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Looking East from Casamero Pueblo

Looking East from Casamero Pueblo

Unmanned aerial vehicles (UAVs), popularly known as “drones,” have become increasingly common in recent years as the technology behind them has developed. Some uses are controversial, such as military applications and uses that might violate privacy expectations or be dangerous to other aircraft, but other uses are more benign and can potentially open up new frontiers.

In archaeology, UAVs are increasingly being used for aerial photography and remote sensing in many places around the world. These are types of research that have been established for decades, but that until recently were prohibitively expensive for most archaeologists since they required both expensive camera equipment and the use of airplanes or helicopters. With the development of both lighter, less expensive cameras and UAVs that are robust enough to carry them, this type of research is now much more practical.

A recent paper by a team of researchers including Jesse Casana of the University of Arkansas and John Kantner of the University of North Florida reported on research using a UAV to take infrared thermal imagery, or aerial thermography, as well as color photography, of sites in the Blue J community south of Chaco Canyon, New Mexico. (Casana has the paper posted on his Academia.edu page.) Kantner has been studying Blue J and the surrounding area for several years and has come up with some interesting results.

Blue J is in an area at the southern edge of the San Juan Basin that is thick with Chacoan outlier communities, most of which date to fairly early in the Chacoan era and many of which were apparently abandoned while the Chaco system was flourishing. Casamero Pueblo is one site very close to Blue J where a great house has been excavated and is open to public visitation. These communities typically have one or more great houses and great kivas, and in fact it is unusually common for communities here to have multiple great houses compared to other Chacoan outlier communities. At Blue J, however, Kantner has so far not identified any great houses or great kivas. As he says on his website:

Turquoise, marine shell, jet, azurite, malachite, and other exotic materials attest to the success of Blue J’s inhabitants. Oddly, however, what was originally thought to be a great house turned out to be a normal residential structure, making Blue J the only community for miles around without Chacoan architectural influence.

Now, part of what’s going on here may have to do more with how archaeologists define “great house” than with anything about Blue J specifically. The function of the monumental buildings that have been given this label remains a point of active contention among scholars, with some arguing that they were primarily residential, perhaps housing community elites or religious leaders, and others arguing that they were non-residential public architecture, perhaps with ritual significance as sites of pilgrimage and/or communal feasting. Kantner belongs to the latter camp, so finding “normal” residential features at a suspected great house removes it from consideration as such, whereas another archaeologist might interpret such findings differently. (It’s worth noting that many if not most excavated “great houses” have showed at least some evidence for residential use, and in some cases they have not been noticeably different from other residential structures in a community except in size and location.)

The focus of the recent study was on demonstrating the potential for using UAVs to do fast, inexpensive survey of large sites and to identify buried features. Blue J is well suited for this on both counts. It is located at the foot of a steep cliff, which has resulted in many sites in the community being covered with substantial deposits of sediment carried by water and wind, making them difficult to identify on the surface. It is also fairly large for a Chacoan outlier community, with over 50 residential sites identified through previous surveys, which makes a fast method of survey over a large area an attractive proposition.

The study consisted of doing several flights with a UAV over the site, at different times of day and night, primarily with the infrared thermal camera to capture differences in temperature that are expected to be present between archaeological features and the dry desert soil. The original intent was to do some of the flights in the hottest part of the afternoon, but high winds ended up making this impossible. The results were nevertheless impressive: one site that had been previously identified through survey and limited excavation showed up clearly in the imagery, with buried walls visible in some of the images. Several other sites that had been identified but not excavated showed up as well, with buried walls again visible. A large circle showing a possible great kiva is particularly interesting given that no great kiva has yet been identified from surface survey.

Obviously further work is necessary to confirm some of the results from the imaging, but this is a very successful demonstration of the potential for this technology to improve survey and site identification so that further research can be focused on the most promising locations for sites. Other sensing techniques such as ground-penetrating radar have also been tried in the Southwest, but they are much slower and can be thrown off by some characteristics of the desert environment. Aerial thermography using UAVs offers another option that seems to have a lot of potential and it will be interesting to see how it is used as the technology continues to advance.
ResearchBlogging.org
Casana, J., Kantner, J., Wiewel, A., & Cothren, J. (2014). Archaeological aerial thermography: a case study at the Chaco-era Blue J community, New Mexico Journal of Archaeological Science, 45, 207-219 DOI: 10.1016/j.jas.2014.02.015

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Looking East from Peñasco Blanco

Looking East from Peñasco Blanco

Today is the winter solstice, which means it’s also the sixth anniversary of this  blog. On these anniversaries I like to write about archaeoastronomy, which is a very interesting topic and an important one for understanding Chaco and Southwestern prehistory in general. Last year I wrote about some research indicating that in the Rio Grande valley, an area generally thought to be outside the Chaco system but that was certainly occupied at the same time as Chaco, there was a long and very consistent tradition of orienting pit structures to the east-southeast, which is the direction of winter solstice sunrise. The winter solstice is very important in the cosmology and rituals of the modern Pueblos, so it makes a lot of sense that at least some Pueblo groups would orient their dwellings based on it.

As I noted at the time, this orientation is very different from that in the San Juan region to the west, including Chaco and Mesa Verde. In this area there is an equally long tradition of orienting pit structures to either due south or south-southeast. I’ve long wondered why this might be, and an article I read recently discusses the issue and proposes some interesting potential answers.

The article is by Kim Malville and Andrew Munro and was published in the journal Archaeoastronomy in 2010 as part of a special issue on archaeoastronomy in the Southwest. Malville is an astronomer who has done a lot of research on archaeoastronomy in the Southwest and identified many potential astronomical alignments, but this article is actually largely about debunking many of the alleged alignments claimed by others, particularly Anna Sofaer and her Solstice Project. Sofaer, an artist who turned her attention to archaeoastronomy after discovering the “Sun Dagger” effect involving a spiral petroglyph on Fajada Butte that on the summer solstice appears (or appeared) to be bisected by a “dagger” of light coming through a slit between large boulders in front of it. Sofaer went on to organize surveys of the major great house sites in Chaco Canyon to identify any celestial alignments in the orientation of their walls, and her team found that virtually all of them did show alignments to the positions of the sun or moon on solstices, equinoxes, or lunar standstills.

Light Snowfall on Fajada Butte

Light Snowfall on Fajada Butte

Sofaer and her collaborators went on to publish these findings widely, and to make a well-known documentary that has often been shown on television and inspired a lot of interest in Chaco. As Malville and Munro show in this paper, however, the evidence for these alignments is very thin. There is little to no justification in Pueblo ethnography for the idea of celestial building alignments, and the alignments themselves are identified with a substantial margin for error that makes spurious positive identifications likely, especially when so many potential alignments are tested for. Particularly concerning is how many of the alignments are to the minor lunar standstill, which is not a very impressive or noticeable event. (The major lunar standstill is a different story, and there is strong evidence at Chimney Rock in Colorado that the Chacoans were familiar with it and considered it important.) Malville and Munro also argue that the fact that most of the alignments are based on the rear walls of sites is also questionable, since there is no evidence that rear wall alignments were or are important culturally to Puebloans.

Instead, they argue that the alignments of rear walls are epiphenomenal, and that they mostly result from the more solidly established concern with the orientation of the front of a site. The bulk of the article is devoting to tracing these frontal orientations across time and space, with a primary focus on Chaco itself and on the earlier Pueblo I villages in the area of Dolores, Colorado that are often seen as being partly ancestral to the Chaco system.

As I noted above, there are two main orientations that persist through time in the San Juan region. One is to due south, and the other is to the south-southeast (SSE). With pit structures these axes are typically defined by a straight line of sipapu (if present), hearth, deflector, and vent shaft. There is often also a measure of bilateral symmetry between features on either side of this line, such as support posts. When there are surface rooms behind a pit structure, they often (but not always) conform to the same alignment, and when the back of a row of surface rooms is straight, it is typically perpendicular to the main orientation. Malville and Munro argue that these perpendicular back walls on many Chacoan great houses, which Sofaer has identified as having alignments to various astronomical phenomena, are really subsidiary effects of the main emphasis on frontal orientation.

The authors start their survey of orientations with the Basketmaker III pithouse village of Shabik’eschee at Chaco. Of 15 pithouses for which they could find adequate information on orientation, 11 faced SSE with an average azimuth of 153.7 degrees and 4 faced south with an average azimuth of 185 degrees. Strikingly, none of the pithouses showed any other orientation.

The north-south orientation isn’t difficult to understand, and Malville and Munro attribute it to use of the night sky for navigation (which would have been easy enough at this time even though there wasn’t actually a north star), and they also mention the widespread presence of Pueblo traditions mentioning origins in the north. While the exact reasons for adoption of this orientation may not be clear, its consistency isn’t unexpected since it’s pretty obvious and easy to replicate.

The SSE orientation, on the other hand, is a different matter. Note that at Shabik’eschee this was much more common than the southern orientation, from which it is offset by about 20 to 30 degrees in individual cases. There is more variation in this orientation than with the southern one (standard deviation of 7.7 degrees versus 2.4), but it’s sufficiently consistent and common that it seems like there must be some specific reason for it. Unlike the southern orientation, however, it’s not at all clear what that might be. Malville and Munro, sticking to their interpretation of orientations as references to places of origin, suggest that in the case of Shabik’eschee it might reflect the fact that some people might have migrated to Chaco from an area that was more to the north-northwest than due north, which seems implausible to me but then I don’t have a better explanation myself.

McPhee Reservoir, Dolores, Colorado

McPhee Reservoir, Dolores, Colorado

In any case, this pattern continues through time. The next set of orientations Malville and Munro look at are those of the pit structures at the Pueblo I Dolores villages. What they find is that SSE orientations are dominant here too, even more so than at Shabik’eschee. In fact, all of the pit structures they looked at had SSE orientations except those at Grass Mesa Village, which mostly faced faced south (although even here there were a few SSE orientations). This is in keeping with other evidence for differences in architecture among different villages at Dolores; Grass Mesa is known for having long, straight room blocks, as opposed to the smaller and often crescent-shaped roomblocks at McPhee Village, which with it is most often compared.

The Duckfoot site, to the west of the Dolores villages but contemporaneous with them, also had a SSE orientation. Further west, however, southern orientations become more common, including at the important village sites of Yellow Jacket and Alkali Ridge, plus some of the earlier Basketmaker II sites on Cedar Mesa in Utah.

There was one more orientation used during the Pueblo I period in the Northern San Juan region, however. At Sacred Ridge, in Ridges Basin near modern Durango, Colorado, the average azimuth of the pit structures is 120 degrees, the same east-southeast orientation corresponding to winter solstice sunrise so common in the Rio Grande. Malville and Munro remark on the similarity to the Rio Grande pattern and consider it “puzzling,” positing some potential ways that it could have come about. They argue, however, that wherever this pattern came from it didn’t last in the north, and they point to the extremely violent end to the occupation of Sacred Ridge as the end of this orientation tradition in the San Juan region (although this may not be strictly true, as discussed below).

From here Malville and Munro turn back to Chaco. Specifically, they look at the great houses at Chaco during its heyday from about AD 850 to 1150. Rather than pit structures, they focus on roomblocks, and they interpret the orientation of a roomblock to be the perpendicular to its long axis (in the case of rectangular roomblocks) or the perpendicular to the ends of the crescent of roomblocks with that shape. They find that most of the great houses have a SSE orientation, in keeping with the general trend throughout the region, as do the three northern outlier great houses of Chimney Rock, Salmon, and Aztec. Since this orientation is very close to the perpendicular of the minor lunar standstill moonrise alignment that Sofaer has proposed for many of these buildings, Malville and Munro argue that this widespread orientation explains the pattern much better than the lunar alignment. Pueblo Alto and Tsin Kletzin have north-south orientations, which is unsurprising since they lie on a north-south line with each other.

A few of the great houses have a more complicated situation. Peñasco Blanco appears to face east-southeast at an azimuth of approximately 115 degrees. This is intriguingly close to the Rio Grande/Sacred Ridge winter solstice orientation, which Malville and Munro do note. Although the unexcavated nature of the site makes it hard to tell for sure, it is possible that this is in fact an example of this orientation surviving much later in the San Juan region than the destruction of Sacred Ridge, although what, if any, connection there might be between the two sites is unclear.

Pueblo Bonito from Above

Pueblo Bonito from Above

And then there’s Pueblo Bonito. While the very precise north-south and east-west cardinal alignments of some of the key walls at this site are well known, it has also long been noted that there is evidence for different alignments and change over time here. Malville and Munro interpret the early crescent shape of the building as having a SSE orientation, and like many others they relate it to the similar size, shape, and orientation of McPhee Pueblo at McPhee Village. They then describe multiple stages of drift away from this orientation toward the cardinal orientation. There is surely something to this interpretation, but a careful look at the stages of construction of the site shows that the picture is probably more complicated. The very first construction at Bonito appears to have been straight and oriented to the south, and to have been incorporated later into the SSE-facing crescent. Subsequent building stages show evidence of both orientations having been present throughout the history of the building.

The complicated situation at Pueblo Bonito provides a convenient segue to the key issue here: what was driving this long-term but consistent variation? Why were two different orientations for buildings present in close proximity for hundreds of years, even as populations moved long distances and adjusted their cultures in profound ways? Malville and Munro suggest that these orientations may reflect longstanding cultural and ethnic diversity in the prehistoric Southwest. Given how long-lived and consistent these patterns are, they propose that they were related to deep-seated cultural identities. This is an intriguing idea that may allow tracking of specific cultural groups across the Southwest over centuries. It also provides another piece of evidence that Chaco Canyon was a multicultural community, and implies that even Pueblo Bonito itself contained groups with diverse backgrounds.

The picture is probably even more complicated than Malville and Munro suggest. They tend to implicitly assume that the orientations of pit structures are the same as those of the room blocks with which they are associated, but at least at Chaco this is not necessary true, particularly for small-house sites, which they also don’t address at all in this study. There are many examples of small houses where the room blocks are oriented to the east but the pit structures are oriented to the south (and possibly also SSE, although I haven’t checked this). This eastern orientation may reflect connections to the south, which have gotten a lot less attention in the literature than connections to the north although they appear to have been pretty important in the origins of Chaco.

In any case, I think this is fascinating stuff. It may not be archaeoastronomy per se, but it seems like a fitting way to mark the solstice.
ResearchBlogging.org
Malville JM, & Munro AM (2010). Cultural Identity, Continuity, and Astronomy in Chaco Canyon Archaeoastronomy, 23, 62-81

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Rio Grande from Coronado State Monument, Bernalillo, New Mexico

Rio Grande from Kuaua Pueblo, Coronado State Monument, Bernalillo, New Mexico

Today is the winter solstice, which also makes it the fifth anniversary of this blog. I tend to like to post about archaeoastronomy on these occasions, and as I mentioned in the previous post I’m currently in Albuquerque and have been reading up on the archaeology of the Rio Grande Valley. Luckily, a recent article I read has a very interesting archaeoastronomical proposal specific to this region, which makes everything come together nicely. Getting to that point requires some explanation of the context first, however.

Today the northern Rio Grande Valley is one of the main centers of Pueblo population, and this was also true at the time the Spanish arrived in the sixteenth century. It’s been clear to archaeologists since the late nineteenth century that the modern eastern or Rio Grande Pueblos belong to the same overall cultural tradition as both the modern western Pueblos (Laguna, Acoma, Zuni, and Hopi) and the prehistoric Pueblo sites found all over the northern Southwest. Within this overall cultural tradition, however, there are noticeable differences in certain aspects of culture between the Rio Grande Pueblos and those further west, as well as between both groups and the prehistoric sites. The long and complicated history of interaction between the Rio Grande Pueblos and the Spanish has both led to cultural changes in this region and made the modern Pueblo residents very reluctant to reveal information about their cultures to anthropologists. Both of these phenomena make understanding the background of Pueblo diversity exceptionally difficult.

As a result, archaeological research in the northern Rio Grande area has proceeded along a somewhat different course from research further west. While extensive early research at well-preserved abandoned sites at places like Chaco Canyon and Mesa Verde led to the formulation of a robust and well-supported relative chronological scheme by the late 1920s that was soon anchored by the absolute dates provided by tree-ring dating, fitting the Rio Grande sites into this sequence proved to be a challenge. Alfred Vincent Kidder’s extensive excavations at Pecos provided clear evidence of continuity between prehistoric and historic Pueblo culture, which allowed the historic Pueblos to be easily placed at the end of the sequence, aligning earlier developments in the east and west proved to be a challenge. Pecos itself was founded quite late in prehistory, and very few other prehistoric sites had been excavated in the Rio Grande area. The so-called “Pecos System” of chronology and culture history was actually based primarily on western sites, and over time it became clear that it didn’t fit the emerging picture of Rio Grande prehistory pretty well. That picture, based primarily on survey and excavation work done by the Laboratory of Anthropology at the Museum of New Mexico starting in the 1930s, by the 1950s resulted in a new framework for eastern Pueblo prehistory.

The main architect of the new system was Fred Wendorf, an archaeologist at the Museum of New Mexico who had done a lot of the work of documenting sites in the region. He published a paper in American Anthropologist in 1954 describing his proposed system, which consisted of five periods:

  • Preceramic: Before AD 600
  • Developmental: AD 600 to 1200
  • Coalition: AD 1200 to 1325
  • Classic: AD 1325 to 1600
  • Historic: AD 1600 to present

Contrast this to the Pecos System, as presented by Joe Ben Wheat in a paper published in the same journal in the same year:

  • Basketmaker II: Before AD 400
  • Basketmaker III: AD 400 to 700
  • Pueblo I: AD 700 to 900
  • Pueblo II: AD 900 to 1100
  • Pueblo III: AD 1100 to 1300
  • Pueblo IV: AD 1300 to 1600

The most obvious difference between the two systems is that the Pecos System contains more periods. A more subtle difference is that in the Pecos System all of the periods are associated with agriculture, which appeared quite early in the Four Corners area. Exactly how early was not quite clear in 1954; Wheat says it was “about the time of Christ.” In the Rio Grande, on the other hand, the Developmental was the earliest agricultural period in Wendorf’s scheme as well as the first ceramic one, preceded by a Preceramic period that was totally undated at the time but that Wendorf suggested may have lasted quite late, even after the beginning of the Developmental.

This pattern of delayed appearance of typical “Anasazi” cultural phenomena in the Rio Grande persisted throughout Wendorf’s scheme. He defined the beginning of the Coalition period by the switch from mineral to organic pigment in pottery decoration, a trend which had been gradually diffusing east from Arizona over the past few hundred years. Similarly, the beginning of the Classic was defined by the appearance of glaze-decorated ceramics, which had appeared a few decades earlier in the Zuni area. The Historic period began with the onset of Spanish colonization. In general Wendorf’s period definitions depended heavily on trends in pottery decoration, in contrast to the Pecos periods which were defined by a broad suite of material culture changes, with architecture especially important. One reason for this was that architecture and other cultural traits were bewilderingly diverse within each of these periods, especially the Developmental, and this diversity was apparent even with the very small number of excavated sites at that time.

Palace of the Governors, Santa Fe, New Mexico

Palace of the Governors, Santa Fe, New Mexico

Wendorf’s scheme was in conflict on various points with a different scheme for Pueblo culture history as a whole developed by Erik Reed of the National Park Service. After Wendorf’s paper was published, discussions between the two led to an updated version of it published under both their names the next year in El Palacio. This paper has been extremely influential and the framework it established has been used by most archaeologists in the Rio Grande area since. The basic outlines of the framework are the same as those in Wendorf’s 1954 paper, with the changes involving the correction of the numerous typos in that paper, the addition of data from more recent excavations, and a somewhat different discussion of attempts to correlate archaeological phenomena with the complex distribution of modern linguistic groups. The latter was a particular interest of Reed, whose theories on it had been criticized by Wendorf in the earlier paper. I find it interesting as well, but I won’t get into it here.

Instead my focus here is on Wendorf and Reed’s Developmental period. Wendorf originally defined this period based on extremely limited information as a time of low population, diverse architectural styles and settlement patterns, and evidence of cultural influence from the San Juan Anasazi to the west. Population was extremely limited until about AD 900, when many more sites appear to have been inhabited and sites began to appear in the northern part of the region for the first time. This is the time of the rise of Chaco, and local Rio Grande ceramics show clear similarities to Chacoan types. Some archaeologists, including Reed, had argued that this rise in population came from an actual immigration of people from the Chaco area, but Wendorf doubted this, pointing out that other cultural traits showed considerable differences from Chacoan patterns. He suggested that while there could well have been some immigration from the west at this time, it was more likely from somewhere like the Mt. Taylor area that was part of the general Chacoan sphere of influence but closer to the Rio Grande, and that the number of people was likely small.

Architecture during the Developmental period was varied, with site sizes ranging from ten to 100 rooms and one to four kivas. The kivas were round and lacked most of the typical Chaco/San Juan features such as benches, pilasters, and wall recesses. They also usually faced east, in strong contrast to Chaco kivas, which usually faced south or southeast, even when they were associated with east-facing surface roomblocks (a common pattern for small houses at Chaco).

While the Wendorf and Reed system has remained in general use among Rio Grande archaeologists, the Developmental period in particular has seen much more data emerge from subsequent research, much of it associated with cultural resource management salvage projects. Cherie Scheick argued in a 2007 article that the period was much more diverse and complex than Wendorf and Reed had portrayed it as, illustrated by two nearby and contemporaneous sites in what is now Santa Fe that nevertheless had quite different ceramic assemblages which would place on in the Developmental period and the other in the Coalition period based on the Wendorf and Reed system. (This sort of thing is a major flaw with chronologies based mainly on ceramic styles, since time is by no means the only factor affecting differences in pottery.) Basically there seems to have been a long transitional period between the Developmental and Coalition in which communities with a variety of ceramic styles existed in close proximity. In particular, the introduction of carbon pigments seems to have been more variable than Wendorf and Reed realized, and they coexisted with mineral pigments for a substantial period. Scheick also points out that, contrary to what some earlier researchers had thought, there are no particular patterns over time in the architecture, such as larger villages developing later in the Developmental period.

Lurking in the background of all this research is the question of the abandonment of the Mesa Verde region and whether any of the apparent increases in population in the Rio Grande correspond to an influx of people from that area. Wendorf and Reed placed this migration in the middle of their Coalition period, with the appearance of a ceramic type, Galisteo Black-on-white, that is very similar to late Mesa Verde Black-on-white, and various other changes in material culture in the region that accompanied a population increase. However, recent research in the Mesa Verde region itself has suggested that the depopulation was a longer-term process beginning much earlier than previously thought, so some of the changes in the early Coalition period, could also be due to immigration. The basic problem is that while there are plenty of individual examples of similarity between San Juan/Mesa Verde culture and Rio Grande culture over a long period of time, there are no sites showing a complete package of San Juan cultural traits. There seems to be an emerging consensus that this is because the migration was primarily not of entire communities moving as units but of smaller units (families or lineages) that joined existing communities in the target region, perhaps ones that they had had earlier contact with through trade or other activities.

Round Kiva at Kuaua Pueblo, Coronado State Monument

Round Kiva at Kuaua Pueblo, Coronado State Monument, Bernalillo, New Mexico

An additional piece of evidence for this idea comes from the paper I mentioned at the beginning of this post, published by Steven Lakatos in 2007. Lakatos did an analysis of features in Rio Grande pit structures (kivas) during the Developmental period. He looked at size, orientation, and presence or absence of a hearth, an ash pit, a deflector, and a ventilator in a total of 131 excavated pit structures in the Rio Grande Valley dating to AD 600 to 1200. He looked at specific types of each of these features and came up with a wide variety of statistical comparisons. The sample sizes for most of the subsamples he looked at are so small, however, that I doubt many of these comparisons are meaningful. His overall conclusions, however, are probably reliable.

Lakatos found that there is a consistent pattern of features in pit structures throughout the Developmental period: hearth, ash pit, deflector, and ventilator, sometimes accompanied by sipapu and/or ash grinding stone, in a row aligned to the east-southeast (average azimuth from true north of 118 degrees for the Early Developmental period and 123 degrees for the late developmental). This is in strong contrast to the San Juan (Chaco/Mesa Verde) kiva pattern, where ash pits are rare, other features like benches and pilasters are common, and orientation is usually to the south or south-southeast. Lakatos notes that this Rio Grande kiva pattern continues into the Coalition period and later, as kivas become more formalized community-scale integrative structures, and while all the features in the complex potentially had originally mundane uses, the formalization of the pattern and its persistence over time suggest that at some point it acquired ritual significance. He notes the ritual importance of ash to modern Rio Grande Pueblos as a way of explaining the ash pit and ash-grinding stone as ritual features. The persistence of the pattern into the Coalition period and beyond suggests to Lakatos that immigrants to the Rio Grande from Mesa Verde and elsewhere not only joined existing communities, but largely assimilated to existing religious and cultural practices in an area that had developed a distinctive identity already. Thus, the reason it is so hard to pinpoint continuity between San Juan and Rio Grande archaeological sites is that the San Juan immigrants changed their culture to conform to Rio Grande practices.

I’m not sure I buy that there was quite as much continuity in the Rio Grande as Lakatos and other Rio Grande archaeologists tend to think. Looking at it from the outside, the ceramic evidence certainly seems to imply at least some continuity with Mesa Verde culture, and a close examination of what little ethnographic information is available on the Rio Grande Pueblos may reveal other traits of western or northern origin. Still, Lakatos’s evidence for continuity in kiva form looks convincing to me, and the patterns he identifies are certainly quite different from those of Chaco and Mesa Verde. The fact that his interpretation meshes well with other research suggesting migration by small groups into established communities is also encouraging.

So what does all this have to do with the winter solstice? Well, Lakatos also calculated the azimuth of winter solstice sunrise for the Albuquerque area in AD 1000, and it was 119 degrees east of north. This is strikingly similar to the average azimuths of the kiva alignments he analyzed, which have small standard deviations indicating strong clustering around the average values. The variation that does exist could easily correspond to local horizon variation in this rugged, mountainous region. Lakatos expresses surprise at this finding, but it makes perfect sense to me. The winter solstice is an enormously important event for the modern Pueblos, as Lakatos discusses, and pointing their kivas toward it would be a natural response to that importance. And with that in mind, I wish all my readers a happy solstice.

ResearchBlogging.org
Lakatos, SA (2007). Cultural Continuity and the Development of Integrative Architecture in the Northern Rio Grande Valley of New Mexico, A.D. 600-1200 Kiva, 73 (1), 31-66

Wendorf, F (1954). A Reconstruction of Northern Rio Grande Prehistory American Anthropologist, 56 (2), 200-227 DOI: 10.1525/aa.1954.56.2.02a00050

Wendorf, F, & Reed, EK (1955). An Alternative Reconstruction of Northern Rio Grande Prehistory El Palacio, 62 (5-6), 131-173

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Mercer Museum, Doylestown, Pennsylvania

Mercer Museum, Doylestown, Pennsylvania

I was in Philadelphia for Thanksgiving, and the next day I went with my family to the quaint nearby town of Doylestown, where we visited two local museums: the Michener Museum (named after, yes, that Michener, who grew up in Doylestown and spent most of his life in the area) and the Mercer Museum. The Michener is basically a local art museum, and we went there to see an exhibit about Grace Kelly, who is a big deal in the Philadelphia area. Not really my kind of thing, but it was fine.

The Mercer, on the other hand, is a really unusual sort of museum. It was established by Henry Mercer, a Doylestown native who had a variety of interests and a good deal of money with which to pursue them. He studied law but never practiced it, instead going into archaeology in the 1890s. I haven’t found much information about his specific contributions to American archaeology, which was in its infancy at that time, except that he apparently supported the authenticity of the obviously forged Lenape Stone that allegedly contains an image of a mammoth and is now part of the Mercer Museum collections (though not on display).

In the late 1890s, however, Mercer came to the realization that the advancement of industrialization meant that most aspects of traditional life in the US were likely to disappear forever, and he began to collect what were then considered mundane objects for the museum of the Bucks County Historical Society. He collected huge numbers of things from all aspects of pre-industrial life, over time branching out to the US as a whole and eventually other parts of the world as well. His collection got so big that he built a new building to house it, using an innovative design and construction approach using poured concrete. He organized the collection thematically by the sorts of societal needs that objects served, and put together display cases by category.

The museum is still much as he designed it, although there have been various changes over the years. It’s a fascinating place, idiosyncratic and full of extremely detailed information. What I found especially interesting, however, was the way the museum’s own self-descriptions explicitly tied Mercer’s collecting of what most people considered “junk” to his earlier interest in archaeology. That is, one way to see what Mercer was doing was taking an archaeological approach to studying and preserving the material culture of the present and recent past, to ensure it would be understood in the future. This approach was quite ahead of its time for both history and archaeology, and the museum that resulted is fascinating and well worth a visit.

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Reconstructed House, Spiro Mounds, Oklahoma

Mississippian societies are best known for their mound centers, with Cahokia in Illinois being the largest and most impressive but by no means the only one. These sites have drawn the interest of archaeologists since the very beginning of American archaeology as a field of study, but the focus on mounds meant that other aspects of Mississippian culture got relatively little attention until much later.

One of these aspects was domestic architecture. While Mississippian mounds, unlike those of many earlier societies in the Eastern Woodlands, often served at least in part as platforms for elite residences, the fact that both these and more humble dwellings were made of perishable materials and did not survive in the damp conditions of the region led their subtle remains to be largely ignored until well into the twentieth century. At this time archaeology as a discipline was rapidly professionalizing, and archaeologists began to shift their focus from acquiring impressive specimens for museum display to investigating the remains of ancient societies in an attempt to understand them as totalities, including the more humble parts.

Partially Reconstructed House, Angel Mounds, Evansville, Indiana

When it came to Mississippian residential architecture, what these newer, more careful excavations revealed was that Mississippian houses were relatively flimsy, at least as compared to the impressive stone architecture of the Southwest and Mexico. Indeed, masonry architecture was apparently totally unknown in the East throughout the prehistoric period, even in areas near outcrops of useful stone. The conception thus entered the archaeological literature that the Mississippians, for all their effort at building mounds, didn’t do much to build substantial houses.

This is kind of a misleading way to think about it, however, as John Bennett of the University of Chicago pointed out in a 1944 article. As he put it:

There can be no doubt that a dwelling or ceremonial structure built of such perishable materials as wood, canes, and grass thatch is hardly as durable or lasting as a stone building. From the standpoint of preservation such construction is “flimsy.” This interpretation unfortunately implies, however, that this architecture was flimsy in terms of its own cultural setting. That is, it represented a poor attempt at sheltering and housing the people.

Bennett goes on to argue that this is a mistaken conclusion to draw, basing his remarks on his institution’s recent excavations at the Kincaid site in southern Illinois, which had exceptionally well-preserved remains of burned houses. Basically, he argues that while the individual materials may have been flimsy, they were put together in an ingenious way that gave the result structures plenty of strength and durability for their intended purposes:

Walls were constructed by placing poles or saplings in a trench and bending these over at the top to produce a peaked or domed roof. Horizontal poles were lashed to the sides, to produce a lattice. Reeds were then lashed to the lattice. The next step was to plaster a thick layer of clay on both sides of this lattice, over the reeds, then to cover this clay with a matted layer of grass fibers. The final step was to cover this grass with cane mats—large and thick for the outside, thinner for the inside. The wall thus formed was nearly one foot thick, and obviously very rigid—hardly a “flimsy” structure.

There was actually quite a bit of variation within the Mississippian tradition in house construction; some areas had straight-walled houses with gabled thatch roofs, while others had houses with more of a curved shape. This basic pattern of wall trenches filled with upright poles which were then covered with some sort of wattle-and-daub was widespread, however, and in some areas the appearance of wall trenches is considered a sign of the beginning of the Mississippian period. It’s true that these houses didn’t last very long and had to be replaced frequently (which has been used in some cases to estimate occupation spans and population totals at certain sites), but any type of construction short of stone masonry would have this drawback in the rainy East. Given that these houses would have provided quite useful shelter with relatively little effort, they seem quite well suited to their context.

Kincaid Mounds, Massac County, Illinois

Speaking of stone, though, why didn’t they use it? Some sites in alluvial plains wouldn’t necessarily have had nearby sources of stone, but this isn’t the case for Kincaid and many other sites. As it turns out, Bennett has an answer to this too:

The proximity of Kincaid to stone outcrops in the hills might make us wonder why the Indians never utilized stone for building materials. The answer is twofold: (1) The southeastern cultural tradition did not include such a trait, and (2) the climate and frequent floods in the bottoms required just such a structure as described. The architecture can be considered as a nearly perfect adaptation to the environment.

It’s interesting to see here, given the early date of Bennett’s article, that he hits on both of the major categories of explanation that have dominated archaeology in recent decades: environmental determinism and cultural specificity. Neither is necessarily all that convincing on its own, but between the two of them they probably cover whatever the true answer was. It’s noteworthy that when Europeans began to settle eastern North America they mostly didn’t build with stone either, instead preferring wood until well into the nineteenth century when cities grew to such a size that local wood resources became scarce and fire became a major concern. This even though they, unlike the indigenous tribes, did have a cultural tradition of building in stone which reached quite a high degree of elaboration in the castles and cathedrals of medieval Europe.

Closeup of Kincaid Mounds Mural, Paducah, Kentucky

One way to interpret this information is to posit that building with stone is sufficiently difficult that people are only going to do it when they have few other options, as in arid regions with little wood and when local wood resources have been largely exhausted. In the forests of the Eastern Woodlands this was never really a problem during the prehistoric period (and well into the historic), so people just built with wood and other easily available materials. Even for monumental purposes, such as mound-building, they used dirt rather than bothering with stone. Ironically, this meant that everything they built except the mounds eventually rotted away in the wet climate, so their ingenuity in this regard wasn’t discovered until rather recently.
ResearchBlogging.org
Bennett, J. (1944). A Note on Middle Mississippi Architecture American Antiquity, 9 (3) DOI: 10.2307/275792

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The Great Plaza and Monks Mound, Cahokia

The greatest of the Mississippian mound centers, by far, is Cahokia. This vast site contains numerous mounds and is located in the American Bottom area of southwestern Illinois, across the Mississippi River from the modern city of St. Louis, Missouri. This is a highly strategic location, very close to the confluence of the two largest rivers on the North American continent (the Mississippi and the Missouri), and about twenty years ago Peter Peregrine published a short paper using graph theory to demonstrate that Cahokia was located at the point of highest centrality in the entire Mississippi drainage, potentially giving Cahokia’s inhabitants the ability to control riverine trade across a large portion of the continent. In addition, the American Bottom is an area of very fertile bottomlands along the Mississippi potentially allowing for substantial agricultural surpluses. As early as 1964 Charles Bareis noted that the configuration of the mounds at Cahokia relative to the meander loops where the Mississippi had changed its course over time indicated that the river had been relatively stable over time in this region, changing its channel much less frequently than in areas further downstream. The combination of fertile soil and a relatively stable, predictable river could have combined with the strategic location within the river system to provide the conditions under which Cahokia rose to prominence.

Ecological/geographical explanations like this for the rise of “complex” societies like Cahokia were quite popular among processual archaeologists from the 1960s to the 1980s, but they have since been challenged by a newer generation of archaeologists influenced by the post-processual movement that began in Europe. As Michelle Hegmon noted in an important summary of the theoretical status of North American archaeology a few years ago, Americanists have generally not been inclined to go all the way over to European-style post-processualism, instead adopting elements of both processual and post-processual approaches in varying ways. Hegmon labels the resulting theoretical orientation “processual-plus,” and that seems like an apt description to me.

With regard to Cahokia specifically, the main voices for the “processual-plus” perspective have been Thomas Emerson and Timothy Pauketat of the University of Illinois at Urbana-Champaign. Pauketat, in particular, has argued vigorously for what he calls a “historical-processual” approach to archaeology, incorporating the insights of processual culture ecology as well as a more historical-particularist approach more associated with post-processualism. One of his more important contributions along these lines has been a 2003 paper discussing both Cahokia and an area to the east, in the uplands surrounding the American Bottom, that contains what he calls the “Richland Complex”: a group of rural agricultural sites that appear to date to right around the time of the rise of Cahokia, circa 1050 AD. Cahokia rose very rapidly, and it’s apparent that the population increase in the mid-eleventh century couldn’t possibly have been due solely to natural increase. Migration from surrounding areas seems to have been a major part of the development of the site, and Pauketat argues that the Richland Complex also shows evidence of having been rapidly settled around the same time. This area was apparently very sparsely populated before this, and the settlements established in the eleventh century show sufficient diversity in material culture to suggest that their resident immigrated from different areas. Some show a particularly distinctive pottery style typical of southeastern Missouri and northeastern Arkansas, also found at Cahokia itself, which suggests migration from that region into the American Bottom at the time of the rise of Cahokia. (This may be particularly important in explaining the Mississippian phenomenon in general, for reasons I’ll discuss in a future post.)

Interpretive Sign at Cahokia

A recent article in Science discussing recent research in the Cahokia area has drawn the notice of Mike Smith at Arizona State, one of the foremost authorities on ancient urbanism. He seems pretty comfortable with the idea that Cahokia was a city (an idea strongly pushed by the interpretive material at the site itself), but he does question the assertion that it had a lower population density than the Maya cities, which apparently had notably low population densities within the urban centers themselves but notably high densities in the rural areas outside the cities:

Now I don’t know the demographic data for Cahokia and its hinterland, but I think the population density within the Cahokia urban center was probably HIGHER than within Maya cities, but the population density of the “Greater Cahokia” region was most likely lower than that of the Maya lowlands.

Maya cities had very low URBAN population densities (even compared to a sprawling modern city like Phoenix):

  • Tikal (Maya):    600 persons per square kilometer
  • New York City:  9,400
  • Phoenix:    1,900

But the Maya lowlands had a very high  REGIONAL population densities:

  • Maya lowlands:  180 persons per sq. km
  • New York State:   150
  • Illinois:   80
  • Arizona:  17

The high density of Maya regional populations (how many people lived on the landscape, whether in large or small settlements) is one of the remarkable features of ancient Maya society. I’d be interested to see how Cahokia fits in comparison with these figures.

Population estimates for Cahokia vary, as you might expect, but I figured I could chime in with Pauketat’s estimates from his 2003 paper. It’s important to note here that Pauketat is an advocate for a larger, more urban Cahokia than that seen by some other archaeologists, so his figures are relatively high compared to some other estimates, but he goes into some detail in this paper about where he gets his figures and his procedure seems reasonable to me.

St. Louis from Monks Mound, Cahokia

For the core area of Cahokia, which is about 1.8 square kilometers in area, Pauketat calculates a population range of 10,000 to 16,000 people at the site’s peak during the Lohmann Phase (ca. AD 1050 to 1100), which equates to a population density of about 5500 to 8900 people per square km. As Smith suspected, this is much higher than Classic Maya cities like Tikal. Indeed, it’s much higher than contemporary St. Louis, which has about 2000 people per square km, and at the high end it approaches the density of New York! Calculating the regional density is trickier because of limited survey coverage in some areas, but for the 300-square-km Richland Complex specifically (a relatively dense rural area), Pauketat calculates a population range of 3000 to 7400 people for roughly the same period, which equals a density of 10 to 25 people per square km. Again, as Smith predicts, this is much lower than the Maya regional density and down with the more sparsely populated US states like Arizona. It’s lower than both Illinois (89 people per square km) and Missouri (34 people per square km) today.

There’s way more to say about Cahokia. The literature on this site is vast, not unlike the literature on Chaco. (Observant readers may have noted some striking similarities between the two sites, which I’ll discuss later.) Given that Cahokia is widely acknowledged these days to have been a city, population density is a useful way to look at it and to compare it to other cities. There are other aspects of this fascinating site worthy of discussion, however, and I’ll have much more on it soon.
ResearchBlogging.org
Bareis, C. (1964). Meander Loops and the Cahokia Site American Antiquity, 30 (1) DOI: 10.2307/277637

Hegmon, M. (2003). Setting Theoretical Egos Aside: Issues and Theory in North American Archaeology American Antiquity, 68 (2) DOI: 10.2307/3557078

Lawler, A. (2011). America’s Lost City Science, 334 (6063), 1618-1623 DOI: 10.1126/science.334.6063.1618

Pauketat, T. (2003). Resettled Farmers and the Making of a Mississippian Polity American Antiquity, 68 (1) DOI: 10.2307/3557032

Peregrine, P. (1991). A Graph-Theoretic Approach to the Evolution of Cahokia American Antiquity, 56 (1) DOI: 10.2307/280973

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United Country Mimbres Realty, Silver City, New Mexico

Inspired by my recent visit to the Gila Cliff Dwellings, I’ve been reading about the Mimbres Mogollon culture of southwestern New Mexico.  As I noted earlier, the cliff dwellings themselves aren’t actually Mimbres, instead belonging to the Tularosa Mogollon culture more common to the north, and they postdate the “Classic” Mimbres period (ca. AD 1000 to 1150, exactly contemporary with the florescence of Chaco further north) by over a century.  They do, however, fall well within the area occupied by the Classic Mimbres, and there is in fact a Mimbres village, the TJ Ruin, within the monument boundaries.  The upper Gila River valley was a major area of Mimbres settlement during the Classic period, and it had some of the largest Classic villages, although it is not nearly as well understood as the Rio Mimbres valley which is often considered the Mimbres “heartland” and which gave the culture its name.  A review article by Michelle Hegmon from 2002 provides a good and relatively recent overview of the major issues in Mimbres archaeology.

The Mimbres are best known for their pottery, some of which features elaborately painted naturalistic designs unlike anything else known from the prehistoric Southwest.  This pottery was painted with black paint on a white slip, as was Anasazi pottery from Chaco and other areas at the time, and many of the abstract geometrical designs that form the bulk of the decorated pottery are reminiscent of Anasazi styles.  There’s no equivalent among the Anasazi to the naturalistic designs, however, which show elaborately detailed people, animals, possible mythical scenes, and much else.  No two designs are exactly alike.  Most of the figurative designs were on bowls which were placed with burials, usually with a “kill-hole” through the center of the vessel, which was then placed over the face of the buried individual.  Iconographic study of Mimbres pottery dates back nearly a century, starting with the work of Jesse Walter Fewkes of the Smithsonian in the 1910s, but in the past 20 years it has been supplemented by studies taking a more technological approach.  Particularly important has been a series of studies using instrumental neutron activation analysis (INAA) to determine the sources of the clay used in the pots and untangle patterns of production and exchange.  The results of these studies have generally been consistent with widely distributed production of pottery throughout the region, which is in contrast to other documented cases of community-level specialization in pottery production known from other parts of the Southwest at various times.  Design analysis has led some to suggest that the finest of the black-on-white bowls were made by a very small number of potters, however, which implies that perhaps a few specialists in villages scattered across the region made almost all of the well-known naturalistic vessels.

Tune Town Music Exchange, Silver City, New Mexico

Speaking of villages, one of the most interesting things about the Mimbres is that theirs were quite different from communities found throughout the rest of the Southwest during the Classic period.  While most areas, including the Chaco region, had communities of loosely clustered small house sites, the Mimbres were aggregated into large, dense villages made up of roomblocks very similar to those that would become increasingly common in Pueblo sites to the north starting in the thirteenth century and continuing into the historic period.  Indeed, some have argued that the Classic Mimbres invented the “Pueblo” as a type of community, and even that many of the social institutions of the modern Pueblos, such as the kachina cult, derive ultimately from Mimbres precursors.  There is definitely a clear continuum in artistic style from Mimbres pottery through Jornada Style rock art to the Rio Grande style of rock art and mural painting that appears among the northern Pueblos beginning around AD 1300.

After the decline of Chaco around AD 1130, the northern Southwest witnessed a pattern of ever-increasing aggregation eventually resulting in the modern Pueblos with their very Mimbres-like plans and institutions.  There have been various explanations offered for why this occurred, and I think those that attribute it largely to increased warfare are among the most persuasive.  There is definitely much more direct evidence for violence after about AD 1150 than before then.  Whatever was causing trouble in Pueblo societies at this time, it seems very likely that solutions drawn from the Mimbres experience became increasingly attractive further north.

But what was that experience?  Why did the Mimbres aggregate into large Pueblos at a time when everyone else lived in scattered small houses?  The Classic Mimbres period coincides with a time of remarkable peace throughout most of the Southwest, so defense seems less likely as an explanation here than it does later on.  Some of the Mimbres pots do show scenes of violence, including a well-known beheading, but it’s not at all clear that these show actual events rather than myths.  In general, there doesn’t seem to be any more evidence for warfare among the Classic Mimbres than anywhere else at the same time, which makes their much denser settlement pattern particularly mysterious.  It may have had something to do with irrigation agriculture, which the Mimbres had probably adopted somewhat earlier under the influence of the Hohokam in southern Arizona, who were by far the most accomplished irrigators of the prehistoric Southwest.  Among the Mimbres, as among other Mogollon groups, there was extensive Hohokam influence early on, which seems to have largely ceased by AD 1000, possibly replaced by increased influence from the Anasazi to the north (although this is controversial).  Steve Lekson, who has done a lot of work in the Mimbres area in addition to his work at Chaco, has argued that the Classic Mimbres consists of “an Anasazi lifestyle supported by Hohokam infrastructure,” and I think there may be something to that.  The labor demands of irrigation may have led to residential aggregation, although it’s important to note that the Hohokam themselves never aggregated to anything like the same degree despite their much more elaborate irrigation systems.

Welcome Sign, Truth or Consequences, New Mexico

What’s even more puzzling about the Mimbres, however, is what they did after the end of the Classic period.  The large villages and figurative pottery seem to come to a rather sudden end around 1150, about the same time that Chaco declined and the northern Southwest entered a long, difficult period of warfare, aggregation, and regional abandonment.  It used to be thought that the Mimbres just “collapsed” at this time, with their ultimate fate unknown, but more recent research, especially in the eastern Mimbres area along the Rio Grande near the modern town of Truth or Consequences, has shown that the real story is more complicated.  Margaret Nelson has been researching settlement patterns in the eastern Mimbres area, and she has found that one notable shift after the end of the Classic period involved the dissolution of the aggregated Classic villages and the dispersal of people into small hamlets, often built on the sites of Classic fieldhouses.  She also sees continued production of Mimbres pottery, although apparently without the distinctive naturalistic designs, for a long time after the end of the Classic.  Hegmon, who has collaborated with Nelson on much of this work, has proposed calling these occupations “Postclassic Mimbres.”  They show much more extensive trade of pottery with surrounding areas than during the Classic period, as well as more variable architecture, implying that whatever social controls had held the large Classic villages together had broken down and been replaced by a more flexible social system.

What’s remarkable about this is that it’s basically the opposite of what was happening everywhere else in the Southwest, where the dominant trend during this period was aggregation.  The Mimbres, at least in the east, were instead dispersing.  The picture is less clear in the Mimbres and Gila valleys further west, but at least some of the Classic villages seem to have continued to be occupied at lower population levels (similar to what was going on at Chaco), while a new type of occupation seen at some sites in the area, known as the Black Mountain Phase, may or may not represent a change in Mimbres culture.  There is debate over whether the Black Mountain Phase actually shows continuity with Classic Mimbres or not.  It’s also possible that some people headed south, to the rising center at Casas Grandes, in which case they would be participating in the trend toward aggregation.

It’s becoming increasingly clear, then, that the Mimbres didn’t really collapse or totally abandon their region in 1150.  Instead, they seem to have sort of splintered, with some scattering to hamlets on the sites of former field houses, others possibly reorganizing their communities into Black Mountain Phase sites, and still others migrating away from their region either south to Casas Grandes or east to the Jornada area, where the very Mimbres-like Jornada petroglyph style seems to appear around this time.  This process of dispersal when everyone else was aggregating, combined with their earlier aggregation when everyone else was sprawling across the landscape, gives a distinct “out of phase” feel to Mimbres cultural dynamics.

I certainly don’t have any solutions to propose to the mysteries of the Mimbres, and as far as I can tell no one else really does either.  They’re among the most fascinating of the many peoples who inhabited the prehistoric Southwest, and while they are by no means the most obscure, outside of specialist circles they are known almost exclusively for their pottery.  The pottery is amazing, of course, and quite deserving of attention, but there’s much more to the Mimbres than their pots.
ResearchBlogging.org
Fewkes, J. (1916). Animal Figures on Prehistoric Pottery from Mimbres Valley, New Mexico American Anthropologist, 18 (4), 535-545 DOI: 10.1525/aa.1916.18.4.02a00080

Gilman, P., Canouts, V., & Bishop, R. (1994). The Production and Distribution of Classic Mimbres Black-on-White Pottery American Antiquity, 59 (4) DOI: 10.2307/282343

Hegmon, M. (2002). Recent Issues in the Archaeology of the Mimbres Region of the North American Southwest Journal of Archaeological Research, 10 (4), 307-357 DOI: 10.1023/A:1020525926010

Hegmon, M., Nelson, M., & Ruth, S. (1998). Abandonment and Reorganization in the Mimbres Region of the American Southwest American Anthropologist, 100 (1), 148-162 DOI: 10.1525/aa.1998.100.1.148

Nelson, M., & Hegmon, M. (2001). Abandonment Is Not as It Seems: An Approach to the Relationship between Site and Regional Abandonment American Antiquity, 66 (2) DOI: 10.2307/2694606

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