“Every Tradesman Must Also Be a Merchant”: Behavioral Ecology and Household‑Level Production for Barter and Trade in Premodern Economies

While archaeologists now have demonstrated that barter and trade of material commodities began in prehistory, theoretical efforts to explain these findings are just beginning. We adapt the central place foraging model from behavioral ecology and the missing-market model from development economics to investigate conditions favoring the origins of household-level production for barter and trade in premodern economies. Interhousehold exchange is constrained by production, travel and transportation, and transaction costs; however, we predict that barter and trade become more likely as the number and effect of the following factors grow in importance: (1) local environmental heterogeneity differentiates households by production advantages; (2) preexisting social mechanisms minimize transaction costs; (3) commodities have low demand elasticity; (4) family size, gender role differentiation, or seasonal restrictions on household production lessen opportunity costs to participate in exchange; (5) travel and transportation costs are low; and (6) exchange opportunities entail commodities that also can function as money. Population density is not a direct cause of exchange but is implicated inasmuch as most of the factors we identify as causal at the household level become more salient as population density increases. We review archaeological, ethnohistoric, and ethnographic evidence for premodern marketing, observing that the model assumptions, variables, and predictions generally receive preliminary support. Overall, we argue that case study and comparative investigation of the origins of marketing will benefit from explicit modeling within the framework of evolutionary anthropology.