This review charts the developments and progress made in the application of stable light isotope tools to palaeodietary adaptations from the 1970s onwards. It begins with an outline of the main principles governing the distribution of stable light isotopes in foodwebs and the quality control issues specific to the calcified tissues used in these analyses, and then proceeds to describe the historical landmark studies that have marked major progress, either in their archaeological applications or in enhancing our understanding of the tools. They include the adoption of maize agriculture, marine-focused diets amongst coastal hunter–gatherers, trophic level amongst Glacial-period modern humans and Neanderthals, and the use of savannah resources by early hominins in Africa. Particular attention is given to the progress made in addressing the challenges that have arisen out of these studies, including issues related to the routing of dietary nutrients. I conclude with some firm, and some more speculative, pointers about where the field may be heading in the next decade or so.