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Archive for the ‘Dendrochronology’ Category

Room 6, Pueblo Bonito

The “Chacoan era” is a period of about 100 years in the eleventh and early twelfth centuries AD during which Chaco Canyon was at the center of some sort of system that covered a large portion of the northern Southwest.  The exact nature and exact extent of that system are endlessly debated, but the period during which it existed is fairly well-established.  The exact dates given for the duration of the system vary among different researchers, and I’ve given various versions of them myself.  Probably the most common ending date is AD 1130, which coincides both with the approximate end of apparent construction in the canyon and the onset of a 50-year drought that is generally thought to have had something to do with the decline of Chaco.  To make it an even century, 1030 is a useful starting date for the Chacoan era, although it doesn’t actually correspond to anything special in the canyon as far as we can tell.  A better starting date might be 1040, which is approximately when the expansion of Pueblo Bonito began, or 1020, which is about when construction began at Pueblo Alto.  Using these starting dates with the hundred-year span gives ending dates of 1140 or 1120, which again are roughly equivalent to the end of major construction in the canyon.  (It’s a lot easier to date the beginnings of phenomena in the ancient Southwest than the ends of them, due largely to the reliance on tree-ring dates.)

Whenever we say the Chacoan era began, it was long after the first great houses in Chaco Canyon were built.  Indeed, the canyon had a long and probably very eventful history well before things really got going in the early 1000s.  During the 900s it may not yet have been important on as large a scale as it became later but it was definitely already a place where things were happening.  The origins of Chaco lie even earlier, however.

Type I and Type II Masonry Abutting at Peñasco Blanco

The first three great houses built in the canyon were Pueblo Bonito, Una Vida, and Peñasco Blanco.  Una Vida is mostly unexcavated and Peñasco Blanco is completely so, so the dating of them relies mainly on tree-ring sampling of exposed wood.  This has shown that these two sites probably date originally to the late 800s, with extensive expansion in the 900s.  The earliest cutting date at Una Vida is from AD 861, while Peñasco Blanco has a cluster of cutting dates at AD 898.  Both have clusters of dates in the 900s that suggest that much of the early construction dates to this period, and both also show expansion later, during the Chacoan era itself.  Beyond that, though, not much can be said about the chronology of these sites.

Pueblo Bonito is a different story.  It’s almost completely excavated, and while the excavation took place a long time ago, it left a lot more exposed wood than at most other sites.  The recent Chaco Wood Project, which sought to sample every piece of exposed wood in the canyon to develop as full a chronology as possible, had its most spectacular results at Bonito.  These were reported in part in an article in 1996 by Tom Windes and Dabney Ford, and the implications of the new dates for the architectural history of the site were more fully explained by Windes in a subsequent book chapter published in 2003.

Beams Sampled for Tree-Ring Dating in Room 227, Pueblo Bonito

To get a sense of the scale of this project, before it began in 1985 there were 163 pieces of wood from Pueblo Bonito that had been tree-ring dated.  By the time the 1996 Windes and Ford article was published, this figure had risen to 4,294.  That’s a big difference!  We now have a much better idea of when different parts of Bonito were constructed, and that has shed important light on developments in the canyon at large and their relationship to events elsewhere in the Southwest.

Before this project, Pueblo Bonito was thought to have been initially constructed in the early 900s, with some reuse of beams from earlier structures accounting for a handful of dates in the 800s.  This interpretation, expressed most influentially by Steve Lekson in his 1986 book on Chacoan architecture, was based largely on a tight cluster of cutting dates at AD 919 from Room 320 in the western part of “Old Bonito.”  The enlarged sample, however, showed that it was actually this cluster that was a fluke, and that other beams from this wing produced dates in the mid-800s that more likely represent the initial construction of this part of the site.  This seems particularly likely because the types of wood represented by these beams are largely piñon, juniper, and cottonwood, locally available species that were widely used early on, before the beginning of large-scale, long-distance procurement of large beams of ponderosa pine and other high-elevation woods.  This suggests that the beams in Room 320 which dated to 919 were probably replacement beams rather than original construction.  This block of rooms at the western end of Old Bonito was probably built around 860.

Room 320, Pueblo Bonito

Lekson thought this roomblock was probably the earliest part of the site.  As it turns out, it was even older than he thought, but evidence from other parts of Old Bonito suggests that it was not actually the earliest part.  A cluster of cutting dates at AD 891 in the northeast part of Old Bonito, which was clearly added onto the north-central part to the west of it, suggests that it was the north-central part that was actually first.  This makes sense just from looking at the plan of the rooms, actually.  This part of the site is less regular and formal in organization than the east and west wings of Old Bonito, and since it lies between them it seems logical that they would have been added on to the original central room suites.  This is a bit hard to interpret, however, since the places where these different parts of the Old Bonito arc would have come together are mostly buried under complicated later construction.

Windes suggests in his 2003 paper that the very oldest part of the site was the block consisting of Rooms 1, 2, 4/5, 6, 35, 36, 37, and 61.  None of these rooms produced wood that could be dated.  Room 6 contains a considerable amount of original wood, which can be seen today under a modern roof put on to protect it, but this is mostly cottonwood, which is very difficult to date.  As noted above, however, the use of local types of wood like cottonwood is a characteristic of very early construction at Chaco, so even though these beams couldn’t be dated they do still provide some evidence that this part of the site is very early.  The western roomblock, dating to around 860, was probably added onto this one.  This implies that the north-central block predates 860, and Windes says it is “probably much earlier” even than that (although he doesn’t explain why he thinks this).

Intact Roof Beams in Room 6, Pueblo Bonito

How much earlier?  It’s hard to say.  The earliest cutting date at Bonito is 828, from Room 317 in the western roomblock, which both Lekson in 1986 and Windes and Ford ten years later considered likely to be a reused beam.  Since the overall distribution of dates in this block suggests construction around 860, this is probably right, and it’s hard to say where the beam would have come from.  Probably not the north-central roomblock, which would probably have still been in use in 860.  Interestingly, this beam is of ponderosa pine.

The north-central roomblock could well date to around 800 or even earlier, and that brings us to an interesting point.  There are a bunch of pitstructures buried deep under later construction in what would have been the original plaza of Old Bonito; these were not extensively excavated, but they probably correspond to the room suites that make up Old Bonito and therefore date to the 800s.  There are two even earlier pitstructures, however, further south in the later plaza of the expanded Bonito.  Neil Judd, who excavated the site in the 1920s, didn’t pay much attention to them because he thought they were too early to have anything to do with Pueblo Bonito itself.  They apparently date to the Pueblo I or late Basketmaker III period.  Back when the consensus was the Bonito itself wasn’t built until 919, it made sense to agree with Judd that these pithouses were too early, but now that we know that the earliest parts of Old Bonito date well back into Pueblo I it starts to look more plausible that there is actually some continuity here.  Since Judd didn’t look very closely at the early pithouses, we have no way of dating them, which is unfortunate, but one possibility that is looking increasingly plausible is that there was no hiatus at all between the occupation of those pithouses and the earliest occupation of Old Bonito.  In that case, Pueblo Bonito as an important, inhabited location (rather than as the building we see today) might actually date back to Basketmaker III.  And, importantly, whoever lived there at that time wouldn’t have been alone in the canyon.  But that’s an issue for another post.
ResearchBlogging.org
Windes, T., & Ford, D. (1996). The Chaco Wood Project: The Chronometric Reappraisal of Pueblo Bonito American Antiquity, 61 (2) DOI: 10.2307/282427

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Pipe Shrine House, Mesa Verde

When I visited Mesa Verde this summer, I noticed a rather odd sandstone block at Pipe Shrine House, one of the mesa-top sites known collectively as the Far View Group.  These sites, like many others in the park, were excavated by Jesse Walter Fewkes in the early twentieth century, and documentation of the work done on them is correspondingly sparse.

Sandstone Block with Spiral Petroglyph at Pipe Shrine House, Mesa Verde

The block in question has a spiral pecked into it.  Not a whole spiral, though; rather, the middle of a spiral, with the upper and lower parts missing, as if the block were cut from a cliff face where a spiral petroglyph had been pecked.  Indeed, the only really plausible way to explain the block is that it was indeed cut from such a cliff face.

Block Incised with Zigzag Lines at Coyote Village, Mesa Verde

This is very odd.  I’ve never seen anything quite like it elsewhere.  There are a few other sites in the Far View Group that have blocks with designs on them, mostly parallel lines, but those are generally incised and they don’t bear much resemblance to common petroglyph designs.  They don’t show any particular evidence of the designs having been present on the stones before they were cut, either.  The spiral, though, is a very common type of petroglyph, and the Pipe Shrine block remains very puzzling.  Who cut that block?  Where?  Why?

Incised Parallel Lines in Building Block at Far View Tower, Mesa Verde

It’s very hard to say.  The fact that the block is at the top of the current wall strongly suggests that it was not originally part of the site.  In sites like this the top stones are generally modern capping put on with cement to protect the original walls beneath.  The spiral block, then, was almost certainly put on in the twentieth century.  It may have been put on by Fewkes himself after he excavated the site; recent dendrochronological research at the Sun Temple, which Fewkes also excavated and stabilized, has shown that he did a substantial amount of rebuilding there, and it’s quite plausible that he did the same at Pipe Shrine House.  If it wasn’t Fewkes, it was probably some later Park Service stabilization crew.

Plaque Describing Work by J. Walter Fewkes at Far View House, Mesa Verde

Regardless of who put the stone where it is now, though, the bigger question is where they got it, and how.  The mystery is amplified by the fact that Mesa Verde is known for having relatively few petroglyphs compared to many other areas with comparable ancient populations.  The stone looks like the same Cliff House Sandstone (Mesa Verde Formation) as the other stones in the wall, although its patina seems to be a slightly different color, which may or may not be relevant to its origin.  There’s no reason to think it comes from anywhere other than Mesa Verde, but that makes it all the more inexplicable that Fewkes or anyone else would have cut into one of the few petroglyph panels on the mesa for building stone when there are few things in the area more plentiful than sandstone.  I’m no expert on Mesa Verde, of course, so it’s quite possible that the story of this stone is well-known or at least published somewhere in the voluminous literature on the archaeology of the area, but if so I haven’t seen any reference to it.  It’s just very puzzling, and I don’t have a clue what the answer is.

Vent at Sun Temple, Mesa Verde

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Chaco Wash Flowing

Chaco Wash Flowing

Chaco Canyon is a pretty dry place.  Its position in the rain shadow of the Chuska Mountains to the west gives it a semiarid climate with an average of about eight and a half inches of precipitation per year.  While it does snow, and that provides some moisture, the major source of water is the summer storms which come during the “monsoon season” from late July to early September and provide about a third of the annual precipitation in most years.

Chuska Mountains from Peñasco Blanco

Chuska Mountains from Peñasco Blanco

This is not the kind of environment in which a spectacular cultural flowering is generally expected.  And yet, the Chaco phenomenon that was centered in the canyon but spread throughout the region in the eleventh and early twelfth centuries was nothing if not spectacular.  Looking at the remains of the great houses in the canyon today, it’s hardly a surprise that many of the most common questions visitors ask are about water.  Where did they get it?  How did they store it?  Was it wetter then than it is now?

Drainage on Mesa Top

Drainage on Mesa Top

The answer to the last question is no, which comes as a considerable surprise to many visitors.  Some of them even seem very skeptical, like I’m trying to trick them.  It defies common sense to think that anything like what we see at Chaco could have arisen in an environment as dry as what we see today.  And, indeed, many early archaeologists who worked on Chaco assumed that the climate must have been more favorable, and there has been a considerable amount of research into this topic over the past few decades, much of it using the precision available through tree-ring studies to great effect.

Side Wash by Chetro Ketl

Side Wash by Chetro Ketl

Rather surprisingly, what that research has shown is that the climate has not changed significantly in at least the past several thousand years.  There were variations in the amount of precipitation on the order of decades, but always within the range seen in modern records.  So while there were wetter periods and drier periods, and these may have corresponded to important events in the development of the Chacoan system, it was always pretty dry, and never an attractive environment for a sedentary agricultural society displaying the level of complexity seen in the archaeological remains.

West Wing of Pueblo Bonito

West Wing of Pueblo Bonito

In that case, then, if Chaco wasn’t a more attractive place to live then than it is now, why on earth did people choose to live there and do the things they did there?  This is, in some ways, the biggest question out there about Chaco, and also one of the most difficult to answer.  There have been various answers proposed, but none of them seems totally convincing to me.  This is one of the most enduring mysteries about Chaco, and it’s likely to remain so for a long time to come.

Drains on West Side of Pueblo Bonito

Drains on West Side of Pueblo Bonito

Okay, so, given that there was no more water available to the Chacoans than there is now, where did they get the water to do everything they did?  This is another very interesting question that has been the subject of considerable research, and in this case we do have some answers (although a lot of questions remain).

Drainage Path over Slickrock

Drainage Path over Slickrock

The main scholar who has worked extensively on this issue is R. Gwinn Vivian, who taught at the University of Arizona for many years until his retirement.  He has probably spent more time at Chaco than anyone else alive today; his father, R. Gordon Vivian, was the park archaeologist for decades, and Gwinn literally grew up at the park and went on to devote his career to the study of Chaco.  His theories about the Chacoan system are in some ways a throwback to an earlier era of archaeological thought, and in recent years whatever consensus there has been about Chaco has largely moved away from him, but his studies of the water control systems in the canyon have been widely considered the most extensive and reliable work on the issue available.

Modern Erosion-Control Measures in Chaco Wash at Pueblo del Arroyo

Modern Erosion-Control Measures in Chaco Wash at Pueblo del Arroyo

In a short but important paper published in 1992, Vivian laid out what is probably the most concise and accessible account of the various activities for which the Chacoans would have needed water and the probable ways they fulfilled them.  He divides the needs into three categories: domestic, construction, and agricultural.  While these were all important, they involved different amounts of water and different levels of immediate necessity.

Cly's Canyon

Cly's Canyon

The most immediate and constant need would have been for domestic water, largely for drinking, washing, and cooking.  The amount required would of course depend heavily on the population of the canyon, which is one of the most contentious issues in discussions of Chaco.  Vivian tends to favor a higher population estimate, and he runs through a series of calculations to get a rough sense of how much water would have been required at different times of year for domestic purposes.  He argues that the main source for domestic water would have been the various seeps and springs in the side canyons, which in historic times were heavily utilized by the local Navajo population and today provide water for the park wildlife as well.  Even given a fairly high population estimate, Vivian concludes that with sufficient maintenance these springs would likely have produced enough water for domestic use except during period of extreme drought.  While domestic use is the most necessary and constant of the needs for water, it also involves by far the least water.

Remnants of Original Wall Plaster at Pueblo Bonito

Remnants of Original Wall Plaster at Pueblo Bonito

The next main need for water would have been construction.  The Chacoan style of masonry architecture required considerable quantities of water for mud mortar and plaster.  While this is obviously not necessarily a constant need, and could easily be postponed if necessary, Vivian points out that it seems to have been more or less continual in the canyon during the height of the Chaco Era, and some of the building projects at the great houses were of sufficient scale to require vast amounts of water over relatively short periods of time.  While it would certainly have been possible for construction water to have come from the same springs that supplied domestic water, Vivian notes that domestic use would surely have been the priority in times of shortage, and he considers it likely that water from these sources would only have been used in small, low-level construction projects (if, indeed, it was used for construction at all).  He considers it most likely that construction water came from runoff impounded in reservoirs or left in pools, either natural or man-made, in the bed of the Chaco Wash after the high flow from the summer storms had subsided.  With the amount of water that flows through the canyon during the summer, it would take just a bit of ingenuity to divert an amount that, in any given year, would likely have easily been sufficient for construction needs.  It is also possible, though hard to determine, that for construction purposes it was mud rather than standing water that was collected.  The amount of mud left in the bed of the wash (and elsewhere) following a large rain would have been considerable, and using it directly would have conserved any remaining liquid water for other uses.  In either case, it seems quite clear that there would generally have been enough water for construction, although the construction events would likely have needed to be timed just right to take advantage of it.

Mud between Housing Area and Visitor Center after Rain

Mud between Housing Area and Visitor Center after Rain

The third major use of water, and perhaps the most contentious among archaeologists today, was agriculture.  The Chacoans were certainly an agricultural people, and abundant amounts of corn, beans, and squash have been found at sites in the canyon.  While there is recent evidence that at least some of the corn was being imported from elsewhere, it has generally been assumed that there was at least some agriculture in the canyon itself.  The main source of water for this, as for construction, would have been the runoff from the summer rains.  Vivian has put considerable effort over the years into studying the elaborate water control systems on the north side of the canyon, involving diversion dams at the base of the cliffs that lead to canals that lead to fields laid out in very formal grids.  While the best-known of these is one just east of Chetro Ketl and can be seen clearly on aerial photography, Vivian argues that there are many other examples of this sort of pseudo-irrigation elsewhere in the canyon, and mentions one example near Peñasco Blanco in particular.  He runs through a number of possible runoff amounts from rainfall events based on modern measurements of annual precipitation, and finds that the amount available for the fields would vary considerably depending on the parameters set for the calculation.  Thus, while the dams, canals, and fields are certainly there, how they would have actually worked is a subject for debate.  Vivian also argues that other sorts of farming, such as planting directly in the path of runoff and on terraces on the mesa tops, would have supplemented the gridded fields.  In the end, despite the ambiguous nature of the runoff calculations, he notes that the very existence and size of the water-control systems suggests that they must have handled quite large amounts of runoff at least some of the time.

Storm in the Distance through Fajada Gap

Storm in the Distance through Fajada Gap

However it was managed and used, and however many people were using it, water was the limiting factor at Chaco.  Anything else the Chacoans needed they could have imported from elsewhere, and there is a growing amount of evidence showing that they did import all kinds of things: wood, corn, pottery, and even stone for tool manufacture (though not for construction).  With the technology they had, however, they couldn’t effectively transport large volumes of water over any significant distance.  They didn’t have the technology to build aqueducts or other sorts of long-distance pipelines, and while they could certainly carry water in jars, and likely did for short distances within the canyon, those jars would both too heavy and too likely to break to carry over the long distances necessary to reach Chaco from any better-watered area.  As a result, they put as much effort as they could into harnessing every drop of water they could find in the canyon, and they seem to have done a fantastic job of it.  Whatever the situation with agriculture, the sheer amount of construction that they were obviously able to accomplish testifies to their success in controlling, managing, and using the scarce water in their dry location.

Rainbow at Fajada Butte Viewing Site

Rainbow at Fajada Butte Viewing Site

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Plaque at Pueblo Bonito Commemorating Neil Judd's Work

Plaque at Pueblo Bonito Commemorating Neil Judd's Work

Pueblo Bonito is the best-known of the sites in Chaco Canyon, and the only one the park currently gives regular tours of. It has the reputation of being the largest as well. These days we generally just describe it as the largest great house in the canyon, but in the past there were many more hyperbolic descriptions. Neil Judd, who excavated about half of it in the 1920s, was particularly known for presenting it as the largest pueblo ever and the biggest building in America until some skyscraper built in New York in the nineteenth century etc. etc.

There are several things wrong with Judd’s view of Pueblo Bonito, which I think has contributed significantly to an overly Bonito-centric view of Chaco as a whole. For one thing, as ably demonstrated by Steve Lekson, Pueblo Bonito is by no means the largest “pueblo” (a problematic term itself) ever built; indeed, many of the later aggregated single-roomblock pueblos are much larger than it, and villages composed of multiple buildings, which is to say most “pueblos” throughout prehistoric and historic times, can be much larger again. Indeed, it’s not clear that Pueblo Bonito is the biggest anything anywhere. At best, it’s the biggest great house in Chaco Canyon, but when we say that we generally have to qualify it by saying “by mass” or something similar, since Chetro Ketl is actually slightly larger in area.

Be that as it may, Pueblo Bonito is certainly big, and it certainly seems to have been important.  There has been much more research on it than on any other great house inside or outside Chaco Canyon, and as a result we know a lot more about it today than we know about most other sites, another reason it may have an outsized influence on interpretations of Chaco as a whole.  Research on Pueblo Bonito has been going on for over one hundred years, and a useful collection of recent thought about it, put together at a conference marking the centennial, is Pueblo Bonito: Center of the Chacoan World, a collection of papers edited by Jill Neitzel of the University of Delaware.  While it’s a little uneven, as collections of papers tend to be, it’s a good way for people who want to go beyond the basic introductory works to get a sense of where current thought on Pueblo Bonito is.

One of the key debates about Chaco these days concerns the amount and type of hierarchy present in Chacoan society, and much of the evidence on which the debate hinges comes from Pueblo Bonito, so it is only natural that a book like this should take on the hierarchy question as one of its main topics.  Neitzel falls very much on the “more hierarchy” side, and while not all of the other contributors quite agree, the structure of the book overall clearly reflects that.  This is not too surprising, since the importance of Pueblo Bonito to the hierarchy debate is primarily in its status as the source for much of the evidence interpreted as showing hierarchy, and people who specialize in studying Bonito tend to therefore be more receptive to hierarchy than those who specialize in other aspects of the Chacoan system.

In addition to hierarchy, the other two topics on which this book focuses are the function and population of Pueblo Bonito.  These are by no means independent of the hierarchy issue, but the evidence used for debates over them is typically different.  It may seem surprising that such basic questions as what Pueblo Bonito was for and how many people lived there would still remain open after over a hundred years of intensive research, but that is in fact the case, and interpretations vary considerably.  As this book demonstrates, different lines of evidence can lead to quite different conclusions about even such seemingly simple issues as these.

Neitzel’s introductory chapter sets out these three themes, along with some basic background about Pueblo Bonito and the history of research on it.  The next nine chapters then discuss various aspects of Pueblo Bonito, studied using various methods, and Neitzel returns in the final chapter to sum up and draw conclusions (shockingly enough, she decides that the evidence presented in the book supports a hierarchical interpretation of Chaco).

Rebar Used to Measure Threatening Rock's Movement Before the Fall

Rebar Used to Measure Threatening Rock's Movement Before the Fall

As I said above, the papers that form the middle chapters are a bit uneven.  Anne Lawrason Marshall’s Chapter 2 on the siting of Pueblo Bonito is interesting, but pretty short and not very detailed.  She notes that while there are some practical aspects of the siting of Bonito, particularly its location on the north side of the canyon where it gets considerable solar radiation, there are also some oddities about it that suggest that symbolic or ceremonial factors were important as well.  The most notable of these oddities is the fact that the great house was built right under a huge rock leaning out menacingly over the canyon, which the Park Service called “Threatening Rock” until it finally fell in 1941 and crushed about thirty rooms of Pueblo Bonito.  Marshall notes that unusual rock formations are considered sacred at some modern pueblos, which suggests that it may have been precisely because of this impressive, dangerous rock, rather than despite it, that Pueblo Bonito was placed where it was.  Seems plausible enough to me.

Roof Beams at Pueblo Bonito Showing Core Samples Taken for Dating

Roof Beams at Pueblo Bonito Showing Core Samples Taken for Dating

Chapter 3, by Tom Windes, is much more detailed.  It’s an account, based largely on very recent tree-ring dating, of the various construction stages of Pueblo Bonito, starting sometime in the mid-800s and continuing at least through 1150 or so.  The data presented here is very valuable just as a reference, though it’s clear even from the other chapters in this book that not all archaeologists agree with all of Windes’s interpretations of that evidence.  His emphasis is largely on the shifts in apparent use of the building through time, rather than on the possible continuities that have been emphasized by some others.  Windes has long been associated with the idea that Chacoan great houses had very few permanent residents, and here he stays true to form by suggesting that “the site’s resident population never exceeded 100 people.”  Overall, however, he is more concerned here with the details of Pueblo Bonito’s construction and occupation history, and he doesn’t make a whole lot of sweeping conclusions based on them.

Rather different from Windes’s approach, and an interesting juxtaposition to it, is Chapter 4, by John Stein, Dabney Ford, and Rich Friedman.  Ford is the head archaeologist at Chaco Culture National Historical Park, while Stein and Friedman have been closely associated for many years with the Navajo Nation’s Chaco Protection Sites project.  Here they are mostly concerned with describing and discussing the creation of an extremely detailed and accurate architectural model, both physical and virtual, of Pueblo Bonito.  They start with an overview of previous reconstructions, particularly artists’ renditions, and they point out the flaws they see in these interpretations when compared to the archaeological evidence and determine to avoid them in their own efforts.

Much of the rest of the article is a serious of images of the final computer models of the various building stages of Pueblo Bonito, with discussion of these stages in the accompanying text.  They are clear about where they have made assumptions and what effect those assumptions have on the resulting model, which is important because pictures can have a persuasive force out of proportion to the accuracy of the data underlying them.  While their reconstructions are mostly in accord with Windes’s interpretations of the various building stages, there are some differences, and these serve to emphasize the importance of the different assumptions used in making these models.

After the discussion of the models comes the discussion of their implications, and it’s here that things start to get a little (but just a little) dubious.  The most dubious of the conclusions here, at least in my opinion, is the decision that Pueblo Bonito was likely designed all at once rather than in stages over the course of centuries.  In their own words, the authors “argue that Pueblo Bonito’s massive building episodes were not designed and implemented on an episode by episode basis by generations of individual architects following their interpretation of established rules.  Rather, [they] propose that Pueblo Bonito may have had a single architect and that succeeding generations needed only to follow the instructions encoded in the tangible foundation alignments, as well as those carried forward by a few individuals as intangible esoteric knowledge.  Perhaps Pueblo Bonito was the vision of one man, made tangible and set in motion in a single lifetime.”

I find this interpretation rather implausible.  As the quote indicates, it rests heavily on the idea that the foundations served at least partially as massive blueprints to guide construction.  I actually don’t have a problem with this idea, which makes sense to me.  Where Stein, Ford, and Friedman lose me, however, is in making the leap from this to the idea that, because the foundations were laid out in advance, they were probably all laid out at once, perhaps by a single man.  While there’s no way to definitively prove or disprove something like this, of course, a look at the actual layout of the building suggests to me at least that if one guy designed a building to look like this he must have been a pretty weird guy.  There are all sorts of oddities in the way rooms relate to each other, most obviously in the dovetailing of the earlier and later versions of the outer curved wall, and while it’s always hazardous to reject an idea about Chaco because it seems to imply a weird way to do things (we have more than enough evidence that the Chacoans did plenty of things we consider weird), in this particular case I think the burden of proof definitely needs to be on those proposing that this complicated building is the result of a single idea.  A look at some of the other great houses, particularly the later ones like Chetro Ketl that are much more regular and could well have been designed at one time, only confirms my impression that something else is going on at Bonito.

The other conclusions in this chapter are less problematic, although they may still be controversial.  The authors reject the idea of Pueblo Bonito as a massive apartment building comparable to modern pueblos such as Taos, and include with this rejection a critique of the concept of “pueblo” as applied to a building like this, and decide that it makes more sense to think of it as a “ceremonial center,” although they caution that that term has some problematic implications as well.  They finish by analogizing Pueblo Bonito first to a machine, then to the beating heart of the “organism” that was Chaco Canyon as a whole.  There’s a certain teleological flavor to these analogies that I find a little unpersuasive, especially in contrast to Windes’s careful documentation of complex and unpredictable change in form and function over time.

James Farmer’s Chapter 5 is a bit of a change of pace.  He discusses various aspects of astronomical alignments and their possible relationship to ritual, not just at Pueblo Bonito but in other parts of Chaco Canyon as well.  As usual in these sorts of discussions, there is a lot of focus on Fajada Butte and the famous “Sun Dagger” petroglyph atop it, as well as some attention to Casa Rinconada, the great kiva that is quickly becoming another focal point for archaeoastronomical research in the canyon.  Farmer approaches these as integrated parts of a single ritual system, and suggests specific ways that they could have been combined in elaborate scheduled rituals.  His discussion is interesting, but a bit speculative, and I can’t help but feel that this sort of research has an unfortunate tendency to overemphasize the importance of the things we know about (e.g., the Sun Dagger) without adequately considering the question of how much there could be that we don’t yet know about.  It also has a tendency to look at the overall layout of buildings and their relationships to each other synchronically without considering the complex construction histories of the buildings, although to his credit Farmer does take the changing orientation of Pueblo Bonito into account in his discussion.  Still, I get the feeling from this sort of thing that people really should wait until more data is available before constructing elaborate theories.  Archaeoastronomy at Chaco is in its infancy, and I’m quite sure there will be many changes in theories and interpretations in the future.

The next chapter, by Mary P. Metcalf, discusses the labor investment involved in constructing Pueblo Bonito.  This is a topic that I think gets a bit more attention than it deserves.  While the amount of labor involved in the Chaco system is certainly an important datum for understanding that system, it’s only useful if it can be properly measured, and I’m very skeptical about the measurements that have been used in research so far.  These tend to be based on measurements of effort expended by modern laborers doing work assumed to be similar to ancient construction, multiplied by measures of the amount of material used in construction of the great houses.  The resulting numbers are in the form of person-hours or equivalent.  Metcalf approaches this in the usual way, depending heavily on Steve Lekson’s early estimates of construction effort and volume of construction material.  She calculates person-hours for each of Lekson’s building stages for Pueblo Bonito, then compares the numbers she gets to similar calculations for other great houses, and also divides them into “civic” and “noncivic” categories, with the distinction basically being “civic” = kiva construction and “noncivic” = everything else.  She uses her results to conclude that Pueblo Bonito was an example of “monumental architecture.”

Kivas in East Plaza, Pueblo Bonito

Kivas in East Plaza, Pueblo Bonito

I have a lot of issues with this.  For one thing, the numbers Metcalf is using for just about everything are so simplified and generalized that it’s hard to take them seriously about anything.  She uses constant values for the volumes of all walls and roofs that don’t have specific published measurements, and while she does make a distinction between the amount of labor required for flat and cribbed roofs, her adjustment to the calculations seems more than a little arbitrary.  The result of all this is that while her final numbers are probably somewhere in the general area of the actual amount of effort, they’re so strongly affected by simplifying assumptions that it’s hard to tell which distinctions are meaningful.

Typical Kiva at Pueblo Bonito

Typical Kiva at Pueblo Bonito

In addition, while the idea of separating “civic” from “noncivic” construction is interesting and possibly useful, it’s more than a little odd that Metcalf makes a straightforward identification of kivas with civic architecture, especially given how heavily she relies on Lekson, who has famously argued that kivas in this period were primarily residential and therefore not civic at all.  It’s hard to say what to make of the ratios of civic to total construction effort on which she bases many of her conclusions, given this.

Finally, even if these numbers can be considered rough estimates of total effort invested in construction, what does that really tell us?  Metcalf rightly notes that person-hours is the only reasonable measurement to use, since, as she puts it, “the amount of time required for construction is affected by many indeterminate factors such as workday length, workforce size, and the efficiency of the builders,” making any conversion to different time units meaningless.  In other words, person-hours can be interpreted either in terms of larger workforces working shorter hours or smaller workforces working longer hours, and in the absence of any additional information on workforce composition or the structuring of work time, there’s no way to tell where to set the balance.  Which is all true enough, of course, but to me at least it seems to substantially reduce the usefulness of the whole exercise.  If we don’t have outside information on either the amount of time spent or the amount of people working, this all seems like just playing with numbers.  The numbers mean something, of course, at least assuming they’re reasonably accurate, but they don’t mean any of the things we actually want to know.  This is no particular knock on Metcalf, who seems to have done a good enough job with the methods available.  It’s just a general complaint about the amount of time devoted to this sort of thing in Chacoan studies in general.

The next few chapters are, I think, some of the most interesting and useful in the book, and they more than make up for the weaknesses in some of the other chapters.  Chapter 7, by Wendy Bustard, is an analysis of access patterns within Pueblo Bonito using space syntax analysis, a set of techniques for studying spatial patterns that I find particularly fascinating and of which I was totally unaware before reading this chapter.  After a brief explanation of what space syntax is and what it can be used for, Bustard proceeds to demonstrate its usefulness by analyzing the access patterns of a variety of different parts of Pueblo Bonito built at different times in the building’s history.  Her results show that the oldest part of the building has access patterns typical of residential use, as does one of the later wings, but the other roomblocks she analyzes have very different patterns, some much more accessible than typical residential spaces, some much less.  The implications for the function of the building and possible changes in it over time are both quite clear and surprisingly ambiguous.

Chapter 8, by Nancy Akins, is a short but very useful summary of information on the burials found in Pueblo Bonito.  Most of the information here comes from Akins’s earlier work on the human remains found throughout the canyon, but it’s collected here in a more accessible place than much of that earlier research.  The burials in Pueblo Bonito were pretty spectacular, especially in comparison to those found in the small sites across the canyon, and Akins’s conclusion that the differences indicate a social hierarchy of at least three levels, with the top two represented by the two burial clusters in Pueblo Bonito and membership in the higher social levels apparently ascribed rather than attained, fit well with the overal tone of this volume.

Metate at Pueblo Bonito

Metate at Pueblo Bonito

The next two chapters, the last two before Neitzel’s concluding chapter, discuss the artifacts found in Pueblo Bonito from different perspectives.  Neitzel’s Chapter 9 talks about the distribution of the artifacts, focusing on the differences between the distributions of “fancy” and “ordinary” artifacts.  One of the most remarkable things about the distribution of the fancy artifacts in particular (turquoise, shell, jet, etc.) is that they are without exception massively concentrated in a mere handful of rooms.  For most types of fancy artifacts one room contains so many more examples than any other that there is a huge gap in the numbers per room between it and the next-highest.  Even more fascinating, these are almost all different rooms; that is, for each type of fancy artifact there is a single room with vast quantities of that particular artifact and lesser (but often still quite high) quantities of other artifacts.  All of these rooms with huge numbers of fancy artifacts are in the northern part of Old Bonito, either in the burial block or the nearby group of rooms with the apparent ceremonial caches of which these artifacts are major elements.  The distribution of ordinary artifacts is generally more dispersed, although some types, such as projectile points, show skewed distributions similar to those of the fancy artifacts, which suggests that the rather arbitrary division between “fancy” and “ordinary” may not have classified all artifacts satisfactorily.  All of these patterns are illustrated with very useful and readable maps of the room distributions, one of the best features of the chapter.

Chapter 10, by Frances Joan Mathien, takes a look at the same artifacts from a rather different perspective, focusing on the “fancy” artifacts, particularly those imported from great distances, and discussing the functions they may have had within the Chacoan system and the changing interpretations and models that have been offered over the past hundred years or so to explain them.  She ultimately decides that the earliest interpretations, offered by George Pepper, the leader of the first controlled excavations in the 1890s, deserve a closer look than they have generally gotten.  Pepper mostly interpreted what he found in terms of similarities to modern Pueblo practices, and he compared much of the apparently esoteric paraphernalia in the northern rooms to the objects used by modern clans in the ceremonies they conduct.  Mathien finds this plausible even in light of more recent models of Chacoan organization, though she acknowledges that demonstrating this sort of thing is no easy task.

Overall, this is a very interesting volume that provides a fairly complete picture of the state of current research on Pueblo Bonito.  It is a little light on the relationship between Pueblo Bonito and the other canyon great houses to the overall Chaco system, whatever it was, but that is largely to be expected given its focus, and the structuring of the chapters around the three questions Neitzel presents in the introduction is a useful way of tying these otherwise quite different studies together.  This is certainly not a book for those who are just starting to learn about Chaco, but it could be quite useful for those who have already read about or visited Pueblo Bonito and want to get an expanded account of current thought on it, with useful references to further, more detailed publications.

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