One of the more debated issues in western North American prehistory is the effect of postglacial maximum warmth and aridity on hunter-gatherer groups. Antevs (1955) described the 'Long Drought,' or Altithermal, as a period of warmer than present conditions, with increased aridity, that occurred between 7500 and 5000 bp. The decrease in effective moisture would have had deleterious effects on vegetative cover and animal populations, as well as landscapes, due to increased erosion. Several scenarios about the impacts of climate on prehistoric groups of the region have been presented. These scenarios argue for: complete abandonment of the basins and plains; technological shifts in tool kits; and an expansion in the diversity of the economy. Palynologocial evidence from northwestern Wyoming indicates that this climatic shift began as early as 9500 years ago. During this time, the forest overstory dimished and the grasslands expanded. Fire frequency may also have increased, creating a landscape with a high degree of patchiness. Modern studies of fire indicate post-burn environments are much richer in species diversity. Thus an increased frequency of fire would potentially create a more economically diverse environment for hunter-gatherer subsistence. Although this time period has been insufficiently investigated in the Park, an economic model can be developed by integrating ecological studies from Yellowstone with data recovered from regional archeological work. This paper will examine these data and the implications for understanding prehistoric economies of the Yellowstone Plateau during the early portion of the Holocene (ca. 9500 to 7500 bp).