Doctoral Dissertation Research: Diet and Habitat of Australopithecus

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Under the direction of Dr. Carmel Schrire, Mr Matt Sponheimer will collect data for his doctoral dissertation. His research will be both methodological and substantive, the first aspect directed to improvement of the technique to determine indigenous carbon isotope ratios in tooth enamel and the second towards reconstructing prehistoric diet and environment. In a widely used anthropological and biological technique, researchers determine the carbon 12-13 isotopic ratio in bone or tooth and use these data to reconstruct aspects of an animal's diet. Because different categories of plants follow different photosynthetic pathways they vary in carbon isotope ratio and this differential is reflected in the animals which eat these plants. Through analysis of fossil remains it is possible to gain insight into both diet and environment. While this technique has produced intuitively reasonable results, a number of aspects require refinement. One involves diagenesis - alteration of fossil material after burial - and in individual analyses it is often uncertain whether all measured carbon was incorporated before the organism's death or whether some derives from surrounding soil. Mr. Sponheimer will conduct experiments to investigate this question. He will also compare isotope ratios from different teeth of modern day pigs fed controlled diets to determine whether between-tooth variation exists. In the second part of his study, Mr. Sponheimer will analyze both hominid and non-hominid mammalian remains from the South African site of Makapansgat. This cave infilling is extremely important to paleoanthropologists because the fossil-rich material contains abundant early hominid remains which are classed in the species Australopithecus africanus. It is known that several hominid species existed in southern Africa and paleoanthropologists wish to understand the different adaptational strategies followed by each. While isotope ratio data is available for one of these, no work has been done on A. africanus. The data which Mr. Sponheimer collects will be of interest to many paleoanthropologists. It will shed new light on early hominid adaptations and the environment which they inhabited. This project will also contribute to the training of a promising young scientist.