YEARBOOK OF PHYSICAL ANTHROPOLOGY 34:283-321 (1991) 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 l3C/''C 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. Carbon, Nitrogen, Stable isotopes, Nutritional ecology, Bone Food and sex, i.e., the ways in which animals obtain access to necessary nutrients and to mates, are the most basic aspects of animal behavior. One can argue that the study of food is primary since without the former the latter becomes irrelevant. In the most recent edition of Human Biology (Harrison et al., 1988), Baker's overview of the variety of methods employed by humans to extract nutrients suggests that dietary adaptability may be the key to the overall success of our species. Humans are able to survive as complete carnivores (e.g., Eskimos), herbivores (e.g., certain cultural/religious groups in India), and almost any combination of these two extremes. The order Primates displays an enormous range of dietary adaptations and i t does not seem too extreme to suggest that such dietary flexibility may have been an important component in the spread of our order, the emergence of our genus, Homo, the evolution of our own species, Homo sapiens, and the variety of socialleconomic/cultural modes of organization evident among humans today. Physical anthropologists have focused on the diets of living humans and other primates and also on recent and not so recent human and primate ancestors. The methods utilized for assessing varieties of foods consumed have been extremely diverse, but can be categorized into two basic types. The first applies to groups, whether the group be a population or species. Group assessment methods include consideration of body size constraints on nutritional requirements (e.g., Fleagle,