J. Brett Hill

Prehistoric demography in the Southwest: Migration, coalescence, and Hohokam population decline

One of the most prominent but least understood demographic phenomena in the precontact Southwest is the disappearance of the Hohokam from the valleys of southern Arizona. Despite extensive research, no widely accepted explanation has been offered. We argue that the failure to identify a satisfactory cause is due to excessive focus on catastrophic phenomena and terminal occupations, and a lack of attention to gradual demographic processes. Based on a combination of macro-regional population studies and local research in the lower San Pedro River valley, we present an explanation for gradual population decline precipitated by social and economic coalescence beginning in the late A.D. 1200s. In the southern Southwest an influx of immigrants from the north led to a shift from a dispersed, extensive settlement/subsistence strategy to increased conflict, aggregation, and economic intensification. This shift resulted in diminished health and transformation from population growth to decline. Over approximately 150 years gradual population decline resulted in small remnant groups unable to maintain viable communities. Small, terminal populations were ultimately unable to continue identifiable Hohokam cultural traditions and consequently disappeared from the archaeological record of southern Arizona, either through migration or a shift in lifestyle that rendered them archaeologically invisible.

Transformation of social networks in the late pre-Hispanic US Southwest.

The late pre-Hispanic period in the US Southwest (A.D. 1200–1450) was characterized by large-scale demographic changes, including long-distance migration and population aggregation. To reconstruct how these processes reshaped social networks, we compiled a comprehensive artifact database from major sites dating to this interval in the western Southwest. We combine social network analysis with geographic information systems approaches to reconstruct network dynamics over 250 y. We show how social networks were transformed across the region at previously undocumented spatial, temporal, and social scales. Using well-dated decorated ceramics, we track changes in network topology at 50-y intervals to show a dramatic shift in network density and settlement centrality from the northern to the southern Southwest after A.D. 1300. Both obsidian sourcing and ceramic data demonstrate that long-distance network relationships also shifted from north to south after migration. Surprisingly, social distance does not always correlate with spatial distance because of the presence of network relationships spanning long geographic distances. Our research shows how a large network in the southern Southwest grew and then collapsed, whereas networks became more fragmented in the northern Southwest but persisted. The study also illustrates how formal social network analysis may be applied to large-scale databases of material culture to illustrate multigenerational changes in network structure.

Land Use and an Archaeological Perspective on Socio-Natural Studies in the Wadi Al-Hasa, West-Central Jordan

In recent years environmental archaeologists have emphasized evidence for human-caused degradation, and attention has been focused on the role of our discipline in debates over contemporary socioenvironmental problems. In a recent American Antiquity forum, van der Leeuw and Redman (2002) argue that current environmental research would benefit from an archaeological perspective on these problems, and that our discipline would benefit from more active engagement in the larger debate. I present research supporting the claim that archaeology has unique and compelling insights to offer socio-natural studies. I make arguments based on spatial statistical and GIS analyses of past land use in the Wadi al-Hasa, west-central Jordan, that environmental degradation in the form of soil erosion has been a problem for agropastoralists in that region for several millennia. Furthermore, I argue that an archaeological perspective on long-term patterns of land use provides information at a scale and resolution that makes it highly suitable for studies of human-environment dynamics. Archaeologys unique data and perspective create an opportunity to contribute in a more explicit manner to the study of contemporary environmental issues that currently lack long-term focus at a scale and resolution that is meaningful to humans.

Modeling agricultural production strategies in the Northern Rio Grande Valley, New Mexico

Diversification in agricultural techniques is a common strategy of risk minimization in nonindustrial societies. However, attribution of suboptimal behavior to risk minimization without consideration of the structure of risk and its environmental context obscures the complexity of agricultural decision-making. The productive potential of a prehistoric agricultural system that includes floodwater and dry farming and stream irrigation is modeled using Geographic Information System (GIS) analysis to evaluate whether diversification occurred as a response to population pressure or as a risk buffering strategy. The estimated productive potential of floodwater and irrigation farming is sufficient to have supported the estimated local population, suggesting that risk buffering is a more likely explanation. Floodwater farming and stream irrigation form a dual strategy that is effective at reducing risk. However, the potential of dry farming for subsistence production is insufficient for buffering more than a 2% productive shortfall. We propose that, within this generally risk-averse economy, dry farming was oriented toward the production of nonsubsistence crops such as cotton.

Spatializing Social Network Analysis in the Late Precontact U.S. Southwest

Abstract In this article we explore the relationship between spatial proximity and indices of social connectivity during the A.D. 1200–1450 interval in the United States (U.S.) Southwest. Using geographic information systems (GIS), we develop indices of spatial proximity based on the terrain-adjusted cost distance between sites in a regional settlement and material cultural database focused on the western U.S. Southwest. We evaluate the hypothesis that social interaction is a function of proximity and that interactions will be most intense among near neighbors. We find that this hypothesis is supported in some instances but that the correlation between proximity and interaction is highly variable in the context of late precontact social upheaval. Furthermore, we show important discrepancies between the Puebloan north and the Hohokam south that help to explain differences in community sustainability in the two regions.

The "Collapse" of Cooperative Hohokam Irrigation in the Lower Salt River Valley

Buried beneath Phoenix, Arizona, are the remains of a once prosperous irrigation society known to archaeologists as “Hohokam” and to local Native peoples (the Akimel O’odham [formerly Pima] and the Tohono O’odham [formerly Papago]) as “Huhugkam.”1 Phoenix is the largest American city north of Mexico underlain by such extensive remains predating European contact, and was so named in hopes that a new civilization would “rise from the ashes” of the ancient. Phoenix and its suburbs are rapidly growing cities with looming social and environmental concerns. These include the destruction of the archaeological record that holds clues to similar problems in the past. Despite generations of research, understanding the decline of Classic period (A.D. 1200–1450) Hohokam society remains a challenge for anthropologists. Multiple hypotheses have been proposed with varying levels of support, but all have been plagued by contradictions, or fail to offer adequate explanation of the broad phenomena at issue. The Hohokam case has been invoked in prominent discussions of collapse (Diamond 2005; Krech 2000; Lawler 2010; Redman 1999; Tainter 1988; Wilcox 2010), and our own research is mischaracterized