Martu ethnoarchaeology: Foraging ecology and the marginal value of site structure

Archaeological investigations of hunter-gatherer site structure have remained largely descriptive, despite significant explanatory advancements by evolutionary approaches to foraging behavior and ecology. To date, calls to incorporate site structure studies within this behavioral ecological framework have largely been ignored. We suggest there is a clear explanation for this. At large spatial extents, human behavior is constrained by patterned ecological variability, as such, a general theory of behavior is likely to characterize key aspects of human decisions. At small spatial extents, human behavior is not constrained by patterned ecological variability, therefore, the human decisions that produce site structure should be driven by mechanical constraints or random variation. However, variation in site structure may be ecologically relevant inasmuch as it informs on landscape level variation in human-environment interactions. Drawing on ethnoarchaeological data collected in collaboration with Martu, Aboriginal foragers in Western Australia, here we test empirically-derived, mechanistic predictions on site size and material size sorting to show how these can inform theoretically-derived, adaptive predictions from the Marginal Value Theorem. Results show that site size increases with the number of occupants and hence, the amount of in-patch foraging competition, while size sorting increases with the duration of occupation and hence, in-patch residence time. Combined, these attributes of site structure can be used as proxies of foraging behavior to explain variability in overall foraging yields. With this approach, site structure can provide insights into foraging decisions that can be examined through a general theory of behavior.