Archive for January, 2010

Pueblo Bonito from Peñasco Blanco

The paper I discussed earlier about evidence that corn was imported to Chaco was interesting, but while it provided important information about the poorly understood “Mesa Verdean” period after the fall of the Chaco system it didn’t address the question of food imports during the operation of that system.  This has been a topic of considerable debate, and the extent to which corn was being imported to Chaco from outlying areas versus being grown in the canyon itself has major ramifications for which theories about the nature of the system seem most plausible.  Luckily, however, that paper was just one in a long series reporting on research done by Larry Benson and others on this topic, and a slightly earlier one by Benson, H. E. Taylor, and our old friend John Stein addresses the question of earlier (and later) periods.

Peñasco Blanco from Pueblo Bonito

This paper uses the same basic methodology of the other one, based on strontium isotope ratios, and it also attempts to use concentrations of other trace elements to further narrow down source areas for corn cobs from archaeological sites.  Unfortunately, however, most of the trace elements the researchers looked at had their concentrations heavily skewed by post-depositional contamination, which made them useless for determining sources.  The only elements that seemed to be mostly unaffected by this problem were potassium and rubidium, so the paper uses the ratio of these two elements as an additional marker for places where the cobs may have been grown, although it cautions that it’s not yet totally clear that this ratio is actually as meaningful as the analysis implies.

Aztec West Great House, Aztec Ruins National Monument

This study looks at more cobs than the other one.  These are from both Chaco and Aztec, and the Chaco ones come from a variety of sources.  The most numerous are from Gallo Cliff Dwelling and are part of the large group with nearly identical radiocarbon dates in the late 12th century that was analyzed in the more recent paper.  This paper conducts a similar analysis and comes to similar conclusions about the wide range of possible sources for these cobs.  This group also includes a few cobs from Pueblo Bonito, Chetro Ketl, and Kin Kletso, although the authors caution that the late dates on these cobs don’t necessarily imply that these great houses were still occupied at this late date; the cobs could also result from people living in small sites like the Gallo Cliff Dwelling dumping their trash in the abandoned buildings.  While most of the Chaco cobs come from this narrow time period, and the Aztec cobs (which have not been carbon-dated) likely date from a roughly comparable time as well, some Chaco cobs are dated to both earlier and later times.  The later ones, some of which date to the nineteenth century, are presumed to reflect the later Navajo occupation of the area.  It’s the earlier ones that are of interest for the light they can shed on the operation of the Chaco system in its heyday.

Pueblo Bonito from Above

There are six cobs with carbon dates earlier than the major drought of the mid-12th-century.  Five of these come from Pueblo Bonito, and one comes from the Gallo Cliff Dwelling.  The Gallo one is puzzling, since all the other Gallo cobs date to much later and cluster tightly together, and the site itself was probably not occupied early enough to account for the early cob.  It’s possible that this date is due to something odd going on with the radiocarbon dating, and in any case it seems hard to generalize from, so I’m not going to discuss it further here and will instead focus on the five cobs from Pueblo Bonito.

Interior T-Shaped Doorway, Pueblo Bonito

Four of these come from Room 3; the other one comes from Room 170.  These are both interesting rooms in their own right, but first let’s talk about the cobs.  Although the authors of the paper classify them only as “pre-AD-1130” (i.e., before the drought that is thought to have coincided with the fall of Chaco), they actually all date considerably earlier than that.  The earliest, which unfortunately seems to have been contaminated and thus unusable for the strontium analysis, is from Room 3 and has a calibrated radiocarbon date range of AD 765 to AD 902 with 95% confidence (2σ).  The other four are somewhat later and cluster tightly together, with 95% confidence intervals of AD 944–1052 (this is the one from Room 170), AD 892–1034, AD 893–1026, and AD 889–1021.  This means that these cobs all date to a period before the Chaco system reached its full florescence, which is generally dated to the late eleventh century.  They also seem to date earlier than the expansion of Pueblo Bonito in the 1040s.  The 95% confidence interval for the cob from Room 170 does make it possible that it dates to the period of the expansion, but at a lower level of confidence (1σ) it has a tighter range of AD 974 to AD 1040, which means it too probably predates the expansion.

Old Bonito

Thus, all these corn cobs seem to have been grown and eaten during the period when Pueblo Bonito consisted only of the original arc of rooms, constructed with early, Type I masonry, that we now call Old Bonito.  This makes their geographical origin even more interesting to investigate.  During this period, consisting of the ninth, tenth, and early eleventh centuries, Chaco Canyon seems to have been growing in regional importance, as evidenced by the construction of the early great houses, but it doesn’t seem to have yet attained the preeminent position and centrality it would achieve in the late eleventh and early twelfth centuries before its collapse.  The earliest cob, which probably dates to the ninth century, which is when the early great houses were first being constructed, would be of particular interest in determining where the people in Chaco were getting their food at that time.  It’s very unfortunate, then, that its origin can’t be determined from strontium analysis because of its apparent contamination.  The other three cobs, however, which probably date to the late tenth or early eleventh century, were included in the strontium analysis, so it’s worth looking closely at what the results of that analysis can tell us.

Type I and Type II Masonry Abutting at Peñasco Blanco

These cobs date to a period when there seems to have been little or no construction at Pueblo Bonito, Una Vida, and Peñasco Blanco, the three earliest great houses in the canyon.  All three saw extensive construction in the late ninth and early tenth century, and major expansion starting in the middle of the eleventh.  The time of the cobs, then, seems to have been a relatively quiet period in the canyon, although the early stages of construction at some of the other great houses, such as Chetro Ketl and Hungo Pavi, may date to this period.  There doesn’t seem to have been a whole lot of great-house construction outside of the canyon, either; there were already quite a few great houses out there, especially to the south in the Red Mesa Valley and to the west along the Chuska Slope, but most had already been built, and the biggest of the outliers, especially to the north, wouldn’t be built until considerably later.

Side Wash by Chetro Ketl

So, if the strontium evidence were to suggest that the cobs from this period were grown in the canyon, that would suggest that local agricultural production was important at Chaco, and it would support theories that attribute Chaco’s rise to regional dominance as having to do at least in part with agricultural surplus during favorable climatic conditions.  If, on the other hand, the strontium evidence were to suggest that the cobs were grown outside of the canyon, that would be evidence in favor of other theories that see the rise of Chaco as due not to local production but to the Chacoans’ ability to somehow acquire food from other areas with better growing conditions.  This would be particularly the case if the cobs came from areas that had early outliers.  It would also be interesting if the cobs came from areas that aren’t known to have had outliers this early but did have them later (e.g., the Totah).  These theories propose a variety of answers for how the Chacoans could have done this, of course, ranging from coercive political domination to inspirational spiritual power.

High Walls at Kin Bineola

So, with that in mind, what does the strontium (and potassium/rubidium) evidence say?  In brief, it supports the latter option.  The strontium ratios in the cobs are close to the values at a few of the sampled sites in and around the canyon, but when the potassium/rubidium ratios are added in, they narrow the potential sources down considerably, and none of the local Chaco sources makes the cut.  So, to the extent that the potassium/rubidium evidence is useful (which, remember, is still not totally clear), it seems that the Chacoans were importing corn at least as early as the early eleventh century, and possibly a century earlier.  This seems to support the theories that hold that local agricultural production was not the main driver of Chaco’s rise, although this is of course a very small sample and it would be foolish to draw too many firm conclusions from it.

Sign at Kin Bineola

So if the corn wasn’t being grown at Chaco, where was it grown?  Unlike with the later cobs, and again likely owing at least in part to the small sample size, the number of potential source areas identified here is pretty small.  A couple are in the Totah near Aztec, but all the rest are in the area surrounding Chaco often called the “Chaco Halo” and consisting of the parts of the Chaco Wash drainage both upstream and downstream from the canyon, including the South Chaco Slope area on the north side of Lobo Mesa.  The specific sampling sites with matching ratios were near a number of important Chacoan outliers, including Kin Ya’a, Kin Klizhin, Kin Bineola, and Pueblo Pintado.  Interestingly, of these four only Kin Bineola is known to have been built at this time, and the others were not built until considerably later, at least in their current form.  The fact that Kin Bineola is one potential source area, as are a few smaller early great houses that were present at this time, suggests that the later outliers may have been built on top of earlier versions, or at least that the communities surrounding them may have been incorporated into the Chaco system earlier than the dates of their great houses would imply.  Of course, it’s also possible that all of these cobs came from one or a few of the areas with known early great houses; the fact that a large number of areas could have grown these cobs doesn’t mean that they all did, and in fact given the small number of cobs it would be impossible for all the areas identified to have contributed to growing them.

Kin Bineola from a Distance

It’s not necessarily surprising to find that nearby areas known to have been in close contact with Chaco would have been supplying it with corn.  Indeed, many of these areas are considerably better for agriculture than the canyon, and there has long been speculation that at least some of the outliers were founded specifically in order to supply the canyon with food.  What is somewhat surprising here, however, is the early date at which this appears to have already been happening.  The great houses at Chaco would not necessarily have been any more impressive than those in many other local communities at this point, and given the lack of construction activity in the canyon it would be quite reasonable to suppose that Chaco was not yet considered exceptional within the region.  This evidence, however, suggests that there was already something unusual going on in the canyon, and that something was getting people around it to supply it with at least some food.

Early Masonry at Kin Bineola

One more thing to consider about these cobs is where they were found.  Since Pueblo Bonito was definitely around at the time they were grown, imported, eaten, and presumably thrown away, and since they were found at Pueblo Bonito, it seems logical to conclude that the rooms where they were excavated were the same rooms where they had originally been tossed.  This is almost certainly not true, however.  Rooms 3 and 170, where they were found, had not yet been built in the early eleventh century.

Room 3, Pueblo Bonito

Room 3 is part of an arc of rooms fronting on the western section of Old Bonito.  Unlike the rooms behind it, however, it is built out of late core-and-veneer masonry, and it was likely built considerably later than those rooms, which are built with early masonry.  The difference is quite noticeable.  The spaces later enclosed by it and the other plaza-facing rooms in this arc was probably originally enclosed by a ramada or awning, or perhaps a wattle-and-daub (or “jacal”) wall, which was later replaced with masonry.  The sequence of construction in this part of the site is hard to untangle, and Room 3 produced no tree-ring dates, but it is pretty clear that it must have been constructed at some point after AD 1040, just judging from the masonry, and the presence of the cobs in it likely dates to a time long after its initial construction when it was used for dumping trash.  One of the other cobs found in this room was part of the late-12th-century date cluster, so that may be when this trash deposit originated.

Room 170, Pueblo Bonito

Similarly, Room 170 is part of the southernmost block of rooms, which was one of the last parts of the site to be built.  It seems to have been built as part of the construction of the southeast corner of the site, one of the largest single building projects in Chaco’s history, which probably took place around AD 1080.  Room 170 has an odd set of internal features; its first story was at some point divided by an east-west wall, and the part of the room north of the wall was filled in, with a space left, however, to allow access to the second floor of both it and the room north of it.  There is also a small opening just south of the dividing wall leading into the next room west, and a step below it.  Again, this room was likely not originally used for trash dumping, and the trash deposits in it likely date to a later period.

Metate Fragment at Pueblo Bonito

Since neither of these rooms was used for dumping trash until quite late, perhaps even after the fall of Chaco as a regional center, why did they contain corn cobs from centuries earlier?  Probably because the trash being dumped in them was being moved from wherever it had originally been dumped.  Where that would have been, who would have been doing this, when, and why are all very difficult questions to answer, but I don’t see any other explanation to reconcile the dates of the corn cobs with their locations.  This also means that, while these cobs were found at Pueblo Bonito, they weren’t necessarily originally brought there.  They may have been, of course, and I’d even go so far as to say that they probably were, but it’s also possible that the trash deposit in which they were originally placed was somewhere else in the canyon, perhaps even associated with another site.

Sealed Vent, Pueblo Bonito

Like all good papers about Chaco, this one answers some questions but opens up others, and it definitely provides plenty of (imported) food for thought.  There’s still a lot we don’t know about the Chacoans, even such basic things as where they  got their food, but the process of finding these things out is quite a ride and full of surprises.
BENSON, L., STEIN, J., & TAYLOR, H. (2009). Possible sources of archaeological maize found in Chaco Canyon and Aztec Ruin, New Mexico Journal of Archaeological Science, 36 (2), 387-407 DOI: 10.1016/j.jas.2008.09.023

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Pithouse Sign, Mesa Verde

Since it seems to be Linguistics Week here at Gambler’s House, here’s another post on Jane Hill’s theory that the spread of agriculture into the Southwest was associated with a migration of speakers of Proto-Northern-Uto-Aztecan (PNUA) from somewhere in Mexico.  Previously I discussed an article of hers from 2001 in which she tried to show that a set of vocabulary items related to agriculture could be reconstructed all the way back to Proto-Uto-Aztecan (PUA), which, if true, would strongly support Peter Bellwood’s argument that agriculture was introduced to the Southwest by speakers of Uto-Aztecan languages migrating north from central Mexico.  I found that article unconvincing.  One reason was that, since almost all of the agricultural vocabulary known from Uto-Aztecan languages quite understandably comes from the southern languages of the family, which were spoken by farming groups, reconstructing that vocabulary all the way back to PUA requires the assumption that PNUA is a valid genetic unit combining all the northern languages, because almost all of the agricultural vocabulary known from those languages comes from Hopi, the only one spoken by a people who primarily practiced agriculture in historic times.  Hill’s 2001 article, however, doesn’t provide much evidence to show the reality of PNUA, which significantly weakens her argument, as do the many problems with the correspondences she does identify.

Basketmaker Pithouse, Mesa Verde

The article I’m talking about now, however, is about a related but somewhat different issue.  Published in 2008, it seeks to show that a set of agricultural terms from PNUA was borrowed into Proto-Kiowa-Tanoan (PKT), presumed to have been spoken by the indigenous hunter-gatherers who occupied the Southwest before the posited PNUA migration, and that a separate set of vocabulary referring to local wild plants and animals was also borrowed into PNUA from PKT.  Here, rather than dealing with the very difficult matter of reconstructing proto-language vocabulary, Hill is dealing with loanword studies, which is generally more fruitful (though still difficult and often frustrating).  The theoretical model for how this borrowing would have occurred is straightforward: speakers of PNUA, practicing an agricultural lifestyle somewhere in the Sonoran Desert, migrated above the Mogollon Rim onto the Colorado Plateau, where they found both a different environment and groups of hunter-gatherers who were very familiar with it.  Since agriculture is a much riskier and more difficult endeavor in this area, with its shorter growing season and less predictable weather than in the Sonoran Desert, hunting and gathering would likely have become more important for the PNUA farmers, and they would have eagerly sought out knowledge of local resources from the local people, who may also have been intrigued by the potential of the unfamiliar agricultural practices of the newcomers.  So, the PNUA speakers introduced the PKT speakers to farming, and in turn the PKT speakers introduced the PNUA speakers to plants and animals important on the Plateau but unknown in the desert.  In the process, some words for these things moved between languages as well.  Hill notes that this implies both that the PKT speakers, formerly hunter-gatherers, chose to adopt agriculture rather than being pushed to marginal areas by the PNUA speakers and that contact between the two groups was not necessarily always antagonistic.  Both of these implications are problematic for Bellwood’s theory of the correlations between language distribution and the spread of agriculture, which holds that hunter-gatherers very rarely adopt agriculture when they come into contact with farming groups expanding out of their homelands with large populations but instead are either assimilated by the farmers or pushed into marginal areas unsuitable for farming.  This is somewhat ironic, since Hill actually makes a very good case for these borrowings, which provides considerable support for some version of Bellwood’s general idea that language and agriculture generally spread together.

Reconstructed Basketmaker Pithouse at Lost City Museum, Overton, Nevada

As in the previous paper, Hill is careful in this one to point out all the potential problems with the etymologies and correspondences she posits here.  There are a lot, especially because Kiowa-Tanoan languages are not very well-documented and PKT reconstructions are much more tentative than P(N)UA ones.  In this case, however, I find most of the correspondences pretty convincing.  With contact linguistics like this, there are some inherent advantages over the sort of “pure” historical linguistics Hill was doing in the earlier paper.  The most important is that loanwords are often pretty easy to identify, especially in well-documented language families.  If a term is found in one language but not in any others in its family, but it’s very similar to a term with a similar meaning in a nearby but unrelated language, it’s pretty easy to conclude not only that an episode of borrowing occurred but also which direction the borrowing went.  This is something of an ideal case, of course, and in practice it’s often not quite as clearcut, but it’s still easier to show that a term was likely loaned into a language or subfamily than that a set of vocabulary can be reconstructed back into a proto-language.

Reoccupied Pithouse, Mesa Verde

In this case, it’s the borrowings from PKT into PNUA that are most convincing.  This is mainly because the PNUA forms are not attested elsewhere in Uto-Aztecan but are quite similar in both form and meaning to what can be reconstructed for PKT (which, again, is not all that reliable).  The loans in the other direction are trickier, in part because Kiowa-Tanoan is a small family and comparisons between branches can’t really be done the way they can for Uto-Aztecan, but given the other loans they seem pretty plausible.  Among other things, these loans provide pretty strong support for PNUA as a valid grouping, which in turn strengthens the argument of the 2001 paper, although it’s important to note that the issue in the 2008 paper is actually rather different, and it’s easy to imagine a group of farmers speaking PNUA migrating out of Sonora or southern Arizona without concluding that their ancestors necessarily migrating out of central Mexico speaking PUA.  PUA could also have been spoken by a group of hunter-gatherers in, say, coastal Sinaloa or Nayarit who adopted agriculture after contact with agricultural groups migrating up from further south, perhaps speaking a language related to Purepecha, much as the PKT speakers later adopted it after contact with PNUA speakers.  Nevertheless, the existence of PNUA is important to Hill’s 2001 argument, and the support for it here does strengthen that earlier argument.

Pithouse Ventilation Sign, Mesa Verde

The implications of this loanword evidence for archaeology are interesting.  It definitely supports R. G. Matson’s argument, based on totally different evidence, that the Western Basketmakers spoke a Uto-Aztecan language and migrated into northeastern Arizona and southeastern Arizona from somewhere further south.  In connection with that argument Matson also surmised that the of the Colorado Plateau and that they spoke Keres or a Kiowa-Tanoan language.  As Hill notes in this article, Keres is an isolate and it would be difficult to use it in this kind of study.  Kiowa-Tanoan, while a small family, does have a sufficient number of languages and enough apparent time-depth to be reconstructed into a form usable for comparisons to PNUA.  It is still fiendishly difficult to figure out what language(s) the inhabitants of any ancient site would have spoken, but the integration of linguistic evidence in studies like this has the potential to shed some light on the issue.

Pithouse Ventilation System, Mesa Verde

To tie this back to Chaco, which seems to have been a pretty important regional center during the Basketmaker III period, the evidence from this article suggests that the Eastern Basketmakers of the Chaco area may have spoken PKT, although they may on the other hand have spoken a language ancestral or related to Keres or Zuni (both isolates).  Or perhaps Chaco was inhabited by more than one linguistic group, as many archaeologists have argued for the later period of its more obvious regional dominance.  This evidence does suggest that whoever was living at Chaco at this time probably was not speaking a Uto-Aztecan language, although it doesn’t entirely rule it out.  There is, after all, no way to tell exactly when this episode of PNUA-PKT contact occurred, although if it involved early contact between farmers migrating in and local hunter-gatherers it would presumably have been rather early in the Basketmaker II period.  Importantly, the fact that the loans seem to have gone both ways shows that whatever contact took place involved both groups continuing to exist as social entities of some sort.  This is not evidence for assimilation, in other words, but for peaceful contact between agricultural and hunter-gatherer groups involving the exchange of information that enhanced the subsistence options of both parties.  The archaeological implications of that are difficult to figure out precisely, but it’s a subject worth thinking carefully about.
Hill, J. (2008). Northern Uto‐Aztecan and Kiowa‐Tanoan: Evidence of Contact between the Proto‐Languages? International Journal of American Linguistics, 74 (2), 155-188 DOI: 10.1086/587703

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"Food for Thought" Sign at Anasazi Indian State Park, Boulder, Utah

The prehistoric peoples of the American Southwest were agriculturalists.  Different societies may have calibrated their mix of farming, hunting, and gathering differently, but they all seem to have done all three eventually, and for most it’s quite apparent in the archaeological record that farming was the predominant method of subsistence.  The crops they grew were corn, beans, and squash, the classic triad of North American agriculture.  These plants are not native to the Southwest, however, so they must have been introduced at some point from Mesoamerica, where they originated.  The introduction of corn, in particular, must have also involved the introduction of agricultural techniques, since it can’t grow without help from humans.  All this is pretty uncontroversial among Southwestern archaeologists.

Box Canyon, Wupatki National Monument

The nature of the introduction of agriculture, however, has been a point of more dispute.  The main arguments have to do with how long it took after the introduction of maize for the societies growing it to become totally dependent on it and thus become primarily agriculturalists rather than hunter-gatherers.  One view, espoused by Chip Wills at UNM, sees the introduction of corn as being gradual, perhaps filtering up from one hunter-gatherer group to another, and increasing dependence on it as taking place in the context of hunter-gatherer subsistence decisions and environmental fluctuations, with the total switch to a fully agricultural lifestyle not taking place until maybe as late as the Pueblo II period.  The other view, associated most strongly with R. G. Matson of the University of British Columbia, sees the introduction of maize as having been rapid and involving a totally different lifestyle from Archaic hunter-gatherers from the get-go.

Dryland Farming Sign at Box Canyon, Wupatki National Monument

Indeed, Matson sees the introduction of agriculture as having been so rapid that it could only have involved the physical migration of people who had already developed a corn-based agricultural lifestyle somewhere in Mexico.  Over the past few years evidence that supports Matson’s view has been accumulating from several sources, perhaps most notably excavations near Tucson that have shown clearly that there were people living in permanent farming villages there at least as early as 1500 BC, only a thousand years after the first such villages appear in Mexico.  Another line of evidence has been testing of human remains from Basketmaker II sites in Utah that has shown that the early Basketmakers were eating just as much corn as the later Pueblo villagers.  Matson has a good explanation of his views and the evidence for them here.  I find his arguments pretty convincing.

San Francisco Peaks from Box Canyon, Wupatki National Monument

People speak languages, of course, and people migrating from one place to another would presumably bring their language with them.  Thus, it’s reasonable to think about how the migration of an agricultural people from Mexico to the Southwest would be reflected in the distribution of languages.  The Australian linguist Peter Bellwood has argued for a general process by which early agriculturalists, who tend to experience much more rapid population growth than hunter-gatherers due to their ability to produce more food more reliably, relieve population pressure in their homelands by migrating into adjacent regions, bringing their language and lifestyle with them.

Nalakihu from the Citadel, Wupatki National Monument

Since the population issues stay with them, however, they will continue to spread out until something stops them, and that something is unlikely to be whatever hunter-gatherer societies occupy the fertile land they want.  Bellwood thus explains the enormous geographical extent of some language families by associating them with the spread of particular agricultural traditions.  This has been somewhat controversial, particularly in regard to Indo-European, as it produces a very specific answer (given Bellwood’s specific assumptions) to the vexing question of where a given language family originated, often called its Urheimat.  Since Bellwood argues that hunter-gatherers are unlikely to adopt agriculture, whether on their own or when exposed to it by contact with farming groups, his model predicts that the Urheimat of a given language family must be somewhere in the region where its agricultural tradition originated.  For Indo-European this means the Fertile Crescent rather than the Eurasian Steppe, which has been the preferred answer for many Indo-Europeanists on various grounds.  This has led to much controversy.

Fields Sign at Nalakihu, Wupatki National Monument

Bellwood has also applied his model to North America, and the language family he has suggested is associated with the spread of agriculture from Mexico to the Southwest is the one language family that extends from one to the other: Uto-Aztecan.  (I can’t find a good map of the full distribution of Uto-Aztecan languages, but the Wikipedia article has a few passable ones of smaller parts of it.)  Since this language family includes both the Nahua-speaking agricultural groups in the Valley of Mexico and the Hopi, who are part of the Pueblo agricultural tradition, it seems like an obvious link between the two and an obvious candidate for the relic of an ancient migration of farmers from Mexico to Arizona.

Entrance Sign, Pipe Spring National Monument

This proposal isn’t without controversy either, however.  The main problem is that Uto-Aztecanists have generally proposed that the Urheimat of the family is likely to be somewhere in the northern part of its range, which has the greatest number of languages in the family and the greatest density of different branches.  Early on some proposed a Great Basin origin at the far northern end of the range, but more recently most specialists have agreed that a more southerly location, perhaps in California or northern Sonora, is more likely.  Only Bellwood and those who buy his arguments, however, have argued for an origin at the southern end.  There are a variety of arguments that have been made against this idea, some stronger than others.  The strongest, I think, is the fact that there are so few Uto-Aztecan languages at the south end and so many further north.  The number of different languages in a family, and especially languages from different branches of that family, in a relatively small area is generally considered a good sign of where that family may have originated.  For Athapaskan, for example, this criterion clearly points to Alaska or northern Canada.  For Uto-Aztecan, it seems to point to either California or Sonora.

Fence between Pipe Spring National Monument and Kaibab Paiute Land

Other arguments, such as those based on the Aztec traditions of a migration from Aztlan in the northwest, I think are much weaker.  One argument that superficially seems strong but I think is also pretty weak is that since the northernmost languages in the family are spoken by hunter-gatherers, the spread of the language couldn’t have anything to do with the spread of agriculture, since that would require that some of these groups had started out as farmers and given up agriculture in favor of hunting and gathering at some point.  And who would do that?

Yucca Sign, Pipe Spring National Monument

Well, it’s true that not a whole lot of groups are known to have made this switch, but there are a few examples, and there’s really no theoretical reason to think it can’t happen.  Certainly in the sort of environment occupied by some ethnographically known Uto-Aztecan groups, like the Paiutes, farming would have been very difficult, but foraging considerably easier.  I think a lot of resistance to this idea is due to the deep-seated evolutionary paradigm with which anthropology as a discipline started out in the nineteenth century.  From this perspective, cultures evolve from “lower” to “higher” cultural levels, and they don’t go back down.  This sort of thinking was discredited long ago, but there still seems to be a lot of resistance to the idea that hunting and gathering could be a more attractive option than farming in some contexts, and that some groups would therefore have chosen it.  (On the other hand, there are those out there who find the idea of a switch to a hunter-gatherer lifestyle very appealing in general.)

Sign Describing Paiute Brush Shelters, Pipe Spring National Monument

Okay, so we’ve got some arguments for and against Bellwood’s theory, but if you look closely you’ll notice that while it’s based primarily on linguistic evidence (and is totally independent of Matson’s archaeological evidence), all that evidence is what I have called “external,” in that it is about linguistic distributions and relationships but has nothing to do with the languages themselves.  Bellwood doesn’t present any internal evidence from the Uto-Aztecan languages themselves supporting his idea that they originated in the south, probably because he doesn’t know much about them.  He seems to be an Austronesian specialist himself.  Jane Hill of the University of Arizona, on the other hand, is a specialist in Uto-Aztecan linguistics, and a while back she wrote an important article attempting to support Bellwood’s theory with internal evidence.

Garden Sign, Pipe Spring National Monument

I say “attempting” because while she makes a good effort, I’m unconvinced by her arguments.  Internal evidence is inherently difficult to find and work with, especially in this case since many of the languages are not well documented.  Hill’s argument rests on the idea that there is a set of words related to maize agriculture that can be reconstructed all the way back to Proto-Uto-Aztecan (PUA), which, if true, would imply that the speakers of PUA were farmers, which, in turn, would strongly support the theory that they were the ones who brought farming to the Southwest.  She attempts to show that certain words in Hopi relating to agriculture are cognate to other agricultural terms in the southern Uto-Aztecan languages, especially the well-documented Nahuatl.  Since these languages are near the far ends of the family’s distribution, if they share the words in question and they can be shown to have originally had agricultural meaning, it becomes quite plausible that the original proto-language had the terms and was thus associated with an agricultural lifestyle.

Community Sign at Nalakihu, Wupatki National Monument

To her credit, Hill is careful to point out the many potential problems and pitfalls with this approach.  For one thing, the internal classification of the Uto-Aztecan languages is a matter of some dispute, and her arguments here depend heavily on positing a “Northern Uto-Aztecan” subfamily consisting of Hopi and the other northern languages.  Virtually all of the farming-related terms present in these languages are only found in Hopi (since the other groups didn’t farm).  If, as many linguists argue, these languages don’t form a single sub-family but instead consist of several sub-families no more closely related to each other than to any of the southern sub-families, the fact that all the evidence comes from Hopi makes it much harder to argue that the words in question go all the way back to PUA.  Hill acknowledges that her arguments depend heavily on positing a northern subgroup, but she doesn’t offer much evidence that such a group exists, and I don’t see any real reason to think it does.  Also, for some reason she consistently cites dates in uncalibrated radiocarbon years, which is an odd and not very defensible choice in a Southwestern context.

Owens Lake, California

More seriously, however, the cognate sets she presents are just not that convincing.  She discusses a total of 21 comparisons, only 9 of which are actually part of what she calls the “Uto-Aztecan Maize Complex.”  Even these nine, however, are riddled with problems of form and semantics, which is not unusual in comparisons like this but doesn’t inspire much confidence in their suitability as evidence for Hill’s argument.  She discusses the problems in detail, but then goes on to act as though she has nonetheless shown the accuracy and relevance of the comparisons, when she really just hasn’t.  (I should note that I haven’t studied any of these languages myself, so I can’t evaluate the data, just the argumentation.)  She even notes that a great number of agriculture terms in Hopi don’t seem to have any connection to other Uto-Aztecan agriculture terms, but she just ignores that to focus on the handful that seem like they might.  And, as I said, even those are iffy at best.

Sleeping Ute Mountain from Escalante Pueblo

Aside from the weak argumentation, it’s actually a pretty good paper, in that it clearly describes the issue and fairly presents the different theories and approaches to it.  Hill is careful to point out the potential counterarguments, and she tries to deflect them, with varying degrees of success.  Certainly I found some parts of the paper convincing, and have drawn on it significantly in writing this post, but overall I just don’t buy her arguments about the data.

Kaibab Paiute Housing Development from Pipe Spring National Monument

Does this mean I think she and Bellwood are wrong about the larger issue?  By no means.  I’m not totally convinced that they’re right, but the idea of a northward migration of Uto-Aztecan speakers is both plausible and nicely complementary to Matson’s archaeological model (which, again, is based entirely on archaeological evidence and totally independent of anything Bellwood and Hill say), which as I said before I find pretty convincing.  I think this paper mostly shows that, as Edward Sapir noted in his much more successful article on internal linguistic evidence bearing on Navajo origins, internal linguistic evidence is hard to find and often of limited usefulness even when it can be found.  It’s not totally worthless, but it can only ever provide a little extra support to theories proposed on the basis of other evidence.
Hill, J. (2001). Proto-Uto-Aztecan: A Community of Cultivators in Central Mexico? American Anthropologist, 103 (4), 913-934 DOI: 10.1525/aa.2001.103.4.913

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Big Hogan, Shonto, Arizona

Although it can be rather difficult to define what it means to be Navajo, it is quite clear from a variety of lines of evidence that speakers of Athapaskan languages, including Navajo and the various Apache languages, have not been in the Southwest for very long compared to most of the other language groups there, and that they came originally from somewhere in Alaska or northern Canada, where Athapaskan languages are also spoken.  This has a number of implications for the culture history of the Southwest, so it’s useful to review just how it is that we are so sure that the Navajos came from the north.

Abandoned Hogan at Tsaya Trading Post, Lake Valley, New Mexico

Linguistic evidence in the form of the distribution of related languages can be  a very helpful guide to understanding prehistoric population movements and other events, but it can be very difficult to interpret.  For one thing, not all language families are equally plausible groupings.  Also, even when a group of languages can be convincingly shown to be related, the events that resulted in their known distribution can be hard to determine from the evidence available.  Both of these factors are clearly important in trying to understand the linguistic map of California, which seems bewilderingly complex at first glance and never really gets any simpler.  Despite the unfortunate way that particular map uses similar colors to identify the various language families, it is a pretty typical example of the way the families are shown, and it makes the problems inherent in this sort of exercise pretty obvious.

California Welcome Sign

The map groups the languages into six families: Penutian, Hokan, Uto-Aztecan, Athapascan, Yukian, and Algonquian.  This classification seems to imply that these six groups are all somehow comparable entities, but that isn’t actually the case at all.  Uto-Aztecan, Athapascan (i.e., Athapaskan, to which Navajo also belongs), and Algonquian are among the largest, best-documented, and most thoroughly studied language families in North America, and their reality as entities is not in any doubt.  All the attested languages in these groups clearly descend from proto-languages that can be reconstructed in considerable detail.  While there is still considerable dispute about how the languages in these far-flung families ended up where they are, there’s no real doubt that they are in fact related and that arguments about migrations and such can proceed from that basis.

Morro Bay, California

I don’t know much about Yukian, but it’s a small family that seems to only include a few languages (maybe just one) in California.  This is hardly unusual; there are many such small families, and while they don’t usually provide much evidence for culture history, they aren’t generally controversial as groupings.

Post Office, Independence, California

The trouble comes with the two remaining groups, Penutian and Hokan.  The status of these as families is very shaky, and many scholars don’t accept that they actually have any reality, being instead just rather arbitrary groupings of many unrelated languages with some superficial similarities.  I don’t know enough about these issues to have an opinion, but in general I’m skeptical about families like these.  And, of course, if the languages in one or both of these families aren’t actually related that drastically reduces the amount of information that can be gained from looking at their distribution relative to each other and to other language groups.

Post Office, Shoshone, California

With that whole issue in mind, and accepting for the sake of argument that Penutian and Hokan do count as real families, lets look at the distribution of the families and see what it might tell us about the prehistory of California. One of the most striking things about the map is that only one of the six families has an entirely contiguous distribution.  This is Algonquian, which only includes two languages in California: Yurok and Wiyot, way up in the northwest.  (There are, of course, many more Algonquian languages outside of California.)  All the other families are mostly contiguous, but interrupted by other language groups at various places.  Two come close; both the Penutian and Uto-Aztecan groups only have a single outlying language and are otherwise contiguous.  Uto-Aztecan is actually contiguous in reality, since the Uto-Aztecan languages along the eastern border of the state continue into Nevada, where they end up connecting to the Northern Paiute territory in the northeast corner.  Penutian, however, is clearly discontinuous, with Modoc at the northern edge of the state separated from Wintu to the south by the Hokan languages Shasta and Achumawi.  Hokan itself is not contiguous at all; in fact, it seems to consist of a variety of languages on the fringes of more contiguous families.  This is one of the reasons a lot of people don’t buy that it is a real family.   Finally, Yukian and Athapaskan seem to be very nearly contiguous in their small areas, with Yukian disrupted by Pomo and Patwin and Athapaskan by the Algonquian languages.

Entrance Sign, Death Valley National Park

What do these patterns of contiguity and interruption mean?  One popular way to interpret them is as indicating migrations of intrusive groups that separate formerly contiguous language families.  In many places this type of analysis works well, but in California it’s tricky.  Who is interrupting whom here?  Clearly the Algonquians seem to have driven a wedge between the two sets of Athapaskan groups, and the Pomo and/or Patwin have probably done something similar to the Yukians, but otherwise it’s hard to tell.  A lot depends on who was where first.  If the Hokans originally occupied almost the whole state, as their fragmented distribution seems to suggest, then a Penutian migration from the north and a Uto-Aztecan one from the northeast seem plausible.  On the other hand, if the Penutians were there first, then a series of Hokan migrations surrounding them, followed by migrations of the other groups breaking up whatever Hokan continuum had resulted, makes sense.  I don’t have an answer to these questions, which have vexed historical linguists for decades.  I’m just using this case as an example of how difficult it can be to use language family distributions to infer culture history.

Navajo Exhibit at Chaco Visitor Center Museum

With that in mind, let’s turn back to the Navajos.  As I mentioned earlier, the Athapaskan family is one of the best-known on the continent, so it’s quite certain that all the Athapaskan languages are related and derive from a common proto-language.  Their widely scattered distribution, then, definitely looks like the result of a series of migrations.  Since the largest area occupied by speakers of Athapaskan languages is in the north, it seems reasonable to conclude that they originated there and that the smaller areas along the Pacific coast and in the Southwest are the result of migrations.  The greater number of Athapaskan languages in Alaska and Canada, and the greater diversity among them, also argues for this point.

Cottonwoods along Shonto Wash, Shonto, Arizona

All these considerations, which are important in answering questions about the nature and direction of migrations, are what might be called “external” linguistic evidence.  They are linguistic in the sense of being about language, but they don’t have anything to do with the specific characteristics of the languages in question.  “Internal” linguistic evidence, on the other hand, involves looking carefully at the vocabulary and structure of the languages themselves and trying to see what, if any, conclusions about culture history can be drawn from it.  This is hard work, and not necessarily rewarding, and it’s no surprise that it’s much less frequently used in these discussions.  When it is, though, it has the potential to shine an interesting light on these questions, and it provides a clear way to confirm or disprove conclusions derived from other evidence.

Snow-Covered Hogans, Shonto, Arizona

Internal evidence often consists of things like loanwords and other evidence of contact with other languages, but Athapaskan languages rarely borrow many words from the languages around them, and Navajo in particular is notorious for its shockingly low level of borrowed vocabulary given the long association of the Navajos with other peoples.  Thus, with Navajo, answers have to be sought in more subtle places.  The famous linguist Edward Sapir wrote an article in 1936 taking a look at this very issue, and he found out some interesting things.  He noted, however, that this sort of evidence is only really useful as an adjunct to external evidence, which is particularly overwhelming in this case:

I shall try to show that there is tangible evidence in Navaho itself for the secondary origin of apparently fundamental elements of Navaho culture, such as agriculture, and that such evidence seems to point to an early association of the culture of these people with a more northern environment than their present one. It may be said—and with justice—that the distribution of the Athapaskan languages is such as to make this historical theory as good as certain, but dialectic distribution is external, rather than internal, linguistic evidence. It is conceivable, if not plausible, that the Athapaskan-speaking tribes were originally massed in the Southwest and gradually rayed out to the north in successive waves of migration. One might argue that the Navaho and, to a greater degree, the various Apache tribes present the non-Pueblo aspect they do, not because of their relative recency in the area of Pueblo cultural development but because, like the Walapai and other Yuman tribes of Arizona, they represent a simpler and more archaic Southwestern culture, which proved impervious, aside from a late Pueblo veneer, to the influence of the more elaborate cultures in their neighborhood. It is true that the linguistic homogeneity of the Southern Athapaskan dialects is such and the dialectic cleavages in the northern Athapaskan area are so profound that the suggested theory fails to carry conviction either to the linguist or to the ethnologist, but here again we are dealing with external linguistic evidence. This external evidence is far more compelling than can be any evidence derived from details of dialectic structure or vocabulary, for it is more direct and sweeping. None the less, the more elusive internal linguistic evidence has its place in giving confirmation to a hypothesis based on linguistic distributions.

Note, by the way, the total lack of any mention of archaeology here.  Both the internal and external evidence for the migration of the Navajos and Apaches into the Southwest come entirely from linguistics, which means, among other things, that there is no way to date that migration.

Shonto Trading Post, Shonto, Arizona

Sapir comes up with four words with interesting etymologies that seem to confirm that the ancestors of the Navajos at one point probably did not live in the Southwest:

  1. The Navajo word for “gourd” is ‘adee’, which also means “dipper” or “ladle” (dippers and ladles in the Southwest generally being made from gourds).  Etymologically, however, the word ‘adee’ clearly means “(animal’s) horn,” and there is plenty of evidence from both Northern and Southern Athapaskan languages to show that the development of this word to “ladle” is a Southern Athapaskan development, while the further shift to “gourd” is unique to Navajo.  This suggests that the ancestors of the Navajos and Apaches originally made ladles out of animal horns, and that the Navajos later began using gourd ladles like the Pueblos but called them by the term they had earlier used for the horn dippers, eventually extending the use of the term to the gourd in general, as well as to dippers made of other materials.
  2. Navajo has a verb sisas meaning “to lie” that applies specifically to seeds being planted, along with a related verb naasas meaning “to sprinkle” referring to not only seeds but also other granular substances such as sand.  There are no cognates to these verbs in other Athapaskan languages, which suggests that they are likely derived from a noun, which in this case clearly seems to be yas (or zas), “snow,” cognates of which are found throughout Athapaskan.  This suggests that the ancestors of the Navajos were not familiar with agriculture but were very familiar with snow.
  3. The Navajo word for “corn” (i.e., maize) is naad́ą́́ą́’.   The second syllable is clearly an old word meaning “food,” but the first syllable is more mysterious and not obviously interpretable by native speakers.  Sapir argues, however, that it derives from a term found throughout Athapaskan meaning “enemy” (or, perhaps better, “foreign”) and often used in the names of other tribes.  This term is probably most familiar to readers of this blog from the term ‘anaasází; if in fact this means “enemy ancestor,” this is the term involved.  In the case of corn, the original meaning would be “enemy’s food” or “food of the foreigners,” presumably meaning the Pueblos and implying that at the time they first encountered corn Navajos not only didn’t farm themselves but perceived agriculture as something foreign to their own culture.
  4. There is an odd verb root, -kééł in the imperfect, used in only a few fixed, idiomatic phrases, that can’t be easily interpreted by native speakers.  One of the more colorful uses of it is as the sacred name for the owl, chahałheeł yił náákéłí, “the one who [?]s back with darkness.”  From this and other contexts in which it is used, the verb clearly refers to some sort of motion, but otherwise there is no way to understand it within Navajo.  Outside of Navajo and Apache, however, and particularly in the northern Athapaskan languages, this root has a straightforward and very interesting meaning: “to travel by canoe.”  This is a common way to get around in northern Canada, of course, but not so useful in the Southwest, and the Navajos seem to have lost all cultural memory of it aside from these few fixed phrases.  The owl, however, is still “he who brings darkness back in his canoe.”

It’s really only the fourth of these that associates the Navajos with a specifically northern origin; the others just imply that they were originally unfamiliar with agriculture, which could have happened if they had been hunter-gatherers in their current location (where it does snow).  Taken together with the other lines of evidence, however, these words further confirm the idea that the Navajos originally came from the north, and in addition they offer interesting glimpses of the Navajo past.
Sapir, E. (1936). Internal Linguistic Evidence Suggestive of the Northern Origin of the Navaho American Anthropologist, 38 (2), 224-235 DOI: 10.1525/aa.1936.38.2.02a00040

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Radiocarbon Pitfalls

Bone Tools at Chaco Museum

Julien Riel-Salvatore has a good post explaining how radiocarbon dating works and how the presentation of dates derived from it in both popular and scholarly contexts can be misleading.  The main issues revolve around the differences between “raw” radiocarbon dates, expressed as radiocarbon years before present (BP), and “calibrated” dates, which have been converted to calendar dates by comparison to the curve representing the changing concentration of radiocarbon in the atmosphere over time, which has been constructed by taking radiocarbon measurements from tree rings and other sources of secure, independent dates.  Because of the difference between the two types of dates, raw dates are typically understate the actual age of things if taken at face value, which is why it’s problematic for them to be reported in popular contexts when calibrated dates are available.  Also, and perhaps more importantly, raw date ranges are normally distributed, but calibrated date ranges are not, since the calibration curve is so oddly shaped.  This means that while the midpoint of a raw date range represents the most likely date within that range, the same is not true for the midpoint of a calibrated date range, and it can be very misleading to treat a calibrated midpoint as an actual date.

Sandals at Chaco Museum

Radiocarbon dating isn’t used much in Southwestern archaeology, since it’s much less precise than the tree-ring dates that are widely available, but as I mentioned recently it’s becoming more common as archaeologists begin to explore new sources of information.  After reading Julien’s post I went back to the Benson paper I had discussed before and saw that Benson used his radiocarbon dates appropriately, focusing on the calibrated dates but not putting any particular emphasis on the midpoints of the ranges.  In a late-prehistoric context, this is the way to do it.

Yucca at Chaco Visitor Center

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Western Burial Rooms in Old Bonito

There are a lot of oddities about the burials found at Chaco.  For one thing, there are remarkably few of them.  This seemed particularly strange to archaeologists in the early twentieth century who thought that the great houses all held large resident populations and that the canyon population must have been very high, and they embarked on many fruitless attempts to find cemeteries outside of the habitation sites.  Recent theories have reinterpreted the great houses as having much smaller populations, which takes care of some, though not all, of the mystery about the “missing” burials.  Nancy Akins, who has studied the human remains from Chaco more intensively than anyone else, has argued that the remainder can likely to accounted for by poor preservation, early looting of trash mounds (which often contain burials) and other sites, and a variety of other factors.  In any case, relatively few of the many sites in the canyon have been excavated, and even fewer have been excavated thoroughly with adequate documentation, so it’s probably best not to try to draw too many conclusions from the limited data available.

There are some other puzzling things about the burials, however, particularly the ones at Pueblo Bonito.  Since Bonito has been almost completely excavated, and these excavations, although they took place relatively early with relatively crude techniques, are fairly well-documented, quite a few conclusions can be drawn about its burials.  For one thing, there really are very few of them, so few that even if recent low population estimates are correct it still must be the case that not everyone who ever lived at Bonito was buried there.  The burials are also clustered primarily in two small blocks of rooms, both in the oldest part of the site.  And, of course, there are the fabulously extravagant burials in one of these clusters that have been the occasion of much speculation on the nature of Chacoan society.

Interior of Reconstructed Great Kiva, Aztec Ruins National Monument

One other thing about the Bonito burials, however, is that they are not gender-balanced.  There are more women than men among the burials, and the women are particularly clustered in the western burial group, whereas men predominate in the northern one, where the high-status burials are.  While it can be risky to try to draw conclusions from the small numbers of burials that are typically excavated from sites, in this case the relative completeness of both the excavation and the documentation means that these are very likely to be almost all the people ever buried at Bonito, which means that the skewed gender ratio is not the result of sampling error but represents something real about Chaco.   Few, however, have looked into what, exactly, this might be.

There is one recent article by Tim Kohler and Kathryn Turner (available in pdf here) that does exactly that, however.  Based on Turner’s MA thesis, the article looks at the issue of gender imbalance in burials at Southwestern archaeological sites and tries to see what, if any, conclusions can be drawn from the data.  Since, apart from a few exceptional sites like Pueblo Bonito, the data is rather sketchy, they are quite up-front about the many problems with sampling, preservation, and other factors that might bias the data, and they are appropriately humble and tentative about their conclusions.  What they find is fascinating, however, and worthy of continued attention.

T-Shaped Doorway at Aztec Ruins National Monument

Since this is potentially a huge topic, Kohler and Turner focus geographically on northwestern New Mexico and southwestern Colorado, where data on burials is generally pretty good.  It’s still not perfect, however, and they point out that of all the burials noted in the published literature less than half could be sexed.  This forms the total corpus of data they examine, and overall it is basically gender-balanced.  They divide it up into smaller sets by both time period and geographical sub-area, however, and this is where things start to get interesting.

For most areas in most periods, the gender ratio isn’t very far from 50-50.  There are a few notable exceptions, however, and, tellingly, they include some of the places that were most important regionally during the time periods in question.  These include the Chaco area in the eleventh century and the Totah area in the thirteenth, both of which have considerably more women than men.  In both cases the samples are dominated by a single well-documented site: Pueblo Bonito at Chaco and Aztec West in the Totah.  Given all the other similarities and connections between Chaco and Aztec, this is a finding of considerable interest.  The other area that has an unusual gender ratio is Mesa Verde in the thirteenth century, where there are more men than women.  Again, this is a well-documented area that was also of considerable importance within the region during this time period.

Cliff Palace and Sun Temple, Mesa Verde

So what does this mean?  Kohler and Turner interpret their findings primarily in the context of the considerable evidence for warfare in the prehistoric Southwest.  They conclude, quite reasonably I think, that the striking symmetry between the excess women at Aztec and the excess men at Mesa Verde in the thirteenth century, a time known from other data to have seen considerable violence throughout the region, resulted from warfare between the two areas in which the people of Aztec successfully captured women from Mesa Verde.  Given that there is also considerable evidence from the La Plata valley during this same period that some women formed a poorly treated, possibly enslaved, underclass, they also suggest that the captured women at Aztec may have been slaves, although confirmation of this hypothesis would require more detailed study of the specific remains.

The eleventh-century Chaco evidence is harder to interpret.  Given the general lack of evidence for widespread warfare during this period, and the further lack of any area with a shortage of women corresponding to the excess of women at Chaco, it is quite possible that this imbalance is fundamentally different from the later one at Aztec and that it arose from some other factor than warfare.  Kohler and Turner definitely seem to want to interpret it as warfare-related, and while there is basically no evidence of fighting at Chaco itself it is certainly plausible that the Chacoans could have been involved in warfare elsewhere.  They acknowledge, however, that despite the intriguing parallel with the Aztec situation it is equally plausible that something else is going on at Chaco, perhaps some form of diplomatic marriage-partner exchange (presumably polygamous) or the enticement of women skilled at particular crafts (perhaps jewelry-making?) to come to the canyon.  As for where these women would have come from, Kohler and Turner acknowledge that in only looking at New Mexico and Colorado they are excluding extensive areas in Arizona and Utah showing varying degrees of Chacoan contact and influence.  It is also possible that the imbalance at Chaco reflects not an excess of women but a shortage of men, perhaps from young men being sent out to found outliers or otherwise expand the system, perhaps even by fighting on the frontiers.  Or maybe Pueblo Bonito isn’t typical, and the imbalance there is made up for by male-dominated burial groups at unexcavated sites in the canyon.

Stairway Leading out of Reconstructed Great Kiva, Aztec Ruins National Monument

Despite the inherent difficulty of coming to firm conclusions about issues like this, Kohler and Turner do a good job of presenting the evidence that is out there and discussing how it might be interpreted.  Certainly more work will be necessary to clarify the patterns they identify and see if they actually represent anything meaningful, and they specifically mention the potential for strontium-isotope analysis and other techniques from physical anthropology that would be helpful in this respect.  The line of research they pioneer in this paper may or may not lead anywhere, but it will be fascinating to follow it in the coming years to see where it goes.
Kohler, T., & Turner, K. (2006). Raiding for Women in the Pre‐Hispanic Northern Pueblo Southwest? A Pilot Examination Current Anthropology, 47 (6), 1035-1045 DOI: 10.1086/508697

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Exterior of Reconstructed Great Kiva, Aztec Ruins National Monument

One of the most interesting and potentially productive lines of research in Southwestern archaeology these days involves the use of chemical analyses of various archaeological materials to extract more information about the societies that used them than is apparent just from looking at them.  The oldest and most established type of research like this is radiocarbon dating, which has historically been used less in the Southwest than elsewhere because it’s both expensive and less precise than tree-ring dating, which was invented in the Southwest and has been extremely important in the study of its prehistory.  Lately, however, archaeologists in the Southwest have been using radiocarbon more and more, since it can be used on anything organic (useful for sites which produce no datable wood but plenty of other organic material) and it’s been around for so long that the dates are considered very reliable.  They’ve also begun to use some other techniques that are newer but have enormous potential, which is already starting to be realized, to illuminate aspects of the past that have been the cause of much debate.

Intact Roof at Aztec Ruins National Monument

The most important of these is strontium isotope analysis, which we’ve seen before in the analysis of the wood brought to Chaco for architectural use.  Like radiocarbon dating, strontium analysis is based on looking at the ratio of two isotopes of an element, one of which is stable and the other of which is produced by the radioactive decay of another element and therefore varies.  Unlike radiocarbon, however, strontium cannot be used for dating on archaeological timeframes, since the half-life of the radioactive decay process involved (the conversion of rubidium-87 to strontium-87) is 48.8 billion years.  It can, however, be used to identify locations, since the amounts of strontium and rubidium in different areas vary a lot and strontium is absorbed unchanged by organisms from their environment.  Thus, in theory, one could test an organic artifact for its strontium ratio, then compare that to the strontium ratios of the water or soil in various places where the artifact may have originated and figure out where it came from.  This would then allow all sorts of archaeological conclusions.

Intact Roof at Pueblo Bonito

Of course, it’s never quite that simple, as the case of the wood shows.  It was relatively easy to use this analysis for the high-elevation types of wood that occur in relatively few places in the Southwest, but when the technique was extended to the very common ponderosa pine beams the number of possible origins increased so much that few definite conclusions could be reached.  There is also the problem of making sure that the strontium ratios found in the archaeological material actually resulted from growth processes rather than contamination by later mineral deposits.  Since this technique is relatively new, the methodology for it is not yet totally worked out, and not every attempt to use it ends up working.

Row of Metates, Aztec Ruins National Monument

Both the promise and the pitfalls of strontium analysis are shown clearly by a new paper by Larry Benson of the United States Geological Survey.  Benson has made something of a name for himself as the main player in the increasingly important analysis of corncobs found in Southwestern archaeological sites.  Corn is a useful plant to use for this sort of thing for a number of reasons:

  • It’s pretty common, especially in sites like cliff dwellings and Chacoan great houses with especially good preservation of organic material.  The Anasazi depended heavily on corn for their diet, so there are corncobs all over the place.
  • It grows quickly.  This is not important from the perspective of strontium analysis, but it means that radiocarbon dating can provide a very accurate range of dates within which the corn was grown and eaten.  This is in contrast to slow-growing plants, such as trees, which have the problem that the part tested may happen to be much older than the date of use.  The combination of accurate dating with strontium-based source determination makes corn a very powerful source of information.
  • It bears directly on a variety of important cultural questions.  Since corn was the main source of food for the Anasazi, finding out if they were growing it themselves or importing it from elsewhere has major implications for models of cultural systems and their means of support.  This is a longstanding issue in the study of Chaco specifically.

This particular paper addresses several issues, both substantive and methodological.  Substantively, Benson analyzes a set of corncobs excavated from the Gallo dwelling in the Chaco campground in the 1950s and adds the data derived from them to the data from earlier studies of cobs from this site as well as from Pueblo Bonito and Chetro Ketl.  He also reports on strontium isotope ratios from several agriculturally productive areas of the Zuni Reservation and adds them to the previously reported data from other parts of the Colorado Plateau.  He then combines this new information with the previously reported data to draw some specific conclusions about the sources of some of the cobs.  Importantly, however, he does not come to any conclusions about the sources of the newly analyzed Gallo cobs.

Metate at Pueblo Bonito

The reason for this lies in the methodological side of the paper, which may be the most important in the context of overall research on this topic.  The cobs Benson reports for the first time here, unlike the previously analyzed cobs, were not burned, and part of the purpose of this research was to see if the procedures used to prepare and analyze the burned cobs could be used for unburned cobs as well.  As it turns out, they can’t, and the strontium ratios from the unburned cobs appear to come from post-depositional mineral contamination rather than growth conditions.  This seems to be because the act of burning effectively “seals in” the trace minerals in the cobs, protecting them from contamination.  While this result is somewhat disappointing, in that it means that the strontium data from the new cobs can’t be used to draw any conclusions, it is important in informing others that if they want to do this kind of research on unburned corn cobs they need to come up with new procedures.  In the course of doing this analysis Benson also uses some data on recent experimental growing of Pueblo varieties of corn in Farmington that provides valuable reference material on just how closely strontium ratios in corncobs can be expected to correspond to the ratios in the soil and water in the area.  The answer is closely, but not perfectly, which is also useful information for future researchers.

Keyhole-Shaped Kiva, Aztec Ruins National Monument

Despite those issues, however, this paper does include some important substantive conclusions.  Although the new cobs couldn’t be used for strontium analysis, they did produce radiocarbon dates, which correspond very closely to the dates on the earlier Gallo cobs as well as some of the ones from Pueblo Bonito and Chetro Ketl.  Interestingly, these dates all cluster tightly around the AD 1180s.  As Benson points out, this is after the major drought of the mid-twelfth-century, which is generally interpreted as marking the “collapse” of the Chaco system and the possible depopulation of Chaco Canyon.  It has long been known that the canyon was occupied later, from the late twelfth century until the total abandonment of the region during the “Great Drought” of AD 1276 to 1299, but it’s unclear if the population at that time consisted of a remnant from the earlier Chacoan occupation or a reoccupation by people from elsewhere who may or may not have been descended from the earlier Chacoans.  In any case, whoever the people were who lived in the canyon in the 1180s, these are their corn cobs.

Keyhole-Shaped Kiva at Pueblo Bonito

They didn’t grow them, though.  In what is probably the most interesting conclusion of Benson’s paper, and certainly the most surprising, he goes through a careful analysis of the strontium data, excluding the data from the unburned cobs, and finds that the values from the cobs do not overlap with any of the locations in the Chaco area, either in the canyon or around it, that have been tested.  It’s certainly possible that they come from somewhere nearby that hasn’t been tested, but at this point a lot of potential growing locations in and around the canyon have been analyzed, so there aren’t a whole lot of additional options.  It’s not a very promising area for agriculture, after all, and pretty much all of the obvious places have now been tested for strontium ratios.

Hubbard Tri-Wall Structure at Aztec Ruins National Monument

So if these cobs didn’t come from Chaco, where were they grown?  Benson compares their strontium ratios to data from several areas in and around the San Juan Basin: in addition to the newly reported Zuni sites, these include Lobo Mesa, the Red Mesa Valley, the Rio Puerco of the West, the Defiance Plateau, Chinle Wash, the Four Corners area, Mesa Verde, the Totah, and the Dinetah.  This covers almost the whole area once occupied by Chacoan outliers, and several places beyond.  The cob ratios turn out to overlap considerably with one of the Zuni areas, the Mesa Verde/McElmo Dome area, the Totah, the Defiance Plateau, Lobo Mesa, and the Rio Puerco valley.  For some reason Benson doesn’t mention the Puerco in the text of the article, but in the figure showing the boxplots of the values for the various regions it clearly overlaps a bit with the cob values.

Tri-Wall Structure at Pueblo del Arroyo

Unfortunately, the strontium analysis itself doesn’t provide any way to choose which of these areas is the most likely source of the corn.  Any of them is consistent with the evidence.  Benson therefore turns to other lines of evidence to narrow down the choice.  He eliminates Lobo Mesa and the Defiance Plateau because of evidence that they were not occupied during this period; he doesn’t go into a whole lot of detail on what this evidence is, which is unfortunate.  As I mentioned above, he doesn’t discuss the Puerco at all, which is also unfortunate.  This leaves Zuni, the Totah, and Mesa Verde as the remaining options.  These are all areas that had Chacoan outliers during the height of the Chaco system and probably experienced immigration of people from Chaco after the system’s collapse, and they were all home to significant populations during this relatively wet period, so they are all plausible sources of corn imported to Chaco.  Benson concludes that the Totah is the most likely source based on the fact that it is the closest of the three areas and the one that seems to have had the strongest connections to Chaco, and while he acknowledges that this is little more than a guess, it sounds plausible enough to me.  Certainly Aztec, which is often interpreted as a successor to Chaco in some sense, was a major center in the late twelfth century, as was Salmon, and the material culture of the people living in Chaco at the time shows considerable influence from areas to the north (although it’s not entirely clear how to interpret this).

Aztec West Great House, Aztec Ruins National Monument

This paper is part of a growing corpus of data, much of it contributed by Benson, showing that the inhabitants of Chaco at various times did in fact import corn to the canyon.  This seems to largely settle one of the longstanding disputes in Chacoan archaeology, and it further points out the pointlessness of trying to estimate the population of the canyon by first estimating its agricultural potential.  What remains puzzling is how this system would have worked, and why.  Beyond the obvious question of who was supplying the corn, which is partially addressed in this paper, the question of what leverage the canyon inhabitants would have had to get those people to supply them remains open.  This paper, in fact, seems to raise more questions than it answers in this respect.  While during the height of the Chacoan system it is relatively easy to come up with theories for how the canyon inhabitants could have acquired supplies from the surrounding area, in the post-collapse period, when the canyon population was tiny and regional importance had clearly shifted elsewhere, explaining how the few people left at Chaco managed to get others to grow food for them becomes a daunting task.  It’s this sort of challenge, however, that I think makes Chaco so fascinating and ensures that it will continue to be a place worth studying for a long time to come.
Benson, L. (2010). Who provided maize to Chaco Canyon after the mid-12th-century drought? Journal of Archaeological Science, 37 (3), 621-629 DOI: 10.1016/j.jas.2009.10.027

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