Wirt (Chip) Wills
Wirt Henry Wills is an American Southwest archaeologist and a retired Virginia Tech Emeritus Professor of anthropology at the University of New Mexico. He has written numerous papers and books on the archaeology of the prehistoric southwest. He is most notable for investigations and excavations in or near New Mexico, including: the prehistoric site at Bat Cave in Catron County, New Mexico, the Mogollon Su site in western New Mexico and Pueblo Bonito located in Chaco Canyon National Historical Park.
ARROYO HONDO IN HISTORICAL CONTEXT: COMPETITION WITH NON-FARMERS
The excavation and analysis of Arroyo Hondo by the School of American Research (now School for Advanced Research) under the direction of Douglas W. Schwartz was – and continues to be - a pivotal juncture in archaeological understanding of the northern Rio Grande Valley. Other essays in this seminar series focus on the impact of the Arroyo Hondo investigations and the legacy of ongoing debate and intellectual inquiry. As much as I would like to add to that broader discussion, I lack the knowledge and rich scholarship that other seminar participants have brought to our discussions about Arroyo Hondo. I feel instead that I have been allowed the privilege of ease dropping on a vibrant and fascinating flux de paroles, full of insights and bold connections.
The exchange of ideas has been impressive, not the least because of how willingly the participants entertained the plausible and implausible as equally interesting and worthy objects of debate. The unassailable and the nearly preposterous bumped into one another routinely as the seminar discussions ranged over the history and the historical meaning of Arroyo Hondo. I didn’t always follow the cartwheeling paths of ideas that such collisions produced but the free-spiritedness of it all has been inspirational.
I have taken that “let’s see where this idea goes” attitude as permission to look at the occupation of Arroyo Hondo from a perspective that is far from conventional and on first take may seem far from relevant. In fact, some of the participants politely noted that they were a little uncertain how to link my contribution to the specifics of Arroyo Hondo. I realize this places the burden on me to explain my argument more clearly, which is that I think the late prehistoric farming villages like Arroyo Hondo were on the losing end of a prolonged historical competition with smaller, highly mobile populations that probably had very little investment in agriculture. In other words, I believe there is a reasonable basis (or anyway an argument worth considering) for thinking that the development of large communal buildings like Arroyo Hondo was one result of a long intertwined history between farming and non-farming populations. Much of what I outline in this essay is based on an earlier paper (Wills 2005) but I hope this new opportunity covers old ground in ways that will promote further discussion.
Late prehistoric farming villages like Arroyo Hondo (or the few that have been extensively excavated) exhibit rapid growth to unprecedented size (hundreds of rooms or more, large spatial footprint) during a period of equally dramatic regional population decline among farmers (Fig. 1). That is to say, pueblos got bigger after ca. AD 1300 as the number of Pueblo people became smaller (Figs. 1-3). Large cooperative groups tend to out-compete smaller, less cohesive groups and their success promotes the formation of similar large groups, and so on in a positive feedback process. This is an unexceptional pattern in population ecology and signals factors that force a population into increasingly smaller spaces, promoting competition within that confined area; a relevant interdisciplinary research literature that relies on the analogy of multicellular evolution arising from competition among single-cell organisms to model the emergence of human corporate groups (for a recent illustrative example, see Salali, Whitehouse and Hochberg 2015. Many factors can confine a population spatially, including habitat change that is too fast for populations to adjust adequately, increased predation (leading to refuge seeking) or the appearance of successful new competitors. Humans presumably have greater capacity for recognizing cause and effect than other animals and more tools for addressing potential problems, but human populations should be no less susceptible to conditions that reduce the amount of space in which they live.
The formation and growth of competitive corporate farming groups in the prehistoric northern Southwest is often (and increasingly) explained by formal historical models in which increased group size co-varies positively with intensification, eventually leading to production inefficiencies, resource depletion and incentives for moving residences (see variously Stone and Downum 1999; Varien and Wilshusen 2002; Kohler, Varien and Wright 2010; Kohler and Varien 2012; Kohler, et al. 2015; Ortman et al. 2016).
When farmers with shifting residential strategies make a move, they acquire an infusion of new resources (land, water, access to non-agricultural resources) that results in initial high return rates. Eventually these returns diminish (as a consequence, for example, of soil depletion), triggering a new move, which shifts a community back along its production curve to a segment with high returns; settlement histories can be read as continued efforts to stay in this part of the curve (Wills 2005). Farming groups moving into new areas may initially recruit other immigrants in order to reach the maximum return rates in the shortest amount of time but then adopt exclusionary policies when returns decline (e.g., Stone 1991). Pressure to achieve maximum rates quickly may be greatest when the economy is least diversified, or when it has few resource inputs beyond cultivation. That is, an economy forced to meet most of its caloric and nutritional demands through food production is likely to aggressively seek high returns, putting a premium on large founding group size.
However, a consequence of achieving high returns through large initial group size is that declining returns are also reached more quickly, setting in motion efforts to exclude or even evict residents, and eventually relocate. These expendable members of the community are likely to be only affiliates of the core social units, and if excluded will either establish dispersed small groups or seek to attach themselves to other larger aggregates (e.g., Levy 1994). Either response by affiliates indicates areas in which agricultural subsistence was possible. In the absence of competition, the best (least costly) solution for farmers is dispersal to “ideal” locations, which may be a balancing between access to production land, natural resources, and labor pools (neighbors). The long-term cycles in which farming settlements shifted between major drainage systems in the prehistoric northern Southwest prior to ca. AD 1300 is a probable example of this sort of long-fallow system (Varien 2002).
However, if farming groups are unable to move to new locales, they will either attempt to maintain return rates through greater labor inputs and/or technological innovations, or perhaps will try to remove competitors in order to open up production space. If neither solution works, say because the environment has changed in ways that will not support farming, then the likely responses are migration to suitable locations outside the impacted region, and/or shifts to non-agricultural economies (e.g., Netting 1990). Archaeologists specializing in the prehistory of the Colorado Plateau overwhelmingly see regional abandonment as a response to external environmental factors (though not necessarily any single one) that preserved agricultural economies by transferring them to better suited localities (Kohler, et al. 2010).
But there is a nagging problem with this interetation. According to Carla Van West’s (1996) geospatial analysis of soil and climate conditions between AD 1000 and 1400, complete abandonment of the 4-Corners was not necessary because there was adequate arable land to support a viable farming population despite drying trends. Kohler (2010) suggests that Van West’s work overestimates potential productivity but he does not seem to contest her conclusion. Recent research suggests that depopulation began in the AD 1200s, prior to the “great drought,” including indications of population segments from the Mesa Verde area appearing in Chaco Canyon during the middle to late AD 1100s, continuing into the AD 1200s. All of which reflects what many thoughtful archaeologists have argued, that the demographic processes were not simple and do not correlate well with episodes of dramatic environmental change (see Kohler, et al. 2012)i and raises a logical question: if complete regional abandonment was not clearly (or indisputably) a reaction to (or solution to) external environmental conditions affecting agriculture, what critical factors are missing in our explanations?
I believe we should consider the possibility that an overlooked factor is the presence of non-farming populations competing for the same resources as farmers. The reason that archaeologists reject (either explicitly or implicitly) a role for such competition seems to be mainly that there is no tangible evidence in the form of diagnostic material culture that points to contemporaneous “non-Puebloan” people before and during the beginning of widespread abandonment in the 14th century. This is an insurmountable problem for many researchers but I am not convinced that our traditional dependency on artifacts attributable to distinct ethnic or linguistic groups is a productive way to look at inter-group competition. Instead, I’d like to suggest that in this case the intangibles may as important and valuable and that it is not an outrageous proposition that the depopulation of the northern southwest that gave rise to Arroyo Hondo and others marks a failure by farmers to compete successfully with a growing population of hunter-gatherers.
THE CASE FOR INTERACTION BETWEEN FARMERS AND NON-FARMERS
The starting point for understanding the demographic dynamics that took place in the northern Rio Grande Valley in the early 14th century AD is much farther back in the past. In the past decade or so, many archaeologists have synthesized the agricultural history of the Southwest and more particularly the Colorado Plateau, and even more have grappled with the nature of social organizations and structures that may, or may not have characterized this very long period of time (see Schachner 2015). What I try to do in this part of the essay is draw attention to the less honored (or essentially non-existent) issue of potentially contemporaneous foragers.
Maize cultivation was present widely in the Southwest by 2000 BC, but the development of agricultural economies (either dietary dependency which is tricky to measure, or settlement dependency, which is easier) came much later on the Colorado Plateau, after 200 BC/AD 200 to 500 (Coltrain, Janetski and Caryle 2007). The distribution of agricultural sites in this very long period is patchy but geographically extensive and there are strong continuities between pre-maize and early maize periods with respect to overall subsistence, food processing technology and settlement characteristics. Ceramic technology was adopted by AD 400 and corresponds to indicators of household organization (large dwellings and interior storage), an increased importance of property rights (burials), and likely winter sedentism on the Colorado Plateau (Crown and Wills 1995; Wills 2012).
During the transitional centuries prior to the development of pottery and afterward, there is evidence for significant levels of violence reflecting raiding (Coltrain, Janetski and Lewis 2012). Raiding is evident in all later phases the prehistoric agricultural period in the northern Southwest, with some examples of apparent village massacres, all attesting to pervasive (if episodic) violent competition (e.g., Cole 2012). In other words, violence between groups was certainly an important feature of agricultural life for a millennium or more prior to the population exodus of the 14th century AD.
Organizational variation among farming groups was low throughout the Southwest until ca. AD 800. Broad similarities between economic strategies would have allowed “shifting” between different degrees of emphasis on food production v. foraging by individual households or residential groups, including “reversals” to full-time foraging. No farmers were completely reliant on cultivated crops and access to critical wild resources may have been more important to group survival than access to arable land. Segmentary societies comprised of distinctive household and corporate groups organized in single settlements are clearly evident after AD 800 in the San Juan River drainage system. There are strong tendencies for large sites to cluster in localities (e.g., Chaco, Mesa Verde, Wupatki) with extensively overlapping agricultural and natural resource catchments. Violence resulting in multiple deaths during is apparent in some locations, and may have exceeded levels in earlier periods. Clusters of segmentary communities in regions suggest alliances rather than intra-cluster competition (see Speilmann 1992), if there were options for occupying other suitable farming localities in the region. In other words, overlapping catchments imply constraints on production (for example, inability to expand field systems locally) originating outside the clusters.
Indirect evidence from throughout the Southwest points to weakly segmented populations on the margins of food producing regions who were full-time foragers, or able to switch between foraging and low-level farming (Upham 1994; Young 1994). For example, trincheras (terraced hillside settlements) established around 1000 BC, at Cerro Juanaqueño in northern Chihuahua, may reflect the intrusion of farming populations into forager territories, according to Hard and Roney (2005). If so, foragers constituted a threat that resulted in costly defensive settlement patterns and suggests that early farmers did not enjoy any inherent competitive advantage.
Documented regional shifting of Pueblo populations on the northern Colorado Plateau between AD 400 and 1200 would have left large geographic areas open to occupation or exploitation by non-farming, or non-Pueblo groups, for periods of several generations. This is long enough for hypothetical forager populations to have established land tenure systems in depopulated areas. If this happened, the return of farming groups to those areas would have presumably been contested. In that respect, it is perhaps informative that the “density” of violence (raiding, scalping, traumas, etc.) as reflected in archaeological sites, was highest along the northern margins of the Pueblo world (especially the San Juan River). This area is a zone of high natural resource abundance and certainly there is a potential for violent competition where fluctuating Pueblo occupation patterns created niche expansion opportunities for non-farming groups.
Those opportunities may have been attractive to Numic forgers were expanding out of the southern Great Basin by AD 1000 (Madsen and Rhode 1994), as well as hunter-gatherers who ranged widely along the eastern margins of the Rio Grande Valley at the same time. By AD 1150, some small farming groups along the northern edge of the Colorado Plateau had shifted to full-time foraging (Barlow 2002), presumably increasing the number of hunter-gatherers. Athapaskan foragers were certainly present by AD 1400 on the Colorado Plateau (Towner 1996) although recent work suggests movement into the northwestern Pueblo region by the AD 1200s (Ives 2013). In short, the northern southwest appears to have had a complex cultural landscape after ca. AD 1000 that included more populations than those we recognize as historical ancestral to modern Pueblo people.
From AD 1100 forward, farming village sites in the northern Southwest (the entire 4 Corners) were almost always defensive in character. Some villages physically enclosed strategic locations and resources (e.g., springs in SW Colorado and SE Utah), many occupied inaccessible cliff shelters, were sited on high ridges or mesa tops surrounded by cliffs, or on terraces with nearby bluffs, or incorporated towers and other defensive features. Approaches to pueblos were typically difficult, and/or required traversing open ground. Individual pueblos had limited access (usually one or two pathways into plazas, no ground floor doors).
After AD 1200 there are few examples of large pueblos with surrounding neighborhoods of small sites (the typical earlier Chacoan community). Field houses occur in some areas, as do extensive field systems in the northern Rio Grande Valley, but residential populations were mainly confined to single communal building (that might multiple linked plazas). In other words, there is little evidence for dispersed autonomous households; farmers reside exclusively in multiple household communal buildings. These types of settlements mainly formed clusters in river valleys or basins which have been interpreted as both linguistic groups and alliances (e.g., Speilmann 1992).
The maximum geographic extent of maize agriculture occurred around AD 1200 (Fig. 4). During a span of less than three centuries, from ca. A.D. 1300 to 1550, farming groups that had occupied an area of more than 300,000 square kilometers were reduced to a few isolated geographic pockets of less than 5000 square kilometers (Fig. 5). This spatial contraction was accompanied by an estimated 90 % decline in the number of farmers (Figs. 1 and 2). Only a fewsites post-dating AD 1300 have been excavated well enough to discern their occupation history with precision (Arroyo Hondo, Pot Creek Pueblo are notable examples), but these exhibit rapid initial growth, followed by partial abandonment or unfinished construction, then complete abandonment within relatively short periods. Population estimates and site distributions for the agricultural sites (especially during the ceramic period) were never great enough to “fill up” the entire Southwest; there was always space for household-based farming, overall population densities were never high and declining population numbers after AD 1300 would have meant a lower density of farmers throughout the larger region. Consequently there is no reason to assume that all areas ultimately utilized by farmers (maximum extent in the AD 1200s) were always used by farmers.
By the time of Spanish contact in the late 16th century, mobile hunter-gatherer groups were everywhere in the Southwest. Although archaeologists often emphasize this period as one of widely dispersed Puebloan isolates, another way to think about ethnohistorical geography is one where farming groups were surrounded by a vast “sea” of foragers. And if Puebloan villages were sloughing off low-ranked households during episodes of relocation or stress prior to European contact, as they did after contact, it is likely that some of these households joined the ranks of mobile foragers. It is perhaps not unfair to suggest that by the AD 1600s, southwestern farmers occupied a small part of a hunter-gatherer world.
Assuming that non-Puebloan populations were always present in the Southwest during the agricultural period, is it likely that they would have competed with farmers and is it imperative that we “see” those foragers directly in the archaeological and it is? I think the answers are yes no. First, foragers competing with farmers may “steal” from the top of the wild resource pool – the more reliant farmers are on wild resources the more susceptible they are to this type of competition - and this loss of resources can drive increasing dependence on agriculture and consequently greater sensitivity to external impact on food production. Foragers with more efficient structures, including flexible mechanisms for opportunistic aggregation, can be extremely competitive with more rigid kinds of sociopolitical organizations, just as farmers with different organizational features but similar economies can represent asymmetrical efficiencies. The point is that organizational strategies vary in terms of competitive success depending on historical context, rather than an inherent advantage in large numbers.
Archaeologists in the Southwest often seem to assume that hunter-gatherers are (or were) at a competitive disadvantage vis-à-vis farmers because the latter occupy well-defined territories, usually in villages that can marshal large numbers of men (or fighters) to deter and retaliate to raiding. A corollary is that migrating farmers should be expected to displace indigenous hunter-gatherers. Yet, during the Spanish colonial period (AD 1598 to 1821) in the American Southwest/Mexican Northwest, a state-level society was notably unsuccessful in mitigating or staunching the geographic expansion and loss of territory to pedestrian (lacking horses) and eventually horse borne hunter-gatherer groups, famously including the Navajo and Apache. The Spanish Colonial “Presidial Line” established in 1770s stretching from Sonora to west Texas to restrict Apache raiding was a strategic failure.
Second, we do not need physical evidence for competitors to find expectable reactions to their presence in the behavior of farmers. Scientists rely heavily on unseen forces in the natural world as explanations for observable phenomena (gravity, magnetism, electricity, radio waves, university administrators) and same logic applies to economic behavior. Thus we should be able to monitor the reaction to a competitive environment in ways other than by direct physical evidence of competition between distinguishable cultural groups. As a working assumption, any time we find Ancestral Pueblo farmers pursuing strategies that are contrary to expectations for simple competition with other agricultural groups (i.e., those with similar economies), it is reasonable to think about constraints imposed by populations with different lifeways.
If the economic loss to farmers was significant enough that some left the region in response, thereby reducing the number of remaining farmers, hunter-gatherers might have gained a numerical advantage, which in turn could have made cryptic dispersal of farming households into remote and inaccessible places ineffectual as a long-term defense. Although some Northern San Juan settlements were large, they weren’t really that big, perhaps few dozen households in the largest cases, so the departure of even a few households might put the community at great risk from predation. A downward population spiral among farmers could have been exacerbated by climate change that made food production less certain, but if movement was driven also by loss of high ranked resources or resource zones to demographically surging forgers, then that might explain why farmers never returned to a previously prime agricultural region.
Is there any empirical support for this scenario? Possibly. If farmers were being deprived of access to high ranked wild resources, we could expect to see those resources fall out of the archaeological record of agricultural settlements. For example, deer are widely considered the highest ranked (with respect to economic returns) faunal resource in the northern San Juan region (Kohler 2010). Research by Driver (2002:159) demonstrated declining numbers of artiodactyl (mainly deer) in Mesa Verde area farming sites through time, including “an almost universal lack of artiodactyls in Pueblo III [AD 1150 to 1300] assemblages” that he attributed to hunting pressure by the farming population. He also noted that artiodactyls were uncommon in some areas with low settlement density but good deer habitat, and that in some sites deer may have been controlled by segments of the community, presumably rather than available to everyone (Driver 2002:160). These patterns are usually explained (quite reasonably) as local resource depletion by farmers but they are also consistent with restricted access (or loss of access) to deer, as a model of hunter-gatherer competition predicts. Parenthetically, if formal explanatory models for regional depopulation by farmers do not include a potential role for competition from foragers, then those models certainly won’t be able to find one.
So why aren’t non-Puebloan farmers a factor in current explanatory models for regional depopulation? Again, southwestern archaeologists rely on cultural markers (especially ceramics and perishables) to “see” different contemporaneous populations and these are strongly linked to direct historical trajectories (hence the perpetual efforts to establish migrants routes of modern linguistic groups). Thus “non-Puebloan” people in the past are only recognizable when there is a material record that can be linked to the present, such as the Dine (Navajo) or Utes of the Colorado Plateau. Interestingly, those markers become apparent to specialists in the century immediately after farming communities quit the northern Colorado Plateau, with the conventional interpretation that initial appearance signals the arrival of new people in an empty landscape. But for the sake of argument, what if this is really when long-term non-farming residents begin to (or are able to safely) express identity (signal it)? Could this be the point when erstwhile marginal groups begin to coalesce in regions from which farmers have retreated?
There are lots of good reasons to assume that foragers living around farming settlements and competing for the same wild resources might actively hide from those farmers. And in hiding they would presumably not leave obvious signs of their presence. It understandable that archaeologists might have a difficult time recognizing the signatures of non-farming people if those people were attempting not to create a material record in the first place. This isn’t a happy thought for archaeologists but it seems like eminently rational behavior for mobile foragers in a competitive world.
I do not claim to know better than my colleagues about how to explain the dramatic (in terms of the final result) movement of farmers off the Colorado Plateau, and I have no illusions that this loose seminar paper offers an explanation around which many specialists will feel the need to rally. But one of the reasons for having seminar discussions is to explore ideas and possibilities that may not be conventional and find out whether their marginality is an accurate reflection of their relevance to an issue, or whether being on the margin is perhaps a sign of where future progress might originate. For the moment, I simply wonder how we would think about the depopulation of the northern Southwest and the overall decline in farming populations if our hypotheses included competition and long-term interaction among economic variants (farmers, hunter-gatherers, part-time farmers, big villages, dispersed households, and so forth), rather than just interaction among one socioeconomic type?
In any case, Douglas Schwartz intended for the Arroyo Hondo discussions to draw that particular place, people and time into a broader understanding about the nature of Puebloan society in the northern Rio Grande Valley. Clearly, Arroyo Hondo was founded and occupied during a period of local population packing and pressure with negative consequences for health and diet (see Wetterstrom and LeBlanc in Schwartz 2016). The community’s rapid growth, abandonment and reoccupation (see Creamer 1993) are consistent with seeking high marginal returns quickly through population aggregation, then moving on, and perhaps back again. The inhabitants of Arroyo Hondo may not have been in direct competition with mobile non-farming groups crowding around the margins and exploiting the interstices of the Puebloan world, but I would bet that Arroyo Hondo and all similar, contemporaneous large northern Rio Grande Pueblos were collectively reacting to a shrinking cultural geography that encouraged the formation of increasingly larger farming villages but did not ameliorate underlying socioeconomic causes of the continued decline in agricultural populations.
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Figure 1. Estimates of overall population change in the Southwest (from Prehistoric
Demography in the Southwest: Migration, Coalescence, and Hohokam Population Decline
J. Brett Hill, Jeffery J. Clark, William H. Doelle and Patrick D. Lyons American Antiquity Vol. 69, No. 4 (Oct., 2004), pp. 689-716)
Figure 2. Number of habitation sites in late precontact Southwest (from Prehistoric
Demography in the Southwest: Migration, Coalescence, and Hohokam Population Decline
J. Brett Hill, Jeffery J. Clark, William H. Doelle and Patrick D. Lyons American Antiquity Vol. 69, No. 4 (Oct., 2004), pp. 689-716)
Figure 3. Sepawe Pueblo, near El Rito, New Mexico, in the Northern Rio GrandeValley. Photograph taken from the southeast. AD 1300 to 1550, 1000+ rooms, ca. 11 hectares, ten plazas. Sepawe is likely the largest prehistoric pueblo in New Mexico.
Figure 4. Maximum geographic extent of prehispanic farming (ca. AD 1200). From Wills (2005).
Figure 5. Distribution of southwestern agricultural populations between AD 1600 and 1700. From Wills (2005).
i In many parts of this essay I am trampling around in areas and research which I do not really know that well, and I may unfortunately misrepresent, misunderstand or simply overlook seminal work by esteemed colleagues. I have not included many, many scholars who have written about the depopulation of the northern Southwest, and to any of those who might read this essay I apologize, but this this is intended to be a thought piece for a seminar and not a synthesis. Hopefully I’ll be forgiven for the times I favor conjecture over caution, although I don’t doubt that any mistakes will be noted and communicated to me with encouragement for corrections.