Tooth Enamel Biogeochemistry and Early Hominin Diets

Biogeochemical studies of hominin dietary ecology began decades ago, and, despite refinements, the basic tools being used and questions being asked have changed little since then. Carbon isotope analyses have had the most impact, with numerous studies showing that up to c.4 Ma, early hominins consumed primarily C3 vegetation, as do extant apes, but thereafter consumption of C4 foods became conspicuous if variable. Paranthropus boisei completely abandoned the ancestral C3 diet by at least 2 Ma to become a C4 consumer, a rarity among primates. These shifts were accompanied by changes in the australopith masticatory package. Applications using trace elements, particularly strontium and barium, as trophic level indicators have been less successful, partly because the distributions of trace elements in foodwebs are poorly understood. Similarly, while the oxygen isotope composition of tooth enamel unquestionably reflects ecology, the influences are complex and too poorly understood to allow unambiguous interpretation.