Amino acid isotope ratios to explore past plant consumption

In archaeological research, past food consumption is often reconstructed by analysing isotope ratios in bones and teeth. Because the stable isotope ratios of carbon and nitrogen are passed on from food to the consumers tissues (with systematic offsets), the analysis of these ratios in skeletal remains can give information on what was eaten. This analysis is currently most commonly performed on bone collagen. However, providing only two data points (one each for carbon and nitrogen), many different food combinations can give rise to the same results. However, bone collagen consists of 20 different amino acids, which have different stable isotope ratios depending on the type of amino acid. Separating collagen (a protein) into its constituent amino acids, and separately analysing the isotope ratios of specific amino acids, rather than the bulk protein, it is possible to gain more detailed information on the tissue composition, and in turn, on the consumed foods. Previous research has shown that even plants that are indistinguishable by bulk stable isotope analyses, may have distinctive amino acid stable isotope ratios. This can be used to gain more detailed information regarding past food consumption. To enable these dietary reconstructions, data on the amino acid stable isotope ratio composition of potential foodstuffs and information on the changes in this composition following consumption and incorporation into bone collagen is required. In this project, plant foods and consumer tissues are analysed for their amino acid stable carbon and nitrogen isotope ratios from present-day organisms, and the results are then applied to the analysis of archaeological remains. This project thereby addresses the scarcity of research on amino acid stable carbon and nitrogen isotope ratios values in archaeological contexts, offering extensive datasets for multiple plant species and growing conditions.