Lithic Transport Patterns, Tool Curation Behavior, and Group Range Estimates: A Model-Based Exploration

The distances that prehistoric hunter-gatherers transported lithic artifacts are often used to estimate how far groups moved across the landscape. Changes in the scales of stone tool transport, likewise, are frequently attributed to changes in group mobility behaviors. It is unclear what effects, if any, technological changes related to the design, manufacture, use, and discard of stone tools would have had on the broad archaeological patterns of stone tool transport that we use to make inferences about group mobility. This paper uses an agent-based model to explore how these human-level behaviors affect the accuracy with which transport distances reflect the scale of group residential mobility. The world of the model represents a simple “tethered” system where patterns of seasonal group movement are centered on aggregation at a lithic source. It includes representations of group-level mobility as well as parameters controlling three basic components that affect the utility of a tool kit: use-life (how many times a tool can be used before it is exhausted), inventory size (how many tools are carried), and frequency of use (how often tools are used over a given period of time). It also includes parameterized representations of “gearing up” behaviors that affect the number of new tools produced at a lithic source. Systematic experimentation demonstrates that these behaviors in combination have significant, patterned, nonlinear effects on the maximum distances with which stone tools are transported from their locations of manufacture. In a large number of cases, the maximum distance which tools are transported prior to discard significantly underestimates the maximum scale of group mobility. Many different combinations of tool production, use, and discard behaviors produce similar outcomes with regard to the scale of tool transport, suggesting that equifinality problems should be addressed as part of any consideration of changes in stone tool transport patterns.