Burned by the fire: isotopic effects of experimental combustion of faunal tooth enamel
Robinson, Joshua R.; Kingston, John D.
Paleoenvironmental reconstructions of hominin fossil localities and archaeological sites are a critical component of understanding the selective pressures involved in the biological and behavioral evolution of our ancestors. Increasingly, these reconstructions are based on the carbon and oxygen stable isotope (δ13Cenamel and δ18Oenamel) composition of herbivore tooth enamel from these sites. Although tooth enamel is subject to diagenetic processes, it is generally assumed to be a refractory substrate that retains the in vivo isotopic signal during fossilization. However, the effects of burning, for which there is extensive evidence, on the isotopic composition of herbivore tooth enamel is often overlooked. Here, the consequences of burning on δ13Cenamel and δ18Oenamel values of five African herbivore taxa are directly tested in a series of controlled combustion experiments up to 1100 °C. Results suggest that δ13Cenamel values are minimally affected by burning up to 700 °C for all taxa, and up to 1100 °C for all but the thin-enameled Madoqua (dik-dik). δ18Oenamel values, on the other hand, are significantly altered at temperatures beyond 300 °C for all taxa, with enamel becoming increasingly and systematically 18O depleted at higher temperatures. This is suggestive of a temperature-dependent biochemical process of exchange with atmospheric oxygen. These results suggest that while δ13Cenamel values from burned teeth are potentially reliable for typical hearth temperatures, strong caution is needed when interpreting δ18Oenamel values from context with evidence of extensive burning.
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