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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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The Twin Mounds from Monks Mound, Cahokia

One of the major areas of interest for the “New Archaeologists” who came to dominate American archaeology in the late twentieth century was mortuary analysis. In keeping with the arguments of Lewis Binford and other leaders of the movement that archaeology as a discipline should be “problem-oriented” and focused on reconstruction prehistoric societies as fully as possible using archaeological evidence, the patterning evident in the way those societies disposed of their dead was held to reveal important information about social structure and the positions held by the deceased in life. Many important studied of mortuary behavior in various cultures were published in this period, including a 1984 article by George Milner on the burial patterns of Mississippian sites in the American Bottom of southwestern Illinois.

Milner’s article is a classic example of the New Archaeology as applied to mortuary patterns, hampered only slightly by the immense complexity of Mississippian mortuary behavior and the scanty evidence from the many burials excavated in the nineteenth century and poorly documented. Noting that most Mississippian burials in this area were placed in dedicated cemetery areas, he divides these cemeteries into three broad categories, reflecting two dimensions of variation in social structure. The categories are elite burials at major centers such as Cahokia, non-elite burials at those same centers, and non-elite burials at peripheral sites (which do not appear to contain elite burials).

By far the most and best information available to Milner was from the third category, and this is the one he focuses the most attention on. There is quite a bit of diversity even within this category of cemetery, but some general patterns do emerge. Cemetery sites are typically either on prominent bluffs above the Mississippi River floodplain or on low ridges within the floodplain, with a trend apparent over time of a shift from the former to the latter. The bluff-top cemeteries tend to be quite large, and they probably represent the dead of multiple rural communities in the general area. This inference is backed up by the diversity of mortuary treatments even within these cemeteries. Some burials are intact, articulated skeletons, often laid out in one or more rows, sometimes with the heads pointing toward a nearby mound center. Others are disarticulated jumbles or bones, often containing the remains of multiple individuals. There is considerable evidence of complicated mortuary treatment involving exposure of the bodies for some period after death, perhaps in the “charnel structures” that accompany some of the cemeteries, followed by secondary burial. Grave goods are rare and usually relatively mundane items such as pottery, although shell beads and certain exotic minerals are found in some cases.

Ironically, burials at the major mound sites are generally poorly documented compared to those in the rural hinterland. This is in part because the former were often excavated haphazardly in the nineteenth and early twentieth centuries, with little or no detailed documentation, while the latter have been largely excavated by systematic cultural resource management salvage projects more recently and extensively documented. Nevertheless, Milner combed through the available data on the mound center burials in the American Bottom, and he comes to a few tentative conclusions about them.

For one thing, there is definitely a big difference between the elite and non-elite burials. The non-elite burials are similar to the ones at outlying sites in many ways, including linear arrangements of graves and modest assemblages of grave goods, but there is also more substantial variation in mortuary treatment, which Milner plausibly attributes to greater diversity within the more populous mound communities, perhaps including more subtle gradations of status than are accounted for by his crude “elite”/”non-elite” dichotomy.

Sign Describing the Twin Mounds at Cahokia

The elite burials, however, are quite different. They are generally in mounds, specifically in conical mounds as opposed to the flat-topped ones that served as platforms for buildings. A common pattern seen at Cahokia and other sites, is for mounds to be paired, with a conical mound accompanying a platform mound. The Fox and Roundtop mounds (the so-called “Twin Mounds”), south of Monks Mound on the opposite side of the Grand Plaza, are the best-known of these paired mounds, but since they are largely unexcavated relatively little is known of their contents. Much of the Cahokia data Milner uses comes instead from Mound 72, which was excavated relatively recently and extensively documented. The very complicated mortuary deposits in this mound include two burials associated with numerous shell beads, as well as various other groups of both articulated and disarticulated remains. One group of articulated skeletons was missing skulls and hands, apparently indicating some sort of human sacrifice.

One of the most striking ways the elite burials differ from the non-elite ones is in the sorts of grave goods. Mundane items such as pottery are generally rare, while very elaborate, labor-intensive artifacts are numerous. The shell beads from Mound 72, also common in several of the other mounds Milner discusses, are one example. Mound 72 also contained various other items, including a cache of finely made chert projectile points, and other exotic materials including copper items were found in other mound burials.

Another interesting characteristic of the elite burials Milner describes is that they are quite communal in nature. Individual burials are not present, and even the most elaborate assemblages of grave goods seem to be associated with large groups of burials within the mounds. This may have important implications for the nature of political power in Mississippian society, although Milner doesn’t go into the implications in any detail in this paper.

Some of Milner’s conclusions in this paper have been superseded in part by newer discoveries and refinements to the chronology of the American Bottom since the time he wrote, but this is still an important paper, not least because of the way it draws on what information is available on the early excavations. The tentative nature of Milner’s conclusions is due in part to those data limitations, but also to the fact that what becomes glaringly obvious from this work is that Mississippian burial practices were extremely complicated and shaped by a wide variety of possible factors, not all of them easily discernible from this type of study.
ResearchBlogging.org
Milner, G. (1984). Social and Temporal Implications of Variation among American Bottom Mississippian Cemeteries American Antiquity, 49 (3) DOI: 10.2307/280355

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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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View of Monks Mound from the East, Cahokia

Monks Mound is both the largest mound at Cahokia and the largest at any Mississippian site, by a huge margin. It’s 100 feet high and about 1,000 by 800 feet at the base, covering more than 18 acres. Its mass is five times that of the second-largest Mississippian mound (Mound A at the Etowah site in Georgia). The thing is just gigantic, and it has long been of intense interest to archaeologists. Back in the nineteenth century there was considerable debate over whether it was an artificial mound at all rather than some sort of unusual natural formation, and even into the early twentieth century there was some discussion of whether it might have been a natural rise of some sort that was built up artificially. Those debates had largely been settled by the 1960s, with increasing evidence that it was in fact an artificial construction like the smaller mounds surrounding and forming the core of the Cahokia site around the Grand Plaza. There still remained a dearth of detailed information on the composition of the mound, however, and after some excavation of various small parts of the mound in the early 1960s the archaeologists working at Cahokia came up with the idea of doing some core drilling to get a more general sense of its composition. They reported their results in a paper published in 1968.

After reviewing the techniques available to them, the researchers decided to go with the heaviest equipment they could find, a truck-mounted rig used to take soil samples for highway and building construction. This rig worked by ramming a three-inch diameter tube down at two-foot increments, after each of which the core sample would be extracted and a new tube attached to take the next two-foot sample. This worked pretty well, although some of the tubes broke loose, broke, or were otherwise lost in the course of drilling. The clay soils of the American Bottom are notoriously tough on equipment, so it’s probably a good thing they chose the most heavy-duty rig they could. They found that the core samples were somewhat compacted from the pressure of the drilling, but this didn’t end up being a major problem for interpreting them.

View of Monks Mound from the South, Cahokia

To check on the accuracy of interpretations derived from the core sampling, a small area adjacent to one of the sampling holes was excavated to get a better look at the stratigraphy. This digging generally confirmed the interpretation of the cores, especially the interpretation of thin bands of limonite, which often forms on exposed surfaces in this area, as indicating discrete construction stages of the mound. The coring and excavation also resulted in the submission of a few pieces of wood for radiocarbon dating to give a sense for the absolute chronology of mound construction. Since this was early in the history of radiocarbon dating, the standard deviations on the resulting dates are so large as to make the results of limited usefulness in delimiting substages within the Mississippian period, but they do show the general period when the mound was most likely under construction to be between AD 800 and 1300, which matches the dating of the Emergent Mississippian and Mississippian periods at Cahokia.

Probably the most important result of this research was the discovery that two of the major construction stages, including the earliest, consisted of massive deposits of black clay which likely came from topsoil deposits in various areas around the mound. The later paper I discussed earlier suggested that some of this clay may have come from the upper layers of the area to the south that would later be filled in to become the Grand Plaza, while the authors of the original paper suggested that some of it may have come from the area to the north along Cahokia Creek. It probably took a hell of a lot of clay to build these layers, so both could easily be right.

Closeup of Monks Mound Sign, Cahokia

Another interesting proposal from the authors of the coring paper is that the other mounds at Cahokia may have postdated Monks Mound. This is based on the fact that the handful of radiocarbon dates from excavations beneath other mounds that had been obtained as of that time were uniformly later (though not necessarily very much so) than the dates obtained from the coring and excavation at Monks Mound. This idea is supported by the fact that some of the other mounds are clearly aligned with Monks Mound. There has been a lot of excavation and reanalysis of older materials since the 1960s, of course, so I’m not sure if this pattern still holds up.

Monks Mound is both so huge and so important that this sort of broad-scale coring, like the conductivity survey done later in the Grand Plaza, is a reasonable way to quickly get a general sense of patterns that would take much longer to uncover via excavation, which might not even be possible to do on account of preservation concerns. This is therefore a pretty important paper. Even though it doesn’t reveal a whole lot of detail about the construction stages of Monks Mound, it’s unlikely that we’ll get much more detail than this without a seriously huge effort.
ResearchBlogging.org
Reed, N., Bennett, J., & Porter, J. (1968). Solid Core Drilling of Monks Mound: Technique and Findings American Antiquity, 33 (2) DOI: 10.2307/278515

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