Compound-specific amino acid isotopic proxies for distinguishing between terrestrial and aquatic resource consumption

Compound-specific amino acid carbon-isotope compositions have shown particular promise for elucidating dietary behaviors in complex environmental contexts, and may also be able to mitigate the effect of many of the limitations inherent to palaeodietary reconstructions. Here, we investigate the efficacy of compound-specific amino acid isotopic proxies in characterizing the consumption of different dietary protein sources using amino acid carbon-isotope compositions for humans and fauna from Rössberga (Early to Middle Neolithic), Köpingsvik (Mesolithic and Middle Neolithic), and Visby (Medieval Period), Sweden. We also assess the explanatory capabilities of an isotopic mixing model when used with essential amino acid carbon-isotope compositions of humans and local fauna. All three isotopic proxies distinguished among humans from the three sites consistently and informatively, and were able to enhance the broad interpretations made using bulk isotopic compositions. The mixing model palaeodietary reconstruction revealed considerable diversity in relative protein source contributions among individuals at both Köpingsvik and Visby. Comparing the mixing model for bulk carbon- and nitrogen-isotope compositions to the model for essential amino acid isotopic compositions further demonstrated the likelihood of underestimation and overestimation of marine protein consumption for both aquatic-dominant and mixed marine-terrestrial diets when using bulk isotopic compositions.     

Probing dietary change of the Kwädąy Dän Ts'ìnchį 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 Kwäd?y Dän Ts'ìnch? 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.     

Lipid Residues from Low‐Fired Pottery

This paper assesses the fate of lipids associated with low‐temperature and pit‐fired pottery to determine to what degree organic compounds persist or are removed during short‐firing episodes below 800 °C. Three different types of clay were fired using contrasting techniques including at 400 °C for 4 h in a muffle furnace, and pit‐firing in which pottery was fired to higher temperatures but for shorter periods of time. Total lipid extracts obtained by solvent extraction of test sherds were screened using gas chromatography‐flame ionization detection (GC‐FID) to determine the lipid concentrations and gas chromatography–mass spectrometry (GC–MS) to identify the organic compounds present. The results showed that firing of clay removes all naturally occurring alkyl lipids; however, during pit‐firing, diterpenoid lipids were introduced into the clay as a condensate from pine ( Pinus spp.) wood used as fuel. These results confirm that alkyl lipids, e.g., fatty acids, can be reliably associated with the use of vessels, although caution is required when interpreting the origins of lipids that might derive from fuel used in firing.     

Evidence for Varying Patterns of Exploitation of Animal Products in Different Prehistoric Pottery Traditions Based on Lipids Preserved in Surface and Absorbed Residues

The excavation of a barrow at Upper Ninepence, Walton in the Welsh Borderlands, U.K., revealed two phases of occupation associated with two different ceramic traditions, namely Grooved Ware (2500bc) and Peterborough Ware (3000bc). The Grooved Ware and Peterborough Ware pits seem to have a mutually exclusive distribution on the site. Screening of the sherds for lipid residues has revealed the presence of remnant fats in a remarkably well-preserved state considering the age of the finds. Investigations of various chemical characteristics of the remnant fats from absorbed and carbonized residues have enabled distinctions to be drawn between fats from non-ruminant (e.g. porcine) and ruminant (e.g. ovine or bovine) origins. Significantly, both ruminant and non-ruminant fats are found associated with the Grooved Ware whereas only ruminant fats are found associated with the Peterborough Ware. The assignments are based upon the distributions of solvent-extractable lipid components and the compound-specific stable carbon isotope values of the major n -alkanoic acids. The results reveal differences in vessel use and indicate possible changes in patterns of animal exploitation or dietary preferences between the two phases of occupation. The results illustrate the importance of residue analysis in archaeological investigations, particularly at prehistoric sites where evidence from faunal remains is limited or absent.