A novel marine dietary indicator utilising compound-specific bone collagen amino acid δ¹³C values of ancient humans

The application of bone collagen stable carbon and nitrogen isotope analysis to human palaeodietary reconstruction in tropical or arid regions is limited by two factors: (i) the overlap in C4 and high marine protein (HMP) consumer bulk collagen δ13C values, and (ii) the unpredictability of bulk collagen δ15N values in regions of extreme aridity (<400 mm of rain per annum). Hence, the identification of HMP consumption among archaeological human populations can be problematic. In an endeavour to identify a more precise marine palaeodietary indicator, a range of collagen samples from archaeological faunal and human bone (n = 14 and 26, respectively), representing a spectrum of C3, C4 and HMP diets, were selected from coastal and near-coastal sites in the Western Cape, South Africa. Samples were subjected to compound-specific stable carbon isotope analysis of their constituent amino acids as trifluoroacetyl-isopropyl (TFA-IP) esters via gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). While human C4 and HMP consumers were indistinguishable with respect to bulk collagen δ13C values (-10.9± 3.7‰ and -11.7±1.5‰, respectively) they were shown to be readily distinguished based on Δ13 CGlycine-Phenylalanine values (+4.0±1.6‰ and +12.0±1.9‰, respectively). The relationship between HMP consumption and elevated Δ13 CGlycine-Phenylalanine values was verified by: (i) the similarly elevated values exhibited by marine species when compared to terrestrial faunal species (+12.5±0.9‰ and +3.2±4.2‰, respectively), and (ii) the strong correlation observed between human Δ13 CGlycine-Phenylalanine and bulk collagen δ15N values (R2, p < 0.001; n = 26), the latter being a well-documented marine dietary indicator. It was concluded that Δ13CGlycine-Phenylalanine values offer considerable potential as indicators of HMP consumption and a valuable substitute for bone collagen δ15N values in arid regions where bulk δ15N values are unpredictable. © 2004 Elsevier Ltd. All rigths reserved.