Archive for the ‘Research’ Category

Utah Welcome Sign

Utah Welcome Sign

The third chapter of Crucible of Pueblos deals with the western part of the Mesa Verde or Northern San Juan region, which basically corresponds to what is now the southeastern corner of Utah. In this context the area is bounded by Cedar Mesa on the west and the Abajo Mountains on the north, as well as by the borders with Colorado and Arizona on the east and south. This is a fairly standard way to define this area archaeologically except that the western boundary is more restrictive than usual, which appears to mainly be a decision based on the near-total lack of sites dated to the Pueblo I period west of the eastern edge of Cedar Mesa. (There are actually Pueblo sites dating to this period much further west in southwestern Utah and southern Nevada, the so-called “Virgin Anasazi,” but they aren’t included in this book at all for some reason.)

The authors divide their study area into a series of physiographic sub-regions based primarily on elevation, which is a useful way to track changes in occupation patterns over the course of the period they discuss. It’s also a different approach to defining sub-regions than most of the other chapters in the book use. These sub-regions are important because the differences in precipitation and growing season length among them seem to have been important factors behind shifting settlement patterns during the period of interest. These shifts seem to have mainly taken place across the region rather than separately in spatial sub-regions such as drainages, as was the case in some other regions.

One way this region differs from others, and especially from the Central and Eastern Mesa Verde regions, is that there has been a relative lack of large-scale salvage excavation projects to provide large amounts of detailed archaeological data. Instead, most data is from surveys and small-scale excavations, and detailed chronological information in particular is missing for most sites that have been recorded. Rough dating of sites to Pecos Classification period at best based on frequencies of a few ceramic types is the norm here, which limits the comparability of data on trends in settlement over time. Nevertheless, the authors of this chapter do their best to come up with a coherent narrative of settlement during the Basketmaker III and Pueblo I periods in this area, which seems to have been an important one for understanding the cultural development of early farming populations and the origins of aggregated villages.

The most striking pattern in the population dynamics of this region in the Basketmaker III and Pueblo I periods is of apparent cycles of population growth and decline on the scale of decades and of greater magnitude than can be explain by internal demographic processes, implying migration into and out of the region multiple times. Most interestingly, these cycles appear to be largely complementary to similar cycles in other nearby regions, especially the Central Mesa Verde region just to the east. This strongly implies that one of the major factors in population changes in both these regions was movement between them.

To go into greater detail, the story told in this chapter begins in the seventh century AD with the expansion of Basketmaker III populations across the region from the narrow area of Basketmaker II settlement along the San Juan River and its major tributaries. The authors attribute this expansion in part to the introduction of beans and pottery, which freed farming populations from dependence on outcrops of limestone to cook with their corn for nitrogen-fixing purposes. Population spread especially into the upland areas with deep soils well-suited to dry farming. Over the course of the Basketmaker III period scattered hamlets began to consolidate into “proto-villages” with public architecture such as oversized pit structures surrounded by scattered households. The authors note the similarity of this pattern to the later Pueblo II great house communities, which is indeed an interesting parallel.

There appears to have been a regional population decline in the early eighth century, although this may be an artifact of the limited data set and difficulty assigning sites to precise time periods. In any case, there is evidence of a noticeable population increase after AD 750, with several villages of tightly clustered households containing public architecture appearing, along with a considerable number of smaller residential sites and a few sites in highly defensive locations, especially at the western edge of the region near Cedar Mesa. The population increase was accompanied by the introduction of a strikingly different type of pottery, Abajo Red-on-orange, which shows many similarities to pottery from the Mogollon region far to the south and likely reflects long-distance migration of some sort. There were still many continuities in architecture and other aspects of material culture, however, which suggests that these migrants combined with local populations rather than replacing them.

The largest and most famous of the villages that developed during this early Pueblo I period is Alkali Ridge Site 13, excavated by J. O. Brew in the 1940s. This site consisted of a series of long, continuous arcing roomblocks, made up of “room suites” of one “habitation” room backed by two smaller “storage” rooms. This is a pattern that would become standard for Pueblo I villages at a slightly later date, and would endure in various forms for centuries. Site 13 consists of six of these arcs, four of which were excavated by Brew. Three of the arcs excavated by Brew also had oversized pit structures with highly formalized features suggesting possible use as public architecture of some sort.

There were other village-sized sites that were established at this time, although few have been excavated. These are among the earliest sites of this size and level of organization in the northern Southwest, and continuities with later sites in other regions suggest they may have been very influential on later developments.

In addition to the early village sites, defensive sites on high, inaccessible promontories began to appear during the early Pueblo I period. These sites have not been studied in any depth, and little is known about them. Some appear to have evidence of extensive residential populations and/or public architecture, while others don’t. One intriguing pattern is an apparent line of them at the western edge of the region along the eastern margins of Cedar Mesa. This, combined with the lack of Pueblo sites to the west, has suggested to some researchers that there was a buffer area or “no-man’s-land” between the Pueblo population in southeastern Utah and early Fremont populations northwest of the Colorado River during this period. It’s worth noting, however, that there were also a few of these apparent defensive sites well within the Mesa Verdean Pueblo region, including the Fortified Spur site near the Colorado-Utah border, so tensions may have been internal as well as external at this point.

During the middle Pueblo I period from AD 825 to 880 there appears to have been a regional population decline, although again this may be due in part to data gaps. It is noteworthy, however, that this is the period of a major population increase in the Central Mesa Verde region to the east, including the formation of the well-known cluster of aggregated villages in the Dolores River Valley, some of which show some striking similarities to earlier Utah villages such as Site 13. It is reasonable to postulate that a pattern of emigration from southeast Utah into southwest Colorado led to this pattern. Southeast Utah wasn’t completely depopulated, however. In addition to scattered small sites throughout the region, there are a very few larger communities firmly dated to this period, including an intriguing site on Elk Ridge called the Pillars that has extensive evidence for middle Pueblo I residential architecture and some tentative evidence for public architecture as well. There are several other sites in the same general area that have more tentative evidence for occupation during this time, and it seems this may have been one of a handful of population clusters in the region during a time of otherwise low population.

After AD 880 population rapidly increased again, and many large villages were built between this point and AD 950. This was a period of rapid depopulation in the Central Mesa Verde region, again suggesting a complementary pattern of migration between the two regions. Many of these new village sites were in highly defensive locations, including some that were nowhere near the frontiers of the region. There is also an intriguing pattern of continuity in location between these early villages and later Pueblo II great house communities from the eleventh century. This pattern is made even more intriguing by two phenomena:

  1. Some of these sites, such as Red Knobs and Nancy Patterson Village, have evidence for masonry roomblocks similar to the “proto-great houses” known from many sites in New Mexico in and around Chaco Canyon during this same time.
  2. There seems to have been another depopulation of southeastern Utah around AD 950, implying that population at these sites was not actually continuous despite these similarities.

It has long seemed to me that southeastern Utah is a crucial area for understanding Chaco. There are several lines of evidence suggesting that at least some people living in Chaco Canyon and involved in its rise to regional dominance had strong ties to Utah, and I suspect those ties were more important in the emergence of the Chaco system than has been generally recognized. This chapter adds some much-needed context on the earlier history of Pueblo populations in Utah, and to me it strongly reinforces those ideas about the importance of Utah to Chaco. The exact nature of these relationships and their importance is still unclear, and the relatively sketchy data available make it harder to figure out, but it still definitely seems like there is something important here.

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McPhee Reservoir and Mesa Verde Escarpment from McPhee Campground

McPhee Reservoir and Mesa Verde Escarpment

The second chapter of Crucible of Pueblos discusses the Central Mesa Verde region, which is defined as basically the southwestern corner of Colorado, bounded on the west and south by the modern borders with Utah and New Mexico, on the east by the La Plata River valley, and on the north by the highlands north of the Dolores River. This is the region where Pueblo I period villages have been most extensively studied, primarily by the Dolores Project during the construction of McPhee Reservoir in the 1980s and in subsequent research by archaeologists building on that work. As a result, there’s not a whole lot that’s new in this chapter for someone who has been following the literature on this topic, although it does make a good introduction to the subject for someone who hasn’t. It also discusses some parts of the area, especially the northern and eastern fringes, that have seen much less research than the well-studied Great Sage Plain (including the Dolores sites) and Mesa Verde proper. Overall, the data assembled here is among the most detailed and reliable available to analyze demographic trends and population movements during the Pueblo I period in the northern Southwest.

Among the key factors that the authors discuss are the inherent attractiveness of this region to early farmers because of its good soil and relatively favorable climatic conditions compared to other nearby areas. Indeed, this is the only part of the northern Southwest that has seen extensive dry farming in modern times, and it is still primarily agricultural in use. This makes it unsurprising that early farmers would have concentrated here, as indeed they did, starting in the Basketmaker III period ca. AD 600 and increasing steadily in population through about 725. These early sites generally consisted of scattered hamlets presumably housing individual families. Villages, which in this context means clusters of multiple residential roomblocks in close proximity, began to appear around 750, often in association with great kivas, which had previously been rare in this region for reasons that are unclear.

Villages to both the west and east, discussed in subsequent chapters, date to the same period as these early ones in the Central Mesa Verde villages, and there was a striking variety in community organization and layout across the broader region. The dissolution of the eastern and western villages seems to have contributed to an influx of population into the Central Mesa Verde area in the early ninth century, resulting in the largest and densest concentration of population seen to that date. Village layout also became more standardized, with two main patterns dominating, one associated with great kivas and another including U-shaped roomblocks that were likely ancestral to later “great houses.” These villages, most extensively documented at Dolores, were however short-lived, and by the early tenth century the area was almost completely depopulated, with the former inhabitants apparently moving primarily to the south, into the southern part of the San Juan Basin, where they seem to have played a key role in the developments that led to the rise of Chaco Canyon as a major regional center in the eleventh century.

As I said before, none of this is groundbreaking information at this point, and I’ve discussed some of the implications of the Dolores data before. It is however useful to have a synthesis of this region during this important period to refer to, and this chapter works well for that purpose.

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McPhee Reservoir, Dolores, Colorado

McPhee Reservoir, Dolores, Colorado

A few years ago I did a series of posts called “Aftermath” that consisted of short commentaries on the chapters in The Prehistoric Pueblo World, a volume edited by Michael Adler that synthesized information on the archaeology of the Pueblo III period (AD 1150 to 1350) in various regions of the Southwest. This period postdated the decline of Chaco Canyon as a major regional center, and understanding it is important for understanding the relationship between Chaco and the modern Pueblos, as well as for understanding some aspects of Chaco itself.

Another period that is of perhaps even greater interest for understanding Chaco is the Pueblo I period (generally defined as AD 750 to 900, but see below), which immediately predates Chaco’s rise to regional dominance. I was therefore pleased to see the publication in 2o12 of Crucible of Pueblos: The Early Pueblo Period in the Northern Southwest, a volume synthesizing information on the Pueblo I period along the same lines as Adler’s effort for Pueblo III. It’s edited by Rich Wilshusen, Gregson Schachner, and James Allison, all of whom have made important recent contributions to understanding of this under-researched period. I’m just now getting around to reading it, and I decided to do a similar series of posts commenting on the chapters as I read them. I’m entitling the series “Foreshadow” to indicate the way developments during this period seem to, well, foreshadow later developments at and involving Chaco.

This post addresses the introduction, which is by the three editors of the volume along with Kellam Throgmorton, who is not otherwise a familiar name (at least to me) but who is thanked in the acknowledgments for his work “reimagining” this chapter. He was apparently a graduate student at the University of Colorado at the time, and has since graduated and is now “doing contract archaeology work in New Mexico.” The introduction as it stands is very engaging and readable, so if that was Throgmorton’s doing I can see why the volume editors took care to thank him specifically.

This introductory chapter is primarily a history of archaeological research on the Pueblo I period in the Southwest, but it also situates that history in the context of archaeological understanding of that period and how it relates to others, which has changed markedly over time. It also explains the reasoning for this volume’s use of “Early Pueblo” rather than “Pueblo I” to describe the period of interest, which is defined more broadly than Pueblo I has traditionally been. As with so much else in Southwestern archaeology, the issues here go back to the classification developed at the first Pecos Conference in 1927. As this chapter makes clear, this was initially primarily a developmental sequence rather than a chronological one, and the Pueblo I period in particular has been misunderstood on this account. This volume therefore uses a more general “Early Pueblo” period of circa AD 650 to 950 to frame the developments in the regions it discusses, which covers the various definitions that have been used for Pueblo I in different areas, as well as parts of Basketmaker III in some because of the importance of immediately preceding events for understanding Pueblo I.

The bulk of this chapter relates the history of understanding of the Pueblo I period by archaeologists. This history follows the familiar sequence of culture history/classification followed by processualism/environmental determinism followed by post-processualism/neohistoricism, but with an emphasis on how the Pueblo I period tended to be subsumed by larger theoretical constructs until the rise of large cultural resource management projects in the 1970s and 1980s massively increased the data available and forced a reevaluation of the period. The most influential of these efforts was the Dolores Project, which happened to occur in an area that was one of the most important centers of Pueblo I village development. The massive scale of this project, the largest ever in the US at the time, led to a much more detailed understanding of the Pueblo I period and the recognition that, rather than a brief interlude in the sequence of development from small hamlets to large pueblos, this was a time of rapid formation of the first major agricultural villages in the northern Southwest, followed by their equally rapid dissolution and a massive outmigration of people from the region. The precision of tree-ring dating allowed for very fine-grained understanding of the chronology, and the results of the project showed a level of dynamism in population movement and culture change that was totally unexpected and hard to fit in the gradual progression paradigm underlying the traditional Pecos classification.

Furthermore, certain aspects of the short-lived Dolores villages were strikingly reminiscent of the well-known Chacoan communities that emerged to the south shortly afterward, which led to the increasingly accepted idea that the formation and dissolution of villages during Pueblo I in the Dolores area were events that directly influenced the rise of Chaco. Indeed, it is now considered quite likely that many of the people who were involved in the development of early great houses at Chaco had moved there from Dolores.

So that’s the main message in this chapter, which also serves as an introduction to the volume itself and the other chapters in it. The next few chapters cover the specifics of settlement patterns in several parts of the northern Southwest, including not just the Mesa Verde region (the focus of most Pueblo I research so far) but also Chaco and its surroundings as well as areas further south and east. The latter two areas are often not addressed very well in research on this period, so I’m very interested in seeing the information on them presented here. The next few chapters cover a few broad thematic issues of interest for understanding this period across all the regions, then there are concluding chapters by Steve Lekson and John Kantner putting all this in a larger perspective. Overall this seems like a well-designed and desperately needed synthesis of an important but poorly understood period in Southwestern prehistory, and I’m eager to dive into the details.

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Looking East from Casamero Pueblo

Looking East from Casamero Pueblo

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

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

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

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

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

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

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

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

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

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Looking East from Peñasco Blanco

Looking East from Peñasco Blanco

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

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

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

Light Snowfall on Fajada Butte

Light Snowfall on Fajada Butte

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

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

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

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

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

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

McPhee Reservoir, Dolores, Colorado

McPhee Reservoir, Dolores, Colorado

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

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

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

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

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

Pueblo Bonito from Above

Pueblo Bonito from Above

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

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

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

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

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Old Bonito from Above

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

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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Plaque Commemorating the Founding of Harvard College, Cambridge, Massachusetts

Plaque Commemorating the Founding of Harvard College, Cambridge, Massachusetts

I’m still working on the follow-up to my DNA post, but in the meantime I’ve seen a few new reports of interesting research in other parts of the world using techniques similar to what I was talking about. This will provide some context for the Southwest-specific research I’ll discuss later, which is still at a much more rudimentary level that hasn’t yet produced such striking results.

First, commenter ohwilleke, in addition to leaving a long and informative comment about analytical techniques and the usefulness of full-genome sequencing as opposed to mitochondrial studies, points to a recent study of modern inhabitants of Rapanui (Easter Island) that shows clear evidence of prehistoric genetic mixture with people from South America. There have long been theories that there was contact between these populations, but this appears to confirm them with the most solid evidence yet, and provides another glimpse of the complexity of human history. (I’ll address the issue of full genomic sequencing, which has not yet been used on any ancient remains from the Southwest to my knowledge, in the follow-up post.)

Second, there have apparently been two new articles (only one of which I could find, since the news story doesn’t even give the title of the journal the other one was published in) using aDNA techniques on ancient remains from Europe. One study, by a large team including David Reich of Harvard Medical School, found three major sources of ancestry for ancient Europeans: early hunter-gatherers, presumably of African origin; early farmers of Near Eastern origin (which seems to strongly support theories that the spread of agriculture across Europe had migration of people as an important component) who apparently interbred with the hunter-gatherer population to some extent; and a previously unknown group with links to Central Asia and possibly associated with the introduction of Bronze Age material culture. The second study, which looked at remains from later dates than the first, appears to have also found a fourth group that entered eastern Europe during the Iron Age.

Finally, reaching back to a much earlier date, a bone found in a riverbank in Siberia yielded the oldest human genome sequenced to date. Radiocarbon-dated to between 43,000 and 47,000 years ago, the genome is particularly noteworthy because it contains a higher proportion of segments of Neanderthal origin than modern human genomes, which apparently has important implications for theories about the initial peopling of the world by modern humans.

Now, I don’t have access to any of these papers so I haven’t read any of them myself. My comments about them are based on the abstracts and the coverage they’ve gotten in the media, which is of course notoriously unreliable when it comes to highly technical subjects. Still, this should give a sense of the kinds of topics DNA studies are weighing in on. As I said before, DNA research in the Southwest is still at a much more rudimentary level, so don’t expect to see this kind of thing any time soon. It is developing, though, and has great potential to answer important questions of archaeological interest. I’ll explain more about the work that has been done in the next post.

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