Speaker: Dr. Richard Lesure, Cotsen Institute of ArchaeologyLesure will report on the work of a team of archaeologists from the UCLA Anthropology Department and Cotsen Institute of Archaeology who are trying to understand the demographic impact of the transition to agriculture at a continental scale. The area of interest is Greater Middle America, roughly from southern Utah (USA) to the Panama Canal. We build on recent studies of the Agricultural Demographic Transition (or ADT) and on efforts to trace expansions by early farmers on scales approaching the continental. Our argument in this paper is that the ADT in Middle America was long and bumpy, involving at least two eras of very rapid population growth. In much of Middle America, those periods of highgrowth can be identified as the demographic effects of, in succession, an Early-Maize Formative and a Maize-Staple Formative. The Early-Maize Formative tended to lead to localized population concentrations (including villages of more than 10 ha) within a larger landscape still sparsely populated. Well attested radial expansions of farmers from agricultural heartlands are instead a recurring feature of the Maize-Staple Formative; their spatial extents prove to be significantly smaller than continental. We suggest that, in Middle America, analysis at a macroregional scale of 10-40,000 km² is crucial in the effort to understand continental-scale patterns in the transition to agriculture.