Archive for the ‘Physical Anthropology’ Category

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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Dorset Culture Exhibit, Carnegie Museum, Pittsburgh,  Pennsylvania

Dorset Culture Exhibit, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania

To wrap up my series on tracing the connections between ancient Pueblo sites like Chaco Canyon and the modern Pueblos, I’d like to discuss a type of evidence I haven’t discussed much but that people often ask about: DNA evidence. This is the most direct way to tie one population to another, at least in theory, but it’s actually quite difficult to draw any specific conclusions from the work that has been done so far, and that’s not necessarily going to improve as more research is done. Which is not to say that research along these lines has been worthless; it hasn’t revealed anything inconsistent with data from other sources so far, but that in itself is interesting and provides support for the other approaches that have been tried. Because this is such a huge and important topic, I’ve decided to break my discussion of it into two posts, one on the archaeological study of DNA in general, and another on the application of these techniques to the Southwest in particular.

There are many different types of DNA analyses that can in theory be done, but when it comes to archaeological questions, especially those involving connections between ancient sites and modern people, it is generally necessary to analyze remains excavated by archaeologists. This involves studying what is known as “ancient DNA” (or “aDNA” for short), in addition to the DNA of modern populations. As Connie Mulligan of the University of Florida noted in an article published in American Antiquity in 2006, aDNA studies have a lot of potential but also a lot of challenges. Some of the major issues involved in aDNA research are preservation of the DNA, without which any study has no chance of success, and interpretation of the results of a successful analysis of ancient material.

Because DNA, like any other organic material, decays over time, aDNA studies are more difficult and expensive than DNA studies of modern populations, and in some cases there is simply not enough DNA left in archaeological material to do any analysis at all. Preservation is a function, in part, of local environmental conditions, which in the arid Southwest tend to be favorable for preserving organic material, so this is less of a concern in this area than in many others.

Another major consideration in doing aDNA analysis is contamination. The technique that makes aDNA analysis possible is called Polymerase Chain Reaction (PCR), which involves taking a small amount of DNA and exposing it to a chemical reaction that creates billions of copies which can then be analyzed. This can be enormously useful, but the reaction is very sensitive and if any extraneous organic material is introduced it is likely to reproduce its DNA instead of the ancient DNA, which can totally destroy the validity of the analysis. The main concern with aDNA analyses of human remains is modern human DNA from the researchers themselves, and this has been an issue with many studies. These days the major laboratories that do aDNA analysis have elaborate procedures to ensure that modern human DNA doesn’t contaminate their samples, and these are typically spelled out in the papers resulting from this research.

Furthermore, as Mulligan discusses, it’s important that researchers have a clear sense of what questions they are asking and how successful aDNA analyses are likely to be in answering them. For example, DNA analysis is unlikely to be able to unambiguously identify a given set of ancient remains as belonging (or ancestral) to a specific tribal group, since genetic affiliation doesn’t correlate with cultural identity at anything close to that level of specificity. In other words, aDNA analysis can potentially identify remains as being of Native American rather than European origin, but it can’t unambiguously identify remains with any particular modern tribe. On the other hand, it is potentially possible to use aDNA studies to identify migrations and population replacement in the past, if the groups in question are sufficiently distinct genetically. Mulligan actually uses an example from the prehistoric Southwest, which I’ll discuss further in the next post, to illustrate how it can be tricky to interpret differences in genetic characteristics between populations, especially at the level of detail at which these analyses are often conducted.

These concerns aside, DNA analysis can certainly be a  powerful tool for understanding the past, especially when aDNA studies can be integrated with studies of modern DNA. A great example of this is a study that was recently published in Science about the prehistory of the North American Arctic. In this paper, which is available free on the Science website, the researchers report on a combination of aDNA and modern DNA analyses that demonstrate clearly that the people of the mysterious Dorset culture that inhabited Arctic Canada and Greenland from about 800 BC to AD 1300 are not ancestral to the modern Inuit inhabiting the same area, who are instead descended from the people of the Thule culture who immigrated into Canada from northern Alaska around AD 1200. This is solid, careful research that shows what DNA studies can reveal about the human past.

Much of the aDNA research in the Americas has focused on mitochondrial DNA (mtDNA), which is contained in the mitochondria of each cell, as opposed to nuclear DNA, which is contained in the cell nucleus. There are two main reasons for this.

One is that mitochondrial DNA is passed on (generally) unchanged through the maternal line, as opposed to nuclear DNA which undergoes meiosis, the process by which DNA from the mother and father is recombined in the course of creating a new embryo, meaning that any part of the genome that has gone through it cannot be easily traced from generation to generation. Mitochondrial DNA, in contrast, is passed on directly from mother to child, and the only changes are whatever mutations develop over time, which can be used to define specific haplogroups, or genetic groupings sharing certain distinctive mutations that are interpreted as indicating shared descent. Within each haplogroup, further mutations can be used to define various sub-haplogroups, which indicate closer relationship among the haplotypes (individual genetic profiles) that comprise them. The Y chromosome, which is passed on directly from father to son, isn’t affected by recombination during meiosis and can be used to trace descent in a similar fashion. However, mtDNA is more widely used for aDNA studies than Y-chromosome DNA, due to an additional difference between mtDNA and nuclear DNA.  Due to the structure of mitochondria, each cell contains many more copies of its mtDNA than of its nuclear DNA, so mtDNA is much more likely to survive in ancient samples than nuclear DNA. This means there is much greater probability that studies of mtDNA using PCR will identify DNA to be replicated, and the result is that the existing database of mtDNA available for statistical analysis is much larger than that for nuclear DNA, including  Y-chromosome DNA. Most aDNA studies in North America, at least, have therefore used mtDNA as a primary focus for research.

Early research on both ancient and modern DNA identified four main mitochondrial haplogroups among Native American populations. These were labeled A, B, C, and D. (Haplogroups are conventionally identified by capital letters, with more specific sub-haplogroups indicated by sequences of numbers and lowercase letters following the haplogroup letter.) These haplogroups all arose from earlier East Asian haplogroups, which agrees with the traditional interpretation that Native Americans descend from Asian groups that migrated across the Bering Strait. Some modern populations in these early studies showed low levels of an additional haplogroup, X, which had previously only been documented in Europeans. There was some question at first about whether this indicated post-Contact admixture with Europeans or an additional “founding” haplogroup, but it was later found in aDNA, showing clearly that it was indeed ancient in the Americas. The implications of this finding are hard to understand, but the general consensus at this point seems to be that the American examples descend from a very ancient and otherwise unknown Central Asian offshoot of the European X haplogroup. Wherever it came from, however, it is now quite clear that X is one of the founding haplogroups in the Americas.

Much aDNA research in North America, then, has focused on identifying the haplogroups of ancient remains and comparing them to those of other populations, both ancient and modern. Much of this research has involved treating assemblages of ancient remains (either from single sites or across a whole archaeological “culture”) as samples that can be compared statistically to samples from modern tribes. I find this dubious, since the ancient samples are typically small and there’s no way to tell how representative they are of the actual underlying population (however it’s defined). The statistical procedures often used to analyze haplogroup frequencies implicitly assume that these are random samples representative of the population, but there’s no real way to know if this is true and in most cases no particular reason to think it is. In theory it’s possible that the modern samples, at least, are representative of their populations, but I suspect it’s often not the case in practice here either. For both modern and ancient samples, it’s likely that other factors, such as level of preservation and willingness to provide samples, have strongly affected the composition of the samples. These factors may or may not have skewed the representativeness of the samples; the point is that there’s no real way to tell.

Given this sampling issue, I think the most conservative and defensible approach is to treat haplogroup distributions as nominal-level data: the most we can really say about a given haplogroup in a given sample is whether it is present or absent. That’s not very helpful, though, and it may be reasonable to take a further leap and treat the distributions as ordinal-level data: this allows us to make use of the fact that some haplogroups are much more common in a given sample than others to make some broad conclusions about haplogroup distributions on a larger scale. What isn’t justified, however, is treating the frequencies of haplogroups in a sample as interval/ratio-level data: using the actual numbers as if they are meaningfully representative of the underlying population, and plugging them into elaborate statistical formulas to compare them to other samples/populations. Not all aDNA studies do this sort of thing, but it’s common enough that I think it’s important to emphasize that it’s a problematic approach at best, and that any conclusions regarding probable relationships between populations based on this method shouldn’t be taken very seriously.

A better way to go beyond the crude data of haplogroup assignment is to sequence additional portions of the mitochondrial genome that are known to contain mutations that define sub-haplogroups within the assigned overall haplogroup. Enough research has been done at this point that quite a few sub-haplogroups are known, and when they show up in multiple samples, either ancient or modern, that provides a much firmer basis for hypothesizing meaningfully close relationships than statistical comparisons of haplogroup distributions among whole samples. Furthermore, since the mutations that define sub-haplogroups can be grouped hierarchically, it’s possible to construct trees showing how individuals in a given sample, or even across samples, that belong to the same haplogroup relate to each other. (Note that this isn’t quite the same as showing how the people were actually related, since we don’t know when the mutations that define these groups actually occurred or how the people whose remains were sampled were related to the people in whom the mutations originally occurred.) There’s a probabilistic aspect to this type of evidence, since there are multiple ways a particular set of mutations could have ended up together in the same haplotype, and determining the most likely sequence of events can require modeling and simulation. The more samples are analyzed, the larger the database of known mutations and sub-haplogroups becomes, and the more reliable the conclusions that can be drawn about relationships are.

So that’s the basic outline of how ancient DNA analysis works and the methodological concerns that need to be kept in mind when evaluating it. In the next post, we’ll look at some of the specific studies that have applied these methods to the Southwest, and what their results can and can’t tell us about Southwestern prehistory.
Mulligan, C. (2006). Anthropological Applications of Ancient DNA: Problems and Prospects American Antiquity, 71 (2) DOI: 10.2307/40035909

Raghavan, M., DeGiorgio, M., Albrechtsen, A., Moltke, I., Skoglund, P., Korneliussen, T., Gronnow, B., Appelt, M., Gullov, H., Friesen, T., Fitzhugh, W., Malmstrom, H., Rasmussen, S., Olsen, J., Melchior, L., Fuller, B., Fahrni, S., Stafford, T., Grimes, V., Renouf, M., Cybulski, J., Lynnerup, N., Lahr, M., Britton, K., Knecht, R., Arneborg, J., Metspalu, M., Cornejo, O., Malaspinas, A., Wang, Y., Rasmussen, M., Raghavan, V., Hansen, T., Khusnutdinova, E., Pierre, T., Dneprovsky, K., Andreasen, C., Lange, H., Hayes, M., Coltrain, J., Spitsyn, V., Gotherstrom, A., Orlando, L., Kivisild, T., Villems, R., Crawford, M., Nielsen, F., Dissing, J., Heinemeier, J., Meldgaard, M., Bustamante, C., O’Rourke, D., Jakobsson, M., Gilbert, M., Nielsen, R., & Willerslev, E. (2014). The genetic prehistory of the New World Arctic Science, 345 (6200), 1255832-1255832 DOI: 10.1126/science.1255832

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Old Bonito from Above

Old Bonito from Above, Including Northern Burial Rooms

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

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

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

Old Bonito from West Plaza Showing Plaza Kivas in Foreground

Old Bonito from West Plaza Showing Plaza Kivas in Foreground

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

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

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

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

Western Burial Rooms in Old Bonito

Western Burial Rooms in Old Bonito

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

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

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

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Kivas in East Plaza, Pueblo Bonito

Kivas in East Plaza, Pueblo Bonito

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

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

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

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

Apparent Kiva at Abo Pueblo, Salinas Pueblo Missions National Monument

Apparent Kiva at Abo Pueblo, Salinas Pueblo Missions National Monument

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Fremont River, Utah

Fremont River, Utah

Today is Cannibal Christmas (for previous installments see here and here), and this time I’d like to discuss some instances of alleged cannibalism well beyond the boundaries of the Chaco system or even the Anasazi culture area. These assemblages are in sites belonging to the poorly defined Fremont Complex of Utah, which is roughly contemporary with Chaco and included people practicing a range of lifestyles including varying amounts of maize agriculture. Beyond those two features, however, the various groups included under the label “Fremont” display so much internal diversity that it has been very difficult for archaeologists to determine what, if anything, the “Fremont Complex” corresponds to in social reality. One widespread characteristic of Fremont groups, however, is evidence of contact with and influence from Anasazi groups to the south, most notably in the adoption of agriculture and pottery but to some extent in other phenomena as well.

It’s possible that whatever practices are behind the mysterious assemblages of extensively mutilated and burned human bones known from Anasazi sites such as Cowboy Wash in Colorado were among the Anasazi influences on the Fremont as well. A paper reporting on assemblages like this at Fremont sites in central Utah was published by Shannon Novak and Dana Kollmann in 2000, around the same time that the Cowboy Wash papers and Christy Turner’s Man Corn were also published and drew considerable attention to the issue of Anasazi cannibalism. That context is important for understanding Novak and Kollmann’s interpretation of the Fremont sites, which explicitly takes Turner’s interpretations as a starting point and presents the Fremont evidence as incompatible with them.

To recap, Turner argues that the cannibalism assemblages in the Anasazi are are associated specifically with the rise of Chaco as a regional system, and further that the driving force behind all of this was Toltecs from central Mexico coming up to Chaco and establishing a violent, hegemonic tributary system involving extensive warfare and cannibalism. (I should note that I have not read Man Corn myself, and this interpretation of Turner’s ideas is based primarily on summaries by other authors who are critical of them, so it’s possible that this is a misrepresentation of Turner; in any case, this is certainly what Novak and Kollmann take Turner to be saying.) This theory is problematic for a whole bunch of reasons, and Novak and Kollmann present some more.

According to Novak and Kollmann, there are three Fremont sites with evidence of cannibalism: Backhoe Village, Nawthis Village, and Snake Rock Village. They are all in close proximity to each other in central Utah (near modern Richfield), and were occupied around the cultural peak of the Fremont period, around AD 1000. This makes them roughly contemporary with the florescence of the Chaco Phenomenon to the south, although it’s important to note that Fremont chronology is mostly based on radiocarbon dates and is less precise than the tree-ring based Anasazi chronology so it’s hard to demonstrate very close correspondences between events in Fremont and Anasazi sites. This will be important in interpreting these cannibalism assemblages, as discussed below.

Although Novak and Kollmann mention three sites with evidence of cannibalism, their paper contains a detailed discussion of only one, Backhoe Village. This is the site with the largest number of cannibalized individuals, eight, compared to three from Nawthis and two from Snake Rock. Backhoe also has a fairly secure context and was carefully excavated, as opposed to Snake Rock, where looting had disturbed the remains and rendered their context unclear.

The assemblage at Backhoe was clustered in a single pithouse and was initially interpreted by the excavators as a secondary burial (otherwise unknown for the Fremont) burned at some point by the same fire that burned the roof timbers found above it. Novak and Kollmann question this interpretation and argue instead that this assemblage instead shows the same signs of cannibalism found at Anasazi sites to the south, including cutmarks and burning. Methodologically they focused on reconstructing the processing sequence applied to the remains, which is an interesting approach that I haven’t seen applied in other analyses of cannibalism assemblages (though it’s possible I just haven’t noticed it). The patterns they found, especially for skulls and long bones, were consistent with the people having been killed (in some cases with “a series of heavy blows to the face”), scalped, dismembered, and roasted. Four men, two women, and two children were represented in the assemblage. This evidence looks convincing to me, and I’m quite prepared to accept the interpretation that this is an instance of cannibalism much like those documented at Cowboy Wash and elsewhere.

Novak and Kollmann then go on to situate their results in the context of Turner’s Chaco-based theory of Anasazi cannibalism. They argue that these sites were well beyond the Anasazi culture area, which is true (there are Fremont sites in close proximity to the Anasazi frontier, but these sites are considerably further north), and that as small agricultural hamlets, they would have little to offer the Chacoan tribute system, which is more questionable. After all, many of the Anasazi communities within the Chacoan sphere of influence were also pretty small and wouldn’t necessarily have had much to offer in tribute. All these communities were growing at least some amount of corn, and at a minimum could have contributed that. The sheer distance from Chaco to central Utah is a better argument against simply extending Turner’s theory to include these assemblages, I think.

Fremont Shield-Bearing Warrior Petroglyph, Moab, Utah

Fremont Shield-Bearing Warrior Petroglyph, Moab, Utah

In contrast to Turner’s theory, Novak and Kollmann tentatively propose that this is perhaps an example of a behavior diffusing from the Anasazi to the Fremont and perhaps acquiring new meanings along the way. This would certainly not be a surprise, given all the other behaviors that appear to have undergone the same process. They note the prominence of warrior motifs in Fremont rock art as context for violence within Fremont society. Finally, they situate the evidence for violence among the Fremont within a pattern of rising violence in the Southwest in general:

Escalated violence within the American Southwest around AD 1000 is apparent, and this violence appears to have reached further north than previously identified. What we may be seeing in the Anasazi Culture Area is perhaps merely the culmination of widespread and endemic warfare. Fortification of Anasazi villages, evidence of numerous trauma deaths, and the butchering of men, women, and children imply more than simply accusations of witchcraft. Violence between neighbours can be vicious, and real and imagined atrocities often accompany this conflict.

Fair enough in terms of explaining these specific assemblages, but from a broader southwestern perspective this looks a little odd. Escalated violence around AD 1000? In most of the Southwest the period from about 1000 to 1150 is actually considered remarkably peaceful, and in the Chaco area this is sometimes explained as some sort of “Pax Chaco” in which the influence of Chaco led to a period of widespread peace. (It is hard to say which way the causation goes, however; maybe the peace was instead a necessary condition for the rise of Chaco in the first place.) Obviously this is in contrast to Turner’s interpretation of the rise of Chaco as involving widespread war and cannibalism in a Mesoamerican fashion, but that interpretation has basically no support in the archaeological record. Almost all of the well-dated and firmly established cannibalism assemblages date to AD 1150 or later, and the earlier ones are generally earlier than AD 900 and date to an earlier period of extensive evidence for warfare and violence.

So what’s going on here? One possibility is that we’re seeing the consequences of the mismatch in chronological precision I mentioned above. “Around AD 1000” may mean very different things at Fremont and Anasazi sites. At the Fremont sites, dated primarily by radiocarbon, this could refer to a period of a couple hundred years, in which case it might extend as late as the post-Chaco period of cannibalism and violence (0r as early as the pre-Chaco one). At Anasazi sites, on the other hand, with their very precise tree-ring dates, “around AD 1000” would generally mean very close to the actual calendar date of AD 1000, maybe within twenty or twenty-five years. This is a considerable difference in precision! It’s also noteworthy that “around AD 1000” is also more or less the conventional date for the “peak” of Fremont settlement and cultural development from roughly 1000 to 1300, so its being applied here could just mean that these sites date to that period, within which the level of violence rose throughout the Southwest (which is certainly true).

Linear Roomblock at Coombs Village (Anasazi State Park), Boulder, Utah

Linear Roomblock at Coombs Village (Anasazi State Park), Boulder, Utah

That said, however, there does actually appear to be a fair amount of evidence that there was in fact a considerably higher level of violence in the Fremont region than elsewhere in the Southwest even in the “Pax Chaco” era. A general summary of Fremont archaeology by David Madsen and Steven Simms discusses some of this evidence. Madsen and Simms describe the period of 1000 to 1300 as one of “demographic fluidity” involving the apparent abandonment of certain parts of the Fremont region and intensified settlement with defensive features in others. This appears to have begun at least in some areas as early as AD 900 and is most noteworthy in the eastern Fremont area on the northern Colorado Plateau, where there also seems to have been a breakdown in the traditional boundary between Fremont and Anasazi along the Colorado River and the expansion of sites with Anasazi features north of the river. It is not clear to what extent this reflects a migration of Anasazi people as opposed to increased Anasazi influence on local Fremont people, but it’s clear that something was going on along the Anasazi-Fremont boundary during the height of the Chacoan era. It’s noteworthy that one site Madsen and Simms mention as having granaries built in a characteristically Anasazi form is Snake Rock, one of the same sites that has a cannibalism assemblage. The puzzling Coombs Village site (now Anasazi State Park in Boulder, Utah), which is clearly Kayenta Anasazi in culture but located very far north in traditionally Fremont country, also dates to around this time. In fact, as Joel Janetski notes in a paper on Fremont long-distance trade, there is some evidence of pottery exchange between Coombs and Snake Rock, about 50 miles to the north.

The upshot of all this is that there was clearly extensive contact between the Anasazi and the Fremont during the Chacoan era, and there is some evidence that it was not nearly as peaceful in this area as it was in the Anasazi heartland at the same time. The much “blurrier” chronology of the Fremont sites makes it frustratingly difficult to pin down exactly what was going on in Utah at the same time as the various important events in the history of Chaco, but these indications that Utah was “out-of-phase” with areas to the south in some ways is, I think, potentially significant for understanding the history of both.

It’s also worth noting that while the actual Anasazi interacting with the Fremont were from the Kayenta and Mesa Verde cultural “branches” rather than the Chacoan, there is reason to think that at least some people at Chaco would have had a keen interest in events in Utah. For one thing, the Janetski paper on Fremont trade notes that while long-distance trade goods like turquoise and shell are much rarer in Fremont than in Anasazi sites, they are present among the Fremont to some extent, and there is some evidence that the turquoise found at some Fremont sites came from the same sources as that at some Anasazi sites, including Chaco. Janetski interpreted this as indicating that the Fremont turquoise came from the Anasazi, which is certain one reasonable interpretation, but he also mentions evidence that some of the Fremont turquoise came from sources in Nevada, which more recent sourcing has confirmed for some of the Chacoan turquoise as well. Maybe, instead of getting turquoise from the Anasazi, the Fremont were giving it to them as part of a wide-ranging trade network. This might even explain why so little turquoise is found at Fremont sites, if they didn’t actually have much interest in it but used it to trade for Anasazi goods that they did want. Interestingly, Janetski also notes that most of the turquoise in Fremont sites appears to date to after the period of its most common appearance in Anasazi sites from 900 to 1100 (which is driven mostly by the vast amounts found at Chaco), which could be explained if the Fremont, having relatively easy access to turquoise from trading partners in the Great Basin, began holding on to it once Anasazi demand weakened with the decline of Chaco.

Edge of the Cedars Great House, Utah

Edge of the Cedars Great House, Blanding, Utah

Much of that is speculative, but if the Great Basin was in fact one of Chaco’s main sources for turquoise, and if some of the trade routes for that turquoise went through the Fremont, Chaco would have a clear interest in the Fremont area. It would certainly have had contact with some Anasazi groups near the Fremont frontier, as there are communities showing Chacoan influence in Utah north of the San Juan River (though not as far north as the Colorado, as far as we know), with Edge of the Cedars in modern Blanding being a clear example. This area would presumably have been the source of whatever migration or influence extended north of the Colorado in this area after AD 1000, so a Chacoan connection is not as implausible as it might seem at first glance. Further west Chacoan influence is harder to see among the Kayenta Anasazi, but some level of contact is at least possible.

It’s not clear what implications this possibility of Chacoan involvement in Utah would have for the cannibalism assemblages Novak and Kollmann discuss, however. For one thing, I think Turner is just wrong that cannibalism in the Southwest is associated with the rise of Chaco; it seems to correlate more closely with its fall. Also, the specific sites in question seem to be beyond the reach of any plausible Chacoan direct influence, although at least one clearly had some contact with the Kayenta Anasazi at Coombs. They could also have been involved in the turquoise trade, of course, and according to Janetski small amounts of turquoise were found at Snake Rock and Backhoe. The lack of any known cannibalism sites between these and the better-known Anasazi examples also limits the extent to which we can figure out what was going on. Interestingly, Novak and Kollmann note that one other site, Turner-Look, which is near the Colorado-Utah border and hence much further east than the other sites and much closer to the Anasazi cannibalism assemblages, has been suspected in the past of having evidence for cannibalism, but they say a recent reanalysis has found no such evidence, although there is some evidence for violence. If more Fremont sites with assemblages like this begin to emerge, especially further east, it might be possible to get a better sense of how this all fits together.
Janetski, J. (2002). Trade in Fremont society: contexts and contrasts Journal of Anthropological Archaeology, 21 (3), 344-370 DOI: 10.1016/S0278-4165(02)00003-X

Novak, S. A., & Kollmann, D. D. (2000). Perimortem Processing Of Human Remains Among The Great Basin
Fremont International Journal of Osteoarchaeology, 10, 65-75


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Plaque atop Monks Mound Showing the Locations of Mounds to the East, Cahokia

One of the distinctive characteristics of Cahokia and its area of strong influence is the prevalence of filed teeth in many human burials. Filing of teeth as a cultural practice was common in Mexico for thousands of years before the Spanish conquest, but further north it is very rare and found mostly at Cahokia and sites in the immediately surrounding area. Gregory Perino published an article in 1967 summarizing the data as of that date on filed teeth at Cahokian sites. He notes that most of the burials with this characteristic were excavated non-professionally and that many of the early excavations were not reported in sufficient detail to know whether tooth-filing was present in the burials they uncovered. Nevertheless, Perino’s article is a useful summary of the evidence at the time.

Interestingly, Perino notes that while most of the reports of filed teeth in North America are from the Cahokia area, there are some scattered early mentions in other regions, including Georgia and the Southwest (!). The Southwestern mention is interesting, as Christy Turner has claimed that some of the remains at Chaco Canyon show filed teeth. None of the other physical anthropologists who have analyzed the relevant remains have noted the same, but that’s not very many people and in general the published physical analyses of the Chaco burials are woefully inadequate. Perino’s reference to a Southwestern example of filed teeth is unclear, but he appears to be citing a previous study of the practice in Illinois which I have not been able to track down.

Setting the comparative question aside, Perino finds three types of tooth filing at Cahokia:

  1. V-shaped notches in the cutting edge of the upper medial and (more rarely) lateral incisors. The number of notches varies from 1 to 4 in the medial incisors and 1 to 2 in the lateral incisors. One example has a single notch in each of the lower medial incisors; this is the only example of filing of any of the lower teeth.
  2. Shallow horizontal grooves along the upper medial incisors above the cutting edge. There can be either one or two grooves, and the grooves can be either parallel to the cutting edge or slightly oblique.
  3. A combination of both of the above types on the same teeth.

Of these, the first category is the most common. The number of notches varies, and they are found more often in the teeth of younger than older individuals, although Perino notes that this is probably because the relevant parts of the teeth have worn away in older individuals. The second and third category are less common, though still somewhat widespread.

Remains of Mounds East of Monks Mound, Cahokia

Perino finds examples of tooth filing both at the Cahokia site itself, particularly in the area of Mounds 19 and 20 east of Monks Mound, and at various locations showing Cahokian influence both to the north in the lower Illinois River valley and to the south in the southern American Bottom. All of the sites he discusses are in the modern state of Illinois. Tooth filing is generally found in only a few individuals in any given burial population, indicating that while it was fairly widespread around Cahokia it was far from universal and generally limited to a small number of people within the society, possibly an elite class. Most of the examples are from men, but there are a few women as well. The chronology of Cahokia was not very well developed at the time, but it appears that the examples of filed teeth mostly date to the height of Cahokia’s power and influence, now dated to approximately AD 1050 to 1200.

Near the end of the paper Perino proposes some suggestions for other areas where similar practices might be identified through further research:

It would not be unreasonable to expect filed teeth to occur in the Tennessee-Cumberland area, in southeast Missouri, and in earlier parts of the Caddoan area, especially at Spiro. Relationships in these areas are noted through trade objects and a  similarity in their religious practices.

These are certainly among the areas showing extensive contact with the American Bottom during the Mississippian period, but they are not the only such areas. What additionally distinguishes them is that they all lie south of Cahokia, and it seems likely that what Perino has in mind here (although he doesn’t say so explicitly) is that these areas may have served as conduits for the transmittal of tooth-filing from Mexico to Cahokia. Be that as it may, as far as I know this practice has not in fact been identified in any of these other areas, which would cast doubt on the idea that it diffused from Mexico to Cahokia, unless Cahokian elites actually went directly there themselves and brought back this (and other?) ideas.

The question of the extent of Mesoamerican influence on Mississippian culture has been hotly debated over the years; the current trend seems to be to downplay the possibility of direct connections and focus on in situ explanations of the Mississippian Emergence. I’m not sure what to think about this, myself. There are a lot of things about Mississippian societies that certainly look very Mesoamerican, at least at first glance, but it’s not clear how many of these are specifically Mesoamerican developments rather than things that typically happen at a certain level of sociopolitical complexity cross-culturally and that are therefore likely to have emerged in the Mississippian context from underlying trends the same way they did in Mexico much earlier. Tooth-filing seems a lot more specific than that sort of thing, though, and I can see it as a strong piece of evidence for direct influence, but the lack of it in the intervening area (if that does in fact turn out to be the case) would be problematic for that interpretation. It seems like a weird thing to do, but it’s not totally unique to Mexico in a global context, so it’s certainly possible that the Cahokians came up with it on their own as well.
Perino, G. (1967). Additional Discoveries of Filed Teeth in the Cahokia Area American Antiquity, 32 (4) DOI: 10.2307/2694083

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