SMALL MAMMALS' TOOTH ENAMEL: A MEANS TO UNDERSTANDING PALAEOENVIRONMENTS

In studies related to human evolution, a key area of investigation has been the environmental contexts in which early hominins lived, and how these environments may have shaped the evolutionary history of the hominins. In attempts aimed at reconstructing past environments, numerous methods have been employed, the most recent one being isotopic analyses of mammalian tooth enamel in order to interpret dietary signatures and subsequently the environmental conditions in which the animal/s lived. In isotopic studies, the traditional way of sampling tooth enamel has involved grinding a portion of the tooth with an abrasive drill bit, and collecting the resulting powder. Although relatively accurate, the analytical methods employed in the analysis of the powder, including the use of phosphoric acid for carbon (d¹³C) and oxygen (d¹⁸O) isotopes require a large amount of sample material. Following the development of the laser ablation GC/IRMS (gas chromatography/isotope ratio mass spectrometry) technique, it is now possible to obtain carbon and oxygen isotope data and subsequently environmental overtones from teeth belonging to very small mammals such as rodents with very minimal damage to the teeth. It is significant that small mammals such as rodents and insectivores have a number of unique characteristics that make them amenable to ecological study. For instance, the habitat-sensitivity, the large numbers of species and rapid turn-over particularly among the rodents render these animals sensitive indicators of the environments and environmental change. Isotopic analyses of rodent incisors, which are continuously growing, therefore, hold promise for yielding information useful for understanding past environmental conditions. The intention of this paper is thus to present some carbon and oxygen isotope data derived from modern rodents originating from different environmental conditions in eastern Africa, and to underscore the importance of building modern analogues from which fossil faunas and their associated environmental conditions may be reconstructed.