand years of history like this really puts things in perspective. Next time I’m on a long trip, I’m definitely bringing Stuart’s book a long.

    The story so far is fascinating—I can’t wait for part two!

  7. 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. […]

  8. Mukund hambarde says:

    Amazing story. Factual history. Can we any link or similarities with other contemporary civilization elsewhere e.g. Egypt, Babylonia, Crete or Indus valley civilization or Gondwana belt in India?

  9. John Baez says:

    It turns out my friend the anthropologist Al Fix wrote a paper about the spread of people through the Americas. He uses findings on mitochondrial DNA to study this issue:

    • Alan G. Fix, Rapid deployment of the five founding Amerind mtDNA haplogroups via coastal and riverine colonization,American Journal of Physical Anthropology, 2005.

    Four major kinds of mitochondrial DNA are found in Amerindians; these are called haplogroups. A quote:

    One of the central questions of Amerind prehistory is the time of entry of the original colonists. MtDNA provides some perspective on this question, but has not definitively resolved it. Thus various dates were derived for each of the haplogroups (Schurr, 2000), but these do not directly date the migration. Silva et al. (2002) argued for a common time of divergence of approximately 21 thousand years before present (ky BP) for sequences outside the control region of mtDNA from all four major haplogroups. In general, however, the data are too few and the methods too uncertain to provide a strong constraint on time of colonization.

    Until recently, most archaeologists believed that the Pleistocene ice sheets barred the entry of Asian hunters into the American continent until the opening of the ice-free corridor around 11 ky BP (Dixon, 1999). Once the corridor was open, colonists rapidly expanded through the North American continent, exterminating the Pleistocene megafauna in a wave of advance that quickly spread to South America (Fiedel, 2000). The model based on this scenario was dubbed ‘‘blitzkrieg ’’ by Martin (1973) to emphasize the lightning-like pace of colonization, reaching the tip of South America in less than 1,000 years.

    The classic blitzkrieg model sought to meet the perceived constraints of glacial timing and the dates provided by archaeologists for the earliest sites in the Americas. The critical dates were the opening of the corridor at ca. 11 ky BP and a series of radiocarbon dates for Clovis sites in North America at about the same time (11.2–10.8 ky BP). Since equally early sites were known from South America, a very rapid spread must have occurred in order to accommodate these dates (Dillehay, 2000).

    Recent discoveries in South America, especially at the site of Monte Verde in Chile, forced a reconsideration of this view. It now appears that people were in South America by 12.5 ky BP, earlier than the opening of the ice-free corridor. Some suggest that this implies a much earlier presence of humans in North America, perhaps as much as 15–20 ky BP (Dillehay, 2000). In any case, the apparent constraint on timing of the entry provided by glacial barriers now seems removed.

    Earlier views held that the coast as well as the continental interior of North America was blocked by ice. New evidence points toward an earlier deglaciation along the coast beginning about 16 ky BP, with a clear corridor by 14–13 ky BP (Dixon, 1999). Thus the date for a possible colonization route around the ice has been pushed back a bit. At the same time, the early dates of archaeological sites in South America indicate that the colonization process was rapid.

    The apparent constraint on the timing of colonization that was satisfied by the blitzkrieg model has now been (partially) removed. An alternative view proposed by Fladmark (1979), that the original migrants entered the Americas along the coasts by boat, has gained increasing attention (Dixon, 1999). This paper will show that the coastal model is consistent with the mtDNA distributional evidence, adding support to this hypothesis.

  10. E. says:

    It has long been known that baskets were made in many styles including watertight, and that properly-constructed baskets can be used for stone-boil cookery of maize. Most recently, Ellwood et al. (Journal of Archaeological Science 40:1, behind Elsevier’s paywall so not bothering to link) demonstrated that heating limestone rocks, which are commonly found in middens of the Basketmaker II people, and using them to stone-boil maize makes nutrients in maize more available for humans. Pottery is not a sine qua non of cookery!

    I see someone else mentioned migration paths above. Steven Mithen’s accessible and well-written After the Ice is a little more recent than Stuart, and you may find it interesting.

    • John Baez says:

      Thanks for the correction! I got the claim that pottery was needed for the transition away from stone-boiling from other forms of cooking from Anasazi America. It sounds like that was oversimplified.

      Every time I look at it in the book store, I find the writing style of After the Ice a bit disconcerting, so I haven’t read it yet. For people who don’t know what I’m talking about, here’s an Amazon review that explains:

      Using an unorthodox narrative device, Mithen explores why, how, and where farming displaced hunting and gathering. Mithen conjures John Lubbock, an English author of a once-popular 1865 history of the Stone Age, and sends him back in time to visit dozens of excavation sites around the world as they appeared when inhabited. Lubbock’s transcontinental perambulations permit Mithen (a practicing archaeologist who describes his digs in Scotland) to underscore one causal factor in the agricultural revolution: the fluctuations of climate at the end of the last Ice Age. Weather, sea level, and zones of plant and animal life changed dramatically in the 15,000 years of Lubbock’s walkabout, and Mithen explains how environmental volatility is scientifically known as he sketches Lubbock observing the various “living” human communities that have been uncovered.

      But I should read it….

      • Todd Trimble says:

        I thought that the name Mithen sounded familiar! I first learned about him through Oliver Sacks’s book Musicophilia, where he describes Mithen’s book The Singing Neanderthals. I haven’t read it, but it sounds sort of interesting. In it, Mithen tries to tackle the difficult problem of what sorts of adaptive functions music-making and musical intelligence might have fulfilled for early hominids (for one might naturally suppose that the emotional power and depth of music felt by humans indicates a long evolutionary history). He puts forth the idea that early hominids like Neanderthals developed a kind of proto music-language; I won’t try to summarize the argument, but you can get some idea of it here, and there are other links given here.

  11. 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.

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