Stable Isotope Ratios of Amino Acids as Proxies for Trophic Position and Dietary Sources

Understanding the diets of hominids and fauna, and the environments in which they lived, has long been a goal of paleoanthropological and archaeological research. While conventional methods such as examination of past plant and animal remains and bulk stable isotope analysis of archaeological tissue have yielded important insights into past diets, the dietary interpretations associated with these methods are sometimes uncertain. These uncertainties can in part be overcome with stable isotope analysis of single amino acids, the building blocks of proteins. Research has shown that their carbon and nitrogen stable isotope ratios can inform of trophic level and dietary sources independent of environmental conditions. Amino acids are valuable dietary markers because each of them has unique metabolic functions and properties. The multitude of data derived from amino acids can therefore be placed into statistical models to explore new resolution of food sources.

While the strengths of applying stable isotope ratios of amino acids for palaeodietary reconstruction are compelling, we are cognisant of the methodological challenges and interpretive knowledge gaps associated with this method. For this reason, our group takes an active interest in understanding how factors such as food preparation, digestive and metabolic processes, and diet quality affect isotope ratios of amino acids. We are also committed to making the method less cost prohibitive and improving data comparability across labs. To learn more about these topics, read our recently published guide on how best to use stable isotope ratios of amino acids: https://doi.org/10.1093/biosci/biac028