The Evolution of Stone Tool Traditions

This study focuses on two broad questions concerning how variability in lithic technology relates to the biological and cultural evolution of humans. First, when did cumulative culture evolve? To address this question, the complexity of lithic technologies spanning hominin evolution was compared to the complexity of non-human primate technologies, and complexity achievable through randomized flaking behaviors in order to identify when lithic technologies developed that were more complex than technologies that may not require cumulative culture. The results suggest that a modern-human like capacity for cumulative culture was likely shared with the last common ancestor between modern humans and Neanderthals, and likely was developing prior to 2 mya. The second question focuses on whether one can reliably detect migrations and population expansions in the Pleistocene through lithic technology alone. To address this question, spatio-temporal variability in technology was compared to variability across cultural traits that do retain evidence of history: phonemes in human languages. Then, variability across technologies was measured in regions where population and migration histories are known a priori: these data include carefully selected assemblages relating to the migrations of Ancestral Puebloan people from Northern Arizona into the river valleys of Central and Southern Arizona, as well as assemblages relating to the expansion of Austronesian speakers into Near, and Remote Oceania. While lithic technologies show similar spatio-temporal patterning to phonemes in languages, suggesting potential for strong historical signal in lithic technology, within Oceania and Arizona technologies either weakly, or do not reflect population history. This is likely in part because prehistoric people tended to rapidly change their technologies to suit new circumstances. The above studies highlight the usefulness of broad, comparative studies of technological variation in addressing questions about the causes of variability in lithic technology and how lithic technology relates to the evolution of the genus homo.