Sealy and her research group measure naturally occurring variations in the ratios of stable light isotopes (mainly carbon, nitrogen and oxygen) to investigate past diets and environments. Isotopic studies of human remains enable inferences about the diet and economic base of human societies, from the emergence of modern humans to the development of hunter-gatherer, herder and farmer societies in southern Africa, and the impact of European colonisation. The research group also studies ancient animal remains to reconstruct past environments, helping us to understand the context/constraints within which humans evolved and lived.