Organic geochemistry

The questions whether the use of animal products, such as meat, fat, and milk, varied regionally and how traditions and practices in the use of animal products changed with the spread of farming, cannot be fully addressed by studies of faunal remains due to behavioural and taphonomic biases. The extraction and identification of organic residues from the matrix of pottery sherds enables us to directly address diet, preferences for specific foodstuffs, and the question of vessel function and use.

Residue analysis in this project will focus on lipids, relatively stable compounds that can remain preserved for long periods, and for which advanced and refined methods for extraction and ample reference data are available. Lipid compounds will be extracted from pottery sherds and characterized by GC/MS (gas chromatography / mass spectrometry) and GC-C-IRMS (gas chromatography-combustion-isotope ratio mass spectrometry) (Evershed et al. 1990; Evershed et al. 1994; Evershed et al. 2002a; Evershed 2009). Targeted compounds include primarily animal lipids, plant lipids and other compounds will be also considered if present. Source materials will be tracked by: 1) Characterization by GC/MS to identify biomarkers (individual compounds diagnostic for specific materials). The method has been used e.g. to demonstrate honey processing by identification of beeswax (Evershed et al. 1997; Regert et al. 2001), and to recognize aquatic resources by the presence of ω-(o-alkyphenyl)alcanoic acids (Evershed et al. 2008a; Craig et al. 2011). 2) Single-compound stable isotope analysis. Compound-specific stable isotope compositions of residue components determined by GC-C-IRMS allow further differentiation of source materials: δ13C values have been used in different archaeological contexts to distinguish between plant and animal fat, ruminant and porcine fat, milk fat and carcass fat, and between fats of C3 and C4 plants (Evershed et al. 2002b; Copley et al. 2003; Craig et al. 2005; Evershed 2007; Evershed et al. 2008a; Steele et al. 2010).

Researchers: Richard Evershed and Jonathan Ethier (research assistant)