What about Apatite? Possibilities and Limitations of Recognising Bone Mineral Residues on Stone Tools

Bone mineral residues derived from stone tool production and use can survive on lithic artefacts for extended periods of time. They thus form a line of evidence for reconstructing Palaeolithic human activities. Despite having been frequently reported on ancient stone tools, the identification of these residues is not without complications, and their diagenesis as well as their potential overlap with residues formed in the burial environment are only beginning to be addressed. We report here environmental and use-related calcium phosphate residues on previously washed and handled Gravettian stone tools from Hohle Fels (Germany) and Abri Pataud (France). The residues were characterised with optical microscopes and SEM–EDS. Our results provide an optimistic note on the preservation of bone mineral residues at sheltered Upper Palaeolithic sites, but also point to multiple and complex origins of apatite deposits on lithic tools. We discuss the characteristics of functional versus taphonomic residues and draw attention to the formation of authigenic hydroxylapatite and its implications for the identification of ancient bone mineral residues from tool use. We argue that this aspect has been largely overlooked by analysts until now. This calls for further refinement of analytical techniques, including continued research into sediment diagenesis and residue taphonomy, as well as the incorporation of production and use-wear evidence to ensure reliable residue interpretations.