Change in raw material selection and subsistence behaviour through time at a Middle Palaeolithic site in southern France.

We apply a resource selection model to the lithic assemblages from 11 archaeological layers at a Middle Palaeolithic site in southern France, the Bau de l'Aubesier. The model calculates how to weight each of 10 variables in order to best match the proportions of raw materials from various potential sources in the lithic assemblages. We then combine the variables into two sets of five each, those related to the characteristics of the raw materials themselves, and those related to the sources and the terrain around them. Running the model with each subset shows that the terrain variables always provide a better match to raw material use than do the raw material variables taken by themselves, but the best model is always the overall (10-variable) model. This means that terrain is most important in every case, but raw material properties also matter. Comparing the percentage contributions of each subset within the overall model, however, shows a clear change in emphasis in the upper layers versus the lower layers of the site. In the lower six layers, the percent contribution of the terrain variables is always greater than that of the raw material variables, but in the upper five layers the reverse is true: terrain still matters, but raw material becomes more important. We also look at faunal and basic tool typological data, which show a progressive change through time, as smaller prey become more important (and large prey less so), and tools and cores proportionally less abundant in the assemblages in the upper layers. We suggest that these results reflect a change in subsistence strategies at the time of a particularly harsh climate near the end of the Middle Pleistocene, and that hominin groups using this site continued to use this new approach throughout the rest of the Pleistocene.