The Archaeology of Obsidian Occurrence in Stone Tool Manufacture and Use along Two Reaches of the Northern Mid-Columbia River, Washington

To explain the occurrence of obsidian artifact variation in a sample from Northern Mid-Columbia River archaeological assemblages, we employed an evolutionary archaeology model to test our hypotheses. This model identified inter-variable relationships between stone tool cost and performance sub-variables to define classifications for the collection of artifact provenance, material, technological, and functional data. Data resampling and a stepwise statistical analysis were used to make arguments for why certain partitions of the data were representative and non-randomly associated across source, time, and space. Non-random associations of data frequencies across these variables revealed that natural selection was the primary causal mechanism structuring obsidian occurrence. Results demonstrated a preference for the manufacture of tools from local, low-quality sources; the use of local sources decreased through time, while source diversity generally increased following the expansion of trade systems, and obsidian occurrence across space differed likely due to environmental factors and proximity to trade hubs