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Archive for the ‘Chaco Canyon’ Category

Old Bonito from Above

Old Bonito from Above, Including Northern Burial Rooms

So far in this series of posts on “tracing the connections” between ancient Pueblo sites like Chaco Canyon and modern Pueblos, I’ve discussed evidence from linguistics and folklore, but of course if the issue is determining which modern groups are physically descended from which ancient ones it’s hard to beat evidence from actual physical remains. Physical anthropology has been somewhat less emphasized in the history of Southwestern anthropology, especially compared to archaeology and ethnography, but there has been a fair amount of this kind of research over the years and it is clearly at least potentially useful in answering these questions.

These days when people talk about physical evidence of genetic connections they often mean DNA, and there have been several interesting recent studies of the DNA of both ancient and modern Southwestern populations that are relevant to my present concern. That topic deserves its own post, however (which I am working on), so for now I’m going to focus on a more “traditional” type of physical anthropological study: the statistical comparison of skull features and measurements.

This sort of study generally takes the form of measuring various attributes of skulls from different archaeological excavations and comparing them statistically to see which ones pattern together. (There are also studies of non-metric features that work somewhat differently, but here I’m going to focus on studies of metric features.) I’m always a bit dubious about the relevance of these studies, since I’m not sure how clear it is that the traits they’re measuring really do correlate with genetic relatedness, but this is a well-established and longstanding field of inquiry so for now I’ll take it as given that the underlying theoretical assumptions are well-founded.

Old Bonito from West Plaza Showing Plaza Kivas in Foreground

Old Bonito from West Plaza Showing Plaza Kivas in Foreground

Turning to Chaco specifically, the most influential studies along these lines are those done by Nancy Akins as part of the Chaco Project in the 1970s and 1980s. It was her work that famously concluded that the two main burial populations in Pueblo Bonito, in the northern and western parts of the site, were most similar not to each other but to two different small house sites elsewhere in the canyon. This was an important finding, in that it implied that the population inhabiting the canyon in its heyday was physically diverse in ways that didn’t necessarily pattern with geographical settlement patterns. This in turn implies that there may have substantial diversity in ethnic and linguistic backgrounds among different Chaco residents as well, an implication that some other lines of evidence also support.

Akins only compared populations from within Chaco Canyon, however. To evaluate the connections between Chaco and later Pueblo sites, comparable measurements needed to be made of remains from later Pueblo sites and compared to Akins’s Chaco data. The most extensive study along these lines that I know of is in a short article by Michael Schillaci and Christopher Stojanowski published in 2002. Interestingly, this article was actually a comment on an earlier article by Peter Peregrine arguing that Chacoan society was matrilocal based in part on the fact that some modern Pueblo groups, such as the Hopis and Zunis, are matrilocal. (Matrilocality is the practice of newly married couples living with the wife’s parents, and it is apparently very uncommon cross-culturally compared to patrilocality, where couples live with the husband’s parents.)

Schillaci and Stojanowski argue that while it’s certainly possible that the matrilocal western Pueblos of Hopi and Zuni are descended in part from the Chacoans, it’s not at all obvious that they have a better claim to such descent than the eastern Pueblos of the Rio Grande Valley, which are generally either patrilocal or bilocal (couples live with either set of parents). To test this idea, they take Akins’s data from Chaco and compare it to measurements made according to the same protocol on several other contemporaneous and later Pueblo populations. These include Village of the Great Kivas, a Chacoan outlier in the Zuni area, as well as Hawikku, a much later ancestral Zuni site. They also include several samples from the Rio Grande area, both contemporary with Chaco and later.

As expected from Akins’s results, Schillaci and Stojanowski found that the different samples from Chaco don’t particularly pattern with each other. Interestingly, in their analysis the northern burials at Pueblo Bonito stand somewhat apart from all the other samples. This could potentially be evidence that these, the richest burials ever found in the Pueblo Southwest, represent a group that was genetically distinct from most other Southwestern populations, but it’s important to keep in mind that the number of samples being compared here is relatively small and there’s no way to know how representative it is, so sampling error is always a strong possibility when patterns like this show up. (Other studies have found that these remains are well within the range of variation typical of Southwestern populations, so the fact that they stand apart from the other groups in this study probably doesn’t imply that they were immigrants from outside the region or anything.)

Western Burial Rooms in Old Bonito

Western Burial Rooms in Old Bonito

Of the other Chaco samples, the western burials at Pueblo Bonito cluster most closely with those from both Hawikku and the ancestral Tewa site of Puye in the Rio Grande Valley. The burials from the small sites in the Fajada Butte area at Chaco pattern most closely with the ancestral Tewa site of Tsankawi, and in fact these two form a somewhat distinct group compared to most of the other samples. Finally, the burials from the small sites of Bc 51 and Bc 53, on the south side of the canyon across from Pueblo Bonito, pattern closely with those from Picuris, a Northern Tiwa Pueblo which is still occupied, as well as with those from the ancestral Tewa sites of Sapawe and Pindi.

Schillaci and Stojanowski conclude from this that there is no good reason to conclude that Chacoan society was matrilocal based on the practices of the likely descendants of the Chacoans, among whom they have identified both eastern and western Pueblos practicing various forms of postmarital residence. They do acknowledge that they weren’t able to include any Hopi samples in the analysis, so the western Pueblos are represented only by the two Zuni-area sites, which leaves open the possibility that the Hopis are closely connected to Chaco, which would strengthen Peregrine’s position and weaken theirs. On the other hand, other lines of evidence suggested somewhat weaker ties to Chaco among the Hopis than among most other modern Pueblos, so this probably isn’t a major problem. In his response, Peregrine notes the possibility that bilocality among the eastern Pueblos is a post-contact development related to declining population and therefore not necessarily relevant to the prehistoric evidence. He doesn’t challenge the overall validity of the analysis, however, which is our main concern here.

This is an interesting study, and it identifies some later sites with at least a high probability of including people descended from the Chacoans, but the facts that these sites don’t particularly pattern with each other and that there was considerable diversity within Chaco itself point to how complicated the picture seems to be. Overall, this evidence seems to support the idea that most of the modern Pueblos include at least some people who are descended from the Chacoans, and it provides particular support for such ties among the Zuni, Tewa, and Northern Tiwa. It also supports the previously existing evidence for considerable population diversity at Chaco itself. As we’ll see in the next post, this is not very different from where the DNA evidence leads.
ResearchBlogging.org
Schillaci, M., & Stojanowski, C. (2002). A Reassessment of Matrilocality in Chacoan Culture American Antiquity, 67 (2) DOI: 10.2307/2694571

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Southeast Corner of Pueblo Bonito

Southeast Corner of Pueblo Bonito

Today is the summer solstice, on which I typically make posts about archaeoastronomy, so I’m going to take a break from my very gradual series of posts on tracing the connections between ancient and modern Pueblos to speculate a bit about the role of astronomy at Chaco. Briefly, what I’m proposing is that the rise of Chaco as a regional center could have been due to it being the first place in the Southwest to develop detailed, precise knowledge of the movements of heavenly bodies (especially the sun and moon), which allowed Chacoan religious leaders to develop an elaborate ceremonial calendar with rituals that proved attractive enough to other groups in the region to give the canyon immense religious prestige. This would have drawn many people from the surrounding area to Chaco, either on short-term pilgrimages or permanently, which in turn would have given Chacoan political elites (who may or may not have been the same people as the religious leaders) the economic base to project political and/or military power throughout a large area, and cultural influence even further.

I don’t have any specific research papers to discuss on this topic because as far as I know no one has really looked at it quite this way. It’s similar in some respects to the theories of the Solstice Project, although I don’t buy that astronomical alignments were quite as important in the Chacoan system as they propose. There is also some overlap with the theories of various archaeologists, but none of them have put the pieces together in quite this way. This may be because it’s demonstrably wrong, but if it is I haven’t seen the evidence that disproves it yet (but would be very interesting in doing so).

This theory first occurred to me when I was reading about Tiwanaku in Bolivia, which was a prehistoric society that, like Chaco, left very impressive physical remains in a very isolated location with few obvious economic advantages. As I noted in my post on Tiwanaku, the similarities actually go well beyond that, extending also to the shifting interpretations by archaeologists and the evidence for astronomical alignments. Most relevant in this context is the theory of John Janusek at Vanderbilt, whose theory of Tiwanaku is the model for the theory I’m suggesting here for Chaco. As he wrote in one paper, which I also quoted in the earlier post:

Tiwanaku’s long rise to power in the Andean altiplano was predicated on the integration of diverse local ritual cults and various symbolic dimensions of the natural environment into a reasonably coherent, supremely elegant and powerfully predictive religion. The shifting physicality of Tiwanaku’s religious monuments attests the construction and ongoing transformation of an urban landscape that not only visually expressed the altiplano’s ‘natural’ forces and cycles, but, via recurring construction and ritual, simultaneously shaped new social practices and Tiwanaku’s ever-increasing political influence and productive coordination, intensification and expansion. Tiwanaku was an imperfect and potentially volatile integration of religious cults, productive enterprises and societies. The material objectification of a seductive religious ideology that infused the monumental centre with numinous natural forces and simultaneously projected those forces across distant Andean realms helped drive Tiwanaku’s very worldly imperial mission.

Tiwanaku was apparently the first society in the altiplano to develop the level of astronomical skill which allowed it to develop such a “powerfully predictive” religion, and my application of a similar theory to Chaco relies on it also being the first place that developed a comparable knowledge of astronomy in the Southwest. I hadn’t really thought about this before reading Janusek’s work, but as far as I can tell it does in fact seem to be the case. Ray Williamson’s somewhat dated but still very useful book on Native North American astronomy (which I reviewed here) doesn’t mention any evidence of Southwestern astronomical knowledge predating Chaco, and I haven’t seen any other publications that do either. Granted, some of the evidence for astronomical evidence comes from rock art which is difficult or impossible to date, but at least when it comes to building alignments, which are more securely datable, the Chacoan great houses seem to be the earliest manifestation of detailed astronomical knowledge. Some earlier sites do show general alignments to cardinal directions and so forth, but the precise alignments to solstices and lunar standstills that are characteristic of Chacoan buildings do really seem to be innovative. I’m not totally certain that there aren’t counterexamples out there, though, so if anyone knows of any I’m very interested in hearing about them.

If this is in fact the case, it opens up several additional lines of inquiry. First, if Chaco was in fact the first place in the (northern?) Southwest to attain detailed astronomical knowledge, where did that knowledge come from? Many discussions of Chacoan astronomy have assumed, implicitly or explicitly, that the answer is “Mexico,” but I’m not so sure. There is definitely extensive evidence of contact with Mesoamerica at Chaco, but it’s all fairly indirect and there are lots of important aspects of Mesoamerican culture that are noticeably lacking. Mesoamerican astronomical knowledge was certainly impressive, and certainly predates the rise of Chaco, but given the general context I think it’s still an open question whether the Chacoans got their knowledge from contacts to the south (either directly or via the Hohokam and/or Mogollon) or developed it independently. This is an area that would definitely benefit from further study.

Secondly, why Chaco rather than somewhere else in the region? This is sort of the key question hanging over everything about Chaco, and so far no one has come up with a broadly convincing answer. I don’t have one either; the astronomy theory I’m proposing here answers the “how” of Chaco but not the “why.” It could be that, as some archaeologists have proposed, the physical setting of the canyon had unique attributes within the region that contributed to its ritual importance from an early period, which from my perspective would have provided the impetus for the development and/or integration of new astronomical knowledge into existing belief systems. Alternatively, as other archaeologists have argued, there could have been economic advantages to the location, which are not obvious to modern eyes but were sufficient to give Chaco an important role in the region, which may have made it a promising place for new ideas to develop or be introduced. And finally, maybe it’s all just a matter of historical contingency: this was where people happened to figure this stuff out, and that’s what made it attractive to others for both religious and economic reasons.

Another question is when this would have happened. Chaco was occupied for hundreds of years, but its florescence as a regional center was relatively brief, lasting roughly a century from AD 1030 to 1130 or so. One natural conclusion would be that the development of new astronomical knowledge happened at the start of this period, but I suspect it actually began earlier, probably during the period (roughly the late ninth and tenth centuries, or the late Pueblo I period) when Chaco was just one of several “proto-great-house” communities in the San Juan Basin that were more or less equal in size and influence. Over time, the advantages of the Chacoan rituals over the others would have become apparent, perhaps through fortuitous stretches of good weather and/or military successes by Chacoan warriors. This would have set the stage for Chacoan influence to expand on a vast scale during the eleventh century.

As the reference to military success in the previous paragraph suggests, I don’t see the expansion of Chacoan religious influence fueled by astronomical knowledge as having necessarily been entirely peaceful. Here again, the parallel to Tiwanaku is instructive. Note Janusek’s reference to Tiwanaku’s “very worldly imperial mission” in the quote above. I suspect what we would today see as “religious” and “secular” impulses were much more intertwined at Chaco, as indeed they have been shown to be in many societies.

All that said, I’m not totally convinced by this theory myself, and there are many strands of the Chacoan record that it doesn’t really seem to account for in an obvious way. I figured this was a good opportunity to toss it out there, though, to see whether it’s worth pursuing further.
ResearchBlogging.org
Janusek, J. (2006). The changing ‘nature’ of Tiwanaku religion and the rise of an Andean state World Archaeology, 38 (3), 469-492 DOI: 10.1080/00438240600813541

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Kivas in East Plaza, Pueblo Bonito

Kivas in East Plaza, Pueblo Bonito

It’s quite clear that, in a general sense, the modern Pueblo people of New Mexico and Arizona are the cultural descendants of the ancestral Pueblo (Anasazi) groups of Chaco Canyon and other parts of the northern Southwest no longer occupied by people of Puebloan culture. Indeed, as the previous post explains, the descendants of the Chacoans are much easier to identify than those of pretty much any other prehistoric society in the Southwest. Nevertheless, the modern Pueblos are quite diverse in many ways. While they all have similar material culture, which is what most clearly shows their relationship to prehistoric sites like Chaco, the Pueblos speak six different languages belonging to four completely unrelated language families, and the linguistic divisions correspond generally (but not perfectly) to differences in other aspects of culture, such as kinship systems, sociopolitical structures, and religious practices.

With so much diversity, it’s reasonable to hypothesize that some modern Pueblo groups have closer connections to particular ancient sites than others. Demonstrating any specific connections has been frustratingly difficult for scholars so far, however. The immense upheavals of the Spanish colonial period led to significant changes in many Pueblos that make it difficult to trace their histories back into the prehistoric period, and archaeology has demonstrated considerable evidence for prehistoric upheavals that similarly obscure continuities of culture and population. Adding to the difficulty are the facts that the Pueblos have long had very similar material culture to each other, which makes it difficult to tell different ethnolinguistic groups apart archaeologically, and that the extensive migrations of the late prehistoric period seem to have involved rapid change in material culture as well, obscure whatever small differences had existed among different Pueblo groups.

On account of these difficulties, for a long time Southwestern archaeologists and anthropologists were often reluctant to try to reconstruct culture history in enough detail to connect specific ancient sites with specific modern Pueblos. In recent years this reluctance has decreased, however, and there is now a fair amount of interest in these questions, spurred in part by the requirements under NAGPRA for demonstrating cultural affiliation of modern groups in ancient sites. It’s interesting to compare this trend to the last period of considerable interest in this topic, which was similarly spurred by the effort in the 1950s to settle Indian land claims. In any case, archaeologists today have proposed various models of Southwestern prehistory to account for the distribution of modern Pueblo peoples.

With this context, and inspired in part by some interesting questions asked by commenter J. R. Barnett, I’ve decided to do a series of posts addressing this issue and the types of evidence available to address it. I’ll be focusing heavily on linguistic evidence, which is of particular interest to me personally as well as being of considerable importance in defining cultural differences among the Pueblos. I will, however, also discuss the evidence from archaeology, physical anthropology (including DNA studies), sociocultural anthropology, and oral traditions. In doing some reading on these topics recently, it’s been apparent that there really is quite a lot of relevant evidence out there. While we will surely never be able to recover every detail of the story, it’s worth taking a serious look at the available evidence to see what we can find out.

Apparent Kiva at Abo Pueblo, Salinas Pueblo Missions National Monument

Apparent Kiva at Abo Pueblo, Salinas Pueblo Missions National Monument

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"Supernova" Pictograph

“Supernova” Pictograph

I recently finished reading Living the Sky: The Cosmos of the American Indian by Ray Williamson. This is a classic work on the archaeoastronomy of North America, and it’s the best introduction to the subject I’ve found. (Granted, there aren’t many out there.) Although it was written in the 1980s, the research it discusses is still quite relevant, and Williamson does a good job of giving a pretty comprehensive overview of research in most parts of the US. The 1970s and 1980s were kind of the heyday of archaeoastronomy in the US, and while there has been continuing research since then, it’s striking how few major discoveries have been made since Williamson’s book was published. Virtually all of the major discoveries I knew about before reading the book are included, plus many others I didn’t know about.

Williamson did quite a bit of research himself on astronomical phenomena at Chaco, which gets lots of coverage in the book. There is some discussion of the Sun Dagger on Fajada Butte, as well as of alignments at Pueblo Bonito and Casa Rinconada and the alleged “supernova petroglyph” near Peñasco Blanco. Williamson gives the latter a lot more credence than others, and actually has a whole chapter on alleged representations of the 1054 supernova in rock art, including several other sites I had not heard about. I’m pretty skeptical about the supernova stuff, but it’s interesting to hear about these other sites.

Reconstructed "Woodhenge" at Cahokia

Reconstructed “Woodhenge” at Cahokia

While the Chaco stuff is interesting, I already knew most of it and Williamson’s account doesn’t add a whole lot to anyone who is reasonably well-versed in it. Where this book really stands out for me is in its discussion of archaeoastronomy in other areas that get less attention, especially the Plains and California, which have a lot of archaeoastronomical phenomena despite their lack of impressive well-preserved architectural sites like those in the Southwest. The chapter on the East is also interesting, with discussion of the famous “Woodhenge” at Cahokia and the “SunWatch” site in Dayton, Ohio as well as other lesser-known sites. Even within the Southwest, Williamson devotes space to research at more obscure places like Hovenweep (which turns out to have a lot of interesting potential alignments) as well as major centers like Chaco.

Williamson also does a good job of connecting the archaeological data to ethnographic reports about astronomical practices among modern groups. There has historically been a tendency for archaeoastronomers, many of whom are astronomers or surveyors by training, to focus on identifying alignments without giving much consideration to the cultural context in which they may have existed. Williamson avoids this pitfall by giving extensive attention to ethnographic practices and their potential connections to the evidence from ancestral sites. He does a particularly good job with respect to the Pueblos, for which both the ethnographic and archaeological data are extensive, but he also includes extensive discussion of the Navajo, Pawnee, and Chumash, and some attention to various other groups. His interpretations of the ethnography at times show a tendency toward oversimplification, and some of his general comments about Native American societies are, well, overly general and imply more widespread commonalities among very different societies than is really reasonable, but he’s not an anthropologist and as such I think these flaws are quite forgivable given all the interesting data he presents in accessible form.

Hovenweep Castle, Utah

Hovenweep Castle, Utah

I also read a 2003 review article on archaeoastronomy in the Americas, written by prominent archaeoastronomer Anthony Aveni, to get a sense of research since the 1980s, but it didn’t add much. For one thing, as mentioned above, the pace of archaeoastronomy seems to have leveled off a lot since then, and it’s striking how many of the references in Aveni’s article are to publications from the 1970s and 1980s. Also, while the article does cover North America as one of its three main sections, it spends much more space on the other two sections, Mesoamerica and South America. This is unsurprising, since the major civilizations in these areas have written records (mostly from the contact period but in the case of the Maya precontact as well) to which archaeological data can be compared. In addition, they have just received more attention in general from archaeoastronomers than cultures further north. Aveni himself studies Mesoamerica, so he has a lot to say about research there.

That said, however, Aveni’s account of North American archaeoastronomy is also surprisingly sloppy and riddled with obvious errors. He refers to Cahokia as “part of the Adena-Hopewell culture,” which is just laughably wrong; Cahokia is the preeminent site of the Mississippian culture, which arose centuries after the decline of Hopewell. He also attributes the Poverty Point site in Louisiana to the Adena, whereas it is actually significantly earlier. His discussion of the Southwest doesn’t contain any obvious errors of that magnitude, but it is very brief and superficial, as is the whole North American section of the paper.

Fajada Butte with Green Vegetation

Fajada Butte with Green Vegetation

Overall, then, I guess I would say that Williamson’s book is a much better introduction to North American archaeoastronomy than Aveni’s article, but that is kind of a trivial conclusion since it’s also much easier to find for the general reader. Even academics who have access to the Aveni paper, though, probably won’t get much out of it on this topic.
ResearchBlogging.org
Aveni AF (2003). Archaeoastronomy in the Ancient Americas Journal of Archaeological Research, 11 (2), 149-191 DOI: 10.1023/A:1022971730558

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Utah Welcome Sign

Utah Welcome Sign

The initial discovery of chemical markers for chocolate on potsherds from Chaco Canyon in 2009 was a hugely significant development in understanding Chaco. The evidence for the presence of chocolate, a Mesoamerican product that couldn’t possibly have been locally grown and is very unlikely to have been gradually traded northward through a series of intermediaries, gave a huge boost to the “Mexicanist” school of thought about Chaco, which holds that many of the unusual aspects of the Chaco system are due to influence from Mesoamerica.

The initial study only involved a few sherds, though, and understanding the exact role of chocolate at Chaco and its implications for Mexican contact needs a much deeper understanding of where and when cacao was present in the ancient Southwest. Thus, soon after the initial discovery further research by a different set of researchers (using somewhat different methods) began to test other pots from Chaco and elsewhere. They did find further evidence that at least some of the famous cylinder jars from Chaco were used in the consumption of chocolate, but they also found traces of cacao in vessels of similar form from the later Classic Hohokam period in southern Arizona, and, most surprisingly, also in vessels from the “small-house sites” at Chaco and elsewhere that are thought to have housed the lower classes of Chacoan society. The previous evidence for chocolate came from distinctive vessels at the “great houses” that are the hallmark of the Chaco system and seem to have been used by elites (though exactly what they used them for remains unclear and controversial). This is exactly the kind of setting where it would be unsurprising to find unusual, exotic things, and indeed the great houses clearly contained many such things in addition to the chocolate. Finding this sort of exotic foodstuff in more mundane pots at the small houses implies that it may have been more widely accessible than previously thought, which has important implications for understanding the nature of the Chaco system.

Well, now things have become even more complicated. The same researchers who did that follow-up study have done another, this time looking at a much earlier period and a different part of the Southwest. They used their same techniques to test for the presence of chocolate in pottery at Alkali Ridge Site 13 in southeastern Utah, a very important early village site dating to the eighth century AD. Site 13 was one of the earliest large villages established in the northern Southwest during the Pueblo I period, and its architecture shows some striking parallels to later Pueblo I villages such as McPhee Village in the Dolores, Colorado area, as well as to some of the early great houses at Chaco and elsewhere that developed even later. The early Pueblo I period in southern Utah is also associated with the introduction of a new type of pottery, San Juan Red Ware, which was widely traded from an apparently rather restricted production area and probably used for ceremonial purposes of some sort. In addition to being a different color from the more common gray and white pottery of the area, San Juan Red Ware also featured a distinctive design system in its decoration, one without obvious local antecedents. Combined with the distinctive architecture, this has led some archaeologists to posit that there was a migration into southern Utah during early Pueblo I from somewhere to the south, bringing these distinctive traits.

In that context, looking for cacao makes sense, as that would be a clear sign of ties to the south and cultural distinctiveness. Dorothy Washburn, who was the lead author on both this and the previous study,  has actually written mainly on design style in ceramics and other handicrafts, focusing on symmetry patterns. Based on the changes she has found in these patterns, she has argued for a very strong Mexicanist interpretation of Chaco, involving actual migration of people from far to the south bringing a distinctive pottery decoration style. She seems to have a similar view about Alkali Ridge, for similar reasons.

In any case, the study found that there was in fact evidence for cacao on several of the vessels found at Site 13, including some (but not all) of the redware ones. The conclusions, understandably, focus on the association between the new ceramic design system and the use of chocolate, but in fact the redware vessels don’t seem to be much more likely to have evidence of chocolate use than the other ones that were tested. It’s quite possible that San Juan Red Ware was associated with consumption of chocolate specifically, but it seems that other types of pottery were also used for chocolate-related purposes.

This is all very interesting, but it’s also confusing and hard to interpret, in a way that the authors of this paper don’t really address. Back when it seemed like chocolate was limited to cylinder vessels at Chaco great houses, that was easy to interpret: chocolate, like many other exotic goods found at these sites, was part of an extensive trading systems for elite goods, probably used for ritual purposes, which the elites of Chaco participated in (and perhaps dominated and directed). Finding it in the Hohokam vessels implied a similar system operating among elites at Classic Hohokam sites, which is consistent with some interpretations of Classic Hohokam society, plus the Hohokam in general show lots of evidence of contact with Mesoamerica in general so the presence of chocolate is much less surprising there than it was at Chaco. Finding it in the small houses at Chaco complicated the story somewhat and implied that the chocolate imported to Chaco wasn’t as restricted as had been thought, but since it was already known to be present at the great houses it’s not too surprising that the contemporaneous small houses had it too.

Alkali Ridge, though, is much earlier and much further north than any of these other sites. Getting chocolate there in significant quantities would have required a pretty elaborate and robust supply chain over a very long distance, much of which was inhabited by societies that are not generally considered to have been capable of this kind of long-distance coordination. Checking some of those intermediate areas (especially the Hohokam region) to see if they too had chocolate this early is necessary to understand the logistics of this.

There’s also the question of time. We now have evidence of chocolate from Utah in the eighth century, New Mexico (and to a lesser extent Colorado and Arizona) in the eleventh, and Arizona in the fourteenth. There are some big gaps there that need to be filled in to determine if these are three snapshots of a long-term and continuous tradition of chocolate consumption in the Southwest (which would have important implications about trade networks and relations with Mexico) or three separate episodes of chocolate being introduced from the south, possibly through population movement (which would have important implications for regional culture history in general). I think the most important place to look for evidence of continuity between Alkali Ridge and Chaco is in the large late Pueblo I villages in southwestern Colorado, especially the Dolores-area ones like McPhee Village. These sites have apparent connections to both earlier villages like Site 13 and later developments at Chaco. If they also reveal evidence for chocolate use, that would be a strong indication of continuity. The most important places to check for continuity between Chaco and the Classic Hohokam would probably be the Pueblo III communities in east-central Arizona, which again show connections in both directions. Both of these sets of sites are among the best-studied in the Southwest and there should be plenty of pots available for these analyses.

Finally, there is a methodological issue here. It’s possible that these tests aren’t actually detecting chocolate at all, but something else. The authors of the recent paper noted this possibility and looked into whether there are any plants native to the Southwest that might have chemical profiles similar to cacao that would throw off the analysis. They didn’t find any, but they note that many plants have not been analyzed in this way and it’s possible there is a different plant that is showing up in these analyses instead. Another possibility is that there is something about their method itself that is leading to false positives. It’s noteworthy that they have been finding much more extensive evidence of chocolate than the team, led by Patricia Crown and Jeffrey Hurst, that did the initial Chaco study found. That team hasn’t published any more about chocolate at Chaco since then, but I hear Crown was able to do some re-excavation in Room 28 at Pueblo Bonito this summer so there may be more from her on this in the future. Ideally I’d like to see a test of both methods on the same vessels to see how they match up.

The ultimate message here is that even important discoveries, like chocolate at Chaco, require many further studies and refinements to interpret properly. We’re nowhere near a full understanding of the true role of chocolate at Chaco or any other site in the prehistoric Southwest, but every study gets us closer.
ResearchBlogging.org
Washburn DK, Washburn WN, & Shipkova PA (2013). Cacao consumption during the 8th century at Alkali Ridge, southeastern Utah Journal of Archaeological Science, 40, 2007-2013 DOI: 10.1016/j.jas.2012.12.017

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Black-on-white Sherd at Pueblo Alto

Black-on-white Sherd at Pueblo Alto

In keeping with what seems to be the recent pattern around here, my previous post led to some interesting discussion in the comments. Frequent commenter marcaeolog provided a link to a pdf version of Anna Shepard’s Ceramics for the Archaeologist, a classic work that challenges some of Florence Hawley’s theories that I discussed in the post. Andy Ward, who has done extensive experimental work attempting to recreate prehistoric pottery-making techniques, then chimed in with some information on his own efforts, focusing specifically on the question of what keeps carbon-based pigments from burning off during firing. Here’s part of his comment:

I have been doing research in just this area by collecting clays and firing them in open mesquite fires. While it is easier to keep carbon based paint on a pot in a reducing atmosphere this doesn’t account for polychromes. To make polychrome with a carbon based paint, like the ubiquitous Gila Polychrome, requires an oxidizing atmosphere. Certain kinds of clays have the ability to hold these carbon paints through a firing, bentonite clay in particular. Modern pueblo potters have used a slip called Cochiti slip which has these properties, ancient potters in cultures such as the Salado had access to similar slips.

As it turns out, Shepard had the same theory, based on her own experiments, which also provided solid evidence against Hawley’s theory, based on experiments with hydrofluoric acid, that it was compounds in the ash of the organic material that reacted with silica in the clay to protect the pigment from burning away. She acknowledged that this was a reasonable conclusion based on the information available to Hawley at the time, but Shepard’s own experiments comparing organic material with and without this sort of ash showed no substantial difference. Instead the biggest factor was clay type:

The most striking fact brought out by these tests is the effect of the type of clay on the permanence of the carbon. Bentonitic and other highly adsorptive clays retained a good black under firing conditions that completely oxidized the carbon on unnadsorptive, sedimentary clays. All of the clays that held the paint well required a high percentage of wafer to bring them to the plastic state and they had high shrinkage. These clays take up much more of the paint solution than the less adsorptive clays, and on drying, the clay plates are drawn tightly together, protecting the film of paint that surrounds them. The effectiveness of hydrofluoric acid in facilitating oxidation of carbon paints is explained by the fact that it attacks the clay, opening the surface and loosening the bond and thus exposing the carbon to air.

The upshot of this in cultural terms is that, contrary to what I said in an earlier post, it seems like the difference between mineral- and carbon-based black pigments is actually technological rather than cultural. Here’s Shepard again:

The relation of the type of clay to the depth of color of carbon paint from a plant extract is not a matter of merely theoretic interest to the technologist. It has a bearing on the distribution of this class of paint because it could not be produced in regions lacking adsorptive clays unless such clays could be obtained in trade. The use of plant extracts is not open to free choice or established merely by custom; it is limited by ceramic resources.

This is particularly interesting given the well-documented expansion of carbon-based pigments at the expense of mineral ones over the course of the late prehistoric period. If special clays were required to make this work, and those clays had restricted distributions, what accounts for the change? In areas that switched from mineral to carbon paint, such as Chaco, was this the result of a change in clay sources? The discovery, perhaps due to increased contact with other areas that had long used carbon, of which local clay sources worked for this? Importation of clay? Importation of finished pots? This raises a lot of questions, which to my knowledge have not received much attention in the archaeology of these areas, despite the fact that it’s now been several decades since Shepard’s research.

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Hachured Potsherds at Casamero Pueblo

Hachured Potsherds at Casamero Pueblo

When I was working at Chaco, people would ask me a lot of questions. I usually knew the answers, but when I didn’t I was quite upfront about saying so. I would often try to find out the answers to questions that had stumped me, but I didn’t always succeed, and many of those questions are the ones that I remember best, even now.

One of those questions had to do with the black-on-white pottery that is a hallmark of Chaco. A guy once asked me what they had used as a fixative to get the paint to adhere to the pottery, and I didn’t know. I didn’t really make much of an effort to find out then, as I didn’t really have any idea where to look. Recently, though, I’ve read two papers that shed interesting light on this question. Understanding them, though, requires some background on Pueblo pottery in general.

Hachured Potsherd at Pueblo Alto

Hachured Potsherd at Pueblo Alto

Basically, there are three main types of paint that were used in the prehistoric Pueblo Southwest. Two of these were in use during the period when Chaco was occupied: mineral and carbon. (The third, lead glaze, wasn’t used until later.) Both were used to produce a black color. Other colors were occasionally produced by a variety of means, but for this period black was the overwhelmingly dominant color of painted ceramics. It’s generally possible for experienced archaeologists to tell mineral and carbon paint apart by sight. Although they both tend to look black on a well-fired pot, there are various subtle differences between the two.

Carbon paint is basically just plant material, usually Rocky Mountain beeweed or tansy mustard, boiled down into an extract and applied to the pot. Mineral paint is made of ground iron-rich minerals, usually hematite, mixed with either water or an organic extract similar to those used alone as carbon paint, and sometimes with clay as well. Both types have been used both in prehistory and among the modern Pueblos. However, there were some marked patterns to usage of the different types of paint both geographically and temporally. Overall, the trend was of increasing use of carbon rather than mineral paint over time, spreading from west to east. Chaco ceramics at the height of the Chaco phenomenon in the eleventh century AD were overwhelmingly mineral-painted, while Chuska and Mesa Verde ceramics, while very similar in decoration and imported to Chaco in large numbers, were generally carbon-painted. Around AD 1100 there was a marked shift, and even Chaco pottery began to be primarily carbon-painted. By the 1200s use of mineral paint only continued in areas on the eastern and southern fringes of the Pueblo world. Distinguishing between carbon and mineral paint is thus quite useful for making inferences about culture history during this period. (In subsequent periods things became much more complicated with extensive long-distance migration and the introduction of glaze paints.)

Sherd with Checkered Pattern, Kin Klizhin

Sherd with Checkered Pattern, Kin Klizhin

Both of the papers I mentioned above are about using more formal means than visual criteria to tell mineral and carbon paint apart. One, by Joe Stewart and Karen Adams, used a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS) system to differentiate the two based on the amount of iron detected in the pigment. The other, by Robert Speakman and Hector Neff, used laser ablaction-inductively coupled plasma-mass spectrometry (LA-ICP-MS), a simpler and potentially less expensive method to distinguish between the two types of paint based on the concentrations of various elements. Both found that the methods they used came up with similar results to traditional visual methods, and were superior for certain sherds with unusual mixes of characteristics that made them visually ambiguous. Speakman and Neff also found a surprising amount of variety in elemental composition even within the “carbon” and “mineral” groups, suggesting that there were multiple “recipes” used to mix paint in prehistory, not just the two broad categories. This isn’t all that surprising given that this is clearly the case in modern times based on ethnographic data, but it’s still interesting.

That’s all well and good, but one thing that occurred to me in reading these papers was that it’s not at all clear why there would be multiple paint recipes, since they all ended up with pretty much the same result and some were definitely more complicated than others. This is particularly the case when considering mineral paint, since in many cases it appears that it was actually mixed with the plant concoctions that were in other places used independently as carbon paint. If boiling down beeweed produced a perfectly suitable black paint, why bother adding hematite? This might well explain why the trend over time was from mineral to carbon paint, but it’s still unclear why mineral paint originated in the first place. It does not appear to have predated carbon paint overall, at least at Chaco, where both carbon and mineral types are present as early as Basketmaker III.

Hachured Potsherds at Kin Ya'a

Hachured Potsherds at Kin Ya’a

The lack of obvious functional reasons for preferring mineral to carbon paint suggests that the choice may have been more a matter of cultural tradition, which is interesting and implies that some sort of cultural differentiation may have been present quite early in the prehistory of the northern Southwest. This isn’t really surprising, as there is plenty of other evidence for this, but teasing out the implications of all these different lines of evidence pointing to differentiation in material culture is a task that archaeologists have only recently begun to take on. It should be interesting to see what more we have to learn from these differences.
ResearchBlogging.org
Speakman, RJ, & Neff, H (2002). Evaluation of Painted Pottery from the Mesa Verde Region Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) American Antiquity, 67, 137-144 DOI: 10.2307/2694882

Stewart, JD, & Adams, KR (1999). Evaluating Visual Criteria for Identifying Carbon- and Iron-Based Pottery Paints from the Four Corners Region Using SEM-EDS American Antiquity, 64, 675-696 DOI: 10.2307/2694212

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