Multi-species analysis of stable carbon and nitrogen isotope data from Qalʿat al-Baḥrayn

Abstract

Isotope analysis of archaeological bone collagen is standard for investigating diet and animal husbandry practices. In the Arabian Peninsula, however, stable carbon and nitrogen isotope analysis is uncommon due to poor collagen preservation. We used a revised extraction protocol for fragile material and obtained collagen from Qalʿat al-Baḥrayn (QAB) adult human (n=19) and animal (n=45) bone. Our work demonstrates surprising variation in adult diets. Despite burial adjacent to the coast and abundant fish remains at QAB, none of the adults was eating a primarily marine-based diet (mean δ 13 C =-17.9±1.5‰ and mean δ 15 N = 13.3±1.4‰). A range of diets seems to have been consumed from a completely terrestrial, C3 diet (n=3), to more mixed diets including variable, small amounts of marine or C4 resources (n=15). This heterogeneity is also found among the sheep, demonstrating variable feeding practices, including possible foddering with dried fish (mean δ 13 C =-16.8±2.1‰ and δ 15 N = 10.4 ±1.9‰). We hypothesize QAB is acting as a draw for different peoples and activity across the islands, while longer temporal change may be visible in the faunal bone. Our results demonstrate that a multi-species analysis of isotopes in Bahrain reveals economic and ecological diversity even within a small island ecosystem.