The First Family of Chaco

Entrance to Room 33, Pueblo Bonito

A fascinating and important article about Chaco was published last week in Nature Communications, an open-access offshoot of the venerable journal Nature (already a good sign). Since it’s open-access, the full text of the article is available free online here.

The researchers behind the article, based mainly at Penn State and Harvard but also including Steve Plog at the University of Virginia and a couple of people at the American Museum of Natural History, sequenced the mitochondrial genomes of several of the people buried in Room 33 at Pueblo Bonito in an attempt to determine if they were related. This addresses a number of outstanding issues in the interpretation of the Chaco Phenomenon, particularly those revolving around the political economy of Chaco and the degree to which it was a hierarchical society. They also radiocarbon-dated the remains and did some additional genetic analysis to confirm the sexes of the people and try to determine any close genetic relationships among them.

The results were striking. All of the tested remains had identical mitochondrial genomes, indicating that they were all related through the maternal line, which in turn suggests strongly that Chaco was a matrilineal society in which this particular maternal lineage had an enormous amount of power and wealth that led it to have the most elaborate burials in the history of Pueblo societies. The radiocarbon dating suggests in addition that people from this lineage continued to be buried in the special crypt in Room 33 throughout the florescence of Chaco, starting in the early ninth century AD and continuing until the early twelfth century. (What exactly happened then remains obscure.) The DNA sex determinations matched those previously determined through osteological analysis 100% as well.

Old Bonito from Above

These results, which are based on carefully controlled analyses and seem very solid, are not exactly surprising, but they do provide apparent confirmation of certain models of Chaco and apparent falsification of others. Specifically, they support models involving robust social hierarchy and inequality, with some lineages having more authority than others and one at the top. Most recent evidence has pointed in this direction, but this study is a particularly strong support for it. Also, they provide support for the idea that Chacoan society was more like the ethnographic Western Pueblos, which are matrilineal and structured around kin groups known as “clans” that derive their power and status from their control of esoteric religious knowledge, than the Eastern Pueblos, which are patrilineal and structured around non-kin-based groups known as “societies” that derive their power and status from similar bases. (If this distinction seems fairly minor, that’s because it is. But in attempting to reconstruct historic societies it’s important.)

It’s important to note that while these results do provide support for a matrilineal model of Chaco, that’s very different from saying they support a matriarchal one, as some media coverage I’ve seen has either implied or stated explicitly. Reckoning descent through the mother’s line is very different from having women run things with men in a subordinate position. The former is quite common cross-culturally, while I’m not sure if the latter exists at all in the ethnographic record. The fact that several of the people buried in Room 33 appear to have been related maternally doesn’t negate the fact that the two most elaborate burials were both of men, and in general there’s no reason to think that Chacoan society wasn’t strongly patriarchal, and plenty of reason to think it was.

Finally, from a methodological perspective this is a particularly interesting paper. The authors say that it appears to be the first use of genomic analysis to determine family relationships in a prehistoric society (i.e., without the availability of written records to check the results). I’m not completely sure that’s correct, but this has certainly not been a common type of study. In discussing DNA evidence a while back, I mentioned that in the Southwest it had mostly been used so far just for determining mitochondrial haplogroups, which provide some useful information but not nearly as much as can be provided by genomic analysis, which at that time hadn’t really been used at all in the Southwest. This paper marks the first major use of this type of analysis in the region, and it shows how powerful it can be. Now that the precedent has been set, it can be used in other contexts to see where this particular matrilineage shows up elsewhere in Southwestern prehistory both before and after Chaco, as well as to address other issues of kinship and identity within Chaco.

Kennett, D., Plog, S., George, R., Culleton, B., Watson, A., Skoglund, P., Rohland, N., Mallick, S., Stewardson, K., Kistler, L., LeBlanc, S., Whiteley, P., Reich, D., & Perry, G. (2017). Archaeogenomic evidence reveals prehistoric matrilineal dynasty Nature Communications, 8 DOI: 10.1038/ncomms14115

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Room 33 Revisited

Room 33, Pueblo Bonito

In my post about the recent radiocarbon dating of macaw remains from Chaco Canyon, I mentioned another paper I’ve been meaning to post about. Published in 2010 by Steve Plog and Carrie Heitman of the University of Virginia, it takes a close look at burial practices at Chaco, particularly focusing on the northern burial cluster within Pueblo Bonito. Within that cluster it focuses on Room 33, the location of the most elaborate burial assemblages ever found in the Southwest.

Plog and Heitman take advantage of their Chaco Archive project, which is collecting and making available lots of archival material on excavations at Chaco that was previously very hard to access, to look back at the field notes from the excavators of Pueblo Bonito, particularly those of George Pepper, who excavated this part of the site in the 1890s as part of the Hyde Exploring Expedition. Pepper took very detailed notes, especially by the standards of the time, and particularly for the rooms in the northern burial cluster he kept track of artifact locations and the positioning of skeletal remains, which makes it possible for Plog and Heitman to plot the vertical and horizontal positions of the burials and grave goods in Room 33 to see what patterns there may be.

They find some interesting patterns in the burial and artifact locations, but the most important data they report are radiocarbon dates, directly on the bones, from ten of the burials, including the ones with the most elaborate funerary assemblages, known as Burials 13 and 14. Burials 13 and 14 had actually already been dated for a different study a few years earlier, which I have discussed before, but Plog and Heitman redated them to see if they the earlier results would be replicated. (They were.)

At this point I should back up and review some basic facts about Room 33 and its burials, as well as some assumptions that had seeped into the Chacoan literature over the years despite not being well-supported by evidence.

Type I Masonry in Room 33, Pueblo Bonito

Facts: Pepper found 14 identifiable individual burials in Room 33. He numbered them in order of discovery, which roughly corresponds to vertical distance from the roof beams, so 13 and 14 were the lowest. Burials 13 and 14 had the most elaborate grave goods by far, including vast numbers of turquoise beads and other ornaments. They were intact and undisturbed, and were separated from the higher burials by a “floor” of wooden planks. The burials above this floor were accompanied by grave goods, but they were mostly disarticulated and appeared to have been disturbed at some point after burial. Pepper proposed that they had been scattered by water flowing into the room at some point.

Assumptions: At some point over the years, the idea entered the literature that these burials dated to the time of the “florescence” of Chaco starting around AD 1030 and lasting for about 100 years. Despite the fact that Room 33 is in the oldest part of Pueblo Bonito and its masonry style indicates that it dates to early in the site’s construction, many archaeologists (starting with Pepper himself) have suggested that it was not originally constructed as a mortuary chamber, and that the burials reflect a reuse of a room that originally had a different purpose. I don’t know where the idea that this reuse coincided with the rise of Chaco as a regional power, or with the advent of monumental construction in the canyon at roughly the same time, originated, but it makes a certain amount of intuitive sense to see the establishment of a crypt with unusually elaborate grave goods would happen at the same time as the enormous labor effort reflected in the expansion of Pueblo Bonito and other early great houses, along with the building of many new ones. However, it’s important to note that there was never a rigorous argument made for a late dating of the burials, bringing in support from the pottery styles reflected in the grave assemblages or any other independent lines of evidence.

And, in fact, the most comprehensive study of Chaco burials to date, that of Nancy Akins as part of the Chaco Project in the 1970s, concluded that the pottery types in Room 33 covered a potentially long timespan, which could mean the burials themselves were deposited over a long period of time. On the other hand, it could also mean that certain “heirloom” vessels of styles that were no longer being produced but that had been kept around might be buried with particularly important people, so this evidence wasn’t dispositive about the late-burial theory.

Old Bonito from Above

Plog and Heitman’s radiocarbon dates, on the other hand, provide firm evidence that the burials do indeed date to a long period, more or less corresponding to the full span of Chaco’s importance as a regional center. Burials 13 and 14 both date to quite early in the history of Pueblo Bonito, with 95% confidence ranges of AD 682 to 870 and 687 to 870 respectively. When averaged with the dates from the earlier study, which were comparable but slightly later, the 95% ranges become AD 691 to 877 and 690 to 873.

That’s very early! It means that these two burials, at least, could easily have occurred at the same time as the initial construction of Room 33, which was likely in the late ninth century. One other burial above the plank floor dates to this period as well. (The bones got relabeled at some point and it’s not clear which sets correspond to which numbers assigned by Pepper, so it’s not possible to say for sure that this was one of the burials immediately above the floor, but it’s a reasonable surmise.) Despite the near-identical age determinations on Burials 13 and 14, the vertical distance between them is by far the highest in the room. This suggests strongly that the large amount of sand separating the two vertically was brought in deliberately rather than accumulating naturally, and they could well have occurred at exactly the same time, or nearly so, very early in the occupation of Pueblo Bonito.

From then on, the dates are more or less continuous up to around AD 1200. The ranges are too wide to come to very firm conclusions on exactly where these later burials fall in the Chacoan sequence, but they do suggest that Room 33 continued to be used as a high-status burial chamber throughout the Chaco Era after beginning to serve that role early on.

This is all very interesting, and Plog and Heitman draw a number of tentative conclusions from it. They argue that this shows that social hierarchy arose earlier in the canyon than often assumed, well before the beginning of construction on a monumental scale, and suggest that the concept of “house society” may be a useful way to interpret Chacoan great houses, with symbolically important spaces like Room 33 serving to legitimize the position of elites through a connection to illustrious ancestors. They also argue that the preservation of the delicate placement of burials and artifacts, as demonstrated in Pepper’s notes, makes it very implausible that the scattering of remains he mentions could have resulted from water intruding as we suggested. Instead, they suggest that some of the scattering could have resulted from disturbance of earlier burials in the course of creating new ones in this small space over the centuries. Another possibility they suggest is that some of the burials are actually secondary, and were placed in Room 33 after having been left to decompose somewhere else for a while. This practice is not documented among the historic Pueblos, but then again lots of the other aspects of the Room 33 burials don’t have obvious modern parallels either.

The evidence for unexpectedly early import of macaws starting around AD 900 in the more recent paper reinforces the evidence in this one for an early development of complexity at Chaco. It’s still not clear exactly what was going on at Chaco in the ninth century, but it’s becoming increasingly clear that it was very important for the subsequent history of the canyon and of the Southwest as a whole.

Plog, S., & Heitman, C. (2010). Hierarchy and social inequality in the American Southwest, A.D. 800-1200 Proceedings of the National Academy of Sciences, 107 (46), 19619-19626 DOI: 10.1073/pnas.1014985107

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Dating the Macaws

Macaw Feathers and Copper Bell on Display at Chaco Visitor Center Museum

One of the most exciting recent developments in the study of Chaco Canyon is the increasing use of scientific analysis of artifacts and other material remains to test and challenge previous theories based more narrowly on traditional archaeology. This includes the use of radiocarbon dating, which is widely used as a basis for developing chronologies in most other parts of the world but has been underused in the Southwest due to the availability of tree-ring dating for chronology building. Particularly with the development of accelerator mass spectrometry (AMS) radiocarbon dating, which requires vastly less material than earlier methods, however, it is now possible to gain direct dates on a very wide variety of materials, including many artifact types as well as plants and human and animal bones. This allows an independent check on dating of material by association with tree-ring dated architecture and pottery, which has been the traditional approach. The increasing use of AMS on the museum collections excavated decades ago from Pueblo Bonito, in particular, is starting to lead to some unexpected and surprising conclusions. This work is largely being done by archaeologists associated with the University of Virginia led by Steve Plog, in collaboration with colleagues at many other institutions.

One recent paper, about a year old now, reported some surprising results from the dating of the bones of one of the most distinctive species found at Chaco: scarlet macaws. These birds are not native to anywhere near the Southwest, and they must have been brought up from very far south in Mexico. They are disproportionately found at only a few sites in the Southwest, one of which is Pueblo Bonito. Traditionally it has been thought that the importation of macaws was associated with the “florescence” of Chaco, the roughly 100-year period starting around AD 1040 when most of the monumental great houses in the canyon were built and Chacoan influence is seen over a very large part of the northern Southwest. For this study, the researchers dated 14 macaws from Pueblo Bonito: 11 from Room 38, which had the highest concentration of macaw remains at the site, two from Room 78, and one from Room 71. Both of these latter rooms are in fairly close proximity to Room 38 within the site. They also dated four macaws from Mimbres sites in southwestern New Mexico, another area with a relatively high concentration of these birds that lies between Chaco and Mexico and thus could played a role in their procurement, and two from Grand Gulch in Utah, which is on the far fringes of the ancient Pueblo world and yet has produced a few macaw specimens.

The results were surprising, and they challenge the traditional association of macaws with the Chacoan florescence. Six of the Chaco birds dated to between AD 885 and 990 (all dates given here are at 95% probability), well before the florescence and a time when Chaco would have been much less impressive architecturally. This is, however, a time when population in the canyon was increasing rapidly through immigration from various areas that were affected by the big changes at the end of the Pueblo I period, as we have seen in my recent series of posts on Pueblo I. The authors of this paper don’t mention this population movement specifically, but they do suggest that this indicates that the later period of monumental construction and other signs of sociopolitical complexity was the result of a long period of developing complexity, which fits the demographic evidence pretty well.

Room 38, Pueblo Bonito

Six other birds date between AD 970 and 1035, which would put them shortly before or possibly at the very beginning of the florescence and building boom. This suggests that trade relations with the far south continued beyond the initial period when macaws were introduced to the canyon. The final two date between AD 1015 and 1155, which suggests they probably were procured sometime during (or even shortly after) the period of florescence. Overall the dates suggest that macaws were procured throughout most of the period of Chaco’s rise from the period when Chaco was first rising to regional preeminence in the ninth and tenth centuries until its loss of preeminence (I think “collapse” is too strong a term for this still poorly understood phenomenon) in the twelfth.

One thing you may have noticed about those date ranges, however, is that they all overlap. Given the statistical uncertainty of radiocarbon dates, this means that it’s possible that these dates indicate a continuous process of importation of macaws from Mesoamerica. (There is no evidence for breeding of macaws at Chaco, unlike at the later site of Casas Grandes in northern Chihuahua.) The clustering of sets of dates, however, suggests on the contrary that importation was sporadic, with possibly just three individual procurements of multiple birds at a time. And additional complication is that the shape of the radiocarbon calibration curve differs at different times through this sequence, which can lead to certain time periods being over- or under-represented in series of dates. To test these hypotheses, the authors did some simulation of random dates throughout the period in question and compared the resulting distributions with the actual distribution of macaw dates. The results were that the early cluster of dates did conform to what might be expected from the effects of the shape of the curve, the middle cluster had more dates than would be expected and the late cluster fewer. This suggests that while it is possible that procurement of macaws was a continuous process, it does appear that a larger number of birds were imported in the late tenth and early eleventh centuries than earlier or later. Of course, this is a small sample, and these apparent patterns may change with more data.

As for the non-Chaco macaws, one of the Mimbres ones dated to AD 895 to 1020, straddling the first two clusters of dates at Chaco, while the other three all dated from around AD 1015 to 1155, as did the two Grand Gulch specimens. This suggests that macaws were present earlier at Chaco than in areas to either the north or south, which further suggests that at least initial importation of macaws to Chaco didn’t necessarily depend on Mimbres middlemen. Macaws have also been found at Hohokam sites in southern Arizona that appear to be in earlier contexts than the ones at Chaco, but none of these have yet been directly dated.

Room 33, Pueblo Bonito

While it may appear initially surprising, the early dates for macaws at Chaco do actually fit with increasing evidence from other sources suggesting that the rise of Chaco and its social and economic power significantly predated its “florescence” as seen in monumental architecture. This includes a study from a few years ago, from the same group of Virginia researchers, that dated human remains from Room 33 in Pueblo Bonito, including the two burials that were associated with enormous numbers of valuable grave goods, and found those two burials long predated the Chacoan florescence and may in fact have been contemporary with the earliest construction at the great house in the mid-ninth century or even earlier. (That paper really deserves a post of its own, which I keep meaning to write, but this brief summary will have to do for now.)

Taken in conjunction with the evidence for regional population movement in late Pueblo I, this study provides more support for the idea that the influx of populations into the canyon in the late ninth century, some bringing ideas developed in the earlier short-lived villages to the north in Colorado, set the stage for the development of new ideas about social organization and hierarchy which may have led to new ideologies and the importation of both goods and ideas from areas far away. The fact that macaws would have to have come from the south, where the archaeology of areas immediately adjacent to the Chacoan region is much more poorly known than that of comparable areas to the north, points to the importance of developing a better understanding of those areas. We still know very little about the exact routes of trade connections to the south, even as the importance of those connections becomes increasingly apparent.

Watson, A., Plog, S., Culleton, B., Gilman, P., LeBlanc, S., Whiteley, P., Claramunt, S., & Kennett, D. (2015). Early procurement of scarlet macaws and the emergence of social complexity in Chaco Canyon, NM Proceedings of the National Academy of Sciences, 112 (27), 8238-8243 DOI: 10.1073/pnas.1509825112

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Watching the Sun

Walls at Wijiji

Today is the winter solstice, and the seventh anniversary of this blog. I’ve traditionally posted about archaeoastronomy on these anniversaries, so I’m going to briefly interrupt my series on Crucible of Pueblos to discuss an interesting article on the evidence for astronomical observations at Chaco Canyon. There turns out to be some overlap, actually, which is interesting.

The article is by Andrew Munro and Kim Malville, who were also the authors of the article on building orientations that I talked about last year on this date, and it was published in the same special issue of the journal Archaeoastronomy in 2010. The content is rather different however. This article summarizes the evidence for specific locations in and around the canyon for which there is evidence of use as solar observation “stations,” including two sites which are newly identified here. (Worth noting here is that Munro left a detailed and interesting comment on last year’s post, in which he linked to his unpublished thesis which contains more detailed and up-to-date information on his approach to archaeoastronomy. I haven’t read it yet, so I’m focusing here on the published articles while recognizing that they don’t have the most recent information.)

Identifying viewing stations is more complex than simply demonstrating alignments, for a variety of reasons. For one thing, based on modern Pueblo ethnography, sun-watching locations were not necessarily marked physically with architecture, rock art, or anything else. This makes their archaeological identification difficult, and probably means that the stations that did happen to have physical markers are probably over-represented.

Identifying these stations also requires careful consideration of how exactly the observation process would have likely worked, what its specific purposes were, and how they could have been met. If, as Munro and Malville argue, the main role of these observations was to fix the dates of ceremonies marking key times in the year, there would have been a practical need to mark not just the date of the ceremony itself, but dates leading up to it which would have given time to prepare for it. Munro and Malville use the term “anticipatory” for stations that would allow prediction of an event in advance, and “confirmatory” for those that would allow observation of the date of the event. There would also need to be a system for communicating the information from the observation stations quickly and easily to other sites in the canyon and beyond.

There is also an important distinction between observation stations and shrines. The former were used for the practical purpose of making observations, while the latter were associated with those observations but used for ritual activities rather than observation, and often were not in locations from which accurate observations could be made. Munro and Malville use the terms “primary” and “secondary” to refer to these different types of sites; secondary stations could include both shrines, which could involve rock art and/or simple architecture, and alignments within or associated with buildings. The well-known, though not universally accepted, alignments at Pueblo Bonito and Casa Rinconada would fall into the secondary category, as would the “Sun Dagger” petroglyph site atop Fajada Butte. In this paper Munro and Malville focus on the primary stations, which they further divide into two categories depending on whether they could be used both to predict significant dates in the solar calendar and to observe them when they occurred, or just to observe the occurrence. For practical purposes the former type would be more useful.

Despite Chaco’s reputation for astronomy, it turns out that good locations for primary observation are pretty rare in the canyon. One key requirement for such a location is a “broken” horizon with obvious landmarks that can be used to track the sun’s (or moon’s) progress along the horizon, but from most great houses the horizon is actually pretty flat and unsuitable for observation. This is presumably due to the flat mesa tops to the north and south of the canyon itself. The number of possible locations for observation stations is therefore reduced to a few areas of the canyon where the horizon is more varied. Munro and Malville list five previously documented stations and add two more based on their own research. (A few more have since been identified.) They are briefly described below.

Fajada Butte with Green Vegetation

Piedra del Sol is a large rock near the current Chaco visitor center that has a wide variety of rock art as well as multiple astronomical alignments. Of particular interest is an apparent viewing station for summer solstice sunrise associated with a large spiral petroglyph on the northeast face of the rock. The horizon as viewed from this spot could allow for both anticipatory and confirmatory observations for the solstice. Even more intriguing, the station has a direct line of sight to the “Sun Dagger” site on Fajada Butte, suggesting that this may have been the location from which the observations were made that allowed the spiral petroglyph at that site to be placed in exactly the right position for the “dagger” of light to pierce it on the summer solstice.

There are multiple identified observation stations in the area of the Wijiji great house at the eastern end of the canyon. One site, 29SJ931, is near a pictograph site on a ledge near the great house and allows observation of the winter solstice. There are some features at the site that are similar to the sorts of features found at post-Chacoan observation sites in the Mesa Verde area, as well as evidence for later Navajo use, so it’s not clear that this site was actually used at all during the Chacoan era. Another site near Wijiji, 29SJ1655, has many Navajo petroglyphs nearby but does also have Chacoan rock art and a possible shrine, suggesting Chacoan as well as Navajo use. This site actually consists of three siting locations, allowing observation of both solstices as well as both equinoxes.

More firmly established as a Chacoan siting station is the Wijiji great house itself. From the northwest corner of the building a notch is visible on the horizon that serves as both an anticipatory and a confirmatory marker for the winter solstice: about two weeks before the solstice the sun rises at the left edge of the notch, and on the solstice itself it rises on the east edge. Since Wijiji was one of the latest great houses to be built in the canyon, it’s possible that it was sited at a location already used as a solstice observation station. As we shall see, it is not the only great house for which this appears to be the case.

Kin Kletso

Further west in the canyon, another late great house, Kin Kletso, shows a similar alignment to the winter solstice, with both anticipatory and confirmatory observations possible but in a different way. Here, looking from the southeast corner of the building toward a nearby cliff about two weeks ahead of the solstice (the same dates as the Wijiji anticipatory alignment) shows the sun rising at the base of the cliff. Over the course of the next few weeks, the same sunrise alignment is visible by gradually moving north along the east wall of the site, until on the solstice itself the alignment is visible from the northeast corner. As with Wijiji, it is possible that Kin Kletso was built at the site of an existing observation station, perhaps associated with the large boulder at the western end of the site. (I mentioned both the Wijiji and Kin Kletso observation alignments in my very first post on this site, as it happens.)

In addition to these previously identified observation stations, Munro and Malville describe two new ones based on their own recent research. Both of these are interesting partly because of what they imply about the date at which these sorts of observations began at Chaco.

29SJ2539 is in the general area of Wijiji, and also near the important Basketmaker III village of Shabik’eschee. The site itself includes a boulder with an alignment allowing for confirmatory observation of the winter solstice sunrise through a notch at the foot of a nearby cliff, along with a wide variety of artifacts and rock art indicating both Chacoan and Navajo use. An immediately adjacent site, 29SJ2538, includes a ledge overlooking the boulder that could have been used for storage but apparently wasn’t. Another nearby site is a small-house habitation that was excavated by Frank H. H. Roberts in 1926, now known as “Roberts Small House.” This site was apparently occupied over a long span of time, from Pueblo I through the post-Chacoan “Mesa Verdean” occupation of the canyon. It contained a large number of turkey bones, giving it the alternative name of “turkey house.” It also contained human remains, including some that have been argued to show evidence of cannibalism. Christy Turner, who initially made the cannibalism claim, identified the remains as dating to early Pueblo II, but Munro and Malville cite more recent research showing that they were actually from an earlier Pueblo I context. They also argue that there is no reason to associate the cannibalism evidence with the evidence for astronomical observation or related ritual practices, but without going into detail.

Looking West from Peñasco Blanco

Finally, Munro and Malville identify a possible observation point for winter solstice sunrise at Casa del Rio, an early great house just west of the canyon that seems to have been an important site in the Pueblo I period, with an exceptionally large trash midden suggesting possible feasting activity involving people beyond those living at the site. From this site (Munro and Malville don’t specify the exact viewing location) the solstice sunrise is aligned with West Point, the high point on the west side of West Mesa that contains a Chacoan shrine and has direct lines of sight to the Peñasco Blanco great house as well as to other shrines from which messages could be quickly sent throughout the canyon and beyond. This close association with the signaling network, in combination with the large amounts of trash (which seems to have been primarily domestic trash associated with food consumption, unlike the more complex contents of the later, more formal mounds associated with Chacoan great houses), implies that Casa del Rio may have been a location where people gathered for feasts and other ceremonies during the Pueblo I period, with at least some of the ceremonies tied to astronomical events such as the winter solstice (or the full moon nearest to it). In this scenario, inhabitants of Casa del Rio would have watched the sunrises over West Mesa to determine the dates of their festivals, then communicated those dates to others by signaling to the shrine on West Point, from which the signal could have been transmitted to many other places.

Speaking of signaling, Munro and Malville also discuss how it could have been done. Fires or smoke signals are possibilities, but another intriguing options would have been mirrors made of selenite, a mineral that can be polished to a high reflective sheen which is found in some natural outcrops in the Chaco area, including one near the observation site at 29SJ2539. Pieces of selenite were in fact found at 29SJ2539 itself, as well as at several other sites in the canyon.

Several interesting patterns emerge from the data compiled by Munro and Malville. First, the winter solstice sunrise appears to have been the most important astronomical event observed by the ancient Chacoans, at least judging from the viewing stations that have been identified so far. This is consistent with modern Pueblo ethnography, which similarly indicates the winter solstice as the most important event and sunrise observations as generally being more important than sunset ones.

Second, there is a strong association between possible viewing stations and so-called “Late Bonito” great houses, those built in the early AD 1100s toward the end of the period of Chacoan florescence, often in the so-called “McElmo” architectural style that is sometimes associated with influence from the north. The relatively standardized sizes and shapes of these great houses, as well as their short periods of construction, suggest an aggressive building program at this time that might have been associated with an attempt to reassert Chaco’s importance at a time when regional focus was starting to shift north to Aztec. Siting these buildings at locations already used as astronomical observation points, and designing them to incorporate aspects of such observation into the buildings themselves, may have been a way for Chacoan leaders to emphasize their esoteric knowledge and spiritual power at a time when it was being challenged.

Finally, and most interestingly from the perspective of the series of posts I’ve been doing lately, Munro and Malville provide tentative but intriguing evidence for astronomical observation points in and around Chaco Canyon beginning in the Pueblo I period. This would to my knowledge make this the earliest known evidence for detailed astronomical observation in the northern Southwest, and possibly in the Southwest as a whole (evidence for the Hohokam in southern Arizona is more ambiguous). That, in turn, provides further support for my theory that the rise of Chaco was enabled in part by the development of a new ideology in which astronomy played a major role.

In this regard it is interesting that one of the early centers for astronomical observation may have been Casa del Rio, which was one of the most important local centers during the late Pueblo I period when the great houses in the canyon proper were just starting to be built. As noted in my earlier post on Pueblo I in the Chaco area, it’s clear that at this time settlement was largely focused to the west of the canyon along the lower Chaco River, which may have been a conduit for migrants leaving the villages in the Dolores, Colorado area when they collapsed in the late ninth century. It may have been these migrants, bringing the lessons they had learned from their experiments in village life and adapting to a new and very different environment, who first began to pay careful attention to the sky, perhaps in an attempt to improve their prospects of survival in an area that is exceptionally arid even for the Southwest. If their initial adaptations were successful, as they appear to have been at least in some places, they may have begun to gain prestige and to attract additional migrants from various areas, who would have brought their own ideas and lessons learned. Astronomy may have been the development that united these people and allowed them to develop a new social order that would go on to underlie the spectacular achievements at Chaco that we see evidence of even today. And when that social order began to be challenged, for reasons that are still unclear, its leaders may have sought to revitalize it through a renewed emphasis on their astronomical knowledge in the form of the Late Bonito great houses.

Obviously this is all fairly speculative, but more and more evidence has been accumulating in recent years to focus and ground such speculation in solid data. Archaeoastronomical research has been a key part of this, and this article is an important contribution to the developing picture.

Munro AM, & Malville JM (2010). Calendrical Stations in Chaco Canyon Archaeoastronomy, 23, 91-106

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Foreshadow: Chaco

Visitor Center and Fajada Butte from Una Vida

Chapter five of Crucible of Pueblos brings us to Chaco Canyon and the surrounding area. This is an area of particular interest for me, and I presume for most readers of this blog as well. While the rise of Chaco in the tenth and early eleventh centuries AD was clearly a development rooted in earlier events, there has long been less information available for the area of Chaco itself than for the areas to the north that have seen extensive relatively recent excavations of sites dating to the Pueblo I period. The Pueblo I occupations of those areas, the subjects of the earlier chapters in this book, are now fairly well understood, although there of course remain a lot of questions and gaps to fill. Further south the picture is still much murkier.

This chapter is written by prominent Chaco specialists Tom Windes and Ruth Van Dyke, and is particularly important and useful because it includes the first published synthesis of the work Windes has been doing for many years to identify sites in and around Chaco dating to the Pueblo I period. This work was written up as part of the series of reports on the work of the Chaco Project, but that report, dated 2006, remains unpublished. I presume that this is a deliberate decision on the part of the National Park Service to keep sensitive information on site locations from becoming public (although I don’t actually know for sure). This chapter, then, appears to serve as the published record of this important work, which significantly alters the conventional interpretation of Pueblo I in Chaco.

The authors define their geographic scope as what they call the “Chaco Basin,” which is essentially equivalent to what is commonly know in the Chaco literature as the “San Juan Basin.” I think this is a useful change to the terminology, since “San Juan Basin” in the hydrographic sense refers to a much larger area than it is used for in this context, and while some use terms like “San Juan Physiographic Basin” to clarify this, it’s more straightforward to redefine the area and use a new term. “Chaco Basin” is a good term to use because the area more or less corresponds to the drainage basin of the Chaco River, including its tributaries, although it extends a bit beyond to the east and south into the Puerco Valley and Red Mesa Valley respectively. However it’s labeled, this region is roughly bounded by the San Juan River to the north, the Chuska Mountains to the west, the Zuni Mountains to the south, and the Jemez Mountains to the east.

Temporally, the authors restrict their attention in this chapter to the period from AD 700 to 925, unlike some other authors in this volume who also address the preceding Basketmaker III period. This is understandable but in some ways unfortunate, since there was an important Basketmaker III occupation of Chaco Canyon that was likely important in setting the context for Pueblo I developments, just as those developments were important in setting the context for Pueblo II. Confusingly, they use the term “Pueblo I” for sites dating from AD 700 to 875 and “late Pueblo I” for sites dating from AD 875 to 925. As we’ll see below, the distinction between these two periods is important in this region, as population and settlement patterns changed significantly at around AD 875. The specific terms they use still seem odd and liable to cause confusion, however.

Part of the reason the authors argue that the Pueblo I occupation in this region is poorly understood is that the ceramic chronology is different from that of the better-known sites to the north, and using the same types to identify time periods for sites in both regions leads to problems. They carefully define the types they use to identify sites to time period, and also use architectural criteria (which are however difficult to apply to unexcavated sites).

Most of this chapter is a summary of what is known about Pueblo I settlement in each subregion of the Chaco Basin, based in large part on hitherto unpublished fieldwork. As a result, I will structure this post according to the same subregions in the same order and summarize the information on each.

Northern and Northeastern Areas

The heading for this section says “Northwestern” rather than “Northeastern,” but it’s clear from the text that this in error. These areas, north and northeast of the Chaco River but still within the drainage of the San Juan, were sparsely populated throughout the Pueblo period. Windes and Van Dyke note that the Largo and Gobernador canyons, to the northeast of Chaco, may have served as conduits for populations migrating south from the Mesa Verde region into the Chaco Basin in late Pueblo I. A recently discovered village at the confluence of Largo and Blanco Washes included a great kiva and at least 22 habitation sites, with tree-ring dates from the great kiva pointing to construction at about AD 828. This area is roughly due south of the Cedar Hill and Ridges Basin areas of the Animas Valley, considered part of the Eastern Mesa Verde region in this volume, which had extensive but short-lived populations early in Pueblo I. The tree-ring dates from the Largo-Blanco village suggest that it may have been associated with the initial migration out of the Ridges Basin/Durango area in the early 800s rather than the larger migration in the late 800s. The Chaco River may have been another conduit for migrants from the north, as Windes and Van Dyke note that surveys have found a major increase in sites dating to the late 800s along the east side of the Chaco, compared to a virtual absense of sites for earlier in Pueblo I. This will be a recurring pattern in the region.

Chaco Canyon Proper and Environs

The initial survey work of the Chaco Project in the 1970s identified a fairly extensive Pueblo I occupation in and around the canyon, and publications from that time posited a gradual increase in population over the course of Pueblo I leading up to the florescence of Chaco as a regional center in Pueblo II. Based on his more recent work with ceramic classification and dating, however, Windes disputes this account. He argues that the number of sites assigned to Pueblo I in those surveys is vastly inflated, and that for most of the Pueblo I period the Chaco area had a small population which increased dramatically, presumably due largely to immigration, in the late Pueblo I period. In this chapter Windes and Van Dyke (though clearly this part is mostly Windes) summarize the results of Windes’s reevaluations of the Pueblo I occupation in and around the canyon, moving from east to west.

Pueblo Pintado Great House at Sunset

At the east end of Chaco Canyon, the Pueblo Pintado area was apparently unoccupied until about AD 875, when it was colonized by two groups who had markedly different material culture and appear to have come to the canyon from different directions. They formed separate site clusters about 3 km apart, north and west of the later great house of Pueblo Pintado.

The first cluster, located just north of the great house, includes one exceptionally large roomblock more than 50 meters long, accompanied by a trash midden that is also unusually large. Based on the temper of early ceramics in this cluster, the people appear to have come from the Mesa Verde region to the north, presumably as part of the mass exodus following the collapse of the Dolores villages in the late ninth century.

The second cluster, 3 km west of the first one, appears to have also been founded around AD 875 but continued in use well into the Pueblo II period. The ceramics are quite unusual in manufacture for the Chaco area and indicate origins to the south in the Mt. Taylor area. Interestingly, the roomblocks in this cluster were aligned along the road connecting the Pueblo Pintado community to the core area of Chaco Canyon, implying that this road may date to the late Pueblo I period.

Moving west, the next major cluster of Pueblo I sites is what is known as the Chaco East community, which also featured a later great house. This area also appears to have been unoccupied until about AD 875, when it was colonized by a group occupying small residential sites, possibly only seasonally. In the 900s the community grew considerably, and initial construction of the great house may date to this period, although it’s impossible to tell for sure without excavation.

Third-Story Walls with Type I Masonry at Una Vida

Fajada Gap, at the eastern end of the main concentration of sites in Chaco during Pueblo II, is one of the areas where early surveys indicated a dense Pueblo I occupation which Windes disputes based on current understandings of the ceramic chronology. In fact, while there was unquestionably a small occupation of the area throughout Pueblo I involving scattered hamlets, this appears to be yet another part of the canyon where there was an influx of people in the late 800s who established the basis for the community that developed subsequently. There are two great houses in this community, Una Vida and Kin Nahasbas, both of which were constructed beginning in the late ninth century.

The largest Pueblo I (pre-875) settlement in the Chaco area is actually outside the canyon, along the South Fork of the Fajada Wash. This community contained 26 sites in an arc along the west side of the South Fork; no contemporary sites are present on the east side. The community is loosely clustered around a complex of four roomblocks which were connected by a short road to a great kiva, and it likely included about 230 people overall. Its main occupation was around AD 800, making it contemporary with the earlier villages in the Mesa Verde region, but the layout of the community is more like later villages such as those at Cedar Hill and in the Largo drainage. (The description of the community in this chapter is very confusing and it’s hard to tell in what respects it’s being described as similar to or different from villages in other regions.)

Many of the potsherds from the South Fork community were tempered with chalcedonic sandstone, which is typical of sites to the south near the modern community of Thoreau. There is also an unusually high abundance of yellow-spotted chert among the chipped stone assemblage, again indicating connections to the south. This type of chert occurs in the Zuni Mountains near Thoreau and is common in sites in that area.

Although this was the largest Pueblo I community in the Chaco area, it appears to have been very short-lived, with little trash accumulation. This suggests that the Pueblo I period was a dynamic time of extensive population movements in this area just as it was in the better-understood areas to the north. The subsequent Pueblo II occupation of the South Fork was much more extensive than the Pueblo I occupation and quite different, with sites dispersed up and down the valley rather than clustered in one area. A similar though somewhat smaller cluster of sites dating to the Pueblo I period was also present in the upper reaches of Kin Klizhin Wash to the west of Fajada Wash.

Old Bonito

Returning to the main canyon, there were a few scattered Pueblo I hamlets between Fajada Gap and South Gap, but the occupation doesn’t seem to have been extensive. Even in South Gap itself, an area of considerable density during Pueblo II and the location of the cluster of great houses known as “Downtown Chaco,” Pueblo I occupation was sparse, with a few scattered sites in the gap. Apparently the only Pueblo I site known in this part of the canyon proper is Pueblo Bonito, where the earliest construction of the great house, known as “Old Bonito,” dates to the mid-800s (or possibly even earlier) and there is also an earlier pit structure excavated by Neil Judd in the 1920s. Judd thought the pit structure reflected an earlier occupation unrelated to the great house, but with improved dating showing that the great house was begun earlier than had been thought the idea of continuity is beginning to seem more likely.

There is no evidence for Pueblo I occupation between South Gap and the mouth of the canyon, possibly on account of flooding creating an intermittent lake on the canyon floor. At the mouth of the canyon itself, the Peñasco Blanco great house, begun in the late 800s, sits atop West Mesa, and right next to it is the important Basketmaker III village of 29SJ423. The period between these two important occupations, however, appears to have involved only minor settlement, although there are a few scattered Pueblo I sites. Just west of the mouth of the canyon, however, is Padilla Wash, which had a substantial Pueblo I occupation (possibly even more extensive than current records indicate, since many Pueblo I sites may have been misclassified as Basketmaker III in earlier surveys), another example of the main centers of Pueblo I population in the Chaco core being outside the canyon proper. Windes and Van Dyke note that Peñasco Blanco may have been an important focal point for migration into the canyon from the west and north during late Pueblo I, and that it was likely more important than Pueblo Bonito at this time.

The Chaco River

As noted above, the Chaco River (formed by the confluence of the Chaco and Escavada Washes at the mouth of Chaco Canyon) was likely one of the main conduits for migrants from the north, but it was much more than that. Pueblo I communities existed all along the Chaco and its tributaries, and some of these communities included early great houses that would have been influential in the development of the great house phenomenon that found its greatest expression in Chaco Canyon in the eleventh century. Windes and Van Dyke discuss a number of these communities, based on field research by Windes to reevaluate areas identified by early surveys as Chacoan outlier communities and to look for evidence of Pueblo I settlement and early great houses.

Just west of Padilla Wash is Kin Klizhin Wash, which was the site of extensive Pueblo II occupation but only has a few Pueblo I sites aside from the cluster at its upper reaches mentioned above. There is a late Pueblo I great kiva known as Casa Patricio in the upper part of the drainage, accompanied by a number of late Pueblo I residential sites; it’s not clear from the writeup here what relationship this site cluster has to the earlier Pueblo I cluster.

Just downstream from the mouth of Kin Klizhin Wash is the very important early site known as Casa del Rio. While this was initially labeled a large Chacoan great house, reexamination indicated that it is actually a composite of two building stages, both relatively early, with much of the bulk of the structure provided by a Pueblo I roomblock measuring 112 meters in length, with a later masonry great house built over the central portion beginning in the late ninth century. The early roomblock is by far the largest in the Chaco Canyon region, more than twice the length of the earliest construction stage at Pueblo Bonito, and it is estimated to have housed about 16 households or 88 residents. Windes and Van Dyke describe it as “reminiscent of those north of the San Juan River,” although again it is not clear what specific characteristics this refers to. A large number of food preparation tools were found in the area, although other residential sites are scarce. This was clearly an important site during the Pueblo I period which may have played a key role in attracting migrants to the area.

Looking North from Kin Bineola

One of the most important tributary drainages of the Chaco River is Kim-me-ni-oli Wash, which extends from the Dutton Plateau north past the current site of Crownpoint. The drainage of this wash includes several great houses and extensive Pueblo settlement, and it likely served as an important conduit between Chaco Canyon and areas to the south and southwest. The extent of Pueblo I occupation, however, seems to be unclear. Windes and Van Dyke mention large circular structures near the Bee Burrow great house that resemble Pueblo I great kivas, as well as small Pueblo I roomblocks in the same general area. The area around the Kin Ya’a great house at the upper end of the drainage appears to not have any Pueblo I occupation based on existing survey data, although there is a large Basketmaker III-Pueblo I site just west of Crownpoint and one arc-shaped roomblock near Kin Ya’a recorded as dating to Basketmaker III looks a lot more like a Pueblo I site. At Kin Bineola, site of a major great house dating to the early 900s or possibly slightlier earlier, there is a very small Pueblo I occupation that increased substantially after AD 875 as in many other parts of the region.

At the mouth of the Kim-me-ni-oli Wash near the current Lake Valley Mission there is a small cluster of Pueblo I sites “architecturally identical” to the South Fork cluster, with very sparse refuse indicating a very short occupation. A later occupation in the late 800s was more substantial, with three masonry roomblocks “sometimes portrayed as small great houses” and “enormous amounts of refuse” that Windes and Van Dyke describe as “excessive for normal domestic activities.”

Further down the Chaco drainage, the Willow Canyon area is unusual in showing evidence of both middle and late Pueblo I occupation in close proximity. The middle Pueblo I community consists of eight sites that show the typical “scattered hamlet” settlement pattern, while the eleven late Pueblo I sites are tightly clustered and associated with a large amount of refuse, leading the authors to interpret this as “a large group” that immigrated into the valley together. These sites show unusual amounts of Type I masonry, associated with later great house construction, although the authors declare that there is no “obvious” great house. It’s not clear what definition of “great house” they are using here, as one site in particular (known as the “House of the Weaver”) shows not only Type I masonry but a prominent mesa-top location with a broad view of the surrounding area, another common characteristic of later great houses. Another community south of Willow Canyon near the later Whirlwind great house also shows a similar pattern but has less information available. The Great Bend area, where the Chaco River turns from flowing west to flowing north toward the San Juan, also shows this pattern. The possible use of the river as a corridor for populations migrating from the north after the collapse of the Dolores villages makes this potentially an important area for understanding regional prehistory.

Chuska Mountains and Chaco River from Peñasco Blanco

The eastern flanks of the Chuska Mountains, which parallel the north-flowing segment of the Chaco River and form the western side of its drainage basin, are also important for understanding Pueblo I settlement but are poorly known. The general pattern seems to be the same as elsewhere in the Chaco Basin, with a scattered occupation in early and middle Pueblo I that sees a huge increase, presumably from immigration, in late Pueblo I after AD 875, but due to depositional factors it’s likely that the earlier Pueblo I occupation has been underestimated. A few sites dating to this period have been excavated through salvage projects. Late Pueblo I sites are more common and seem to provide more evidence for the use of the river as a corridor from the north. The largest concentrations are in the Skunk Springs and Newcomb areas, both of which would become major Chacoan outlier communities in Pueblo II. At Newcomb, at least, there seems to be some evidence of a preexisting Pueblo I occupation. It’s not clear if there is any similar evidence at Skunk Springs, where the earliest stage of construction on the great house seems to date to late Pueblo I. Given the importance of Chuskan imports to Chaco at its peak, more research on the background of these communities would be helpful in understanding Chaco’s origins.

The Red Mesa Valley

The Red Mesa Valley is the area between the Dutton Plateau on the north and the Zuni Mountains on the south. It is topographically rather than hydrologically defined, and straddles the Continental Divide, with the western part drained by the Rio Puerco of the West and the eastern part drained by the Rio San Jose. This means it falls outside of the “Chaco Basin” as hydrologically defined, of course, but its culture history means that it makes sense to include it with areas to the north for purposes of this chapter. This valley was presumably an important travel corridor prehistorically, as it certainly was historically with the railroad and Route 66 running through it and remains today with Interstate 40.

Casamero Pueblo

This area has been the main focus of Van Dyke’s research, and it is clear that she rather than Windes is responsible for most of this section of the chapter. The same issues of ceramic identification as in the Chaco Basin make understanding the Pueblo I sequence here difficult, but the same basic pattern appears to apply as further north. Early in Pueblo I there was a small, scattered occupation, exemplified by a site on the mesa above the later Chacoan outlier community of Casamero. This site consists of at least two arcs of surface rooms fronted by five to seven pit structures, and resembles White Mound Village further west along the Puerco, which was excavated by Harold Gladwin in the 1940s and dates to the late 700s and early 800s. Another site like this from the same period was excavated near Manuelito during the construction of I-40 in 1961.

This sparse population expanded immensely in late Pueblo, when many of the later Chacoan great house communities were founded. Some of the earliest great house construction in the region took place in these communities, which Van Dyke has elsewhere used to argue that great houses were not initially associated particularly with Chaco Canyon specifically. The huge increase in population at this time seems to indicate immigration, but this chapter doesn’t address the issue of where the people in this area might have come from. Given the similarities to the communities to the north in the Chaco Basin, that seems like an obvious point of origin (with earlier origins probably further north in the Mesa Verde region), but developments to the south are poorly understood and can’t be ruled out as important factors. As noted above, some of the immigrants to Chaco Canyon and its surrounding area appear to have come from the south rather than the north, and southern origins would presumably be even more likely for the Red Mesa Valley populations given their location. The fact that the influx here appears to happen at the same time as the northern one is an interesting complication, however.

The Eastern Chaco Basin

This area, stretching from the area south of Chaco Canyon across the Continental Divide to the Rio Puerco Valley of the East, shows very little evidence for Pueblo I occupation. Today this is a very sparsely populated area used mainly for cattle ranching, primarily on private land, so there has been little archaeological survey, but what survey has been done shows very little prehistoric occupation at all. Only two exceptions are noted by Windes and Van Dyke. One is a recently discovered Pueblo I community southeast of Mt. Taylor, about which little is known. Detailed information from the survey that identified this community is apparently not going to be released. It’s not clear from the brief writeup if this has anything to do with the fact that the survey was for proposed uranium mining.

The other exception is the Puerco Valley of the East, around the later Chacoan outlier of Guadalupe. Here, survey by Eastern New Mexico University in the 1970s identified a “modest but scattered” Pueblo I occupation, which increased substantially in late Pueblo I and Pueblo II, culminating in the Guadalupe community with its apparently close connections to Chaco Canyon. Windes and Van Dyke note that the Puerco may have served as an important conduit connecting the Chaco Basin to areas further east, although it remains poorly understood. The eastern associations of Chaco are poorly understood in general, and this appears to be the case as much for Pueblo I as for Pueblo II.

Storm in the Distance through Fajada Gap

After going through the detailed geographical summaries, the authors briefly address some region-wide issues important for understanding the patterns they describe. They acknowledge environmental factors as probably important in understanding population shifts, pointing in particular to an apparent “spike” in rainfall in the immediate area of Chaco Canyon between AD 885 and 905 that might have served as a “pull” factor bringing people in from other areas. Conditions in the Chuskas and Red Mesa Valley appear to have been generally unfavorable during this period in which they, too, saw significant immigration, so clearly rainfall totals weren’t the only factor.

They also discuss violence, noting that there is very little evidence for it in this region, particularly in the central Chaco Basin, during Pueblo I, especially compared to areas further north where burned structures are common. There are more burned structures in the Chuskas and near Mount Taylor, on the edges of this region, however, and it is possible that the lack of them in the central basin relates more to the lack of construction wood than to any lack of violence. The authors suggest that, given the known evidence for strife and community abandonment in the Mesa Verde region, one attraction of the Chaco Basin might have been its relative emptiness, which may have drawn people into this much harsher and less fertile region. There’s a general tendency for settlement to cluster around drainages and particularly at  confluences of drainages, likely because these locations offered the best agricultural potential in a very dry area even by Southwestern standards. Regardless of what it was that initially drew people into this area, it’s becoming increasingly clear that this influx of population was a key factor in the later rise of Chaco.

Peñasco Blanco Framing Huerfano Mesa

The authors also discuss visibility and sacred geography, which has been a key concern of Van Dyke’s in her previous work. Many of the prominent community buildings in late Pueblo I sites in this region, whether or not they can be considered “great houses,” are situated in locations where important regional landmarks can easily be seen. This indicates that the concern with visibility associated with later Chacoan great houses likely had its roots in this period.

Finally, the authors summarize community settlement patterns in the region. One interesting pattern they note is that in late Pueblo I communities great houses and great kivas don’t tend to occur together, with great houses being more common in the Chaco Basin and great kivas in the Red Mesa Valley. This suggests that two different community integration systems may have been in place in the region during this time. The great house pattern at more northerly sites is interesting in the context of the “proto-great-houses” apparently present at some Dolores area communities further north, especially McPhee Village, and it’s quite likely that there is a direct connection between the two. Great kivas are also common further south, and while they were present at some Mesa Verde Pueblo I sites they weren’t very common. This suggests that at least some of the Red Mesa Valley late Pueblo I communities were in fact settled by immigrants from the south rather than from the Chaco Basin. Some of the earliest communities showing both features were in Chaco Canyon, and it may well be that one factor in the rise of Chaco was the ability of emerging elites there to combine the two traditions into a new social and ideological system, one that would spread far and wide, remaking the course of Southwestern prehistory.

Great Kivas A and Q, Pueblo Bonito

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Orientation and Identity

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

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

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

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.

Malville JM, & Munro AM (2010). Cultural Identity, Continuity, and Astronomy in Chaco Canyon Archaeoastronomy, 23, 62-81

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The Evidence from DNA in the Southwest

Old Bonito from Above

Having introduced the basics of archaeological use of DNA evidence, and discussed some other applications of DNA studies in archaeology, let’s take a look at the data relevant to the Southwest specifically. For modern populations in North America overall, there are some broad trends that have been identified in mitochondrial haplogroup distribution by region, as first elucidated by Joseph Lorenz and David Glenn Smith of UC Davis in 1996. They only looked at haplogroups A, B, C, and D, since haplogroup X had not yet been identified as a founding haplogroup at that time. Their results showed that there are definite patterns in haplogroup distributions by region. For the Southwest specifically, they found most groups showed very high levels of B and low levels of A, despite the fact that A was the most common haplogroup in their sample overall. The main Southwestern groups that showed high levels of A were the Athabascan-speaking tribes (Navajo and Apache), which is unsurprising since northern Athabascan groups, along with most other groups in the Arctic and Subarctic, are almost exclusively A, and it’s well established that the southern Athabascans immigrated into the Southwest from the north relatively recently. Some other Southwestern groups show some representation of A as well, which Lorenz and Smith attribute to intermixing with the Athabascans (although as I’ll discuss below this doesn’t seem to be the whole story). Similarly, the Navajos and Apaches showed substantial representation of B and C, unlike their northern cousins, and this is probably due to intermixing with the Pueblos and other Southwestern populations.

A subsequent study by Smith, Lorenz, and some of their students at Davis looked specifically at haplogroup X, which had been identified in both modern and ancient Native American samples by then and was established as a founding haplogroup. They found it widely distributed among modern populations speaking a variety of languages but particularly among speakers of Algonquian and Kiowa-Tanoan languages. The Kiowa-Tanoan connection is of particular interest for Southwestern purposes, of course, as this is one of the main language families spoken by the eastern Pueblos in New Mexico. In this case, haplogroup X was found in the Kiowa and Jemez samples. This is very interesting since the Jemez are Pueblo and the Kiowa are not, and the relationship between the Kiowa and the Tanoan-speaking Pueblos is a longstanding mystery. It’s hard to know how to interpret the haplogroup X data in this connection. Since X is so rare overall the fact that it is so concentrated in certain groups seems meaningful somehow, but since it’s still pretty rare in those groups and little follow-up research on this has since been done it remains quite mysterious.

Turning to the ancient evidence, the first work in the Southwest was associated mostly with the University of Utah. In 1996 Ryan Parr, Shawn Carlyle, and Dennis O’Rourke published a paper reporting on aDNA research on the remains of 47 Fremont individuals from the Great Salt Lake area, 30 of which could be assigned to a haplogroup. The Fremont have always been something of a mystery, with many Southwestern cultural features but living on the northern fringes of the Southwest and having some notable differences from Pueblo cultures to the south. What the Utah researchers found, however, seemed to show the Fremont patterning genetically with the Pueblos rather than with other groups in the Great Basin or Plains. Haplogroup A was completely missing from their sample, while B was by far the most common haplogroup and C and D were also present in small numbers. This seems to clearly rule out one theory about the Fremont, which is that they were composed in part of Athabascans on their way south from the Subarctic, and also casts in serious doubt other theories linking them to later cultures on the Plains (where haplogroup A is also very common). It’s true that there is internal cultural variation within the construct “Fremont” and it’s quite possible there was genetic variation as well, but the Great Salt Lake Fremont were the furthest north of the identified subdivisions and the closest to the Plains, so if even they show more genetic similarities to the Southwest that is strong evidence against theories associating them with areas to the north and east.

It’s also noteworthy that the Fremont distribution is in contrast to what Lorenz and Smith found among modern Numic peoples who now occupy the Fremont’s Great Basin home. The Numic Paiute/Shoshone sample that Lorenz and Smith looked at lacked haplogroup A, but it showed a very high proportion of haplogroup D (the highest in their whole study, in fact) and a low proportion of B and C. This doesn’t totally rule out some Fremont contribution to Numic ancestry, but it makes it seem unlikely that there was substantial genetic continuity between Fremont and Numic populations, which supports the “Numic Expansion” hypothesis for the late prehistory of the Great Basin. Smith and his student Frederika Kaestle later published a paper making this exact argument, using not only the Fremont data but additional ancient remains from the western Great Basin to argue that the differences in haplogroup frequencies supported a replacement of the earlier Basin inhabitants by the Numa.

Following up on this research, a subsequent paper by the same Utah researchers added in data from the Anasazi. They successfully assigned 27 Anasazi samples to haplogroups. Of these, 12 were from southeastern Utah, 9 were from Canyon del Muerto, 4 were from Canyon de Chelly, and 2 were from Chaco Canyon. Of the Chaco remains, one came from the debris in Room 56 at Pueblo Bonito, a part of the north burial cluster in Old Bonito which was very crudely worked over by Warren K. Moorehead in the 1890s. The other I can’t seem to find any specific information on. All of the Anasazi remains analyzed in this study were from the collections of the American Museum of Natural History, which makes me surprised that only two Chaco samples were involved. It’s possible that more were analyzed but only these two produced enough DNA to work with. In any case, if in fact there are more Chaco remains at the AMNH that have not yet been analyzed for DNA it would be very helpful to analyze them.

The results of this analysis were consistent with the standard archaeological understanding that the modern Pueblos are the descendants of the Anasazi. B was the most common haplogroup, with smaller levels of A and C. D wasn’t present at all, and two of the specimens didn’t fall into any of the four haplogroups, implying that they might have belonged to X. (The two Chaco samples belonged to haplogroups B and C; the sample from Room 56 belonged to haplogroup B.) Note that A is present here in populations dating well before any likely admixture with Athabascans, which is evidence against Lorenz and Smith’s contention that the presence of A in modern Pueblos can be attributed entirely to mixture with Athabascans.

Based on the dominance of B and low levels of other haplogroups, these researchers concluded that the Anasazi remains they analyzed were not significantly different from the Fremont remains they had analyzed earlier, adding further support to their contention that the Fremont pattern with the Pueblos. Note, however, that the Fremont hadn’t shown haplogroup A at all, while the Anasazi had it at a low but still respectable level (22%). Also, the Fremont showed a low level of haplogroup D, which the Anasazi didn’t have at all. These differences don’t necessarily mean the Fremont and Anasazi weren’t related, of course, but they do show how much that similarity is a judgment call supported by questionable statistics. In this case one big problem with the statistical analysis was treating the haplogroup frequencies as ratio-level data, which implies that they are meaningfully representative of the underlying populations despite the very small and non-random samples. This is highly implausible. This problem means that the authors’ conclusions about whether differences between samples were “significant” or not in a statistical sense is not really meaningful since it can’t reasonably be expected to generalize to the populations, which are what we really care about.

In addition, as Connie Mulligan pointed out in the general paper on aDNA that I discussed previously, the differences that the Davis researchers found between the haplogroup frequencies of the Fremont and Numic samples, which they used as evidence of a lack of population continuity, were actually quite similar statistically to the differences the Utah researchers found between the Fremont and Anasazi, which they interpreted as not being significant! This disconnect goes to show that there’s actually quite a bit of subjective judgment in interpreting results like this, despite the superficial impression of “objective” statistical data.

One way to overcome this confusion would be to increase the number of samples analyzed and try to make them as close to representative of the underlying populations as possible. That would certainly help, but the fundamental problem of defining the ancient population of interest, and the apparent impossibility of analyzing a sample from it that could be assumed to be truly representative, are daunting challenges. A more productive approach, which subsequent research has in fact been following, is to do more in-depth analysis of available samples, so that more detailed data than crude haplogroup assignments are possible.

One way to do more in-depth analysis would be to move away from relying exclusively on haplogroup assignments and look instead at the nuclear genome. Sequencing the whole nuclear genome provides vastly more, and more statistically robust, information than mitochondrial haplogroup assignment, as commenter ohwilleke pointed out in response to my initial DNA post. Most of the studies mentioned in my previous post in other parts of the world have used this methodology, with very informative results. This type of analysis has, however, not been done on ancient remains from the American Southwest to my knowledge. I’m not sure why exactly, but there are various reasons including cost and level of preservation of remains that could account for this lacuna.

Instead, Southwestern researchers have mostly doubled down on mitochondrial haplotype analysis and extended its reach by looking at further mutations within the defined haplogroups to identify sub-haplogroups that can further narrow down genetic relationships. This has been a productive line of investigation, as exemplified by a very interesting paper from 2010 dealing with Chaco-era sites in the area of Farmington, New Mexico.

B-Square Ranch, Farmington, New Mexico

The paper, by Meradeth Snow and David Glenn Smith of Davis and Kathy Durand of Eastern New Mexico University, analyzed human remains from two sites on the B-Square Ranch, a large ranch that includes most of the land south of the San Juan River in Farmington. The ranch is owned by the Bolack family, which has long been prominent in local and statewide affairs. Its patriarch for many years was Tom Bolack, who was governor of New Mexico for a brief period in the 1960s and was also well known for his elaborate produce displays at the State Fair. His son Tommy Bolack, who took over management of the ranch when Tom died, has long had an interest in archaeology and did his own excavations in various of the many archaeological sites on the ranch. In recent years rather than continuing his own excavations he has worked with Linda Wheelbarger, a professional archaeologist who teaches at San Juan College in Farmington, to conduct field schools in the summers for SJC students as well as analyses of artifacts and human remains from both these recent excavations and his own earlier amateur work.

Among these analyses was the aDNA analysis of remains that Bolack excavated from the Tommy and Mine Canyon sites, two small-house sites on the ranch dating to the Chaco era. The Tommy site is slightly earlier, dating to approximately AD 800 to 1100, while the Mine Canyon site dates to approximately AD 1100 to 1300. Since the Tommy site seems to have been abandoned at approximately the same time the Mine Canyon site was founded, one obvious interpretation is that the Mine Canyon site was founded by the same people who had previously lived at the Tommy site. The DNA evidence, however, challenges this interpretation and suggests a more complicated story.

For this study, 73 samples were sent to Davis for aDNA analysis. This included a mix of tooth and bone samples. Of these samples, 48 (65.7%) could be assigned to a mitochondrial haplogroup. Of these, 26 were from the Tommy site and 12 from the Mine Canyon site.

The successfully analyzed samples from the Tommy site showed a typical distribution of haplogroups for a Southwestern population: 3% A, 69% B, 14% C, and 14% D. (This study didn’t look for haplogroup X, and all successfully analyzed samples fell into one of the other founding haplogroups.) The Mine Canyon sample, however, showed a very unusual distribution: 58% A, 33% B, 8% C, and 0% D. This is an exceptionally high proportion of haplogroup A, which is generally fairly rare in the Southwest except in Athabascan groups which are generally thought to have arrived in the region well after these sites were abandoned. Haplogroup A is also very common in Mesoamerica, which makes its dominance in a Chaco-associated site particularly intriguing given the evidence for contact with Mexico seen at Chaco Canyon itself and some outlying Chacoan sites.

The authors are careful to note that these are very small sample sizes, which makes sampling bias a very real possibility to account for this sort of striking result. They compare these distributions to several other ancient and modern Southwestern and Mesoamerican populations using Fisher’s exact test and find, unsurprisingly, that the Tommy site sample isn’t significantly different from other ancient Southwestern populations but is significantly different from all the modern populations as well as the ancient Mesoamerican ones. The Mine Canyon sample, on the other hand, was found to be significantly different from all the ancient Southwestern samples as well as all the modern Southwestern ones except the Athabascan Navajo and Apache, while it wasn’t significantly different from any of the ancient or modern Mesoamerican samples. This result is clearly driven primarily by the unusually high proportion of haplogroup A at Mine Canyon, which means it doesn’t really add much to the paper. Although Fisher’s exact test does take into account the small sample sizes, it doesn’t address the more fundamental problem with this sort of use of statistics on this type of data which can’t really be trusted to be representative of the underlying population of interest. This is the sort of thing I was talking about in the earlier post under the somewhat tongue-in-cheek label of “elaborate statistical techniques” on data that don’t necessarily fit the necessary requirements for their use. This sort of technique is not actually very elaborate compared to more sophisticated statistical analyses used for studies of whole genomes, where the number of data points is immense and they can actually be assumed to be representative of the analyzed individual’s full ancestry. Calculating P-values for differences between two samples based on four data points for each, when neither sample is necessarily representative of its underlying population of interest, is not very useful, but very common in mtDNA studies at least in the Southwest. To their credit, the authors of this paper are well aware of the weaknesses of this part of it and are careful to downplay the significance of the statistical analysis.

With these intriguing preliminary results, the researchers attempted further sequencing to identify more specific mutations that might define sub-haplogroups and clarify relationships on a more granular scale. Of the 48 samples that could be assigned to haplogroups, 23 were successfully sequenced for mutations in a region of the mitochondrial genome known to be highly variable. (Note how small the sample gets with subsequent levels of analysis.) Poor preservation was a major problem at this point, and there wasn’t enough genetic material remaining to construct the sort of network diagram that is often included in papers like this, showing specific mutations and the relationships they imply between specific ancient and modern samples.

The most interesting results from this further sequencing were with haplogroup A. Of the 8 samples initially identified as belonging to this haplogroup, 6 samples from the Mine Canyon site showed two distinctive mutations that are otherwise known only from 3 modern Zuni samples, along with one Tohono O’odham and one Chumash sample. Importantly, this set of mutations is unknown from both Mesoamerican and Athabascan groups. This is strong evidence that the dominance of haplogroup A at the Mine Canyon site does not indicate either migration from Mesoamerica or an early Athabascan presence in the Southwest; instead, it seems that this site just happens to have had an unusually high proportion of a rare but natively Southwestern lineage which survived into modern times at Zuni (and may have had some connections further west). The samples belonging to haplogroup B similarly showed the dominance of a sub-haplogroup distinctive to the Southwest and unknown in Mesoamerica.

The differences between the Tommy site and the Mine Canyon site in haplogroup frequencies, while they may well be a function in part of the small sample sizes, may also provide evidence for complex population movements within the late prehistoric Southwest. The exact parameters of these movements can’t be defined until more evidence is available from other areas, however, especially Chaco Canyon and the Mesa Verde region.

Overall, despite the poor preservation of the samples involved, this study provides important support for a finding that has come out consistently across all lines of evidence relating ancient to modern Pueblo people: there is a lot of evidence for continuity over time on a regional scale with complex movements within the Southwest, but little to no evidence of significant population movement into or out of the Southwest in recent centuries. (There is a whole other debate about the extent of population movement into the Southwest much earlier, at the time when agriculture was first introduced, which I haven’t discussed much in these posts and which isn’t of much importance for the specific issue I’m addressing here.) I think there is a lot of potential for more detailed reconstruction of movement within the Southwest based on a combination of lines of evidence, but we’re certainly not there yet.

I’ve gotten some questions about how the DNA evidence relates to the issue of hierarchy at Chaco. I’ll have a more extensive post on the evidence for social hierarchy, which I think is extensive, but the short answer is that DNA doesn’t really provide any evidence one way or the other on this point. Since all evidence points to a general pattern of population continuity in the Southwest at least since the introduction of agriculture, the genetic patterns of any elites that arose wouldn’t be likely to differ in any noticeable way from those of the commoners they rose from. Indeed, the one sample to be analyzed for mitochondrial DNA that is very likely to come from an elite Chacoan context, the sample from Room 56 at Pueblo Bonito, belonged to haplogroup B, the most common in both ancient and modern Southwestern populations. It’s theoretically possible to imagine an elite group immigrating into the Southwest from Mesoamerica, and theories have been proposed along these lines, but the DNA evidence doesn’t particularly support this, and it’s much more likely based on all lines of evidence that the rise of an elite at Chaco was a primarily indigenous development involving some indirect influence from Mexico but little to no permanent population movement over that distance.

This is the last substantive post in my series about “tracing the connections” between the ancient and modern Southwest, although I will probably do a follow-up post linking to all the others for the convenience of readers. Overall, I think these posts have shown that we have substantial evidence from various perspectives that the modern Pueblos are the descendants of the ancient Anasazi (and other prehistoric Southwestern groups), but the evidence we have so far is not sufficient to connect any specific ancient sites with any specific modern pueblos. I am hopeful, however, that that may change as more evidence comes in and we are able to tie together new data with the evidence we already have to make some more specific connections.

Carlyle SW, Parr RL, Hayes MG, & O’Rourke DH (2000). Context of maternal lineages in the Greater Southwest. American journal of physical anthropology, 113 (1), 85-101 PMID: 10954622

Kaestle FA, & Smith DG (2001). Ancient mitochondrial DNA evidence for prehistoric population movement: the Numic expansion. American journal of physical anthropology, 115 (1), 1-12 PMID: 11309745

Lorenz JG, & Smith DG (1996). Distribution of four founding mtDNA haplogroups among Native North Americans. American journal of physical anthropology, 101 (3), 307-23 PMID: 8922178

Smith DG, Malhi RS, Eshleman J, Lorenz JG, & Kaestle FA (1999). Distribution of mtDNA haplogroup X among Native North Americans. American journal of physical anthropology, 110 (3), 271-84 PMID: 10516561

Snow, M., Durand, K., & Smith, D. (2010). Ancestral Puebloan mtDNA in context of the greater southwest Journal of Archaeological Science, 37 (7), 1635-1645 DOI: 10.1016/j.jas.2010.01.024

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The Stars Bursting in Air

"Supernova" Pictograph

Happy Fourth of July, everyone.  The Fourth is actually a pretty important date for the study of Chaco, but in a roundabout (and somewhat controversial) way.  It all has to do with a very famous pictograph panel below Peñasco Blanco at the west end of the canyon.  While the interpretation of this panel is a matter of considerable debate, one way it’s been seen is as a record of an astronomical event that is known to have occurred during the height of Chaco’s power and influence: the supernova of 1054, which formed the Crab Nebula.

We know from several Chinese reports that the “guest star” resulting from the supernova first appeared on July 4, 1054 and continued to be visible day and night for almost two years.  There are a few Japanese records of the supernova as well, along with one report from the Arab world.  No clear-cut and unambiguous accounts are known from Europe or elsewhere in the world, although a few rock art panels in the Southwest have been proposed as representing the event.  The most famous of these is the one at Chaco, which is often referred to as the “Supernova Pictograph” (even by the park itself in a sign at the site).  It consists of three symbols painted onto the rock face in red: a hand, a crescent, and a starburst-like shape.  It’s the starburst that has been interpreted as representing the supernova itself, of course, and the crescent has been seen as representing the crescent moon.  On the morning of July 5, the moon, which was a crescent at the time, would have appeared in roughly the same relationship to the supernova, as seen from the pictograph site, as the relationship between the two symbols on the panel.  Furthermore, the handprint points in the direction one would have looked to see this at at the time.  The combination of the three symbols together, plus the fact that this would have happened at a time of considerable activity in the canyon, has led some to suggest that this pictograph panel was created to commemorate this historic event.  The specific location may have been an established sun-watching position, from which the new star was seen unexpectedly and recorded.

Sign at the "Supernova Pictograph"

It all sounds fairly plausible as it goes, but there are some problems with this theory.  Probably the biggest problem is that the specific set of symbols on the panel is known from ethnographic evidence to have been used by the Zunis to mark generic sunwatching sites, with the crescent representing the moon, the starburst representing the sun, and the hand marking the location as sacred.  Now, it’s certainly possible that these symbols came to be associated with this activity as a result of the observation of the supernova at this site, but as far as I know there’s no reference to the supernova in ethnographic descriptions of astronomical observation at Zuni or any of the other modern Pueblos, so this is a pretty tenuous claim.

Furthermore, while the 1054 supernova would certainly have been noticeable at Chaco, there was an earlier supernova in 1006 (also recorded by the Chinese, and possibly by the Hohokam in southern Arizona) that was much brighter, and it’s not clear why the Chacoans wouldn’t have recorded that one too.  It took place before the Chaco system really got going on a regional scale, but there was plenty of activity in the canyon during the 900s, so people there would presumably have seen it.  It’s possible that it was recorded too, at some other site that hasn’t been found or that has disappeared in the thousand years that have elapsed since the event (note that the existing Supernova Pictograph has only survived because it was under a protective overhang), but again, there’s not any evidence for this.  The Chacoans are definitely known to have kept careful track of regular patterns in the skies, such as the solstices and the lunar standstills, so they surely would have seen unusual events such as supernovae, but it’s not clear how they would have reacted to them or how inclined they would have been to record them.

View Looking East from "Supernova Petroglyph"

So it’s not really clear how to interpret the Chaco pictograph.  I think the balance of evidence at this point leans slightly against it being a representation of the supernova, but I could be talked out of that position if some additional evidence for the supernova theory can be found.

Others, however, have proposed even more extreme theories based on the 1054 supernova.  Among the more noteworthy of these is a proposal by Timothy Pauketat and Thomas Emerson, in a 2008 article in the Cambridge Archaeological Journal, that the rather sudden florescence of the Cahokia site in Illinois around AD 1050 may have had something to do with the supernova.  The theory they present is interesting, but hard to effectively support.  For one thing, dating methods in the Midwest are much less precise than in the Southwest, so pinning down any event to the year is usually not possible.  There is certainly a suggestive correspondence between the sudden rise of Cahokia and the supernova, however, and this is supported by the apparent use of stellar imagery and symbolism at Cahokia and the importance of the stars to later cultures in the area, so there may well be something to this.

Opening at Casa Rinconada That Channels Sunbeam at Sunrise on Summer Solstice

I’m a bit troubled, however, by the reliance of Pauketat and Emerson on evidence from Chaco and the way they interpret it.  For one thing, they say that the Supernova Pictograph is “above” Peñasco Blanco, when it’s actually below it, and not visible from the great house itself.  More importantly, they say of the effect of the supernova:

Some believe that this particular cosmic event, which left behind the Crab Nebula, was commemorated in architecture and iconography at the time or in subsequent years. The most compelling evidence for this comes not from the Cahokia region but from the American Southwest, where a tree-cutting date places the construction of the largest and most isolated ceremonial building in Chaco Canyon, Casa Rinconada (noted for its many astronomical alignments) to AD
1054.

Now, it’s true that there is a single tree-ring cutting date from Casa Rinconada that dates to 1054.  This is, however, the only tree-ring date for the site, so while it’s plausible that it dates the construction of the site this definitely cannot be stated as definitively as Pauketat and Emerson state it here.  There is no specific provenience information available for this beam, so there’s no way to tell how it was used and whether it can plausibly be said to date to the initial construction of the site.  The general architecture of Casa Rinconada is consistent with a construction date in the 1050s, but without more specific information tying it to a specific year on the basis of one unprovenienced beam is unwarranted.

Looking through Solstice-Aligned Opening at Casa Rinconada toward Aligned Niche

Furthermore, even if Rinconada was built in 1054, that doesn’t establish that it was built because of the supernova.  There was extensive construction in the canyon throughout the mid-1000s, associated with Chaco’s apparent rise to regional dominance, and this began well before 1054.  The major expansion of Pueblo Bonito began by the 1040s at the latest, and various other construction projects at other sites in the canyon dates to this general period.  Rinconada could easily have been part of this general process without any specific relationship to the supernova.  Indeed, there’s nothing about Rinconada that seems to refer to the supernova, despite the various astronomical alignments (some of them controversial as well, it should be noted) identified there.

None of this means that the supernova didn’t have an important role at Cahokia, of course, and it doesn’t even rule out an important role at Chaco itself.  It does mean, however, that developments at Chaco shouldn’t really be used as evidence for developments at Cahokia, even though the two sites are contemporaneous and Chaco can be dated much more precisely.  Cahokia may well have risen as a result of the 1054 supernova, but neither the Supernova Petroglyph at Chaco nor the one tree-ring date at Casa Rinconada provides evidence that it did.

Pauketat, T., & Emerson, T. (2008). Star Performances and Cosmic Clutter Cambridge Archaeological Journal, 18 (1), 78-85 DOI: 10.1017/S0959774308000085

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An Interesting Macaw-Related Fact

Room 38, Pueblo Bonito

In a recent post, I noted the limited distribution of macaw remains within Pueblo Bonito.  While this site has a much higher number of macaws than any other Chacoan site, and more than almost every other site in the prehistoric Southwest, within the site macaw remains were highly concentrated.  All macaws were found in the eastern half of the site, and most were in the eastern part of “Old Bonito” at the northern end of the overall site, particularly in Room 38, which had twelve.  This suggests to me that macaws were closely associated with whatever social group lived in or used that part of Pueblo Bonito.

It’s hard to say what that social group was, but it’s possible that the burials in a complex of four rooms in the northern part of Old Bonito were associated with it.  Associating these burials with the eastern rooms in Old Bonito is perhaps a bit of a stretch, since the burial rooms are actually in the western half of the Old Bonito arc, but they’re just barely on the west side, and there is a separate set of burial rooms at the far western end of Old Bonito that could be plausibly associated with whatever social group lived in or used those rooms.  There is no equivalent set of burial rooms in the eastern part of the arc, although there are a few isolated burials of infants and fetuses.  (Two of the infant burials, in Rooms 306 and 309, were associated with macaws.)  The eastern end of Old Bonito was covered over by later construction and is poorly known, but there is no evidence that it ever held a mortuary complex comparable to the one at the western end.  Given the circumstances, I think it’s plausible that the northern burial complex was associated with the group (or one of the groups) associated with the eastern part of Pueblo Bonito, perhaps in addition to the group associated with the immediately adjacent room suite at the west end of the northern part of Old Bonito, if this was indeed a different group.

Western Burial Rooms in Old Bonito

Analysis of the Pueblo Bonito burials by Nancy Akins for the Chaco Project found that, judging from cranial attributes, the northern and western burial groups were distinct from each other but internally homogeneous.  This suggests that they probably represented kin-based social units, and that the site consisted of at least two of these units, perhaps occupying or using different areas.  Akins couldn’t find a very large sample of burials from other sites in the canyon for comparison, but she was able to compare burials from three small sites in the canyon.  One of these, Bc 59, is across from Bonito on the south side of the canyon near Casa Rinconada, while the other two, 29SJ299 and 29SJ1360, are in Fajada Gap, a few miles east and the location of a substantial community of small houses and two great houses (Una Vida and Kin Nahasbas) in close proximity to Fajada Butte.

While the two burial populations in Pueblo Bonito weren’t particularly similar to each other, they more closely resembled the small site samples.  Specifically, the western burial population was similar to the one from Bc 59, while the northern burial group was more similar to the Fajada Gap group.  Importantly, the two Bonito groups were both more similar to these small-house populations than they were to each other.  This suggests that kinship connections among different sites in the canyon were complicated and didn’t break down on straightforward great house v. small house lines.

Bc 59 from Casa Rinconada

What does all this have to do with macaws?  Well, there is only one small house site at Chaco (as far as I know) that has produced macaw remains, and that site is… 29SJ1360, one of the sites with burials that patterned with the northern burial group at Bonito!  As reported by Peter McKenna in his report on this site, which was excavated by the Chaco Project, a few macaw bones were found in the fill from one of the pit structures.  While there were only a few bones found, they were all unique, suggesting the presence of only one macaw, and from various parts of the body, suggesting that the whole macaw was present.  This fill was only casually screened for artifacts and was later used to backfill the pit structure, so the rest of the macaw is probably still there.  This site also had an unusual architectural feature, a small bin attached to the outside of one of the roomblocks, that according to McKenna looked “remarkably like a parrot bin.”  One important feature that appears to have led to this conclusion was the presence of an adobe “plug” in the north wall, presumably reminiscent of the stone plugs used with “cage stones” at macaw pens at Casas Grandes, where there is substantial evidence for the keeping and breeding of macaws a few hundred years later.

This is all pretty tentative, of course.  Very few sites at Chaco have been excavated, so we have very little sense of the overall distribution of rare finds such as macaw remains.  Still, two separate lines of evidence (biological relationship and association with macaws) seem to point to a strong connection between the northern/eastern part of Pueblo Bonito and at least some sites in the Fajada Gap community, which is not particularly close to Bonito.  Given the rarity of macaws, especially, this seems significant.

Fajada Butte with Green Vegetation

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Chaco before Chaco: The Basketmaker III Period

Basketmaker Pithouse, Mesa Verde

The Basketmaker III period (ca. AD 500 to 750) is a very important time for understanding the prehistoric Southwest.  Maize agriculture had been introduced earlier, although exactly how early is still a matter of debate, and it was definitely well-established by the immediately preceding Basketmaker II period, but Basketmaker III saw the introduction of beans, pottery, and the bow and arrow, all of which led to major changes in the lifestyles of local agriculturists.  Residence was in pithouses, which are clearly ancestral in form (and probably in function) to the “kivas” of later sites, and while these are usually found isolated or in very small groups, there are a few known examples of large “villages” containing dozens of pithouses.  The processes that led to the formation of these sites, as well as their relationships to the more common isolated sites, are very poorly understood, but it seems pretty clear that residential aggregation in certain locations during this period set the stage for the later formation of large villages during the succeeding Pueblo I period and afterward.

Two of the largest and best-known Basketmaker III villages are in Chaco Canyon.  The better-known of these, by far, is called Shabik’eschee Village, and it is located on the lowest terrace of a finger of Chacra Mesa at the east end of the current Chaco Culture National Historical Park.  Shabik’eschee was excavated by Frank H. H. Roberts in the 1920s as part of the Smithsonian/National Geographic project led by Neil Judd.  The main focus of the project was the excavation of Pueblo Bonito, but Judd had other members of the team, including Roberts, excavate several other sites in and around the canyon as well.  Roberts published his results in 1929, and this publication has been enormously influential in shaping subsequent interpretations of Basketmaker III villages and the period as a whole.

Looking South from Peñasco Blanco toward 29SJ423

The Chaco Project in the 1970s did some additional work at Shabik’eschee, as well as at the other Basketmaker Village in the canyon.  This site, known as 29SJ423, is just south of Peñasco Blanco at the far west end of the canyon, near the confluence of the Chaco and Escavada Washes.  It is situated in a similar location to Shabik’eschee, on a lower terrace of West Mesa (but above Peñasco Blanco, which is on the lowest terrace).  Tom Windes excavated a small portion of 29SJ423 in 1975, but he and other Chaco Project personnel soon came to the conclusion that additional excavation there would not be worth the considerable effort involved.  The collections from this excavation are important, however, since they were acquired using more careful, modern methods than Roberts’s.  Similarly, a very small amount of additional excavation at Shabik’eschee in 1973 has provided important supplemental information with which to evaluate Roberts’s interpretations.

Windes and Chip Wills published an article in 1989 looking back at Roberts’s interpretations at Shabik’eschee in the light of the additional knowledge gained by the Chaco Project excavations.  They concluded that some of Roberts’s ideas, such as his proposal that the site had two discrete periods of occupation separated by a hiatus during which it was abandoned, are likely untenable, and they also concluded that the site was considerably larger than Roberts thought.  They agreed with Roberts that some of the pithouses had been abandoned and their materials were used in subsequent construction, but they saw this as more of an ongoing process related to the short use-life of pithouses and the demands of demographic processes rather than a discrete series of two occupations.  They also saw more spatial patterning in the layout of pithouses within the site than Roberts did, suggesting that the pithouses grouped into what might be family residence units, although they were quite tentative in this finding and did not use these groups as units for any subsequent analysis.

Pinyon Trees, Pipe Spring National Monument

Wills and Windes also posited a novel interpretation for the site as a whole.  Rather than seeing it as a permanent agricultural village, they saw it as a site of occasional gatherings of more mobile families practicing a “mixed” subsistence strategy of small-scale agriculture along with hunting and gathering.  In their interpretation, a small number of families inhabited Shabik’eschee permanently, while others joined them periodically to take advantage of the site’s proximity to piñon woodlands in years with bountiful piñon-nut harvests.  They based this theory on the presence of two types of storage facilities at the site: household-level storage in the antechambers associated with some but not all of the pithouses (presumably the residences of permanent residents) and community-level storage bins scattered around the site.  The idea is that occasional surpluses of corn or whatever would be stored in the bins, and the people who lived at the site permanently watched over it and protected it.  Whenever there was a plentiful crop of piñon nuts, which happens at irregular intervals in the fall, people who lived the rest of the time in scattered locations throughout the area would congregate at Shabik’eschee to take advantage of this and stay for the winter.  If conditions in the spring were good for planting, people might stay longer and plant their crops in the area, but if not they would move on to more attractive planting locations.  Other pithouse villages, such as 29SJ423, would presumably have served similar purposes, allowing periodic aggregation to take advantage of various localized resources.

This is an interesting theory, but it’s based on exceptionally thin evidence.  Wills and Windes even concede that they are spinning this whole story purely from the nature of the storage facilities at the site, and they note that there are other ways to interpret the communal bins in particular.  Instead of protecting food stores during periods of reduced occupation, they may just have functioned to protect them in general.  The shape of the bins makes it more difficult to access their contents, which Wills and Windes interpret as evidence for a sort of semi-caching, but it would also just provide better protection from the elements, vermin, etc. for the contents.  Basically, there’s just no reason from the available evidence to buy the Wills and Windes theory.

"Pithouse Life" Sign at Mesa Verde

Indeed, the assumptions behind this theory seem problematic to me.  The ethnographic comparisons Wills and Windes use to support it are mostly from hunter-gatherer societies, and indeed their model seems to imply that the residents of Shabik’eschee were basically hunter-gatherers who did some farming on the side.  Such societies exist, and may well have existed at certain times in the ancient Southwest (such as the late Archaic), but recent studies have shown with increasing certainty that heavy dependence on agriculture was widespread already in the Basketmaker II period.  Wills and Windes seem to see the Basketmaker III inhabitants of the Chaco area as just beginning to experiment with adding agriculture to a hunter-gatherer lifeway, but it’s much more likely that they were full-time agriculturalists and had been for centuries.  They did of course still do some hunting and gathering, as their Pueblo descendants have continued to do up to the present day, but while this may in some sense qualify as a “mixed” economy that shouldn’t obscure the important fact that Pueblo societies have been overwhelmingly farming-based societies since well before the occupation of Shabik’eschee.

I think this interpretation, and others like it which were popular in Southwestern archaeology in the 1980s, results in part from the enormous influence of Lewis Binford on the development of processual archaeology.  Binford’s personal research and expertise were largely on hunter-gatherer societies, and the guidelines he set forth for “archaeology as anthropology” that were eagerly followed by young “New Archaeologists” were heavily influenced by that background.  Wills and Windes cite Binford several times in this article.

Excavating the Lift Station Site in the Chaco Maintenance Yard

Be that as it may, this is an important article just in providing an updated take on the facts about Shabik’eschee, which as Wills and Windes note has been very important in the interpretation of ancient societies generally.  It contains relatively little information about 29SJ423, but it does briefly discuss this site as a comparison.  It says even less about the much more numerous isolated Basketmaker III sites in the canyon, but it notes that Chaco Project surveys identified at least 163 pithouse sites from this period.  One that they didn’t find, because it was deeply buried under the ground, was later found by the park in the course of trying to build a lift station for the septic system.  This site, informally known as the Lift Station Site, is a Basketmaker III pithouse that was excavated while I was working at Chaco.  One of the more interesting things it revealed was an apparent location for pottery manufacture.

One of the major problems with trying to understand the Basketmaker III period at Chaco is precisely that the site are typically deeply buried, so it’s hard to even know how many of them there are.  It’s clear that this was a period of significant population in the canyon, but it’s hard to tell how many sites were occupied simultaneously.  This problem is exacerbated by the difficulty of dating many of the sites.  Tree-ring dates are often hard to obtain from the scarce wood found at excavated sites, and Shabik’eschee is particularly poorly dated.  The few tree-ring dates available seem to suggest it was occupied at some point after the mid-500s, but there are no cutting dates so any greater precision is impossible.  29SJ423 did produce two cutting dates, at 550 and 557, so it seems the two villages were most likely contemporaneous.  The isolated sites are even harder to date, of course, but the Lift Station Site produced corn that was radiocarbon dated.  I don’t know the dates that resulted, but I did hear that they were earlier than was expected based on the pottery types found.

Whole Pot from the Lift Station Site

The size of the Basketmaker III occupation at Chaco, and particularly the presence of the two large villages, has important implications for understanding the subsequent history of the canyon that I think are just beginning to be realized.  The local population seems to have declined during the subsequent Pueblo I period (ca. AD 750 to 900), when people seem to have begun to move in large numbers to higher elevations where they formed some really large villages.  However, it’s not clear that Chaco was completely abandoned during this period, and recent improvements in dating the early great houses in the canyon have shown that some of them, especially Pueblo Bonito, go back further than was once thought.  Pueblo Bonito is now known to have been begun no later than 860, and the earliest part of it may date much earlier, possibly to 800 or even before.  This means that the gap between the Basketmaker III villages and the earliest great houses suddenly looks a lot smaller, and may disappear entirely.  There are pithouses under the plaza at Pueblo Bonito that may date to very early Pueblo I or even Basketmaker III, and there is a small Pueblo I occupation at Shabik’eschee that dates as late as 750.  This suggests that these two iconic sites in Chacoan archaeology, generally interpreted in very different ways, may actually overlap in occupation.  This would require some serious modifications of the ways the origins of the Chaco system are often interpreted.

Chaco had been an important place for a very long time when it started to become a major regional center around AD 1040.  It’s looking increasingly plausible, though by no means certain, that it had been continuously occupied for 500 years at that point, and even if there was a brief gap between the Basketmaker III villages and the first Pueblo I great houses it is very unlikely that is was long enough for people to have forgotten about Chaco and what had happened there.  Even if many of the people who built and/or occupied the early great houses in the 800s hadn’t been born at Chaco, they probably knew it was there long before they made it their home.

Wills, W., & Windes, T. (1989). Evidence for Population Aggregation and Dispersal during the Basketmaker III Period in Chaco Canyon, New Mexico American Antiquity, 54 (2) DOI: 10.2307/281711

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