Gas Chromatographic Analysis of Fatty Material From a Thule Midden

Abstract

Fatty material from a Thule Eskimo site on Herschel Island, Yukon Territory, Canada was analysed by gas chromatography and thin layer chromatography. The fatty acid composition of the samples was then compared with published data for a number of marine species which could have been food sources for the Thule peoples. The samples appear to be derived from seal or whale, or a mixture of these, but what is more surprising is that the fats have changed so little over the 1000 year period of their burial.

Analytical strategies for discriminating archeological fatty substances from animal origin

“…Some of these polyunsaturated acids give rise to the formation of specific degradation markers in the form of cyclic compounds that are discussed below. Nevertheless, the presence of saturated and monounsaturated fatty acids with an even carbon number that range from C 20 to C 24 , together with a high proportion of palmitic acid and minor amounts of myristic and stearic acids, are generally C for both C16:0 and C18:0 fatty as compared to marine resources considered as deriving from marine resources (Morgan et al, 1984;Patrick, de Koning, & Smith, 1985;Copley et al, 2004). Among the monosaturated fatty acids, gadoleic acid (eicoseinoic acid, C 20:1 ), behenic acid (docosenoic acid, C 22:1 ), or/and nervonic acid (tetracosenoic acid, C 24:1 ) indicate a marine origin (Patrick, de Koning, & Smith, 1985).…”

“…These biomarkers undergo chemical and bacterial transformations during the use of vessels in which they are preserved or during post-depositional burial. Polyunsaturated fatty acids in particular are highly susceptible to degradation and have thus never been encountered in archeological samples (see below for the details of the degradation pathways, Morgan et al, 1984;Patrick, de Koning, & Smith, 1985). Some of these polyunsaturated acids give rise to the formation of specific degradation markers in the form of cyclic compounds that are discussed below.…”

“…The first investigations of lipids preserved in various archeological matrices focused on GC of the fatty acids released by saponification (Condamin et al, 1976;Morgan et al, 1984;Patrick, de Koning, & Smith, 1985). However, this approach has several disadvantages (Evershed, Heron, & Goad, 1990).…”

“…Fresh fats derived from marine animals are characterized by a set of common criteria including (i) long-chain polyunsaturated fatty acids that contain more than 20 carbon atoms, (ii) palmitic acid is the most prominent saturated fatty acid, and (iii) specific isoprenoid fatty acids (Hilditch & Williams, 1964;Ackman & Hooper, 1968;Malins & Wekell, 1970;Morgan et al, 1984;Patrick, de Koning, & Smith, 1985;Hansel et al, 2004). These biomarkers undergo chemical and bacterial transformations during the use of vessels in which they are preserved or during post-depositional burial.…”

The Effects of Lipids in Stable Carbon Isotope Analysis and the Effects of NaOH Treatment on the Composition of Extracted Bone Collagen

“…Analysis of lipids has long been used in archaeology to determine the origin of organic residues buried in the soil (Morgan et al, 1984) or contained in ceramic vessels (Condamin et al, 1976;Patrick et al, 1985;Heron et al, 1991). In those studies, preservation is the prerequisite for further interpretation.…”