Isotopes and Diet in African Hominins and Hunter-Gatherers

Abstract

Stable isotope methods are firmly established as a key tool for investigating the diets of ancient humans, offering insights into broad dietary composition at the scale of an individual’s life. African archaeology and ecosystems have played an important role in the global development of stable isotope approaches, but archaeological applications have been constrained in many African settings by poor preservation conditions for organic remains and limited institutional capacity for large analytical sampling programs. Yet growing numbers of research and training laboratories around the world, declining relative analytical costs, and increasing familiarity among archaeologists and paleoecologists with both the prospects and limitations of stable isotope approaches, all indicate that such methods will continue to increase in importance for modern archaeological practice. Complex ecological patterning in carbon, nitrogen, and other isotopes within Africa offers a rich background for interpretation. Carbon isotopes largely reflect patterning in vegetation, with the major isotopic distinction between tropical grasses and most other plants aiding the reconstruction of broad food classes. Aquatic and terrestrial environments may also differ sharply in carbon isotope patterning, providing a tool for investigating marine food exploitation. Nitrogen isotope patterning, by comparison with carbon isotopes, is more complex and less well-characterized in many African environments but has been useful for identifying the consumption of marine resources. Other isotopes, including sulfur, strontium, oxygen, and metal isotopes, such as calcium and zinc, may offer complementary insights that can help to interpret ancient food systems. Analyses of enamel carbon isotopes from eastern and South African hominins have demonstrated the significance of diverse dietary resources for millions of years among several groups of hominins, including the gracile and robust australopithecines and early Homo. The puzzle of extensive consumption of 13C-enriched foods, especially among the eastern African robust australopithecines, has driven wide-ranging research into the dietary diversity of hominin species, targeting questions of ecological niche separation and dietary flexibility. In southern African coastal settings, stable isotope evidence for differential access to dietary resources among foraging groups has demonstrated the maintenance of more sedentary, territorial settlement systems during some periods in the Holocene. Research in these fields is ongoing, with new insights emerging from applications of alternative isotopic systems, increased sampling resolution, and sophisticated statistical modeling approaches.