The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Diets of early hominins: alternative hypotheses for the isotope data


1Anthropology, University of California at San Diego, 2Division of Morphological Sciences and Biostatistics, Wright State University, 3Anthropology, Northern Arizona University

Thursday 10:15-10:30, Grand Ballroom II Add to calendar

Stable carbon isotope ratios in tooth enamel of early hominins from 5 sites across Africa suggest they fed on some amount of C4-based foods. Estimates fall between 30% and 50% C4-based foods for Australopithecus africanus, Paranthropus and early Homo sp. and close to 80% for Australopithecus boisei (Lee-Thorp and Sponheimer 2006 Yrbk. Phys. Anthropol. 49:131–148; van der Merwe et al. 2008 S. Afr. J. Sci. 104:153-155). The percent of C4-based foods is calculated by comparing the hominin data with endpoints defined by data from fossil browsers (C3) and grazers (C4).

The stable carbon isotope ratios in diet can also be estimated using the offset between the ratio in diet and tooth enamel. Our group’s meta-analysis of data from laboratory animals with digestive physiologies similar to our own shows an offset around 10‰. The value is 14‰ in large bodied experimental (Passey et al. 2005 JAS 32: 1459-1470) and free-ranging East African fauna (Cerling et al., 2003 J.Mammology 84: 456-470) that rely on extensive fermentation for energy extraction. Using 14‰ the diets of early hominins would be 100% C3-based foods with the exception of Australopithecus boisei. Our new analysis of free-ranging fauna and the earlier meta-analysis also imply differences in offsets when feeding on C3- versus C4-based diets. We propose that early Homo sp. ate some C4-based foods assuming digestive physiologies similar to our own, Australopithecus boisei relied largely on C4-based foods irrespective of digestive physiology, and the other early hominins, employing extensive fermentation, ate a largely C3-based diet.

Funding provided by the Regents of the University of California (MJS).

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