A Multi-Dimensional Approach to Investigate Use-Related Biogenic Residues on Palaeolithic Ground Stone Tools

Recent advances in the role played by dietary carbohydrates in human food webs during the Palaeolithic highlight that starchy foods were part of the diet well before crop domestication. Although certain plants can be eaten raw, intentional processing such as mechanical reduction using stone tools and thermal treatment readily increases the assimilation of nutrients for metabolic functions and for storing. We present a multi-techniques approach designed to combine micro to nanoscale analyses applied to percussive stones to identify their function using micro-wear traces and use-related biogenic residues. The starch grains extracted from functionally active areas of the ground stone tools were scanned using optical microscopy (OM) down to the nanoscale (SEM) and by applying different spectroscopic and spectrometric techniques like FTIR, ToF-SIMS, and IRMS. The combined analyses carried out at different resolutions - morpho-structural and molecular levels - contribute to an unprecedented methodological refinement regarding the intentional processing of starch-rich plants as early as 40,000 years ago at the boreal latitudes. Our preliminary data on pestles and grinding stones from Early Upper Palaeolithic sites of the Pontic steppe (Moldova and Russia) show the suitability of the analytical techniques involved and also the difficulties encountered in detailing authentication procedures of ancient starch candidates.