Probing dietary change of the Kwädąy Dän Ts'ìnchį individual, an ancient glacier body from British Columbia: II. Deconvoluting whole skin and bone collagen δ 13C values via carbon isotope analysis of individual amino acids

Abstract

The remains of the Kwädąy Dän Ts'ìnchį individual, a frozen male human, were recovered from a retreating glacier within the Tatshenshini-Alsek Park in British Columbia in August 1999. In order to provide information on both the geographical origin of this individual and low long he spent in the remote interior region prior to his death, molecular analysis and compound-specific carbon isotope analyses were performed on individual amino acids purified from his skin and bone. Gas chromatographic quantification of constituent amino acids of both tissues revealed a molecular distribution characteristic of collagen, dominated by glycine and to a lesser extent proline, hydroxyproline and alanine. Chiral gas chromatography indicated that protein preservation in both tissues was exceptional. Carbon isotope analysis of a faunal assemblage from an earlier prehistoric site from southern British Columbia provided reference dietary amino acid δ 13C values for terrestrial (deer and domestic dog) and marine species (salmon and sealion), showing clear separation in all amino acids, particularly glycine which was extremely 13C-enriched in the marine animals. The distinction between terrestrial and marine organisms was increased by exploring Δ 13C Glycine-Phenylalanine values (6.6 ± 0.6‰ and 15.0 ± 2.1‰, respectively), which were higher in the latter by approximately 8‰, mirroring the increased δ 15N Bulk collagen values observed for the marine animals ( R 2 = 0.78; p < 0.001). The Kwädąy Dän Ts'ìnchį individual's bone had a similarly elevated Δ 13C Glycine-Phenylalanine value of 15.6 ± 1.0‰, indicating his extreme reliance on marine dietary resources throughout early life. The skin amino acid δ 13C values were consistently lower than those observed for bone, with a concurrently lower Δ 13C Glycine-Phenylalanine value of 12.7 ± 0.9‰. The shift between the carbon isotope composition of bone (long-term diet) and skin amino acids (short-term diet) confirmed a sudden divergence away from marine food sources in the last months of life, consistent with his discovery 80 km inland.