El Castillo (Cantabria, northern Iberia) and the Transitional Aurignacian: Using radiocarbon dating to assess site taphonomy

Abstract The majority of archaeological remains found at El Castillo in northern Iberia were excavated between 1910 and 1914 by Hugo Obermaier. Since the 1980s El Castillo has been studied through a detailed analysis of Obermaier's original excavation notes, the cleaning and study of the extant section, and the excavation of material in the shelter entrance. Radiocarbon dating of charcoal from the modern (1980s onwards) excavation suggested that unit 18, corresponding to Aurignacian Delta of the 1910s excavation, was significantly earlier than other Aurignacian assemblages in western Europe. Combined with a reanalysis of the lithic and osseous industry, these dates led to the suggestion that material in unit 18 and Aurignacian Delta was a transitional industry, showing a gradual transformation of the Mousterian into the Upper Palaeolithic. The conclusion has profound implications for understanding the appearance of the Upper Palaeolithic in western Europe. However, the theory has been heavily debated, with criticism focusing on the analysis of the lithic and bone assemblage as well as the chronology. We focus on the latter, and assess whether the original dates were accurate, whether they were well associated with the archaeology, and whether there was vertical and lateral variation in the age of the assemblages within unit 18 and Aurignacian Delta. New radiocarbon dates on humanly modified bone suggest that in the new area of excavation, unit 18 is found to be earlier than 42 cal kBP, with no evidence of material of a younger age. In contrast, in the old excavation area, Aurignacian Delta does include material of a younger age. This suggests that discussion of the Transitional Aurignacian can only include material from unit 18, in the new area of excavation.