Just returned from a week-long trip to northern New Mexico and southwestern Colorado with my family. The intellectual highlight of the trip was certainly the detour through Chaco Canyon in northwestern New Mexico.
For those unfamiliar with the canyon it is the largest of the Anasazi (a Navajo term translated "ancient ones" or "ancient enemies") sites that dot the four corners region and include the more famous Mesa Verde area which we also visited along with some 200 other sites. The term Anasazi although still found in the literature has been superseded by "Ancestral Puebloans" as the result of the connection modern Pueblo tribes (the 19 tribes that now occupy the Rio Grande valley in the region of Albuquerque) feel for the Anasazi and the fact that most now believe that the Anasazi migrated to the Rio Grande basin.
Of course, what most folks find interesting about the Anasazi and Chaco Canyon in particular is that they largely abandoned these settlements in the 1100s in what has become somewhat of a mystery for archaeologists.
This topic was even more interesting to me since the ruins at Chaco Canyon were the subject of a chapter of the 2004 book Collapse: How Societies Choose to Fail or Succeedby Jared Diamond that I'm currently reading. Diamond is the author of the Pulitzer Prize winning Guns, Germs, and Steel and while that book tracked the rise of civilization since the last ice age, this one discusses societal collapses throughout history and posits the reasons for their decline using a five-point framework. In addition to the Anasazi, Diamond profiles other ancient societies including the Easter Islanders, the islanders of Henderson and Pitcarin, the Mayans, and the Greenland Norse settlements. Diamond then hopes to tease out some lessens from these previous collapses for modern society.
To get to Chaco Canyon you take a 21-mile trip on a dirt road off of state highway 550 several hours northwest of Albuquerque. My wife was not amused as we rumbled along through the desert to what is now a National Park and a World Heritage Site that sees 75,000 visitors per year. After having a little lunch at a picnic site near the Visitor's Center we registered at the center and were ready to take a look around.
The visitor's center is located in the southeast corner of the canyon and we took the loop road northwest towards Pueblo Bonito (PB), the largest of the Chacoan "Great Houses" in the canyon. PB was occupied from the 800s to the mid 1100s and consists of 600 rooms and 40 kivas (the below ground cylindrical structures the use of which is still debated). During its heydey PB was the largest man made structure in pre-Columbian North America and contained structures four or five stories high.
Following Diamond's five point framework he views the contributing causes of the collapse of the Anasazi civilization like so:
The second environmental impact was related to farming techniques used by the Anasazi. When they first populated the canyon they likely relied on flood plain agriculture by allowing their crops (corn primarily) to be watered by the periodic summer rains that washed through the canyon. The canyon itself was well situated to catch rain from a variety of locations on the mesa above. However, as the population grew the Anasazi began diverting water into channels for irrigation, clearing vegetation, and building dams. The unanticipated result was that by 900AD rushing water cut deep channels (arroyos) in the canyon. Once water ran down these arroyos (a couple of which we passed on the loop road and which were cut more than 10 feet below the level of the bottom of the canyon) it was actually below the level of the fields and without pumps it became useless. The Anasazi dealt with the problem by using other schemes allowing them to stay in the canyon but it certainly decreased the efficiency of their food production in an already somewhat difficult environment.
One can imagine that after several years of crop failures the peasants may have become disenchanted with the ruling elite (like those living in PB) and revolted. The result was that the canyon was almost completely abandoned between 1150 and 1200 (the last dated construction at PB was from just after 1110, again using tree ring analysis, and the last construction anywhere in the canyon is dated at 1170). Interestingly, there are several places within PB where you can see the cores cut out of logs used to build various rooms that have been used to date the room. Evidence suggests that the people simply moved on because of the lack of pottery and other things of value that would have been taken.
It's not hard to imagine that once support from outlying areas ceased, perhaps due to their own problems dealing with drought or a lack of confidence in the rulers at Chaco, the society might collapse in a hurry.
In addition, there is evidence of warfare and cannibalism (a notion completely absent from the standard tourist fare at Chaco and Mesa Verde as you can imagine) from other Anasazi sites suggestive of increased competition for decreasing resources. One of the sites we visited at Mesa Verde was "Balcony House" which because of its accessibility only through ladders and toe hold cuts into the limestone, was almost certainly a defensive settlement and one of the last occupied at Mesa Verde. Our kids, of course, loved the climbing making their parents somewhat nervous.
While at the visitor's center I picked up a copy of The Archaeology of Chaco Canyon: An Eleventh Century Pueblo Regional Center, which is a collection of essays on a variety of topics related to the research at the canyon under the auspices of the "Chaco Project" which began in the mid 1960s and continued through the mid 1980s. The book is a kind of final report on the findings of the project. It is written in a fashion that even non-experts can enjoy and I found it very entertaining.
Many times the authors disagree but what I found most interesting was the ongoing debate regarding the interpretation of Great Houses like PB. Was their significance primarily political or was it ritual? In other words, was the Anasazi society a hierarchical one with centralized authority centered in places like PB or was it a more egalitarian society and PB served as a pilgrimage site?
Diamond assumes the former interpretation, that Stephen Lekson articulates in his introductory chapter "Chaco Matters" published in the book I referenced above. One of the most interesting aspects of that essay is how Lekson ties changing modern intellectual models to the interpretation of the Anasazi in vogue at any particular time. The current trend seems to favor the interpretation of Chaco as a ritual center in the midst of an essentially egalitarian society. It seems to this non-expert, however, that the idea of Chaco as the center of a hierarchical society with a ruling elite makes more sense. Some of the points that Lekson makes in its favor include:
Interestingly, there is evidence of road systems throughout the four corners region and roads that lead out of Chaco Canyon to the north and southwest. From my cursory review of the book mentioned above, it doesn't appear significant work has been done on identifying the uses and paths for these roads. Some may been used for commerce, and other had a ritual or spiritual significance. Either way, the presence of such structures indicate central organization. In addition, it is now known that there was potentially a line of site system in place that could have been used for communication among at least some of the Great Houses. For example, from Farview House at Mesa Verde one can see all the way to Chaco.
In any case, one of the things I took away from both books and our recent trip is that although Chaco Canyon is one of the most intensely studied sites in the world, there is still plenty of research to be done and plenty of interpretation that is controversial.