Resource Structure and Human Organization.- Grassland Ecology.- Ungulate Ecology.- Patterns of Forage Production on the Great Plains.- Eighteenth- and Nineteenth-Century Climate and Bison Adaptations on the Great Plains.- Recent Population Movements on the Great Plains.- Ecological Relationships in Recent Plains Society.- Recent and Paleoindian Environments of the Southern High Plains.- Paleoindian Adaptations on the Great Plains.- Paleoindian Responses to Environmental Change on the Southern High Plains.- Summary and Conclusions.