Jeffrey S. Dean

Human Behavior, Demography, and Paleoenvironment On the Colorado Plateaus

Archaeological and paleoenvironmental data are integrated in an investigation of culture change among the Anasazi of the American Southwest by a conceptual model of the interaction among environment, population, and behavior, the major determinants of human adaptive systems. Geological, palynological, and dendrochronological reconstructions of low and high frequency environmental variability coupled with population trends are used to specify periods of regional population-resource stress that should have elicited behavioral responses. Examination of these periods elucidates the range of responses employed and clarifies the adaptive contributions of mobility, shift of settlement location, subsistence mix, exchange, ceremonialism, agricultural intensification, and territoriality. These results help differentiate responses that are triggered by environmental variability from those stimulated primarily by demographic or sociocultural factors. These analyses also demonstrate the adaptive importance of amplitude, frequency, temporal, spatial, and durational aspects of environmental variability compared to the commonly invoked but simplistic contrast between “favorable” and “unfavorable” conditions.

Prehistoric Long-Distance Transport of Construction Beams, Chaco Canyon, New Mexico

Identification of spruce (Picea) and fir (Abies) construction timbers at Chetro Ketl in Chaco Canyon, New Mexico, implies that between A.D. 1030 and 1120 the Anasazi transported thousands of logs more than 75 km. These timbers came from high elevations, probably in mountains to the south (Mt. Taylor) and west (Chuska Mountains) where Chacoan interaction was well established. Survey in these mountains might disclose material evidence of these prehistoric logging activities.

The Medieval Warm Period on the Southern Colorado Plateau

Several questions concerning the Medieval Warm Period (MWP), an interval (A.D. 900 to 1300) of elevated temperatures first identified in northern Europe, are addressed with paleoenvironmental and archaeological data from the southern Colorado Plateau in the southwestern United States. Low and high frequency variations in alluvial groundwater levels, floodplain aggradation and degradation, effective moisture, dendroclimate, and human adaptive behavior fail to exhibit consistent patterns that can be attributed to either global or regional expressions of the MWP. There is some suggestion, however, that climatic factors related to the MWP may have modified the regional patterns to produce minor anomalies in variables such as the number of intense droughts, the occurrence of specific droughts in the twelfth and thirteenth centuries, the prevalence of low temporal variability in dendroclimate, and the coherence of some low and high frequency environmental variables and aspects of human adaptive behavior. These results suggest that the MWP does not represent warming throughout the world. Rather, it was a complex phenomenon that probably was expressed differently in different regions.

Environmental Characteristics of the a.d. 900–1300 Period in the Central Mesa Verde Region

ABSTRACT This paper has a threefold purpose. First, it reviews environmental evidence proposed to account for the final migrations from the Northern San Juan region: the Great Drought (A.D. 1276–;1299), the advent of the Little Ice Age (ca. A.D. 1200), and a prolonged period of climatic irregularity that began in the thirteenth century (ca. A.D. 1250–;1450). Second, it characterizes environmental variability for the A.D. 900–;1300 interval. Finally, it suggests how altered environmental conditions, interacting with demographic and social factors in the middle of the thirteenth century, may be linked to the migration from the region by Puebloan populations.

MESA VERDE SETTLEMENT HISTORY AND RELOCATION

Abstract At the beginning of the thirteenth century A.D., the Mesa Verde region was densely inhabited by Ancestral Pueblo peoples. By the end of that century, Ancestral Pueblo peoples no longer permanently inhabited the region. We present detailed reconstructions of precipitation based on tree rings from five geographic subregions of Ancestral Pueblo occupation (Mesa Verde, Tsegi/Kayenta, Chama, Cibola, and Santa Fe) and a consideration of distributions of archaeological ceramic styles and types from four corresponding Ancestral Pueblo subculture areas (Mesa Verde, Kayenta, Cibola, and the Northern Rio Grande) in order to explore Ancestral Pueblo strategies of adaptation to farming under conditions of often inadequate precipitation. Our analyses examine and corroborate the notion that Ancestral Pueblo peoples of the Mesa Verde region maintained long-term relationships of social interaction primarily with groups that were proximate and also experienced different and complementary patterns of precipitation. These social relationships, along with development of a marked gradient in precipitation, may have facilitated eventual migration pathways from the Mesa Verde region to the northern Rio Grande. Abstract Al comienzo del siglo 13, la región de Mesa Verde estuvo densamente habitada por los Indios Pueblos Ancestrales. A fines del mismo siglo, la región estaba desierta. Usando con detalle modelos reconstructivos de precipitación basados en la dendrocronología de cinco areas géograficas (Mesa Verde, Tsegi/Kayenta, Chama, Cibola, y Santa Fe) y la distribución arqueológica de estilos cerámicos en quatro régiones cultural de los Indios Pueblos Ancestrales (Mesa Verde, Kayenta, Cibola, y Rio Grande) evaluamos un modelo de adaptación de los Pueblos Ancestrales ante los patrones de variabilidad de precipitación. Nuestro análisis examina y corrobora la noción de que la gente de los Indios Pueblos Ancestrales mantuvieron relaciones de interacción social a largo plazo con grupos cercanos que también experimentaron diferentes y complementarios patrones de precipitación. Estas relaciones sociales, con el desarrollo de un gradiente marcado en la precipitación, pueden haber facilitado los eventuales caminos de migración desde la región de Mesa Verde hasta el norte del Río Grande.

Eleventh-century shift in timber procurement areas for the great houses of Chaco Canyon

Significance The iconic great houses of Chaco Canyon occupy a nearly treeless landscape and yet were some of the largest pre-Columbian structures in North America. This incongruity has sparked persistent debate over the origins of more than 240,000 trees used in construction. We used tree-ring methods for determining timber origins for the first time to our knowledge in the southwestern United States and show that 70% of timbers likely originated over 75 km from Chaco. We found that a previously unrecognized timber source, the Zuni Mountains, supplied construction beams as early as the 850s in the Common Era. Further, we elucidate shifting dynamics of procurement that highlight the importance of a single landscape, the Chuska Mountains, in the florescence of the Chacoan system. An enduring mystery from the great houses of Chaco Canyon is the origin of more than 240,000 construction timbers. We evaluate probable timber procurement areas for seven great houses by applying tree-ring width-based sourcing to a set of 170 timbers. To our knowledge, this is the first use of tree rings to assess timber origins in the southwestern United States. We found that the Chuska and Zuni Mountains (>75 km distant) were the most likely sources, accounting for 70% of timbers. Most notably, procurement areas changed through time. Before 1020 Common Era (CE) nearly all timbers originated from the Zunis (a previously unrecognized source), but by 1060 CE the Chuskas eclipsed the Zuni area in total wood imports. This shift occurred at the onset of Chaco florescence in the 11th century, a time with substantial expansion of existing great houses and the addition of seven new great houses in the Chaco Core area. It also coincides with the proliferation of Chuskan stone tools and pottery in the archaeological record of Chaco Canyon, further underscoring the link between land use and occupation in the Chuska area and the peak of great house construction. Our findings, based on the most temporally specific and replicated evidence of Chacoan resource procurement obtained to date, corroborate the long-standing but recently challenged interpretation that large numbers of timbers were harvested and transported from distant mountain ranges to build the great houses at Chaco Canyon.

North American Tree Rings, Climatic Extremes, and Social Disasters

Tree-ring reconstructed climatic extremes contemporaneous with severe socioeconomic impacts can be identified in the modern, colonial, and precolonial eras. These events include the 1950s, Dust Bowl, mid- and late-nineteenth century Great Plains droughts, El Ano del Hambre, and the seventeenth and sixteenth century droughts among the English and Spanish colonies. The new tree-ring reconstructions confirm the severe, sustained Great Drought over the Colorado Plateau in the late thirteenth century identified by A.E. Douglass and document its spatial impact across the cultural heartland of the Anasazi. The available tree-ring data also indicate a succession of severe droughts over the western United States during the Terminal Classic Period in Mesoamerica, but these droughts are located far from the centers of Mesoamerican culture and their extension into central Mexico needs to be confirmed with the new suite of millennium-long tree-ring chronologies now under development in the region. The only clear connections between climate extremes and human impacts are found during the period of written history, including the prehispanic Aztec era where codices describe the drought of One Rabbit in Mexico and other precolonial droughts. The link between reconstructed climate and societies in the prehistoric era may never be made irrefutably, but testing these hypotheses with improved climate reconstructions, better archaeological data, and modeling experiments to explore the range of potential social response have to be central goals of archaeology and high-resolution paleoclimatology.

Desert Dendrochronology: Tree-Ring Dating Prehistoric Sites in the Tucson Basin

ABSTRACTArchaeological tree-ring dating in the Southwestern deserts has been thwarted by the absence of the conditions necessary for dendrochronological dating: the recovery from prehistoric sites of a sufficiently large number of potentially datable charcoal samples and the existence of local master tree- ring chronologies that extend back into the prehistoric period. Recent archaeological collection and tree-ring chronology building have altered this situation to the extent that two Tanque Verde phase sites in the Tucson Basin, the Gibbon Springs Site and the Whiptail Ruin, have produced the first prehistoric tree-ring dates thus far achieved in the desert lowlands. One house at the Gibbon Springs Site and six houses at the Whiptail Ruin date to the A.D. 1230s and 1240s, placements that fall near the middle of the traditional phase time span, A.D. 1150 to 1300. This dating establishes the absolute contemporaneity of the two sites, creates a reference point for dating ceramically related sites, provides ...

La 2298: The Oldest Pueblito Revisited

ABSTRACTTree-ring dates from Tapacito Ruin (LA 2298), the earliest securely dated Navajo pueblito, have played a central role in the interpretation of the Gobernador phase of Navajo history. Although previous research provided general parameters for the site occupation, the lack of provenience data for many of the tree-ring specimens left several questions unanswered. Research conducted in 1990 confirms the early occupation of the pueblito and offers suggestions concerning the site occupation and its role in post-Revolt Dinetah.

Reflections On the Foundation, Persistence, and Growth of the Laboratory of Tree-Ring Research, Circa 1930–1960

Abstract On the occasion of the 75th anniversary of the Laboratory of Tree-Ring Research, it is appropriate to reflect on the origin of the LTRR and the oft overlooked early period of its history. The period from the “Bridging the gap” event in 1929 to the semi-retirement of A.E. Douglass in 1958 was a crucial time in the development of the LTRR. Although this paper focuses on the history of the LTRR between those events, at points the history of the LTRR is, essentially, the history of the field, making a holistic understanding all the more important. The information presented here is rooted in a series of transcribed historical lectures delivered in 1992 and 1993 by Director/Professor Emeritus Bryant Bannister, and several historical reports composed by him between 1963 and 1998.