14.12 - Stable Isotope Evidence for Hominin Environments in Africa

Abstract

Various aspects of the paleoenvironment of hominin evolution can be quantified using stable carbon isotopes. There are distinct differences in the carbon isotope ratios of plants and differences in their response to ecological variables, depending on whether the plants use the C3 or C4 photosynthetic pathway. These differences can be used to estimate the fraction of woody cover and to determine diet histories of different mammal groups. In addition, absolute temperatures can be determined using coupling between carbon and oxygen isotopes in paleosol carbonate. When applied to paleoenvironments of hominin-bearing deposits in East Africa, these applications of carbon isotopes show that these environments ranged from grassy woodlands to grasslands and show little evidence of forested conditions. In these hominin-bearing deposits, any forested conditions must have been confined to riparian corridors. The earliest hominins used little, if any, C4 resources in their diets. The diets of the later australopithecines and Homo reflect significantly greater C4 resources, while C4 resources predominate diets of Paranthropus boisei.