Complex lithic assemblage variation in Arnhem Land, Australia, was initially explained by suggestions that multiple cultural groups had co-existed or that a single group had used different toolkits as they moved seasonally to exploit temporary resources. These models have proved untenable and differences in assemblage composition across the landscape are now explained in terms of procurement economics: as knappers rationed, recycled, and substituted artifacts in response to the varying cost of obtaining replacement stone in each location. The economics of raw material use, and its articulation with technological strategies suited to different contexts of mobility and risk, provides mechanisms that can explain the persistence of geographical differences in artifact assemblages but which can also make sense of temporal subtle changes in technological activities. Unlike earlier archeological theories, we can now conclude that site function and identity of the local residence groups were factors of little significance in the production of assemblage differences.Questions of why lithic assemblages display variation have been central to the explorations of Paleolithic societies on every continent. Increased understanding of lithic technology and more detailed paleoenvironmental reconstructions have, over recent decades, led to revision of many models about the character of assemblage variability and its articulation with past physical and social environments. In the context of Australia, where Paleolithic technology and economies existed until the last few centuries, reconceptualizing prehistoric ways of life involved abandoning linear models of cultural progression and recognizing that Paleolithic economic and technological systems were elaborate and dynamically changing (Hiscock 2008). These qualities are illustrated in new models of Lithic Materials and Paleolithic Societies Edited by Brian Adams and Brooke S. Blades