The formation of lithic assemblages

Research into the processes that form the archaeological record is an important component of archaeological practice because formation processes are a key link between the materials that archaeologists study and prehistoric societies that they seek to understand. Computational modeling is a comparatively new technology with potential to provide new insights into the dynamics of human societies, but which has been minimally applied so far in the study of archaeological formation processes. We use computational modeling as an experimental environment to examine processes that form the archaeological record of lithic assemblages. This is especially important for lithics because it is a largely extinct technology and we cannot directly observe the accumulation of lithic assemblages over time frames comparable to those represented in the archaeological record. We systematically evaluate the individual and combined effects of the length of stay at sites, raw material distribution, differences in activities performed with lithics, and movement patterns on lithic assemblages that accumulate over different time intervals. Not surprisingly, increased access to raw material decreases the frequency of retouched artifacts in assemblages, while tasks that require more lithic use produce assemblages with higher retouch frequencies. While length of stay affects the density of lithic accumulations at sites, it has little effect on assemblages composition. Mobility patterns alone have limited impact on assemblage composition. However, mobility coupled with place provisioning or individual provisioning, associated with logistical and residential mobility strategies respectively, have significant impacts on assemblage composition consistent with prior empirical studies. Counterintuitively, the artifact palimpsests of multiple occupations that characterize most archaeological deposits may provide better information about human ecology and changing adaptations than assemblages that represent snapshots of a single or a few occupations. This work provides valuable new, quantitative insights into the information about past human social, ecological, and technological practices embedded in lithic assemblages.