Probing dietary change of the Kwäday Dän Ts'ìnchi individual, an ancient glacier body from British Columbia: I. Complementary use of marine lipid biomarker and carbon isotope signatures as novel indicators of a marine diet

The remains of the preserved ice body from the Kwäda{ogonek}y Dän Ts'ìnchi{ogonek} discovery were recovered from a retreating glacier in the Tatshenshini-Alsek Park, British Columbia in August 1999. Despite the remote location 80 km inland, bone collagen stable isotope analysis indicated that the individual spent much of his life in a region rich in marine foods (δ¹³C -13.7‰ and δ¹⁵N +17.9‰). Since finds of such bodies are exceptionally rare we undertook detailed lipid analyses in order to assess their preservation and determine whether they might provide new insights into the individual's dietary life history. Molecular fingerprinting and compound-specific carbon isotope analysis were performed on individual lipids extracted from his bone (turnover approximately ≥1 year) and skin (turnover approximately several weeks). A considerable abundance was observed of C_12:0, C_14:0, C_16:0, C_16:1, C_18:0 and C_18:1 fatty acids (FAs), cholesterol and hydroxy FAs (the latter being decay products). Most unusual was the presence of long-chain hydroxy FAs (LCHFAs), 10- and 12-hydroxyeicosanoic acid and 10- and 12-hydroxydocosanoic acid, in the bone. The latter components are most likely the products of microbially mediated hydration of the double-bonds of C_20:1 and C_22:1 FAs, the latter almost certainly originating from the consumption of a largely marine-based diet. A suite of three isoprenoidal lipids, phytanic acid, pristanic acid and 4,8,12-trimethyltetradecanoic (TMTD) acid, was also detected supporting the notion of a significant marine component of the diet for a substantial part of his life. In contrast, the skin lipid composition was dominated by C_{16:0 FA}, with lower abundances being observed of the marine LCHFAs and isoprenoidal compounds, suggesting reduced reliance on coastal marine foods in the last period of life. This interpretation is supported by the enhanced marine dietary signal observed in the bone than skin FA δ¹³C values.