Article

Tracking changing environments using stable carbon isotopes in fossil tooth enamel: an example from the South African hominin sites

Department of Archaeological Sciences, University of Bradford, BD7 1DP, UK.
Journal of Human Evolution (Impact Factor: 3.73). 12/2007; 53(5):595-601. DOI: 10.1016/j.jhevol.2006.11.020
Source: PubMed

ABSTRACT

The environmental contexts of the karstic hominin sites in South Africa have been established largely by means of faunal associations; taken together these data suggest a trend from relatively closed and more mesic to open, drier environments from about 3 to 1.5 Ma. Vrba argued for a major shift within this trend ca. 2.4-2.6 Ma, an influential proposal that posited links between bovid (and hominin) radiation in Africa and the intensification of Northern Hemisphere Glaciation. Yet faunal approaches often rely on habitat and feeding preferences of modern taxa that may differ from those of their extinct predecessors. Here we explore ways of extending (13)C/(12)C data from fossil mammals beyond denoting "presence" or "absence" of C(4) grasses using the evolution of open environments in South Africa as a case study. To do so we calculated the relative proportions of C(3)-, mixed-, and C(4)-feeding herbivores for all the hominin sites for which we have sufficient data based on (13)C/(12)C analyses of fossil tooth enamel. The results confirm a general trend towards more open environments since 3 Ma, but they also emphasize a marked change to open grassy habitats in the latest Pliocene/early Pleistocene. Mean (13)C/(12)C for large felids also mirrored this trend.

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    • "1.9–1.7 Ma which is the time-span covering Strata 12 to 11 at Wonderwerk Cave. It has been associated with the development of the Walker circulation (Cerling et al., 1988; Hopley et al., 2007; Maslin et al., 2014) and was characterised by expansion of the savannah biome (Hopley et al., 2007) resulting in a shift in large mammal communities to more grazing species (Bobe and Behrensmeyer, 2004; Lee-Thorp et al., 2007). Our carbon and oxygen stable isotope data for Strata 12 at Wonderwerk Cave, indicate a generally arid, C 3 environment with a small component of C4 plants. "

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    • "These changes manifest terrestrially as an expansion of C 4 grasses predominantly in regions experiencing a reduction in rainfall (Ehleringer et al., 1991, 1997; Hopley et al., 2007a). Analysis of biomineral carbonate δ 13 C demonstrates the presence of C 4 vegetation the early Pliocene (Ségalen et al., 2006) with the most significant environmental change to open, grassy landscapes only occurring after 2 Ma when arid conditions became dominant (Hopley et al., 2007a; Lee-Thorp et al., 2007). The Plio- Pleistocene Thabaseek Tufa δ 18 O data (− 6.5‰ to − 5.7‰; mean = −6.0‰; "
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    • "1.9–1.7 Ma which is the time-span covering Strata 12 to 11 at Wonderwerk Cave. It has been associated with the development of the Walker circulation (Cerling et al., 1988; Hopley et al., 2007; Maslin et al., 2014) and was characterised by expansion of the savannah biome (Hopley et al., 2007) resulting in a shift in large mammal communities to more grazing species (Bobe and Behrensmeyer, 2004; Lee-Thorp et al., 2007). Our carbon and oxygen stable isotope data for Strata 12 at Wonderwerk Cave, indicate a generally arid, C 3 environment with a small component of C4 plants. "
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    ABSTRACT: Ostrich eggshell is abundant in many archaeological and palaeontological sites throughout Africa, making it a popular material for radiocarbon dating. However, ostrich eggshell is also a powerful tool for reconstructing climate and palaeoenvironment, as well as ecological changes. Here we present three different methods that have produced climatic and environmental information on the same samples: stable carbon and oxygen isotopes on inorganic carbonate, pore size count and shell thickness measurements. As a case study we present new results for the Oldowan and Earlier Stone Age layers at Wonderwerk Cave (Northern Cape, South Africa), for the period ca. 2 - 1 Ma. The data, independently collected using the three different methods, provide a remarkably coherent picture of past environmental and climate change for the arid interior of South Africa, where such data from terrestrial archives is rare. Independently, the methods demonstrate the occurrence of significant moist phases in an overall arid setting. The isotopic data show changing amounts of C3 and C4 plants, although ostriches are opportunistic grazers with a preference for tender green plants. This record can be compared to other proxies from the region to research for drivers of climate change in southern Africa’s summer rainfall region.
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