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Archive for the ‘Hydrology’ Category

Shannon Bluffs, South of Farmington, New Mexico

One reason for the relative lack of information available on the prehistory of the Totah is that the presence of all those big rivers leads many sites to be buried under alluvium and/or destroyed by flooding and changes in the courses of the rivers.  As a result, many sites are not visible at all on the surface, and this is particularly the case for small sites, especially since the local architecture for much of the Pueblo period relied heavily on adobe and cobble masonry, which is much less durable than the sandstone masonry typical of Chaco and Mesa Verde.  Thus, aside from really big sites like Salmon and Aztec, many Totah sites are only discovered with very deep excavation or erosion.

Linda Wheelbarger’s chapter in the Salmon synthesis volume, reporting on the findings of the Totah Archaeological Project on the Bolack Ranch just south of Farmington, emphasizes this in pointing out how many of the sites on the ranch were not visible in any way from the surface and were only discovered inadvertently, such as when breaches in irrigation ditches lead to swift erosion, revealing sites well below the ground surface.  The most obvious sites are on the terraces above the river, and these are also some of the largest sites (including some probable Chacoan great houses), but it’s not clear if they are actually the largest or if there are larger ones buried somewhere in the floodplain.   Most of the known floodplain sites are small houses, but they are quite numerous, and Wheelbarger is able to define five “communities” along the southern bank of the San Juan between the confluence of the Animas River to the west and the Gallegos Wash to the east.  These tend to be at the confluences of various side drainages (including the Animas and the Gallegos) with the San Juan, which is a pattern noted elsewhere in the San Juan Basin as well, including to some degree at Chaco itself.

Plaza at Salmon Ruin

This is something to keep in mind when evaluating the conventional wisdom that the area around Salmon Ruin was largely uninhabited when construction of the building began around 1090.  The basis for this very common assertion is an extensive site survey done in the area around Salmon by the San Juan Valley Archaeological Project in the 1970s in conjunction with excavations at Salmon.  This survey revealed only four small sites within 1 kilometer of the great house that might have been contemporary with it, and only 12 such sites within 6 km.  In his chapter on the function of Salmon in the synthesis volume, Paul Reed explains the survey and its limitations:

The survey did not entail 100 percent coverage because of the complexity of land ownership and lack of permission to survey some parcels.  Nevertheless, much of the territory in the 1 km area around Salmon was surveyed.  As a caveat, it is likely that flood deposits from the San Juan River, along with alternating cycles of erosion, may have concealed or removed other sites located on the floodplain below Salmon.  We have no way of knowing how many such sites may have been present.  With the data that are available, however, it is clear that Salmon was not the center of a large community of surrounding small pueblos; rather, Salmon largely comprised the entire community.

Reed is clearly aware that it is likely that any sites that may have existed on the floodplain are no longer visible, but he nevertheless concludes that “it is clear that Salmon was not the center of a large community of surrounding small pueblos.”  Well, no, it isn’t clear, even “with the data that are available,” unless you make the totally unwarranted assumption that the available data do in fact reflect the reality despite their obvious shortcomings.  It’s worthwhile to note that the handful of sites that were identified were mostly on the terraces, rather than the floodplain, which means that they don’t have much relevance to the issue of how many sites there were in the region overall.  It’s certainly possible that Salmon was founded in a vacant area, as Reed concludes, but it’s important to note (as he does) that this would make Salmon quite unusual among Chacoan great houses, which usually were built among contemporaneous small sites both in Chaco Canyon itself and at outlying communities.

West Wing of Aztec West and Terrace to the North

A somewhat comparable situation exists at Aztec, although there is evidence of a fairly substantial residential district on the terrace above the West and East great houses.  Very little is known about the extent of settlement on the floodplain around the main “downtown” district, and some have argued that Aztec, too, was founded in an area without substantial prior settlement (with the terrace-top houses presumed to postdate the initial construction of the great houses), whereas others have argued that there probably was some sort of existing settlement there that is no longer visible because of the river-side location.  In either case it is clear that Aztec was a larger and presumably more important community within the region than Salmon.

There isn’t any way to settle this issue without extensive testing and excavation, which is unlikely to happen any time soon, but I just want to flag it to emphasize that a lot of the ideas that get entrenched in the archaeological literature are not necessarily well founded, and it’s important to understand the evidence behind them and how strong it is.

Terrace North of Salmon Ruin with Salmon Museum at Top

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Totah Theater, Farmington, New Mexico

In comments to my post on Salmon Ruins, John Barton asks for more discussion of this area, which is surprisingly poorly understood given its obvious importance to Southwestern prehistory as a whole and the Chaco system in particular.  Wolky Toll has a chapter in the Salmon synthetic volume discussing the Totah region (named from the Navajo name for the Farmington area), and particularly the La Plata subregion, which is becoming somewhat better understood due to a major salvage archaeology project along New Mexico Highway 170, which parallels the La Plata River from the Colorado border south to its confluence with the San Juan just west of Farmington.  Toll has played a major role in this project, and his chapter has interesting things to say about the Totah in general and the La Plata valley in particular.  I don’t really buy all of his interpretations of Chaco; he’s one of the major proponents of a view of Chaco as a regional ceremonial center drawing pilgrims from throughout the San Juan Basin, including the Totah, but with a minimal population permanently resident in the canyon.  He’s particularly associated with the view that even the small-house residents at Chaco only lived there for part of the year, having other residences in other communities, especially along the Chuska Slope to the west.  I’m more inclined to see Chaco as some sort of hierarchical system with at least a relatively large permanent population, mostly in the small houses, though I’m not sure which version of this idea (and there are many out there) I find the most convincing.

Still, Toll knows a lot about the Totah.  He even introduced the term to archaeological use in an important chapter in a previous edited volume that he coauthored with Peter McKenna.  One of the important points he makes in the newer chapter is that while this region has historically been treated as part of either the Mesa Verde region to the north or the Chaco region to the south, it really has an independent identity and cultural trajectory that has been obscured by seeing it entirely in terms of migration or influence from north or south.  This is not to say that the Totah was isolated from developments to the north and south; far from it.  It’s really more accurate to see the whole San Juan basin as a single cultural region, with remarkable uniformity in many cultural expressions and changes over time.  The specific manifestations of those cultural processes were not necessarily identical, of course, but there’s more similarity than archaeologists are often inclined to say.

Mesa Verde Museum

Part of the problem here is just the way archaeology developed in the Southwest.  As Toll notes, the activities of the Wetherill family had a huge influence on which areas came to be considered most important to the interpretation of regional prehistory.  They were not the only influential figures, of course, but they definitely did a lot to put Mesa Verde and Chaco specifically on the radar of the archaeological profession as well as the general public.  In any case, the way things developed was that Mesa Verde and Chaco became well-studied, with major excavation projects in the late nineteenth and early twentieth centuries producing huge numbers of artifacts and a general understanding of the chronological sequence of pottery types and other artifacts.  Once tree-ring dating provided an absolute chronology for the whole region, the general outline became clear: Chaco flourished in the eleventh century then declined in the twelfth, while Mesa Verde hit its peak later, in the thirteenth century, shortly before the whole region was abandoned around 1300.

This was a bit of a shift from the more evolutionary approach to culture history encapsulated in the original Pecos Classification, developed at the first Pecos Conference in 1927 and described by Alfred Vincent Kidder in a short article in Science at that time.  This system saw both Chaco and Mesa Verde, with their big, impressive masonry “pueblos,” as belonging to the Pueblo III or “Great Pueblo” period.  The tree-ring dates, however, showed that Chaco’s peak actually occurred earlier, coincident with the widespread small sites that marked the Pueblo II period.

Aztec West Great House, Aztec Ruins National Monument

Turning back to the Totah, the main excavation project there in the early twentieth century was conducted by Earl Morris at Aztec Ruins.  This was the largest site complex in the area, and it clearly indicated some level of social and cultural importance.  What Morris found there, however, instead of a unique and clearly indigenous material culture, was a mix of what seemed to be Chaco and Mesa Verde material culture.  The early deposits showed clear similarities to Chaco, as did the architecture of the site, which Morris interpreted as evidence for a close cultural connection to Chaco.  After this period, however, Morris saw evidence for an extended hiatus with little evidence of any sort of occupation or use.  After that there was another, quite different suite of material culture that looked much more like Mesa Verde.  Morris interpreted this sequence as an initial Chaco-affiliated occupation followed by abandonment and reoccupation by immigrants from the Mesa Verde region to the north.  In an important chapter in the Salmon synthesis volume, Gary Brown, Peter McKenna, and Tom Windes argue persuasively that Morris was actually wrong about this, and that while the construction and early occupation of Aztec does indeed show substantial connections to Chaco, there was probably not any abandonment or hiatus, just a period of somewhat reduced construction activity at a time of widespread drought and environmental hardship in the mid-twelfth century.  This lull was followed by extensive occupation and construction in the thirteenth century, especially at the east ruin (which Morris didn’t excavate).  The occupants at this time did have pottery similar to that used at Mesa Verde, but that doesn’t mean they were immigrants from there, and it’s much more likely that they were primarily local people who had been living at Aztec all along.  Everyone in the region at this point was making the type of pottery now known as “Mesa Verde Black-on-white,” and there’s no particular reason to think that any groups in the Totah had links to Mesa Verde, which itself seems to have been remarkably isolated during this period, with few trade goods found at the many excavated sites in the region despite its large population.  A similar story seems to obtain for Salmon, with an early Chaco-affiliated occupation followed by a period of continued occupation but little major activity, then an increase in population and activity before the final depopulation of the entire region.

So why did Morris get this wrong?  One reason, which Toll emphasizes, is that the mere fact that Chaco and Mesa Verde have been much more extensively studied than the Totah means that ceramic types (and other types of material culture, but pottery is the most important for cultural classification) have become associated with one or another of these areas, so that when they are found elsewhere in the region they are taken to indicate influence or migration from Chaco or Mesa Verde rather than a regionwide stylistic trend uniting all of these areas.  The latter is more likely, however, especially for the Totah, which was a major population and cultural center throughout the Pueblo II and III periods.  In her chapter in the Salmon synthesis volume, Lori Stephens Reed describes the discovery that the ceramic types found at Salmon and Aztec that have traditionally been classified as “Cibola” (Chaco) or “Northern San Juan” (Mesa Verde) types based on temper and design were mostly made within the Totah, judging from the type of clay used for the paste and slip of the vessels.  Rather than define new types, she just adds the qualifier “Animas Variety” to the existing type designations to indicate this local origin.  This makes sense from an Ockham’s Razor perspective, but as Toll notes in his chapter it’s really the type names themselves that have led to the downplaying of the local factor in the prehistory of the Totah.

Mesa Verde Escarpment from 2009 Pecos Conference at McPhee Campground

The best example of this is the very widespread thirteenth-century pottery type known as “Mesa Verde Black-on-white,” which is found all over the place but has tended to be interpreted as indicating some sort of influence or migration from Mesa Verde.  This is highly improbable, however, since Mesa Verde was gaining rather than losing people for most of this period (until the very end), and the people there don’t seem to have been very actively engaged in regional trade.  This strongly suggests that Mesa Verde Black-on-white is probably of local origin wherever it is found, despite the name.  Toll even muses more than once about how interpretations of Southwestern prehistory might be different if it were called “Aztec Black-on-white” instead.  It’s quite clear that Aztec was a very important site during this period, perhaps not as important as Chaco had been earlier but certainly more important than any single site in the Mesa Verde area.  And yet, because Mesa Verde has been more intensively studied, until quite recently it has been accorded an enormously important role in regional dynamics during this period that closer examination is revealing to be mostly undeserved.  Chaco has received a similarly privileged position for its period of florescence for similar reasons, but it seems to have actually been roughly as influential as this assumption implied.  (Something of an archaeological Gettier case.)

But why didn’t the Totah get the early attention that would have gained it the pride of place in Southwestern archaeology occupied by Chaco and Mesa Verde?  Ironically, a big part of the answer seems to be tied precisely to the geographic factors that made it such an important area in the first place.  One of the main reasons Mesa Verde and Chaco attracted early attention from archaeologists and pothunters was that their isolated locations left them unbelievably well-preserved.  The sites were very obvious on the landscape, many had stood relatively well due to either their massive construction (at Chaco) or their sheltered locations (at Mesa Verde), and they were sufficiently hard to get to that subsequent inhabitants and explorers hadn’t done them much harm.

Animas River, Farmington, New Mexico

The Totah, however, is an enormously attractive and productive agricultural area.  This is presumably what attracted people to Salmon, Aztec, and other communities in prehistory, and it definitely attracted huge numbers of Anglo settlers in the late nineteenth century who proceeded to plow over, loot, and otherwise damage the numerous archaeological sites they found before archaeologists had even heard of them.  The really big sites, like Salmon and Aztec themselves, managed to remain in relatively good condition until they could be professionally excavated, but innumerable smaller sites have likely been completely destroyed.

The local environment has also led to decreased visibility for these sites directly, by covering them with alluvial silt that makes them difficult or impossible to see from the surface.  As a result, we have little sense of how many sites are out there today, let alone how many were there initially before the farmers and the pothunters got to them.  Again, this is in contrast to the harsh environments of Chaco especially, and Mesa Verde to a lesser extent, where there are no permanent rivers to bury sites so deeply.  Furthermore, modern development in the Totah has been extensive, and there’s very little information about what lies underneath the rapidly growing modern towns of Farmington, Aztec, and Bloomfield.  For all of these reasons, the Totah remains surprisingly understudied, despite its obvious importance for understanding Southwestern prehistory.  Luckily this is starting to change a bit, at least on the conceptual level, with publications like Toll’s and Reed’s that point out the distinctiveness of this area and its independent identity.  The Totah has stood in the shadow of Chaco and Mesa Verde for a very long time, but it now seems to be finally coming into the light.

Chaco Street in Aztec, New Mexico

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Sleeping Ute Mountain and Surrounding Landscape from Four Corners

If you stand at the Four Corners monument and look in the direction of Colorado you will see Sleeping Ute Mountain dominating the view.  From this direction you are looking at the southwest side of the mountain, and in front of it you see the southern piedmont.  On the right side of the piedmont, though not visible from this distance, is Cowboy Wash.  It’s one of several ephemeral streams running from the mountain itself across the piedmont to the San Juan River.

One thing that might strike you about the view from this perspective is that it looks like an awfully dry, desolate, uninhabitable wasteland.  And you would be correct to think that.  The southern piedmont of Sleeping Ute Mountain is an extremely arid and inhospitable environment even by the standards of the Southwest, which is saying something.  It’s only a few miles from Mesa Verde to the east and the Great Sage Plain to the north, both areas that get relatively abundant rainfall and supported large and prosperous prehistoric communities, but it is worlds away from them environmentally.  While those areas get sufficient rainfall to support dry farming, and the Great Sage Plain is commercially farmed even today, the southern piedmont does not, and any type of agriculture there would have to rely on some sort of irrigation.  Today the Ute Mountain Ute tribe has a large irrigation project in the area, using water brought in from McPhee Reservoir, 45 miles to the north, via the Towaoc Canal.  The construction of the reservoir and the canal was part of the Dolores Project, which involved substantial archaeological excavation of the inundated area that significantly improved archaeological understanding of the prehistory of the region.  This work took place from 1978 to 1985 and was known as the Dolores Archaeological Project, the largest salvage archaeology project in US history.

McPhee Reservoir, Dolores, Colorado

The creation of the irrigated fields on the piedmont resulted in further salvage excavations in the 1990s.  Among the sites excavated was 5MT10010, which contained considerable evidence of a gruesome incident of probable cannibalism around AD 1150.  It is not the only site in the area to show evidence of cannibalism during this period; in fact, three other sites in the same community, excavated slightly earlier in connection with the construction of the canal, also showed evidence of having been destroyed in an incident involving extensive processing of human remains in a way suggesting cannibalism, and there are several other sites in the area showing similar assemblages, most from the same period but at least one from a later period.  It is at 5MT10010 that the most solid evidence for actual cannibalism, as opposed to processing of bones in a way that may or may not indicate actual consumption of human flesh, in the form of a coprolite that tested positive for the presence of human muscle tissue.

There are many questions that arise from these findings, but one of the most puzzling is also one of the simplest: what were people doing living at Cowboy Wash in the first place, and how did they manage it?  After all, they weren’t building giant dams and canals of the sort involved in the Dolores Project.  In many parts of the Southwest, especially upland areas like Mesa Verde, dry farming using only rainfall was standard during this period, and water control techniques were generally used only for domestic water if a nearby spring or other reliable source was not available.  There are a few springs on the southern piedmont that probably would have supplied sufficient domestic water for the small number of people living there, but the rainfall would definitely not have been sufficient to farm with.  The only source of water at all sufficient for agriculture would have been the occasional floods, from spring snowmelt and summer thunderstorms, that would flow through Cowboy Wash itself and the other drainages on the piedmont.  None of these flows permanently today, and there is no evidence that they ever did.  As at Chaco Canyon, then, which is similarly dry, farming would have to have been based on some sort of technique for capturing the floodwater.

Flowing Chaco Wash and Cliffs below Peñasco Blanco

There are a variety of ways this might be done, including diverting the rainwater from cliffs, as was done at Chaco, planting along the sides of the drainage where the floods would regularly overflow the banks, and what is known as “ak-chin” farming, as practiced by the O’odham of southern Arizona, which involves planting right in the path of the runoff at places where the velocity of the water is relatively low, as at the mouths of tributaries to main arroyos.  There are no sheer cliffs on the southern piedmont like the ones at Chaco, so probably a mix of overbank and ak-chin farming would have been practiced at Cowboy Wash.

A paper by Gary Huckleberry and Brian Billman addresses the nature of farming at Cowboy Wash, and also addresses a related issue, which is whether periodic entrenchment of arroyos due to drought played a role in the patterns of abandonment and migration that characterize Southwestern prehistory.  It is pretty clear by now that the paleoclimatological record shows periods of drought corresponding to periods of abandonment of certain parts of the Southwest, and one proposed mechanism for how this would have worked is that drought would have led to increased erosion and/or hydrological changes in the water table that led to the entrenchment of arroyos, which would have been disastrous for populations dependent on certain types of floodwater farming (especially overbank), as the broad floodplains of the local drainages would have been replaced by deep channels that took the water away quickly instead of letting it overflow to water the crops.  Ak-chin farmers would not necessarily have been affected to the same degree, but if the side drainages they used became entrenched as well they would not have been able to use their techniques either.  Thus, drought would lead to arroyo-cutting, which would lead people to leave formerly productive areas for others that were less affected.  This theory has been proposed as an explanation for certain events at Chaco, with the idea being that some of the social changes late in the Chacoan occupation were due to degradation of the Chaco Wash and the need to change agricultural strategies.  The phenomenon of arroyo-cutting in general is richly illustrated in historic times at Chaco.  The early reports of the Chaco Wash from the nineteenth century indicate that it was a shallow, meandering drainage, much like the current condition of the Escavada Wash to the north and the “Chaco River” that is formed by the confluence of the two at the western end of the canyon and flows north to the San Juan.  By the early twentieth century, and accelerating since then, however, the Chaco Wash through the canyon has cut down significantly and there is a very deep arroyo channel apparent today.

Entrenched Arroyo at Chaco

The drought-downcutting-abandonment theory makes sense as far as it goes, but as Huckleberry and Billman point out there are some problems.  For one thing, the extent to which arroyo-cutting is actually linked to drought, rather than other factors including the specific geology of the area, is hotly debated and there is no consensus.  The idea that while drought may be one factor causing arroyo-cutting there are other factors involved as well is supported by the fact that in different drainages in the Southwest that have been studied in depth the periods of arroyo-cutting do not necessarily correspond to region-wide droughts or other climatic changes.  In some areas they do, but in other areas they don’t.  At Cowboy Wash specifically, the available evidence indicates that the wash began to entrench sometime before AD 950, and that it began to refill with sediment sometime between AD 1265 and 1400.  If abandonment does in fact correspond to arroyo-cutting, then presumably the Cowboy Wash area should have been abandoned between 950 and 1265, and possibly occupied before and after this.  If downcutting results from drought, there should also be evidence of drought during the 950 to 1265 period.

The basic upshot of the Huckleberry and Billman paper is that neither of these expectations is met.  The evidence for drought conditions at Cowboy Wash generally matches that for the rest of the region, with the major droughts in the mid-twelfth century and late thirteenth century AD and several smaller droughts at irregular intervals before then.  This doesn’t show any particular relationship to the stratigraphic evidence for arroyo-cutting, which seems to have been going on to some degree throughout the period from AD 950 to at least AD 1265.  Furthermore, the evidence for settlement doesn’t line up either.  The marginal nature of the Cowboy Wash area implies that it would probably not have been occupied for most of prehistory, and this was indeed the case.  There were a few ultimately unsuccessful attempts to colonize the southern piedmont, however, and they don’t show any particular relationship to the periods of arroyo-cutting (although they do perhaps relate to periods of drought).  The first agricultural occupation of the area came during the Basketmaker III period, when a few pithouses were apparently used seasonally as summer fieldhouses, presumably associated with nearby fields, from about AD 600 to 725.  After these were abandoned, at a time which may correspond to a drought, the area does not seem to have been occupied again for more than three hundred years.  Then, around AD 1050, a few permanent, year-round sites were built.  These seem to have been occupied for only a few years, however, as there was no significant buildup of trash associated with them.  After they were abandoned, three larger villages, including one at Cowboy Wash, were established around AD 1075.  These had extensive trash deposits and seem to have been occupied for one or two generations.  These communities were apparently abandoned, however, when the next occupation began in the 1120s by a population with apparent links to the Chuska Mountain area to the south.  This occupation at Cowboy Wash is the community that was apparently destroyed around AD 1150 (again coincident with a major drought) when its inhabitants were mutilated and cannibalized.  After this event, the area was once again abandoned until about AD 1225, when two new communities were founded, including one again at Cowboy Wash.  Within a few decades the population at Cowboy Wash appears to have aggregated at Cowboy Wash Pueblo, following a typical pattern for the region.  Also typical of the region, the whole southern piedmont seems to have been abandoned by AD 1280, at the time of the “Great Drought” that coincides with major changes throughout the Southwest.

Entrenched Chaco Wash from Cliff Top near Pueblo Bonito

So basically, all of the attempts at year-round occupation of the southern piedmont seem to have occurred during the period that Cowboy Wash was being downcut.  While these were all ultimately unsuccessful, some lasted for a few decades, so clearly they were able to grow some food at some times.  This strongly implies that at least in this case, arroyo-cutting was not particularly linked to abandoned, although drought probably was.  Huckleberry address the issue of how farming could have been done during periods of downcutting by looking at Cowboy Wash and its tributaries today.  They find that while some portions of the main wash, especially, are indeed heavily downcut, other portions are not, and they label this type of drainage a “discontinuous ephemeral stream,” which is to say, a normally dry wash with some portions that are severely downcut and others that are not.  On the uncut portions, which include much of the length of the tributaries, overbank or ak-chin farming could easily be done today, and this was presumably the case in antiquity as well.  The hydrology of the area is such that the areas of downcutting would not have been stable, and would have tended to migrate upstream, but the complexity of the system is also such that this would not have made the entire system unusable; while some parts were being newly cut, others would be filling in, and prehistoric farmers would merely have to move their fields around a bit rather than abandoning the area entirely.

All that being said, however, the question of why people were trying to settle this quite harsh and difficult area in the first place.  It is interesting to note that the attempts at settlement generally came during periods of relatively favorable environmental conditions, which would have made this area a bit less forbidding than usual, as well as during times of increased regional population, when all the good land may well have been taken and some people were forced to seek out the more marginal areas.  The violence that appears to have accompanied the drought of the twelfth century, especially, suggests that when the good times came to an end social relations got very bad very fast.  Huckleberry and Billman suggest that the reason people did end up abandoning Cowboy Wash, the times when they were not attacked, was merely drought itself, which they were unable to cope with as well as other populations, even those who also used floodwater farming techniques, because the size of the watershed was relatively small and the amount of rainfall feeding the washes was also small, so the total amount of water they had to work with was much smaller even in good times than at place like Chaco with large watersheds.  In that context, even a small decrease in annual precipitation could be devastating, leading to failed harvests and the need to move away.

Non-Entrenched Escavada Wash from New Mexico Highway 57

Indeed, there is evidence that the time of the massacre at Cowboy Wash was very difficult for the people there.  Archaeobotanical studies of pollen and other plant remains showed that there was apparently little or no maize in or around 5MT10010 at the time of abandonment, which is quite surprising for a Pueblo site.  The plant remains that were there were mostly from wild plants such as chenopod, amaranth, and tansy mustard, all of which would have been available in the spring and likely would have been intensively collected if there were no stored corn available due to a failed harvest the previous fall.  In addition to pinpointing the season in which the incident occurred, this implies that times were very tough for the inhabitants of 5MT10010, and perhaps for their attackers too.  The coprolite showed no sign of having plant material in it, which suggests that whoever left it had not just eaten some corn at home before setting out to attack 5MT10010.

Another paper associated with the project, by Patricia Lambert, suggests another problem the Cowboy Wash inhabitants apparently had: disease.  In this paper Lambert reports on analyses of ribs of individuals at 5MT10010 and other sites in the Cowboy Wash area dating to various periods of occupation that had lesions on them suggestive of those seen in modern collections of individuals known to have died of tuberculosis and (to a lesser extent) other respiratory diseases.  These lesions were found in 11 of 32 individuals from Cowboy Wash that had enough of their ribs left to examine.  One of the individuals with lesions was from 5MT10010.  This was an adult woman who was not one of the victims of the attack at site abandonment but who had instead died earlier and been formally buried.  Lambert also examined comparative collections of remains from Pueblo Bonito at Chaco and Elden Pueblo near Flagstaff Arizona.  Only 3 of the 45 individuals from Pueblo Bonito and 2 of the 20 from Eldon Pueblo had similar lesions, suggesting that this disease was much more prevalent at Cowboy Wash than at these other sites, even though it was not absent at them.  Lambert notes that tuberculosis is an opportunistic disease that tends to strike people whose systems are compromised by other problems such as hunger and stress.  The evidence for physical violence in the Cowboy Wash sample, even setting aside the cannibalism assemblages, was much greater than in the other two samples as well.  Combined with the harsh environment, this suggests strongly that Cowboy Wash was a difficult place to live for several reasons.  Farming was possible but risky, and when conditions turned bad both hunger and violence from other hungry people were constant threats.

Given this context, the occurrence of extreme events such as cannibalism incidents at Cowboy Wash starts to make some sense.  Cowboy Wash is a place of extremes.
ResearchBlogging.org
Huckleberry, G., & Billman, B. (1998). Floodwater Farming, Discontinuous Ephemeral Streams, and Puebloan Abandonment in Southwestern Colorado American Antiquity, 63 (4) DOI: 10.2307/2694110

Lambert, P. (2002). Rib lesions in a prehistoric Puebloan sample from southwestern Colorado American Journal of Physical Anthropology, 117 (4), 281-292 DOI: 10.1002/ajpa.10036

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Ledge at Wukoki Pueblo, Wupatki National Monument

Wupatki is a very dry place even by the standards of the Southwest, with annual precipitation averaging about 8 inches.  Human habitation in such an arid landscape is therefore highly dependent on capturing as much available moisture as possible.  It appears that the prehistoric inhabitants took advantage of the volcanic ash laid down over the area by the eruption of Sunset Crater in AD 1064 for farming purposes since it acted as a mulch, retaining water from the summer rains that would otherwise have evaporated in the heat and strong winds.  For other purposes such as drinking, cooking, and construction, however, water trapped in the soil isn’t very useful, so other sources needed to be found.  As at Chaco Canyon, which is similarly dry, some of this water would have come from a few springs in the area, especially in the dry season, but it would also have been useful to capture as much of the runoff from the summer rains as possible.  Due to the geology of the Wupatki area, this water could only be used for floodwater farming in a very few places, but there were other ways to take advantage of it.

One such way was apparently shown by a discovery made by two National Park Service archaeologists in the 1940s.  While out evaluating sites for stabilization needs, Albert Schroeder and Philip Van Cleave found some potsherds on the ground in sufficient number to make them think that they might be reconstructible into something approaching the original vessel.  They picked up the sherds and dug a bit into the ground beneath them to see if there were any more.  Sure enough, just under the surface of the ground there was a whole ring of sherds in place, indicating the presence of a broken but substantially complete jar that had apparently been deliberately buried.  They excavated it and took some pictures, and Schroeder wrote up a short article on the discovery for American Antiquity which was published in 1944.

Small Site on Ledge, Box Canyon, Wupatki National Monument

The jar was of the ceramic type Moenkopi Corrugated, which Schroeder dates to AD 1075 to 1275.  This is unfortunately a quite wide date range, encompassing almost the entire period of substantial prehistoric occupation of Wupatki, so it is not possible to say at what point during the occupation the jar was buried.  From its position, however, Schroeder was able to determine that it was likely placed to capture runoff from the summer rains.  It was buried in the sand underneath one of the sandstone ledges that are so common at Wupatki, so one possibility is that it was placed to capture runoff from the ledge.  Indeed, it seemed that the part of the ledge above the jar naturally collected runoff from a wide area of the sandstone outcrop.  At the time Schroeder and Van Cleave found the jar, however, the water pouring off the ledge fell somewhat short of where the jar was.  Schroeder suggested that there may have been some erosion in the period between the time the jar was buried and the time it was found, such that at this time of placement the ledge extended further out and the runoff may have poured directly onto the jar.  If this was not the case, however, the jar was probably buried with the sand level with or a bit higher than the rim, so that runoff from the sandy ground around the jar rather than the ledge above would flow into the jar.

Either way, it seemed apparent to Schroeder that the purpose of the jar was likely to collect water, which makes sense in such an arid environment.  He admitted to being somewhat unsure of the details of his proposal, and he did not venture any theories as to what the water would have been used for or why a jar was used in this way to collect it.  Obviously the amount of water in a single jar would not have been much for agricultural purposes, so I suspect the water was used for household use.  To be so used, depending on how close the household in question was (which Schroeder unfortunately did not mention), the jar could either have been dug up after filling or left in place.  In the latter case, the water could have been taken out with a ladle and transferred to a canteen or some other sort of vessel for transportation.

I don’t have any sort of major point to make about this paper, but it’s interesting as an example of the kinds of adaptations people make to harsh environments.  Wupatki would have been a hard place to live in prehistoric times, but people gave it their best shot.
ResearchBlogging.org
Schroeder, A. (1944). A Prehistoric Method of Collecting Water American Antiquity, 9 (3) DOI: 10.2307/275790

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T-Shaped Doorway at Lomaki, Wupatki National Monument

The paper by Glenn Davis Stone and Christian Downum that I mentioned in the last post, which evaluated the archaeological record of the Wupatki area of northern Arizona in the light of Ester Boserup‘s theory of agricultural intensification, was based largely on the data from an extensive archaeological survey of Wupatki National Monument done by the National Park Service in the 1980s.  This data is presented in a more complete form in an earlier paper that Downum cowrote with Alan Sullivan.  This paper looks at the previous models proposed for the settlement and abandonment of Wupatki in the context of the new data from the survey.

Cinder Cones from the Citadel, Wupatki National Monument

The most influential model for the prehistory of Wupatki has been that presented by Harold Colton of the Museum of Northern Arizona based on work done in the 1930s and 1940s.  Colton saw the extreme aridity of Wupatki as having discouraged settlement there until the eruption of Sunset Crater Volcano in AD 1064 spread a layer of volcanic ash over the area.  This ash acted as a natural mulch to retain water from the infrequent rains which would otherwise evaporate from the thin soil.  Colton looked at the large number of sites that seemed to have been built in the aftermath of the eruption and saw a “land rush” in which people from all over the local area come to Wupatki to take advantage of the improved conditions for farming from the ash fall.  Over time, however, the ash cinders began to blow away in the strong winds and the productivity of the land declined, so the people began to aggregate into the large pueblos for which the Wupatki area is best known.  Once in these aggregated villages, the poor sanitary conditions of living in such close quarters, combined with the continuing decline of agricultural conditions, forced the abandonment of the whole area some time in the thirteenth century.

Wall Abutment, Wupatki Pueblo

This is a plausible story on the face of it, but Colton’s account has been challenged more recently by other archaeologists who point out that a great many of the structures built soon after the ash fall that Colton included in calculating the population increase were small, ephemeral structures that probably served as field houses or other special-use locations rather than year-round dwellings.  This implies that Colton was double-counting both these impermanent structures and the actual permanent houses of the people who used them, thus coming up with inflated population figures on which he based his “land rush.”  The systematic nature of the survey in the 1980s provided the opportunity to determine just how many sites there really were and how many actually served as permanent dwellings.

The Citadel and Sunset Crater from Lomaki, Wupatki National Monument

As Downum and Sullivan tell it, the results basically vindicate Colton’s critics.  The vast majority of the structures found were small and relatively impermanent, with few artifacts.  In addition, a careful tabulation of sherd types at most of the sites showed that the immediate post-eruption period, far from being the land rush of Colton’s theory, was actually a time of relatively limited occupation.  There were more sites from this period than from the pre-eruption period, when the area was nearly uninhabited, but still not very many.  It was not until a few decades later, starting around AD 1130, that building began to really pick up, as indicated by both sherd types and tree-ring dates.  The high point of construction didn’t come until the 1160s, a century after the initial eruption.  (It is actually not clear how long the eruptions continued after the beginning around 1064, and there may well still have been occasional activity by the volcano this late or even later.)  Construction seems to have effectively ceased by 1220, and the area was probably abandoned not long after that.

Beam Sampled for Tree-Ring Dating, Wupatki Pueblo

The upshot of all this for Colton’s theory is that, while it does seem to be true that the ash improved the suitability of Wupatki for agriculture, people didn’t immediate act to take advantage of this.  Downum and Sullivan propose that this may have been because it took some time for the effects of the ash fall on the soil to manifest, but I think a more plausible explanation for this can be found by looking outside the immediate area to the larger region.  The decades after 1130 were a time of extensive drought throughout the northern Southwest.  This is when Chaco collapsed (or at least declined), and there were likely extensive migrations all around the region.  In this context, people may have come to Wupatki less from the “pull” factor of the beneficial effects of the volcanic ash and more from the “push” factors of drought and/or political instability elsewhere.  Of course, there were at least some people farming at Wupatki before this, so the fertility of the area may have become well known at the same time as things were deteriorating elsewhere, making both push and pull factors part of the regional dynamics.

Great Kiva at Wupatki Pueblo

In line with the arguments in the later paper by Downum and Stone, Downum and Sullivan here argue that agriculture for most of the period of occupation of Wupatki was extensive rather than intensive.  They do claim, however, that intensification came right at the end of the occupation period, after 1220, on the basis of more intensive usage of the sites from that period based on sherd counts.  This is kind of dubious, and it appears that Downum changed  his mind about it in the eight years between this paper and the later one.  Intensification at this can, however, be incorporated into the argument made in the later paper that intensification was impossible in this area due to ecological conditions.  Once people began to leave the area, perhaps spurred by increased warfare and/or continuing climatic instability, those who remained would not necessarily have been able to secure access to the large amounts of land they had had claimed earlier as part of the consolidated political groups associated with the large pueblos in the Stone and Downum model.  These few remaining farmers may then have attempted to intensify production on the smaller amounts of land available to them.  Given the aridity of the area, however, this would not have worked reliably enough to allow them to stay, so within a few decades or less they would leave as well, leaving the entire Wupatki area abandoned by 1275.  Note that this is when the famous “Great Drought” associated with the abandonment of Mesa Verde and other areas began, so the aggregation and abandonment processes associated with Wupatki may well have been different from the similar processes elsewhere in the Southwest.

Upper Walls Built on Rock Outcrop, Wupatki Pueblo

Since I’ve been taking note of the scholarly context of the papers I’ve been discussing lately, I should point out that this one is very much an archaeology paper, and a classic processual one at that, with lots of statistics and an explicit model of interactions between people and the environment.  This certainly makes it more “scientific” than, say, the later paper by Downum and Stone, which is more anthropological and not very scientific at all, but as with many such archaeological papers the scientific trappings are somewhat superficial.  This is definitely not as rigorous an attempt at quantitative social science as the economics paper on plowing and gender roles I discussed a little while ago, for instance.  I would therefore argue that this is only science in a somewhat questionable expansive sense, and not necessarily anthropology at all, despite the frequent claims of processualists to be doing “archaeology as anthropology.”  Again, however, that doesn’t mean it’s not worthwhile scholarship.  Regardless of how it’s classified, this is interesting research that can serve as a useful source of data for a variety of other studies such as the one Downum later did with Stone.
ResearchBlogging.org
Sullivan, A., & Downum, C. (1991). Aridity, activity, and volcanic ash agriculture: A study of short-term prehistoric cultural-ecological dynamics World Archaeology, 22 (3), 271-287 DOI: 10.1080/00438243.1991.9980146

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Wupatki Pueblo

The paper I discussed earlier on the connection between plow-based agriculture and highly inegalitarian gender roles was based on a theory proposed by Ester Boserup.  Boserup was a Danish economist who had a lot of interesting ideas about the relationship between population growth and agricultural intensification.  She’s best known for arguing that intensification of agricultural production is a response to population growth, rather than a cause of it as Malthus proposed.  The basic idea is that the default mode of agricultural production is extensive, i.e., requiring a lot of land but relatively little labor.  As population grows, however, the amount of land available per person declines, so people need to get more production out of each unit of land.  This generally requires more work, and the amount of production per unit of work declines.  That is, although the overall amount of food produced increases, the amount of food produced for the amount of work expended to grow it declines.  Thus, people will only intensify agricultural production when they are forced to do so by increasing population.

The Citadel at Wupatki National Monument

This model has been very influential, but it has also been criticized on a number of fronts.  Many of these relate to the underlying assumptions, which Boserup didn’t really make explicit.  The model assumes that the amount of land available is fixed, and doesn’t make allowances for other responses to increased population growth such as trade, migration, and conquest.  There have also been a number of cases in which the model doesn’t seem to apply, either because increased intensification does not in fact require more work or because putting more work into intensified agriculture does not in fact increase crop yields.  (Note that these objections come largely from cultural anthropologists based on ethnographic data.)

Rooms at Wupatki Pueblo

A 1999 paper by Glenn Davis Stone and Christian Downum (available here) tries to incorporate the criticisms of Boserup’s model into a recasting of the model that sees it as applicable only under certain circumstances, namely where increased labor is both necessary and sufficient to raise production.  When this is the case, one option for coping with increased population pressure is what they term “Boserupian intensification,” which is basically the process Boserup described in which people work harder and get higher total yields but lower yields per unit of work on a fixed amount of land.  There are other options, however, including migration and trade, for dealing with population growth in this context, and in other contexts where Boserupian intensification is not an option because of ecological conditions those other options comprise the whole set of possible responses.  In conditions where intensification is possible without harder work, due to new technology or innovative techniques, population pressure ends up not being much of a problem.  Examples given in the paper include raised-field agriculture in the Andes and rice paddies in East Asia.  In other conditions, however, such as arid environments where the weather is very unpredictable, intensification through increased labor just doesn’t work to increase yields reliably, and population pressure becomes a very big problem that must be addressed through other solutions.

Entrance Sign, Wupatki National Monument

Stone and Downum illustrate their proposal through an examination of Wupatki.  This is a very arid part of northern Arizona with similar climatic conditions to Chaco Canyon.  Like Chaco, it was also (rather mysteriously) a major population center in prehistoric times.  Wupatki’s heyday came mainly in the twelfth and early thirteenth centuries AD, a little later than Chaco’s in the eleventh and early twelfth.  Many years ago Harold Colton of the Museum of Northern Arizona proposed that the rise of Wupatki was a response to the eruption of Sunset Crater Volcano in 1064, which covered the area with volcanic ash that served as a natural mulch and greatly increased local fertility, leading to a massive influx of population.  This theory has been challenged more recently but it seems to still have a large number of adherents, and Stone and Downum seem to be among them.  They take the idea of increased fertility from the volcanic ash for granted and look at what happened once people started to move into the Wupatki area.  There have been proposals that the increased population pressure from immigration led to intensification of agriculture at Wupatki in a classic example of Boserupian intensification, but Stone and Downum look carefully at the evidence and conclude that there is very little evidence of any intensification.  Instead, they argue that the vast majority of the Wupatki area is totally unsuitable for intensification; there are very few places where any kind of irrigation or floodwater farming can be practiced, and for the most part the only way to grow anything is to extensively dry-farm the open spaces.  Thus, intensification was not an option, and other options for dealing with population pressure must have been pursued.

Dry Land Farming Sign at Box Canyon, Wupatki National Monument

The strategy they see as most likely is political consolidation to secure claims to land.  Since the necessity of extensive agriculture made holding on to as much land as possible a necessity, coming up with effective means of demonstrating and enforcing land rights was a high priority.  They see the most likely way this would have happened is the formation of political units organized along ethnic lines.  It is always difficult to recognize ethnicity in the archaeological record, but Wupatki has long been known as a “frontier” area occupied by people of three distinct archaeological “cultures”: Kayenta Anasazi, Sinagua, and Cohonina.  These presumably don’t correspond exactly to “ethnicities” in the modern sense, but there are notable differences in material culture among the three, and Stone and Downum identify two main clusters of settlements including large, impressive pueblos.  One of these, centered on Wupatki Pueblo, seems to show Sinagua affiliations, while the other, centered on the Citadel, shows more Cohonina affiliations.  The place of the Kayenta Anasazi in all this is unclear.  They don’t seem to have a cluster of their own, and Kayenta-affiliated sites are spread all over the area.

Wall at the Citadel, Wupatki National Monument

Stone and Downum see the construction of large, aggregated pueblos as a sign of group power intended to impress others with the legitimacy of the group’s claims to land and other resources, and they suggest that relatively few people might have actually lived in the pueblos themselves despite being affiliated with them politically.  For this system to work, the groups’ land claims had to be backed with the credible threat of coercive force, and there is indeed some evidence of violence at Wupatki that may reflect occasional instances when this force needed to be shown.  (There is an interesting parallel here to a more recent article on a different part of the Southwest which I will discuss at some point.)

Wall at Wupatki Pueblo

To illustrate the plausibility of their interpretation of Wupatki, Stone and Downum rely on analogy to contemporary ethnic groups in central Nigeria.  This is an area where Boserupian intensification is in fact possible and some groups have dealt with population pressure through intensification.  Other groups, however, have responded instead by organizing along ethnic lines to defend their land claims through the threat and occasional application of violence.  Stone is a sociocultural anthropologist and this part of the paper is based on his fieldwork in the area.  This is a good example of what (sociocultural) anthropology can contribute to interdisciplinary scholarship.  Ethnography produces an enormously rich, textured body of qualitative data that can be used to test hypotheses and models to explain social phenomena.  Those models can come from anthropology itself, of course, but they can also come from other disciplines, such as economics in this case.  Downum is a Southwestern archaeologist, and his role in this paper seems to be in providing the data about Wupatki.  Much of the data comes from an extensive survey of sites within Wupatki National Monument which has greatly increased the amount of information available about this interesting but poorly understood area.

San Francisco Peaks from Wukoki Pueblo, Wupatki National Monument

I think the arguments in this paper are pretty plausible.  There are some questions about the application of the theory to Wupatki, but it seems to fit as well as any other explanation I’ve seen for the processes of aggregation and abandonment that marked this period of Southwestern prehistory.  The basic idea is that aggregation occurred because of political consolidation, which came about to secure land claims in the face of population pressure and inability to intensify production.  Along with this consolidation came increased conflict, and ultimately that conflict and poor climatic conditions led to abandonment.  This is similar to the model I have proposed for the role of warfare in spurring aggregation and abandonment, although there I focused more on warfare specifically as a response to resource scarcity rather than political consolidation as the response and warfare as the result of that.  This is really a difference of emphasis, however, and the basic idea is very similar.  What Stone and Downum’s theory doesn’t explain, however, is the widespread nature of the aggregation and abandonment processes across the northern Southwest, even in places with much better ecological conditions such as Mesa Verde where intensification would presumably have been an option in a way it wasn’t at Wupatki.  They acknowledge this, and make no claim to explain anything beyond the specific local situation, but it’s an issue that is worth thinking about in evaluating theories like this.

Interior Room at Wupatki Pueblo

Since I’ve been talking a lot lately about disciplinary issues in academia, it’s worth noting that this paper seems to be to be pretty much entirely a cultural anthropology paper.  It uses archaeological data, and one of the authors is an archaeologist, but the overall analysis lies squarely within the realm of (sociocultural) anthropology.  It’s well-done, too, and quite serious and empirical.  I suspect its authors are probably among those who consider themselves “scientific anthropologists” and are outraged by the American Anthropological Association’s moves toward removing “science” from the definition of the field.  I wouldn’t call this science, though.  There’s no hypothesis testing or statistical analysis, and the analysis is basically comparative and qualitative.  It doesn’t go so far in that direction as historical papers like Robin Ganev’s, which I discussed in the previous post, but it’s nowhere near as scientific as the economics paper on plowing that I discussed in the post before that.  What I take from this is that scholarship doesn’t need to be scientific to be serious.  Indeed, in a paper like this one of the main advantages is to take a more “scientific” theory like Boserup’s and evaluate it from a more qualitative perspective to define the unstated assumptions behind it and the conditions under which it applies.  I still maintain that anthropology is not a science, but that doesn’t mean it isn’t worthwhile or doesn’t count as serious scholarship.
ResearchBlogging.org
Stone, G., & Downum, C. (1999). Non-Boserupian Ecology and Agricultural Risk: Ethnic Politics and Land Control in the Arid Southwest American Anthropologist, 101 (1), 113-128 DOI: 10.1525/aa.1999.101.1.113

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Civil Engineering Plaque at Mesa Verde

I’ve previously discussed water control technologies at Chaco, where they were particularly important given the extreme aridity of that area even by Southwestern standards.  There is abundant evidence, however, that water control was a widespread activity throughout the ancient Southwest, even in areas with more reliable water sources.  The best-studied water control systems have been the impressive large-scale canal systems built by the Hohokam in southern Arizona, but less elaborate systems are known in the northern Southwest as well.

Among the better-studied of these systems are those in the Mesa Verde area of southwestern Colorado.  In comparison to Chaco especially this area is much more suitable for agriculture.  The Mesa Verde proper in particular is high enough that it gets quite a bit of regular precipitation, and it is generally thought that the majority of agriculture on the mesa throughout its occupation was dry farming on the mesa top, depending only on direct rainfall.  Interestingly enough, however, there is extensive evidence of water control features even in this more favorable environment.  A detailed description of some of them can be found in an article by Arthur Rohn published in 1963.  He focused on two main types of soil and water control: checkdams forming small terraces, presumably agricultural, along intermittent drainages and large reservoirs, probably for domestic water.  The checkdams, which have since been discovered in other parts of the greater Mesa Verde region such as Hovenweep as well as other regions of the northern Southwest (including Chaco), consisted of small masonry walls, laid without mortar, which served to hold back water and soil which would otherwise drain right off the mesa top during rainstorms.  Some drainages had dozens of these, typically about a yard high and a few yards apart.  Most had been breached at some point after the abandonment of the area and were visible only as rock alignments of varying lengths and heights, but some apparently still held soil and water back well enough that they were covered in vegetation, preventing Rohn from observing much about them.  The agricultural function of these terraces is suggested by the frequent association with them of small structures generally interpreted as seasonal field houses.

Checkdam, Hovenweep National Monument

It is not at all clear, however, why the people on Mesa Verde would have needed to go to the effort to build all these terracing systems when they had so much fertile land right on the mesa top.  Rohn calculated that the likely extent of the terraces added only about 1% of the total area of tillable land on top of the mesa.  He suggested several potential reasons for their construction, including depletion of mesa-top soils, increasing population and subsequent need for more intensive farming, and cultivation of specialized crops of high value that made the additional effort invested in constructing the terraces worthwhile.  Ultimately, however, Rohn had insufficient data to come to any firm conclusions about the purposes of the terraces, and as far as I can tell the situation has not improved much since his time despite the much more extensive paleoclimatic data now available.

The other water control features that Rohn described were the large reservoirs associated with certain of the more densely populated areas of the mesa.  Most of these consisted of large dams, much larger than the small checkdams, across certain canyon heads, where they likely impounded water either for use right there or to soak down through the porous sandstone to feed springs underneath.  These reservoirs thus used the natural characteristics of the canyon heads and required relatively little additional effort to store water for human use.

Far View Reservoir, Mesa Verde

The best-known reservoir on Mesa Verde, however, which Rohn described in detail, was quite different.  Rohn called it Mummy Lake, which was the standard name for it in his time, but it is now often known as Far View Reservoir.  This is a large oval masonry structure, of mostly artificial construction and about 90 feet in diameter.  It is near the cluster of sites known as the Far View Group, including Far View House, which is often claimed to be an outlying Chacoan great house.  These sites mostly date to the Pueblo II period in the eleventh and early twelfth centuries AD (contemporaneous with the height of the Chaco system), which makes them earlier than the most impressive sites on the mesa, which date to the Pueblo III period (late twelfth and thirteenth centuries AD) when Mesa Verde apparently had its highest population.

Far View Reservoir Intake Channel, Mesa Verde

Far View Reservoir was apparently not used for agricultural irrigation, as it has an intake channel but no outlet.  It was fed by an elaborate canal system upstream that channeled water to down the mesa.  Rohn noted that the intake channel was of quite sophisticated design:

The feeder ditch coming from the north did not empty directly into the north side of the reservoir, but rather ran by the west uphill side until it met the mouth of the intake channel at the southwest corner. There water was diverted into the inlet around a right-angle turn and conducted in a northeasterly direction into the reservoir. Such a complicated maneuver caused the suddenly slowed water to drop its silt burden in the intake channel, which could be easily dredged, rather than in the deepest part of the reservoir, where dredging operations would be difficult and would muddy the water.

Trenching of the reservoir by Earl Morris in 1934 revealed that the original bottom lay about 12 feet below the intake.  This would give the reservoir a maximum capacity of about 76,000 cubic feet, equivalent to about 1.74 acre-feet or 568,000 gallons.  That’s a lot of water.

Since there was no outlet from the reservoir, it presumably didn’t feed a system of irrigation canals.  What, then, was this water for?  Rohn’s answer, with which most other archaeologists have agreed, was that it was used for domestic water.  Trenching of the walls of the reservoir revealed pottery of Pueblo II date, contemporaneous with the nearby Far View sites, which makes sense.  A small ditch led off from the main ditch leading to the reservoir, emptying some of the water diverted from upstream into a small drainage with a series of checkdams similar to those documented elsewhere on the mesa, which were presumably farmed by the Far View residents.  Most of the water, however, went into the reservoir, from which it could be easily extracted with pots and brought home for cooking and other daily uses.  Residents of other parts of the mesa seem to have used nearby springs (perhaps fed by canyon-head reservoirs above them) for their domestic water, but there are no springs near the Far View group, so this elaborate reservoir seems to have been built to support the community there, which as Rohn pointed out was the largest concentration of population on this part of the mesa before the Pueblo III period.

Cliff Palace, Mesa Verde

At some point in late Pueblo II or early Pueblo III a very elaborate ditch was built carrying water from the Far View area south almost to the very end of the mesa.  This ditch skirts the Far View sites, suggesting that they were still occupied when it was constructed, but it heads toward the major cliff dwellings to the south that became the major focus of occupation in late Pueblo III.  It’s not clear exactly what this ditch led to, but the fact that it heads toward the major cluster of sites including Cliff Palace, in an area with few springs but a very large population during late Pueblo III, suggests that it likely supplied domestic water for these sites, especially after the abandonment of the Far View sites allowed the intake channel to Far View Reservoir to be blocked and all of the water from the whole system to be brought south.

Rohn mentioned in his article that while Far View Reservoir is the only such reservoir known from this part of Mesa Verde proper, there are several other such facilities known from elsewhere in the region, especially in the Montezuma Valley to the northwest.  A more recent article by Rich Wilshusen, Melissa Churchill, and James Potter (from 1997) provides a valuable summary of information known on reservoirs throughout the region, as well as detailed information on one reservoir studied intensively by the Crow Canyon Archaeological Center.  This reservoir is known as Woods Canyon Reservoir after Woods Canyon Pueblo, a late Pueblo III site nearby.  Also in this general area are a Chaco-era (late Pueblo II) outlying great house known as the Albert Porter site and a site called Bass Ruin that apparently dates to the poorly understood early Pueblo III period, in between the decline of Chaco and the rise of the large aggregated pueblos and cliff dwellings in late Pueblo III.  This reservoir much less elaborate than the Far View one, consisting merely of an earthen dam built across a natural drainage, impounding the water behind it.

Excavation of both the dam and the impounded reservoir area, along with surface collection of sherds, showed that the dam was likely constructed during early Pueblo III or possibly earlier.  An innovative use of tree-ring dates from trees growing on top of the dam in the 1950s, which must have begun growing after the reservoir no longer held water, put the date of dam failure at no later than about AD 1350.  Assuming that it would have taken a century or two for the reservoir to fill with enough sediment for the dam to fail, the authors put the likely usage of the reservoir in early Pueblo III.  These two lines of evidence converge nicely.

White Ware Bowls at Chaco Visitor Center Museum

Another striking aspect of the potsherd evidence was the extraordinarily high prevalence of white wares (77%) and of jars (71%).  The predominance of white wares and the low occurrence of gray utility wares suggests that most of the sherds came from white ware jars used to carry water from the reservoir to habitation areas which broke in the process, and the lack of bowls shows that those habitation areas were not in the immediate vicinity of the reservoir.  Habitation sites usually have assemblages consisting mainly of gray ware jars, which were used for cooking, with large numbers of white ware bowls, which were used to serve food, as well.  The authors mention that previous work at Far View Reservoir (after Rohn) had shown a similar distribution of ceramic wares and forms, and the few sherds mentioned in Rohn’s article also show this distribution.  Given this, as well as the lack of nearby canals or soils suitable for farming, the authors conclude that this reservoir was likely used primarily or solely for storage of domestic water, as Rohn had argued for Far View Reservoir.  They also note that the dating was surprisingly early; these reservoirs are usually found in association with late Pueblo III aggregated sites, and there has been a frequent assumption that they served those communities.  The evidence from Woods Canyon, however, suggests that the reservoir was actually constructed well before Woods Canyon Pueblo, at a time when the local population lived at Bass Ruin or even in the Chacoan community around the Albert Porter site.

Gray Ware Jars at Chaco Visitor Center Museum

In addition to this interesting information about this one reservoir, the authors collected all the information available at the time on other reservoirs in the Mesa Verde region, including the extensive information published only in the so-called “gray literature” (i.e., reports from salvage excavations and other cultural resource management projects that are not easily available to the general scholarly community).  From this data set they find that there are two main categories of reservoirs: those built as integral parts of late Pueblo III aggregated villages and those like Wood Canyon Reservoir built near such villages but probably dating to an earlier period and associated with Chaco-era or immediate post-Chaco communities.  This implies that these large reservoirs may not have been a response to drought as climatic conditions deteriorated in the twelfth and thirteenth centuries, as is often assumed, but that they may instead have been monumental public architecture, like great houses, great kivas, and roads, associated with Chacoan communities and used to sustain the large populations of those communities.  As conditions did deteriorate, however, the existence of these communities and their dependable water sources may have encouraged others to join them, leading to the well-known process of aggregation and formation of large villages during the late Pueblo III period.

Furthermore, the creation of these large, permanent features would have required substantial labor and indicated a commitment of a community to a particular location for the long term.  This was likely a new development in the northern Southwest during Pueblo II, perhaps associated with Chacoan influence; previously, sites had been mostly occupied for quite short periods of time, and people seem to have moved very frequently.  From the eleventh century on, however, the trend is toward increasing commitment to particular localities, although the actual sites in which people lived didn’t necessarily last very long.  Multiple sites occupied one after another in a given area, with the general trend toward increased aggregation and more defensive locations, is typical throughout the Mesa Verde region in the period between AD 11oo and 1300, when the whole area was abandoned.  The role of Chaco Canyon, which is both one of the longest-occupied areas in the prehistoric Southwest and one where water control is most necessary, in all this is interesting to ponder.

Pueblo Bonito and Basin with Captured Rainwater

Finally, it’s worth noting the distinction between different uses of water here.  The largest quantities of water would have been needed for agriculture, but only at certain times of the year, and with careful planning the seasonal rains and spring runoff could be harnessed to adequately water the crops.  The amount of water needed for domestic use was much smaller, but it was needed all the time.  Springs were likely adequate for domestic use as long as populations remained small, but as larger communities developed in some areas with few springs more elaborate measures were necessary to ensure sufficient water was available at all times.  This was most obvious in very dry places like Chaco, but even better-watered areas like Mesa Verde began to have to deal with these issues as population increased and the climate changed.
ResearchBlogging.org
Rohn, A. (1963). Prehistoric Soil and Water Conservation on Chapin Mesa, Southwestern Colorado American Antiquity, 28 (4) DOI: 10.2307/278554

Wilshusen, R., Churchill, M., & Potter, J. (1997). Prehistoric Reservoirs and Water Basins in the Mesa Verde Region: Intensification of Water Collection Strategies during the Great Pueblo Period American Antiquity, 62 (4) DOI: 10.2307/281885

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Lost City Museum, Overton, Nevada

Yesterday the water level in Lake Mead hit its lowest point since the lake was originally filled in the 1930s.  John Fleck was there to mark the occasion, and he has some interesting thoughts on this historic event.  The importance of this milestone is more symbolic than practical; the lake level has not yet become low enough to trigger an actual shortage of water.  Nevertheless, this is an important reminder of the importance of water in the Southwest and the brave new world it is entering as the climate changes and conditions become both drier and less predictable.

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Houses with Yards, Colorado Springs, Colorado

Today is Blog Action Day, and the topic is water.  I did a post for this last year when the topic was climate change, so I figured I’d do it again.  Water is obviously a huge issue, especially in the arid Southwest, so there are a lot of directions I could go with this.  I did an earlier post on the importance of water at Chaco, which is certainly worth linking in this context.  For Blog Action Day, however, I thought a discussion of a rather different issue,  a bit far from my usual fare here, would be interesting.

One of the most noteworthy characteristics of urban sprawl is inefficient use of land, symbolized most obviously by the suburban development pattern of single-family houses on large lots.  Whatever space on these lots is not covered by the building footprint or a driveway is typically divided into yards.  Front and back yards are nearly universal in suburbia, and found at a smaller scale in some urban areas as well, and on particularly large lots side yards are found as well.  These yards are generally interpreted today as being for recreational use, and backyards in particular often have recreational amenities like swimming pools, but at least in my experience people don’t seem to use this space for recreational purposes to nearly the degree you might expect given the sheer amount of it.  Maintaining a yard is also a major effort in time and resources, especially if it is covered with a grass lawn which requires regular mowing and (at least in more arid regions) watering.  The amount of energy and water expended on these activities is huge, and for what?  A big empty space that isn’t generally used for much of anything.  This is not to disparage the choices of people who prefer to have large amounts of space on their property or like maintaining lawns, just to say that I really don’t understand the appeal, and judging by the popularity of apartment-style living where it is available it seems I’m not alone.  Plenty of people, it seems, find the amounts of open space provided by public parks and other public or semi-public areas to be perfectly adequate for their needs.  And yet, we still have all these yards.  In most suburban areas they are essentially mandated by setback requirements in zoning and subdivision codes.

So how did we get here?  Obviously it’s a complicated story, and I’m sure there are many different parts to the answer.  One important aspect of the story that doesn’t seem to get much attention is described by Jon Peterson in an article on the nineteenth-century sanitary reform movement and its influence on American urban planning.  As Peterson describes it, the origin of the yard is something of a byproduct of a series of important changes in urban sanitation and waste management in response to the rise of the industrial city.

Aragon Handyman Service Sign, Albuquerque, New Mexico

Up until about 1850, every house in America, rural or urban, had two things which were absolutely necessary for life: a well and a cesspool.  In rural areas, where most people were farmers, everyone had lots of land, so siting these so that contamination of the water supply was not a major issue would presumably have been pretty easy in most places.  Even in towns, lots were generally large enough to maintain a safe distance between the well and the cesspool.  In  preindustrial cities, lots were smaller than in typical towns, but there was still no public provision of water or sewerage, so people still had wells and outhouses on their small urban lots, and disease could be a problem.  As long as cities remained small, however, these problems were manageable.  Garbage, too, would generally be stored on-site until someone took it away, and waste kitchen and washing water would often be dumped right into the street.   There were sewers, but they were used exclusively for carrying away excess stormwater and preventing flooding (basically like storm sewers today), and dumping waste in them was illegal.

The problems with this system, such as it was, became most glaringly apparent once industrial growth led to massive increases in city size.  This happened first in Britain, where by the early nineteenth century the filthy conditions of fast-growing cities were atrocious, and the decision to deal with the problem by allowing waste to be dumped in sewers only made things worse.  Remember, these were storm sewers, and water only flowed through them when it rained.  The rest of the time, all sorts of waste accumulated and clogged them up.  By the 184os it was clear that the problem had reached crisis proportions, and the social reformer Edwin Chadwick came up with the idea of dealing with it by introducing a system by which water would be provided to houses and used to flush waste through a system of sewer pipes laid out so as to use gravity to carry the waste away.  This was known as “water-carriage sewerage,” and it was the principle upon which all subsequent sewer systems were based.  The full implementation of the idea in a slightly different form in London came in the 1860s under Joseph Bazalgette.

Water Tower, Hammonton, New Jersey

In the US, industrialization had not yet progressed very far at that point, but the nation’s few cities were growing, and other factors were making the waste problem worse.  Probably the most important was the introduction of public water supply in the 1840s.  Once people no longer had to depend on their own wells (which would become less productive as more people moved into the area with their own wells, lowering the water table) or cisterns, they began to use vastly more water, much more than the engineers who designed the water systems had anticipated, and the excess water overloaded the cesspools and created many of the same problems that British cities had been experiencing for a while.  US sanitary reforms were impressed with the sewerage ideas coming out of Britain and argued for sewer systems to be implemented in American cities.  Boston and New York, which had the biggest problems, accordingly put in extensive but largely uncoordinated sewer lines in the 1850s and 1860s.

In the 1870s, as industrialization began to take hold and American cities began to grow rapidly, the problems with the traditional water and waste disposal systems became apparent to more and more cities, and the use of sewers proliferated from then on.  This led to a considerable improvement in urban public health, although the other health problems resulting from the expansion of urban industry may have made this improvement less apparent at the time than it is from our perspective today.

Houses with Yards, Hammonton, New Jersey

So what does all this have to do with yards?  Peterson mentions briefly, near the end of his article, what he calls an “illustrative but little appreciated impact of sanitary reform upon urban land use,” namely, new uses for the space on urban lots formerly occupied by wells and cesspools.  Once urban households had running water and water-carriage sewerage, they no longer needed to devote space outside the house to these necessities of life, and they could use that space instead for recreation.  Thus, the yard was born.  In the biggest and fastest-growing cities, of course, rising land values in the late nineteenth century led most of these earlier lots to be bought up and used to build tenements, skyscrapers, and other high-density uses that maximized the amount of the lot used productively and destroyed both the houses and the yards that had been there before.  In smaller cities and towns, however, this didn’t happen to nearly the degree it did in places like New York and Chicago, and the yard remained.  Around the turn of the century civic improvement associations around the country associated with the City Beautiful movement encouraged the planting of grass, flowers, and other plants in these vacant parts of household lots to beautify them.  This is the origin of the lawn.  Later, this particular idea of beauty would be incorporated into the self-consciously suburban developments of the 1920s, and from there to the sprawl of today.  And so here we are, with big empty spaces filled with grass, the result of technological improvements in sanitation intersecting with emerging ideas of civic beauty.
ResearchBlogging.org
Peterson JA (1979). The impact of sanitary reform upon American urban planning, 1840-1890. Journal of social history, 13 (1), 83-103 PMID: 11632375

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View from the Pacific Coast Highway, California

Speaking of agriculture, one of the blogosphere’s noted experts on farming and water issues in California has an interesting post setting out some opinions and predictions that are apparently controversial in California water policy circles.  The post is intentionally phrased in a polemical way, and most of the items in the list involve normative judgments.  That’s not really my style, of course, but I do agree with most of the points even if I wouldn’t have phrased them in the same way.  The point about the inability of local jurisdictions to deal effectively with large-scale problems is particularly obvious from the perspective of New Jersey, which is like a textbook case of home rule run amok.  Some of the points are more California-specific, and I don’t know enough about the context to have any opinion on them.

Morro Bay, California

What I find more interesting than the judgments are the predictions.  Personally I try to avoid making specific predictions, because it’s an easy way to look foolish in retrospect, but sometimes the context is such that some things look pretty inevitable.  For example, it’s a virtual certainty that Lake Mead will reach its lowest point ever later this year.  Here are the predictions from OTPR’s post that I find pretty convincing:

Society as a whole will become poorer; at the same time, the costs of everything ecosystem-based will rise sharply.  People will be herded in from the exurbs and suburbs by the cost of everything.

Agriculture will substantially contract due to lack of water.  The ballsy part here is that I actually estimate an amount of three million acres, down from 9 million.   I predict the lost acreage will be from the west side, the Delta and most lands currently in alfalfa.

People will live in smaller places and eat less meat, because meat will become very expensive.

The ecosystem based part of our economy will contract for the next hundred years (at least).  We shouldn’t look for the gains of growth economies to lift us painlessly out of recession.

We could select and plan for a pleasant future; we could choose a transition that minimizes the pain of shrinking.  We are in the realm of minimizing pain, not expanding to additional consumption.

Now, I don’t necessarily agree that all of these things will happen exactly as OTPR phrases them.  A lot also depends on scale; OTPR is very focused on California, which I think is indeed very likely to end up with less agriculture and fewer people over the next few decades, but I think it’s pretty likely that the US as a whole will continue to grow for a while, with the growth being more concentrated as some regions shrink considerably and others, including the Northeast and maybe the Midwest, growing as their abundant water and other advantages begin to attract people from elsewhere in the country.  Increased resource costs will also probably compel more efficient land-use patterns, which may mean people moving in from the suburbs to the cities but may also mean denser development within the existing suburbs.  I don’t know if this particular recession is going to mark the end of the long-term pattern of continual economic growth, but without going too far in a Malthusian direction I do think it’s clear that historic growth rates can’t continue forever.  OTPR frames that as society becoming poorer, which is one way to think about it, but I do think it’s important to realize that the US is extremely wealthy by world-historical standards right now, so there’s a lot of potential for reductions in overall wealth and living standards that stop well short of becoming a “poor” society.  I suspect the future for the US looks a lot like the present in western Europe, which is to say, not so bad.

Los Angeles Department of Water and Power Office, Lone Pine, California

So what does all this have to do with archaeology?  One point is just that a thorough understanding of the past is important for a thorough understanding of present conditions and future possibilities, but beyond that general level I do think there are some specific things about Southwestern archaeology in particular that are very relevant to our current conditions.  This has become more obvious in recent years as the “collapse” literature has begun to move more into the popular consciousness, thanks largely to Jared Diamond (which I think does go at least some distance toward counteracting the problems with his own portrayal of the issue). The prehistoric Southwest is an important point of comparison because it’s one of the classic examples of societal “collapse” (although I think that can be a misleading way to portray the archaeological evidence, which I’ll discuss in more detail later); because it is about as well-documented as a prehistoric culture area can be, thanks to the fine-grained chronology possible through tree-ring dating and the good preservation conditions of the arid environment; and because the Southwest is one of the regions currently grappling with some of the exact same issues, which makes study of the prehistoric events in the same region obviously relevant.  The Southwest is also relevant in a more analogical sense for the rest of American society, I think, although that’s a case that has to be explicitly argued rather than merely asserted.  The best example of such an argument I’ve seen so far is David Stuart’s Anasazi America, which deserves more attention that it seems to have gotten.

Owens Lake, California

In general, I think too much of the “collapse” conversation in the public discourse has focused on the causes of collapse, and possible ways to deal with them in a preventative manner, and there has been nearly enough attention to the effects of major changes in societal structures.  Again, this is a place where Southwestern archaeology can play an important role, since we may not be able to tell what led people to abandon large regions and change their lifestyles significantly (though we can certainly speculate and argue about that all we want), but we can tell, at least in a rough sense and on a large scale, what they did afterward and where they went.  I think this is one of the things OTPR is most right about: that we are now looking at dealing with shrinking populations, maybe lower living standards, and almost certainly large-scale migration.  We can deal with that in a variety of ways, some better than others, but we are no longer in a position to prevent it entirely.  I don’t think that’s necessarily a bad position to be in, actually.  But that’s a topic for later.

Monterey Bay, California

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