O12: Analysis of Chilean mummies’ hair: Recent advances for their characterization

Abstract

Introduction Among human remains from museum collections, mummies have intrigued researchers for a long time. There are subject to many researches in order to understand the mummification processes, to improve conservation and restoration protocols and to infer some interesting clues about the corresponding civilizations. We focus here on a corpus of Chilean mummies from the San Miguel de Azapa (Arica, Chile). The present work aims to study the conservation state of hair and to detect the heavy metal presence [Boston & al. (2009). Interciencia, 34:5, 338–343]. These aspects are related to the environmental conditions in which the individual lived, as well as various hair treatments performed. Furthermore, the molecular fingerprint of the material may have been modified by anthropic or natural alterations [Charrie-Duhaut & al. (2007). J. of Archaeological Science, 34, 957–967]. This complexity makes this research a true analytical challenge. Methods The hairs of mummies were first dated by measurements of carbon 14 using accelerator mass spectrometry (AMS) [Richardin & al. (2011). Archaeol. Anthropol. Sci., 3, 379–384; Richardin & al. (2013). Radiocarbon, 55:3–4, 345–352]. We undertook morphological and structural analyses (scanning electron microscopy – SEM – and infra-red spectroscopy), to obtain a global overview on the conservation state of hair. The heavy metals presence was studied by X-ray fluorescence and by SEM-EDS (energy dispersive X-ray spectroscopy). We are currently developing a proteomics approach (MALDI-MS and nanoLC-MS/MS analyses) in order to find out the amino acid sequences of keratin molecules and their alterations [Barthelemy (2011). PhD thesis, University of Strasbourg]. Results Radiocarbon dating has shown that the mummies are from the Archaic (8000–1000 BC) and Formative (1000 BC – 500 AD) periods. According to the first analyses, hair surfaces (cuticle) seem well preserved. On the surface and inside the hair fiber, lead, iron and bromine are detected in significant amounts, and arsenic is also present in some cases. Conclusion This work enables to better situate the corpus of mummies in their historical context, and to deny the fact that they came from the archaic Chinchorro. On the other hand, the detection of arsenic in some hair samples seems to suggest that some individuals suffered from chronic poisoning due to arsenic. The proteomics approach, currently in progress, should enable to confirm the first conclusions on the good preservation state of the hair and to study the interactions between heavy metals and keratin molecules. In this regard, it is crucial to develop as a first step an extraction protocol of the hair proteins, in order to preserve the non-covalent interactions.