Comparison of aspartic acid racemization between mammoth and human dentinal tissues

Comprehensive research has revealed the complexity and heterogeneity of amino acid racemization (AAR) in biological samples. Therefore, to date, inherent uncertainties in relative dating as well as in determination of age at death have highlighted the significance of further investigations to explore aspartic acid kinetics in biominerals. Here we present data on an archaeological sample obtained from a mammoth tusk, in comparison to a previously well-described biomineral, to modern human dentin.

Since no experimental investigations were carried out on this topic earlier, we provide the first estimates on racemization kinetics and time dependent tendencies in mammoth dentin. We analysed our samples using a protocol, which has been adopted for tooth dentin investigation. We measured different racemization rates amongst mammoth dentin layers.

Significantly, an overall low racemization rate was detected compared to human dentin. Kinetic experiments were performed by heating the samples, and linear correlations were established between racemization rates and heating time. The results allow us to derive racemization rate constants and activation energy for both samples. Extrapolation for ambient temperature showed increased velocity in mammoth dentin, which can be explained by biodeterioration of ancient collagen and by diagenetic changes in amino acid composition influenced by environmental conditions.