Alternative interpretations of intermediate and positive d13C isotope signals in prehistoric human remains from southern Mendoza, Argentina: The role of cam species consumption

Abstract

During the last several years, information from stable isotopes has been used to discuss the role of maize agriculture in prehistoric economies of southern Mendoza. Because maize is one of several sources of 13C enriched carbon, a full evaluation of prehistoric diets requires data on a range of potential C3 and C4 plant resources. In this paper, we present stable isotope data (N = 89) for a suite of five previously unstudied edible cacti possessing a Crassulacean acid metabolism (CAM) photosynthetic pathway. Our results show that these plants have δ13C values overlapping C4 photosynthesizers such as maize. In order to understand their potential economic importance, we present additional procurement, processing, and nutritional data from actualistic experiments and the published literature. Using these data, we show why low levels of CAM plant consumption should be expected and how doing so may mimic a pattern of isotopically mixed diets often attributed to maize use.