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9 Contribution of Stable Light Isotopes to Paleoenvironmental Reconstruction.

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Title: 9 Contribution of Stable Light Isotopes to Paleoenvironmental Reconstruction.
Authors: Lee-Thorp, Julia, Sponheimer, Matt
Source: Handbook of Paleoanthropology; 2007, p289-310, 22p
Abstract: In this chapter, we focus attention on the potential linkages between hominin evolution and environmental change in Africa, as shown by the stable light isotope evidence. We begin with an overview of the principles and the materials typically available to produce this kind of stable isotope data. Carbon isotope analyses of faunal enamel, soils, and ostrich eggshells provide good evidence for the emergence of C4 grasses ca. 5–8 Ma, broadly concordant with hominin bipedalism. Although C4 grasses remained a modest yet variable component of the vegetation for millions of years, the associated biomass may have quickly become an important foraging resource for hominins. Rather than a climate-driven ˵pulse″ ca. 2.4–2.8 Ma, evidence from East and South Africa suggests a significant change to more open, grassy ecosystems ca. 1.8 Ma, broadly concordant with the emergence of early Homo. On present evidence, there appears to be only a weak overall aridification trend for the entire period from ca. 4 Ma. Speleothem and other evidence points to deep-rooted cyclicity in floral and rainfall shifts, which suggest that obliquity and precessional orbital cycles were important drivers of environmental variability. In relation to climate and environmental influences on hominin evolution, a revised ˵Savanna″ hypothesis may yet be compatible with the ˵variability selection″ hypothesis. [ABSTRACT FROM AUTHOR]
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DOI: 10.1007/978-3-540-33761-4_9
Database: Complementary Index
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