An archaeological test of the “Exchange Expansion Model” of contact era change on the Northwest Coast

Recent anthropological studies show that traditional views of indigenous communities in the wake of European colonialism are constrained by Eurocentric biases. These biases can be overcome, in part, by greater reliance on archaeological data as an independent line of evidence and increased attention to indigenous internal sociocultural processes. This study uses these strategies to examine colonial era shifts in indigenous exchange systems on the Northwest Coast of North America. Obsidian artifact data from late precontact and early postcontact deposits are used to test what I call the “Exchange Expansion Model” (EEM) of colonial period shifts in Northwest Coast exchange systems. According to the EEM, both the volume and geographic scope of supralocal exchange among indigenous communities increased as a result of European influences. This study tests the model using obsidian artifact data from three Lower Columbia River sites – Cathlapotle (45CL1), Clahclellah (45SA11), and Meier (35C05). The results support the hypothesized increase in volume, but not the hypothesized increase in geographic scope, of indigenous supralocal exchange. To explain the departure from expectations, I propose a revised version of the EEM which considers more fully how Native demography and internal sociocultural dynamics developed in the context of introduced diseases, horses, and the fur trade. I suggest these variables facilitated increases in the flow of prestige goods, but declines in the flow of less valued goods such as obsidian, from interior sources to the Lower Columbia River. Exchange alliances between Lower Columbia Chinookans and nearby Willamette Valley inhabitants were more resistant to disruption, so obsidian importation from the Willamette Valley to the Lower Columbia stabilized, and perhaps intensified, during the postcontact era. These findings illustrate the power of archaeology for empirically testing ethnohistorical models of colonialism and for illuminating the significance of indigenous internal sociocultural processes in colonial entanglements.

► The Exchange Expansion Model posits contact era increases in NW Coast Native trade. ► I test the model with analyses of obsidian artifacts from Columbia River sites. ► Results show postcontact increases in intensity but not geographic scope of trade. ► The EEM does not capture the complexity of colonial era shifts in Native exchange. ► A revised model more fully considers Native demography and internal social dynamics.