Enamel amino acid racemisation dating and its application to building Proboscidean geochronologies

• Main Author: Dickinson, Marc R.
• Other Authors: Penkman, Kirsty ; Lister, Adrian
• Published: University of York 2018
• Subjects: 540
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.759956

Analysis of the predictable breakdown of proteins and amino acids in ancient biominerals enables age estimation over the Quaternary, but to date, its application to mammalian remains has been challenging. It has been postulated that enamel is a suitable biomineral for the long-term survival of endogenous amino acids and thus, it can be used for age estimation. Directly dating mammalian remains is integral to understanding mammalian evolution and for understanding palaeoecology and palaeoclimatology. Analysis of multiple amino acids for geochronological studies is typically achieved using a RP-HPLC method. However, the low concentrations of amino acids coupled with high concentrations of inorganic species makes accurate determination of amino concentrations challenging. The initial focus of this thesis covers the development of a novel method for the separation of amino acids from inorganic species. This was initially attempted via a HILIC SPE, but was later superseded by a biphasic separation method, which was shown to greatly improve the RP-HPLC analysis of amino acids in enamel. Bleaching experiments have shown that the amino acids isolated from enamel through prolonged exposure to a strong oxidant, exhibit effectively closed system behaviour, signifying a potentially stable environment over geological time-scales. Elevated temperature experiments investigating the processes of intra-crystalline protein degradation do not appear to match the fossil patterns, reinforcing the need for a comprehensive understanding of the underlying mechanisms of protein degradation. The methods developed in this thesis have been used to build an enamel amino acid racemisation geochronology based on Proboscidean teeth from UK sites with independent evidence of age. This model has shown good adherence to the UK stratigraphical framework, signifying enamel is a suitable biomineral for AAR age estimation. Finally, enamel AAR has been used in a pilot study to begin to build a chronology for elephants from the isle of Sicily. This framework has been constructed to aid in understanding the process behind island dwarfing of insular elephant species on Sicily.