Enhanced functional data retrieval from Palaeolithic stone tools by lipid analysis

Despite the great potential of lipid biomarkers in archaeological science, their analysis in stone tools has been overlooked. The lipid retention capacity of Palaeolithic stone tools, along with the potential utility of the biomarkers they may harbour as a functional proxy, remains largely unknown. Here, we extracted lipid biomarkers from flint flakes and limestone pebbles from the Middle Palaeolithic site of El Salt (SE Spain) and analysed them using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Adjacent sediments were also analysed for comparison. We provide evidence that Palaeolithic stone tools preserve a diverse array of lipid biomarkers including fatty acids, n -alkanols, sterols and terpenoids, the analysis of which allowed us to determine whether the tools were used and/or hafted. The isotopic characterization of individual fatty acids preserved on tools’ working edges enabled us to identify lithic residues as fats resulting from the processing of ruminant animal species, or as lipids from non-ruminant animal and/or plant taxa. This introduces into functional studies a novel approach that adds taxonomic resolution and complements current techniques such as use-wear and micro-residue analyses. Our findings highlight the remarkable preservation potential of biomolecular remains within the Palaeolithic record and underscore the importance of exploring them in different kinds of materials and contexts. • Lipid analysis is employed to assess lithic tool function. • Palaeolithic stone tools may preserve a wide range of lipid biomarkers. • Spatial differences in the stone tool lipid content may provide insights on tool use. • Biomarker identification on specific areas of stone tools may provide insights into worked materials and hafting. • Isotopic compositions of fatty acids are useful to identify the biotic source of stone tool molecular residues.