We developed a new approach to identify vulnerabilities to water insecurity across entire archaeological culture areas by combining a paleohydrological model of the sensitivites of hydrological systems to droughts with least-cost analyses of the costs to acquire domestic water. Using a custom Python script integrated into ArcGIS Pro software, we calculated the pairwise one-way cost in time for walking between 225 water sources and 5,446 Ancestral Pueblo cultural sites across the Jemez and Pajarito Plateaus of the Jemez Mountains, New Mexico. This allowed us to identify whether periodic hydrological droughts occurring between AD 1100 and 1700 increased water acquisition costs across these regions. We found that hydrological droughts increased travel times in both regions to durations exceeding modern standards for water insecurity. Beginning in the fourteenth century, greater underlying hydrogeological sensitivities to droughts and the decline of a dual-residence pattern caused by population losses made the remaining aggregated communities of the Pajarito Plateau much more vulnerable to water insecurity than those on the Jemez Plateau. This would have upended long-standing relationships between communities and water on the Pajarito Plateau during a time when socioeconomic integration across the northern Rio Grande Valley pulled people toward valley bottoms.

To evaluate a model of the travel-route selection process for upper Ohio Valley Paleoindian foragers (13,500–11,400 cal BP), this study investigates archaeological data through the theoretical framework of landscape learning and risk-sensitive analysis. Following initial trail placement adjacent to a highly visible escarpment landform, Paleoindians adopted a risk-averse strategy to minimize travel outcome variability when wayfaring between Sandy Springs, a significant Ohio River Paleoindian site, and Upper Mercer–Vanport chert quarries of east-central Ohio. Although a least-cost analysis indicates an optimal route through the lower Scioto Valley, archaeological evidence for this path is lacking. Geomorphic and archaeological data further suggest that site absence in the lower Scioto Valley is not entirely due to sampling bias. Instead, evidence indicates that Paleoindians preferred travel within the Ohio Brush Creek–Baker's Fork valley despite its longer path distance through more rugged, constricted terrain. Potential travel through the lower Scioto Valley hypothesizes high outcome variability due to the stochastic nature of the late Pleistocene hydroregime. In this case, perceived outcome variability appears more influential in determining travel-route decisions among Paleoindians than direct efforts to reduce energy and time allocation.

This article systematically and quantitatively characterizes interaction dynamics and community formation based on changes in spatial patterns of contemporaneous households. We develop and apply a geospatial routine to measure changing extents of household interaction and community formation from AD 600 to 1280 on the Mesa Verde cuesta in southwestern Colorado. Results suggest that household spatial organization was shaped simultaneously by the maintenance of regular social interaction that sustained communities and the need for physical space among households. Between AD 600 and 1200, households balanced these factors by forming an increased number of dispersed communities in response to population growth and variable environmental stressors. However, as population rebounded after the megadrought of the mid-1100s, communities became increasingly compact, disrupting a long-standing equilibrium between household interaction and subsistence space within each community. The vulnerabilities created by this change in community spatial organization were compounded by a cooler climate, drought, violence, and changes in political and ritual organization in the mid-1200s, which ultimately culminated in the complete depopulation of the Mesa Verde cuesta by the end of the thirteenth century.