Scott G. Ortman

HISTORICAL ECOLOGY IN THE MESA VERDE REGION: RESULTS FROM THE VILLAGE ECODYNAMICS PROJECT

Using the occupation histories of 3,176 habitation sites, new estimates of maize-agriculture productivity, and an analysis of over 1,700 construction timbers, we examine the historical ecology of Pueblo peoples during their seven-century occupation (A.D. 600–1300) of a densely settled portion of the Mesa Verde archaeological region. We identify two cycles of population growth and decline, the earlier and smaller peaking in the late-A.D. 800s, the later and larger in the mid-A.D. 1200s. We also identify several episodes of immigration. Formation of aggregated settlements, which we term community centers, is positively correlated with increasing population and the time elapsed in each settlement cycle, and it persists during periods of regional population decline, but it does not correlate with climatic variation averaged over periods. Architectural and land-use practices depleted pinyon-juniper woodlands during the first cycle, but more stable field systems and greater recycling of construction timber resulted in more sustainable management of wood resources during the second cycle, despite much higher population densities. Our estimates for maize production are lower than previous estimates, especially for the A.D. 1200s, when population reached its peak in the study area. Even so, considerable potential agricultural production remained unused in the decades that immediately preceded the complete depopulation of our study area.

Rethinking the Pueblo I Period in the San Juan Drainage: Aggregation, Migration, and Cultural Diversity

ABSTRACTThe Pueblo I period (A.D. 750–900) in the northern Southwest was a dramatic time that witnessed large-scale population movements and the formation of the first large pueblo villages. By A.D. 860, there may have been more than 10,000 people settled in villages north of the San Juan River in southwest Colorado and southeast Utah. The populations of these villages appear to have come from at least two distinct cultural backgrounds. By A.D. 890, the population of this region had declined by at least two-thirds. Migration of substantial village populations to the south must be considered in any explanation of developments in the subsequent Pueblo II period, including the Chaco phenomenon.

Empirical bayesian methods for archaeological survey data : An application from the mesa verde region

Cultural resource databases represent the single largest compilations of archaeological site data, but these databases are seldom used in research because they were designed for management purposes, evolved from paper-based inventories, contain significant interobserver variation, and record information inconsistently. In this paper we present methods designed to alleviate these problems in an analysis of more than 3,000 ancestral Pueblo habitation sites from southwestern Colorado. Our methods draw heavily upon Bayesian statistical concepts and utilize the rich excavation records of our study area to quantify the relationship between surface evidence and excavation results using probabilities. This approach offers a number of advantages over ad hoc, judgmental approaches, and produces a more empirically justified history of ancestral Pueblo settlement in our study area. We believe methods like these have great potential for reconstructing settlement patterns from survey data.

The pre-history of urban scaling.

Cities are increasingly the fundamental socio-economic units of human societies worldwide, but we still lack a unified characterization of urbanization that captures the social processes realized by cities across time and space. This is especially important for understanding the role of cities in the history of human civilization and for determining whether studies of ancient cities are relevant for contemporary science and policy. As a step in this direction, we develop a theory of settlement scaling in archaeology, deriving the relationship between population and settled area from a consideration of the interplay between social and infrastructural networks. We then test these models on settlement data from the Pre-Hispanic Basin of Mexico to show that this ancient settlement system displays spatial scaling properties analogous to those observed in modern cities. Our data derive from over 1,500 settlements occupied over two millennia and spanning four major cultural periods characterized by different levels of agricultural productivity, political centralization and market development. We show that, in agreement with theory, total settlement area increases with population size, on average, according to a scale invariant relation with an exponent in the range . As a consequence, we are able to infer aggregate socio-economic properties of ancient societies from archaeological measures of settlement organization. Our findings, from an urban settlement system that evolved independently from its old-world counterparts, suggest that principles of settlement organization are very general and may apply to the entire range of human history.

Conceptual metaphor in the archaeological record : Methods and an example from the American Southwest

This paper attempts to unify recent theorizing on cultural meaning in material culture using the notion of conceptual metaphor. Research in several disciplines suggests that conventional metaphorical concepts are central to cultural cognition. Ethnographic studies and psychological experiments indicate that conceptual metaphors are expressed in numerous forms of human expression, including speech, ritual, narrative, and material culture. Generalizations on the nature and structure of metaphor emerging from cognitive linguistic research can be used to develop methods for reconstructing ancient metaphors from archaeological evidence. In a preliminary application, I argue that pottery designs from the Mesa Verde region of the American Southwest were conceptualized as textile fabrics, and suggest that connections between these media derived from a worldview grounded in container imagery. The ability to decipher conceptual metaphors in prehistoric material culture opens up many new avenues for research, including the role of worldview in cultural evolution, and the discovery of cultural continuities between archaeological cultures and historic ethnolinguistic groups.

Accumulations research in the Southwest United States: middle-range theory for big-picture problems

Accumulations research examines three variables fundamental to understanding the archaeological record: time, population size, and the accumulation of artifacts. This type of research has been conducted for over a century, and remains productive because it addresses both basic archaeological problems and questions of broad anthropological interest. This paper illustrates the principles and benefits of accumulations research by analyzing the accumulation of cooking potsherds at ancestral Pueblo archaeological sites in south-western Colorado. Evidence is summarized to demonstrate that cooking potsherds are an especially good artifact category for accumulations research. Then, an annual accumulation rate for broken cooking potsherds is developed and used to analyze the occupation spans of nineteen small habitation sites. Finally, the relationship between midden accumulations and occupation span is used to analyze the occupational history of a large village. Throughout, accumulations research is used to tie together historical patterns in site structure, agricultural intensification, household residential mobility, land tenure, village formation, and political development.

The social consequences of climate change in the Central Mesa Verde region

Abstract The consequences of climate change vary over space and time. Effective studies of human responses to climatically induced environmental change must therefore sample the environmental diversity experienced by specific societies. We reconstruct population histories from A.D. 600 to 1280 in six environmentally distinct portions of the central Mesa Verde region in southwestern Colorado, relating these to climate-driven changes in agricultural potential. In all but one subregion, increases in maize-niche size led to increases in population size. Maize-niche size is also positively correlated with regional estimates of birth rates. High birth rates continued to accompany high population levels even as productive conditions declined in the A.D. 1200s. We reconstruct prominent imbalances between the maize-niche size and population densities in two subregions from A.D. 1140 to 1180 and from A.D. 1225 to 1260. We propose that human responses in those subregions, beginning by the mid-A.D. 1200s, contributed to violence and social collapse across the entire society. Our findings are relevant to discussions of how climate change will affect contemporary societies.

Settlement scaling and increasing returns in an ancient society

Ancient Mesoamerican settlements obey the same scaling laws as modern cities despite vast differences in economy, technology and political organization. A key property of modern cities is increasing returns to scale—the finding that many socioeconomic outputs increase more rapidly than their population size. Recent theoretical work proposes that this phenomenon is the result of general network effects typical of human social networks embedded in space and, thus, is not necessarily limited to modern settlements. We examine the extent to which increasing returns are apparent in archaeological settlement data from the pre-Hispanic Basin of Mexico. We review previous work on the quantitative relationship between population size and average settled area in this society and then present a general analysis of their patterns of monument construction and house sizes. Estimated scaling parameter values and residual statistics support the hypothesis that increasing returns to scale characterized various forms of socioeconomic production available in the archaeological record and are found to be consistent with key expectations from settlement scaling theory. As a consequence, these results provide evidence that the essential processes that lead to increasing returns in contemporary cities may have characterized human settlements throughout history, and demonstrate that increasing returns do not require modern forms of political or economic organization.

THE BETTER ANGELS OF THEIR NATURE: DECLINING VIOLENCE THROUGH TIME AMONG PREHISPANIC FARMERS OF THE PUEBLO SOUTHWEST

The central Mesa Verde and the northern Rio Grande regions housed two of the densest populations of prehispanic Pueblo peoples in the North American Southwest. We plot incidence of violent trauma on human bone through time in each region. Such violence peaked in the mid-A.D. 1100s in the central Mesa Verde, and in general was higher through time there than in the northern Rio Grande region. In the central Mesa Verde, but not in the northern Rio Grande, there is a tendency for violence to be greater in periods of low potential maize produccción per capita and high variance in maize produccción, though these structural tendencies were on occasion overridden by historical factors such as the expansion and demise of the Chacoan polity and the regional depopulation. Violence generally declined through time in the northern Rio Grande until the arrival of the Spanish, even as populations increased. We propose that this decline was due to the combination of increased social span of polities, the importance of inter-Pueblo sodalities, the nature of religious practice, “gentle commerce,“ and increased adherence to a set of nonviolent norms.

DNA analysis of ancient dogs of the Americas: identifying possible founding haplotypes and reconstructing population histories.

As dogs have traveled with humans to every continent, they can potentially serve as an excellent proxy when studying human migration history. Past genetic studies into the origins of Native American dogs have used portions of the hypervariable region (HVR) of mitochondrial DNA (mtDNA) to indicate that prior to European contact the dogs of Native Americans originated in Eurasia. In this study, we summarize past DNA studies of both humans and dogs to discuss their population histories in the Americas. We then sequenced a portion of the mtDNA HVR of 42 pre-Columbian dogs from three sites located in Illinois, coastal British Columbia, and Colorado, and identify four novel dog mtDNA haplotypes. Next, we analyzed a dataset comprised of all available ancient dog sequences from the Americas to infer the pre-Columbian population history of dogs in the Americas. Interestingly, we found low levels of genetic diversity for some populations consistent with the possibility of deliberate breeding practices. Furthermore, we identified multiple putative founding haplotypes in addition to dog haplotypes that closely resemble those of wolves, suggesting admixture with North American wolves or perhaps a second domestication of canids in the Americas. Notably, initial effective population size estimates suggest at least 1000 female dogs likely existed in the Americas at the time of the first known canid burial, and that population size increased gradually over time before stabilizing roughly 1200 years before present.