No Solid Foundation for the Use of Ochre-based Compound Adhesives at Le Moustier

Adhesives are commonly sought-after residues due to their current use as a proxy for early human cognitive traits. Identifying adhesives is a complex task due to the preservation bias associated with the archaeological record and the organic nature of the residues. Although important information concerning prehistoric behaviour is being inferred from glue identification and use, it is rarely identified through molecular and elemental compositions. In a recent study by Schmidt et al. (Ochre-based compound adhesives at the Mousterian type-site document complex cognition and high investment, Science Advances, 2024, Vol. 10, Issue 8), they attempted to use such procedures to understand the nature of a black residue found on four out of five artifacts excavated at the beginning of the twentieth century from the upper rock shelter of Le Moustier. They claim that they succeeded in identifying the oldest compound adhesives found in a European context. The presence of compound adhesive in the Middle Palaeolithic has several implications for technological and cognitive human evolution. In this paper, we evaluate the reliability of the argument used by the authors to defend the presence of compound adhesives on the studied artefacts. Upon this evaluation, we encountered several uncertainties that put into question the adhesive identification that the authors claimed. These uncertainties should be addressed before the result from this study can be used for further inferences about past human behaviour.