The analysis of more than 1,300 flotation samples from thousands of excavated cultural features dating to the San Pedro phase (1220–730 BC) at the Las Capas site in southern Arizona provides evidence of long-term continuity and change in plant cultivation and collection practices in response to environmental disturbances during the Late Archaic period (2100 BC–AD 50). Although preceramic foodways in the region are widely considered to have been stable for roughly 2,500 years following the introduction of maize prior to 2100 BC, analyses of macrobotanical data reveal that moderate-intensity flood events during the Middle San Pedro phase (930–800 BC) preceded the greatest richness and diversity of harvested plants, while reliance on maize was reduced. In contrast, in periods with little environmental disturbance maize was more dominant, with less diversity in other cultivated and foraged plants. Novel cultivation, processing, and foraging practices were initiated in response to disturbance but persisted after floodplain conditions stabilized. It is argued that the reciprocal relationship between disturbance and botanical diversity is integral for understanding the long-term resilience of Late Archaic foodways and that this relationship is best modeled using ecological theories termed the Intermediate Disturbance Hypothesis and the Intermediate Productivity Hypothesis.

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This article examines large-scale spatial and temporal patterns in the agricultural demographic transition (ADT) of Mesoamerica and southwestern North America (“the Southwest”). An analysis of published settlement and subsistence data suggests that the prolonged ADTs of these regions involved two successive eras of rapid population growth. Although both periods of growth were fueled by the introduction or development of more productive domesticates, they had distinctive demographic and social consequences. The first phase of the ADT occurred only in a scattering of favorable regions, between 1900 and 1000 BC in Mesoamerica and 1200 BC–AD 400 in the Southwest. Its demographic consequences were modest because it was underwritten by still rather unproductive maize. During this phase, increased population was confined mainly to a few agricultural heartlands, whereas surrounding regions remained sparsely populated. The second phase of the ADT was more dramatic in the spatial scale of its impact. This “high productivity” phase unfolded between 1000 and 200 BC in Mesoamerica and AD 500–1300 in the Southwest, and it was fueled by more productive maize varieties and improving agricultural technologies. It was accompanied by sweeping social, economic, and political changes in both regions.

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