With National Science Foundation support Dr. Charles Trombold and David Browman will study the local effects of late Epiclassic political and environmental disintegration on the northern Mesoamerican frontier between ca. AD 800-1100. Excavations focus on changes in community organization within a large hinterland site, Bosque Encantado (MV-206) and nearby agricultural terraces located in close proximity to the large ceremonial center of La Quemada in the present Mexican state of Zacatecas. This center and its hinterland are important because within a relatively short period of time La Quemada devolved from a key civic/ ceremonial center with large regional sustaining population and elaborate monumental architecture to a ruined shell with an ephemeral dispersed population. Some scholars suggest that this was part of a much larger abandonment of nearly 100,000 km2 by full-time agriculturalists in northern Mexico that ultimately resulted in the fall of Tula around AD 1180. Taking advantage of this unique prehistoric frontier situation, the objective is to determine the range of social responses ultimately tied to the failure of La Quemada as a complex political entity and the associated processes of local level demographic change.
Excavations at the site of Bosque Encantado take place within the context of two architecturally and culturally defined levels of community organization that best reflect change and continuity over time. These include macro-level plaza compounds and the households that compose them. Plaza compounds are spatially discrete residence/ activity areas that are the largest socially defined architectural entities aside from the site itself. They include rooms, public and special purpose architecture and activity areas most closely associated with any given sunken plaza. Focus on households, the constituent units within these compounds, can indicate rate of abandonment, precursor stress adaptations and occupational continuity. Placing these studies in the context of community organization is the most effective way to approach a variety of scales and hierarchical levels including the individual household, household clusters, plaza compounds and ultimately the community as a whole. Study of the nearby agricultural terraces is integral to the overall goals by providing a wider background of demographic responses to economic or political fragility. This helps to distinguish and evaluate the relative importance of variables that may have played a role in abandonment.
This research ultimately deals with a single question that has current political and nearly universal implications: What are the effects and adaptive responses of a failing complex polity on its constituent population at the local level? Historically no less than at present there has been intense interests by scholars and governments on the reasons and social effects of political/ economic disintegration. On a fundamental level, however, the broadest impact of this research is integration of current research, teaching, and reciprocal foreign collaboration.
The present research was a continuation of our previous 1998 NSF-funded research within a one-kilometer radius of the large fortified ceremonial center of La Quemada in Zacatecas, Mexico. The objective of this research was to determine the range of social responses ultimately tied to the failure of La Quemada as a complex Epiclassic (~AD 600-800) political entity and the associated processes of local level demographic changes. The framework for research consisted of testing two competing hypotheses to account for the evident intensification of agriculture: (1) risk reduction as a response to environmental deterioration, or (2) population pressure. In order to evaluate these hypotheses, excavations were conducted on two habitation sites, MV-206 (Bosque Encantada), MV-266 (La Jabonera) and the major terracing system associated with La Quemada. Activities at MV-206 included 100% block excavations of 4 additional contiguous plaza compounds to determine variability in settlement layout and architectural detail, collection of over 12 additional AMS radiocarbon dates to refine ceramic and architectural chronology, collection of over 65 additional pollen/ macrobotanical samples from controlled stratigraphic contexts for paleoclimate reconstruction, and analyses of the d13N and d13C data from human bones for preliminary dietary reconstruction. Activities on MV-266 (La Jabonera), a small habitation site located contiguous to the La Quemada agricultural terraces, consisted of 100% block excavation of the main plaza precinct and 8 associated room platforms. Pollen and diatom samples were also taken from these stratigraphic excavations. As at site MV-206, excavations here were usually conducted in one meter square grid units to insure fine-grained provenience recordings. This strategy enables determination of activity areas specific to architectural and within-site locations. Activities on the nearby La Quemada agricultural terraces included sampling 9 of the 19 terrace levels. A total of 27 test units were excavated on these terraces and the 14-meter wide causeway that transects them. These units yielded 111 samples from controlled stratigraphic levels for studies of pollen, phytoliths, diatoms, soil chemistry composition and cultural artifacts. A website was established (http://artsci.wustl.edu/~trombold) as part of the data access plan. Before research began, for heuristic purposes of selecting the most plausable hypotheses for this region's agricultural intensification (climatic stress vs. population pressure), we postulated that both the agricultural terraces and site MV-266 were somewhat later than La Quemada's major occupation (i.e., post AD 900) and that they reflected environmental deterioration. Results of excavations in the 3 areas indicate that MV-206, MV-266 and the agricultural terraces were all coeval during La Quemada's apogee (ca. AD 600-800). Moreover, the pollen profiles studied from these locations indicate that climate conditions had not changed remarkably from that of the present. Preliminary analyses of diatoms and sponge spicules found in various stratigraphic levels on the terraces suggest a general ubiquity. The latter indicates that these materials may be found naturally in the soil and, as such, could have limited use for climatic reconstruction. Architectural variability was also present when comparing sites MV-206 (Bosque Encantado, MV-266 (La Jabonera) and the previously excavated (in 1986) site MV-138 (Las Adjuntas), even though these were all roughly coeval. The terraces also showed distinct construction styles. In general, site MV-138 in the Pilarillos site aggregate was composed of completely enclosed rectangular courtyards with square platforms. Sites MV-206 and MV-266 in the La Quemada site aggregate, however, were mostly composed of incompletely enclosed courtyards. Moreover, the latter two sites were mostly composed of "winged" platforms surrounding a central plaza. Three distinct terrace construction styles were present. These were discrete to specific areas of the lower La Quemada hillside in that the different styles were never used together. It is not certain yet whether these differences reflect temporal, functional or sponsorship variabilites. The most massive and widely used here were constructed of low double parallel slab stone foundations approximately 1.5m apart, between which was filled with cobble and stone rubble. Morphologically they resemble causeway construction, except that they follow elevation contours and are invariably perpendicular to the hill slope at approximately 30 meter intervals. Clearly this style of terrace construction required considerable planning and labor investment. Because this style is only found in immediate proximity to La Quemada, these terraces are thought to be the result of centralized political sponsorship to reduce erosion and enhance agricultural productivity. The second style consists of single rows of upright boulders that are only located in close proximity to site MV-266 (La Jabonera). The third style consists of low berms of soil and small cobbles. These are most common in terracing works found throughout the valley, most notably in vicinity of sites MV-206 and MV-321, and the eastern slope of Cerro Coyotes in the Pilarillos site aggregate.
