Collide-a-scape

Chaco Canyon is often discussed in the “collapse” literature as a prime example of societal collapse, often tied to climatic change and sometimes to ecological overshoot (although that part’s pretty dubious).  Both Jared Diamond and Joseph Tainter use it as an example of societal collapse in their respective books on the subject.  It’s easy to see why; Chaco is remarkable for its impressive remains in a very harsh and unpromising setting, but it’s clear that those impressive remains date to a remarkably short period of time, and that something happened afterward that changed things considerably and led to a near-total cessation of further activity in the canyon.

The human occupation of Chaco Canyon goes back a very long way, but the key developments that made it an important regional center seem to have begun in the AD 800s with the initial building of a few “great houses,” which in that period were large masonry structures similar in layout and construction techniques to the “small houses” in which most Southwestern people lived at the time but much on a much larger scale.  These early great houses, including Pueblo Bonito and Una Vida, show considerable signs of residential use in their earliest parts, and it seems that they were at least initially residential structures.  It’s not at all clear what inspired their construction, but there were similar structures being built in other parts of the region at the time, so Chaco may not have been particularly special at first.  Over the course of the next hundred years, however, something seems to have happened to make Chaco a major regional center, and starting around AD 1030 a building boom in the canyon in which the existing great houses were expanded using much more elaborate techniques and an even larger scale of construction coincided with the construction of entirely new great houses both in the canyon and throughout the San Juan Basin of northwestern New Mexico and beyond into Colorado, Utah, and Arizona.  These “outlying” great houses were mostly placed in existing small house communities, which continued to be occupied, and were connected to the canyon via an elaborate road system.

Over the next hundred years, construction both inside and outside the canyon continued almost without pause, and at the same time a vast amount of material of all kinds was brought into Chaco from a vast surrounding region: turquoise, shell, copper bells, macaws, and other exotic materials, as well as more quotidian items such as pottery, construction timbers, and corn.  Then, around AD 1130, everything seems to have come to an abrupt halt.  Construction of great houses, after a shift around AD 1100 toward a different type of architecture, seems to stop entirely by around 1125, and activity in the canyon slowed to a crawl at that point.  There was probably at least a small population remaining until the depopulation of the whole region in the late 1200s, but it was nowhere near as large as the apparent population at the system’s height.  It is this decline in activity that collapse theorists seek to explain when they look at Chaco as a case study.

So what happened?  There are various theories out there.  Many point to a prolonged period of drought from around 1130 to 1180, which coincides suspiciously closely with the end of major activity at Chaco, as having somehow led to the collapse, although this explanation is somewhat problematic given that earlier droughts, especially a short but severe one in the 1090s, didn’t have nearly the same effects on the system.  Others argue that political, social, or economic instability within the Chaco system itself, whatever its nature, was the main cause of the collapse, with drought perhaps playing a subsidiary role.  Most people agree, however, that Chaco is indeed an example of societal collapse.

But is it?  Let’s look at some of the criteria for defining collapse, using Diamond’s list:

1. Collapse involves a major loss of population.
2. Collapse involves a loss of complexity.
3. Collapse occurs over a large geographic area.
4. The changes brought about by collapse persist for a long time.

Measuring the population of Chaco at any time is surprisingly difficult, but given the much lower level of activity after 1130 I think it’s safe to say that there was a major decline of some sort.  The extent to which Chaco was a complex society at all is disputed, but I find the arguments for complexity more convincing than the arguments against it, so let’s take relative complexity as a starting point and see if there’s evidence for a loss of it.  Recall Ben Nelson’s definition of complexity:

Social systems are considered complex if they are comparatively large demographically and spatially, encompass multiple settlements in an integrated political structure, and exhibit horizontal and vertical social differentiation. Other properties associated with complexity are hereditary ranking, production of surplus and its appropriation by an elite, craft specialization, and long-distance exchange.

Large demographic scale is basically the same as population, so that one’s covered.  We’ll get back to spatial scale and settlement pattern later.  There isn’t much evidence for horizontal social differentiation at any point in the Chacoan archaeological record, but the vertical differentiation implies by the elaborate burials in Pueblo Bonito does seem to end around 1130.  Ranking goes along with vertical differentiation, and surplus and its appropriation are controversial and hard to find in the archaeological record, as is craft specialization.  That leaves us with long-distance exchange, which does continue to go on at Chaco, but at a much lower level than before.  So yes, I think it’s fair to say that Chaco became less complex according to most of the criteria that can be used to assess complexity there.

That brings us back to spatial scale, and here’s where things get tricky.  It turns out that the evidence for reduced activity at Chaco Canyon after 1130 doesn’t correspond to a similar reduction in activity in most other parts of the Chaco system at the same time.  Indeed, some areas, such as Aztec Ruins on the Animas River to the north, see a marked increase in activity after 1130, and both Aztec and the Mesa Verde area further north see continued activity on a large scale, indicative of a large population, until the depopulation of the whole area in the late 1200s.  The area to the west doesn’t see such dramatic growth, but it does seem to keep on going without much change after 1130.  Similarly, while the area immediately south of Chaco seems to have been largely depopulated even earlier than the canyon itself, the area further south continued to see activity long after, indeed up to the present day at Zuni Pueblo.  And in many of these areas, especially at Aztec and at the northern and southern extremes of the original Chaco system, the outlying Chacoan great houses seem to have continued to be used, though perhaps not the same way as they were originally intended to be used, long after the cessation of great house construction in Chaco itself.

So it seems that the Chaco “collapse” really only applies to a single location, Chaco Canyon itself, and not to the society as a whole.  Indeed, some archaeologists have interpreted these data as showing not so much the collapse of the system centered on Chaco but a series of changes in it, possibly including a shift in emphasis away from Chaco itself toward Aztec, which replaced it as the center of the system.  Whether or not some form of the system that developed at Chaco continued at Aztec, it’s clear that there were a lot of changes going on in the region during the 1100s, including an apparent movement of population away from Chaco, probably at least in part to Aztec and Mesa Verde.  The lack of continued construction on the scale seen from 1030 to 1130 and the reduced level of trade do seem to suggest that the Chacoan system declined in power and influence after 1130 whether or not it moved to Aztec, but there turns out to be very little evidence of a “collapse” occurring over a large spatial scale, although the changes do seem to persist for a long time.

So what are the implications of this for studies of collapse in general?  It’s hard to say, but I think one lesson is that it’s important to look at these things on the societal level rather than on individual sites or localities, no matter how important or central they seem.  Some Southwestern archaeologists now prefer the term “reorganization” to “collapse” for situations like the changes at Chaco after 1130 and the contemporaneous events in the Mimbres Valley of southwestern New Mexico.  It’s certainly quit different from the massive depopulation of the whole Four Corners region in the late 1200s, which however doesn’t fit well into “collapse” models either because there’s little evidence of a system on any level larger than the individual community during this period, with the possible exception of a rump Chacoan system operating on a small scale out of Aztec.  That event, which corresponds to another prolonged drought, is of interest in its own right, but this post is long enough already.

Hi, I’m teofilo.  As Keith mentioned earlier, I will be guest-blogging for him this week.  As he also mentioned, I am currently a graduate student in urban planning (at Rutgers) and have also worked seasonally at Chaco Canyon.  People often see that combination as rather incongruous, but I think it actually makes a lot of sense, and part of what I’ll be doing here this week is trying to show how the two go together.  I’ll especially be focusing on the concept of societal collapse, which is something that gets discussed a lot in both archaeology and planning, at least in certain circles.  Chaco has often been drawn into these discussions as an example of collapse in the archaeological record that can be useful as a cautionary example in dealing with current challenges such as climate change.  That’s reasonable enough, but I think there are some pretty serious problems with the ways some people have tried to bring Chaco into the modern collapse/sustainability conversation.  I’ll be discussing that in more detail in the days to come.

I do have my own blog, Gambler’s House, which focuses on Chaco but also discusses Southwestern archaeology more generally along with a wide variety of related subjects.  Most of the posts I do there are rather different from the sort of thing I’ll be doing here, so I doubt I’ll be doing much cross-posting this week, but if you’re interested in this stuff there’s plenty more to see over there.

Anyway, I’m glad to be here, and I thank Keith for the opportunity to expand my horizons a bit and engage with a different sort of audience than I’m used to.  It should be an interesting week.

The exhibits in Chaco Culture National Historical Park, like many archaeology exhibits, depicts Indians wearing only loincloths. Yet, as my favorite archaeology blogger points out,  there is ample historical and archaeological evidence that ancient Puebloans (more popularly known as the Anasazi) wore clothes. Imagine that!

He rightly concludes that this false representation

has more to do with the preconceptions of the people who made the dioramas than with what people at Chaco and elsewhere actually wore.

I recently wrote two stories for Archaeology magazine about the clash of history, science, and culture in the American Southwest. The main piece in the Nov/Dec issue juxtaposes Navajo claims to famous prehistoric sites, such as Chaco Canyon, with new archaeological data. This latest material evidence reinforces the strong scientific consensus that the Navajo didn’t arrive in the Southwest until sometime in the 1500s.

The accompanying web-only piece illustrates how Navajo oral history deeply shapes the views and beliefs of Taft Blackhorse, a Navajo archaeologist who I spent time with while reporting on these stories. I will say that I grew quite fond of Taft and his colleague, John Stein. They were generous hosts and there’s a part of me rooting for them to continue their maverick ways and quixotic quest. That said, I have no doubt that many archaeologists will be shaking their heads in disbelief at some of the statements they make.

Combined, the two stories reveal an interesting dilemma for archaeologists who strive to reconcile data-driven science with information gleaned from a culture’s oral tradition.

I’ll have more to say on all this shortly, as I suspect others will offer their own commentary, some who I know have already read the print story. I look forward to a spirited exchange.

One final thought: while writing these stories, I was reminded of something I once read in an essay by geographer D.W. Meinig, in this classic book:

Any landscape is composed not only of what lies before our eyes, but what lies in our heads.