Building a better eggtimer: Amino acid dating of ostrich eggshell from South Africa

Summary

Chronology underpins our understanding of the past, but beyond the limit of radiocarbon dating (~50 ka), sites become more difficult to date. Amino acid geochronology, which uses the time-dependent breakdown of proteins in biominerals, has the potential to date the whole of the Quaternary. Ostrich eggshell (OES) is often associated with archaeological sites in Africa, as early humans utilised them as a food source, water carriers and for artistic purposes. OES’s calcitic structure potentially offers a "closed system" of intra-crystalline proteins encapsulated within the calcite, which is imperative for accurate amino acid dating.

We have rigorously tested these intra-crystalline proteins through high temperature degradation studies and independently dated, well-stratified OES from the key archaeological sites of Elands Bay Cave and Pinnacle Point. If OES has been heated prior to or during burial, this can confound the age signal. Using a new UHPLC chiral amino acid analysis method we have found 6 markers that enable identification of "heated" OES, and therefore significantly increases the age resolutions and accuracies possible. We also demonstrate the potential of mass spectrometry in helping to unravel the complex nature of protein diagenesis, with successful extraction and sequencing of peptides from OES samples ~71 ka

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This Resource is Part of the Following Collections

• Building the Hunter-gatherer’s Paleoscape on the South African Coast: the archaeological record   •
• Society for American Archaeology 80th Annual Meeting, San Francisco, CA (2015)

Keywords

Spatial Coverage