PALEOINDIAN TRADITIONS AND ADAPTATIONS BEFORE AND DURING THE YOUNGER DRYAS IN WESTERN NORTH AMERICA

In a period of some 2000 years, Paleoindians in western North America experienced two profound events: the loss of several genera of large mammals and the Younger Dryas climatic reversal. This paper investigates these events and their effects on Paleoindian adaptations. The first securely dated Paleoindian manifestation in western North America, the Clovis culture, appears shortly before ca. 13,000 calendar years BP, prior to the onset of the Younger Dryas and megafaunal extinction. Clovis sites are known across the region, and include mammoth and bison kill sites as well as isolated caches of stone tools. After the loss of the majority of the megafauna and at approximately the beginning of the Younger Dryas, the Folsom culture appears over much of the region. Likely the successor of Clovis, Folsom is joined by other, apparently separate, Paleoindian manifestations such as Plainview/Goshen, Agate Basin, and Western Stemmed before the end of the Younger Dryas at ca. 11,700 calendar years BP. Significant changes in site types and lithic assemblage composition are evident in these post-Clovis cultural traditions. Using an evolutionary ecological approach, it is proposed that while Clovis adaptations to Allerod environmental conditions probably featured a broad diet, mammoth and bison were likely the highest ranked resources. This is supported by features of lithic technological organization, including tool design and patterns of raw material consumption and transportation. Post-Clovis technological reorganization, at least for the Plains and Southwest, includes smaller weapon tips and new approaches to tool design and raw material economy. These features are proposed to be the result of an economic focus on bison, the sole large mammal to survive extinction and to undergo a rapid increase in numbers during the Younger Dryas. Post-Clovis subsistence strategies in the Great Basin and Far West remain unclear, primarily to a paucity of dietary information. Whatever their causes, megafaunal extinction and the succeeding Younger Dryas climatic interval seem to have prompted significant reorganization of western Paleoindian subsistence and technological strategies.