Aurignacian grinding stone from Surein I (Crimea): “trace-ing” the roots of starch-based diet

•Methodological refinement for functional analysis of Palaeolithic ground stones.•Optical light and scanning electron microscopy applied for surface texture and starch analysis.•Mapping of the functional related features.•Surein I (Crimea) is the oldest direct evidence of grinding stone used to process USOs.•Homo sapiens dietary flexibility and adaptation to Pontic steppe plant resources.