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.