Refinement of reconstructed ancient food webs based on the nitrogen isotopic compositions of amino acids from bone collagen: A case study of archaeological herbivores from Tell Ain el-Kerkh, Syria

Abstract

We determined the stable nitrogen isotopic composition (δ 15 N) of amino acids in bone collagen from samples of three archaeological herbivores (cattle, sheep, and goats), collected from the Tell Ain el-Kerkh Neolithic site in Syria. Bulk collagen δ 15 N values exhibited significant differences between the three species (by up to 3.2‰), and were strongly correlated with those of glycine (R 2 = 0.87), the most abundant amino acid in bone collagen. On the other hand, the δ 15 N values of two other minor amino acids (glutamic acid and phenylalanine) in the different samples were within narrow ranges (0.9‰ and 0.5‰, respectively), and exhibited either weak or no correlation with those of bulk collagen. The trophic position estimated by the δ 15 N values of glutamic acid and phenylalanine (2.0 ± 0.1) is consistent with that of herbivores. These results suggest that the δ 15 N values of bulk bone collagen may vary among herbivores, partly on account of their differing amino acid compositions, whereas the trophic position of different herbivores is faithfully preserved in the δ 15 N values of glutamic acid and phenylalanine.