Stable isotope analyses in human nutritional ecology

Extracting nutrients is of upmost importance to the survival of any individual or species. One of the distinguishing characteristics of the order Primates is the vast range of nutritional adaptations it exhibits. Within our own species all manner of adaptations are practiced and it has been a major focus of research to determine when and where these various patterns originated. We present one method based on stable isotope analysis in human tissues and discuss its contributions. The ratios of 13C/12C and 15N/14N vary among various pools (i.e., the atmosphere, the oceans, plant communities, trophic levels). These differences are transferred to humans via the foods they eat. The major differences in carbon occur between two photosynthetic pathways (C3 and C4), which in the New World permits tracing the introduction of maize (a C4 plant) and in Asia permits tracing the introduction of millet (also a C4 plant). The marine and terrestrial systems have distinctive isotope ratios of both carbon and nitrogen. Thus, the dependence on marine resources has been traced throughout several areas of the New and Old Worlds. We discuss several potential sources of variation including sex, age, nutritional status, among others. We conclude with some suggestions for future research.