Stable isotope and proteomic insights into Bronze age human dietary life history at Köhne Shahar, Northwest Iran

Abstract

Interest in subsistence strategies practiced by the Kura-Araxes communities in Southern Caucasus and the highlands of the Near East has a long history, yet direct studies of paleodiet at the scale of the individual are few. We apply serial sampling of carbon and nitrogen isotopes in 17 teeth representing 11 comingled individuals at the Kura-Araxes early Bronze Age site Köhne Shahar (KSH) in northwestern Iran. Proteomic analyses of dental enamel show seven females and four males. Isotopic results indicate an agro-pastoral diet with little or no C₄ millet. Individual isotopic biographies reveal a dietary life history that includes weaning between 1.5 and 3.7 years of age (average = 2.4 years), followed by a stable early childhood diet with little intra-individual variation through age 10 years. Isotopic shifts around 12–14 years of age suggest a change in diet that may correspond to marriage and the establishment of new household units focused more on plant foods. Gradual isotopic shifts between 14 and 20 years may represent such households developing livestock herds and increasing meat consumption. Stability in diet across this transition is consistent with village endogamy. Sex-linked differences in the age of weaning and childhood δ¹⁵N values hint at differences in learning and enculturation practices. Males and about half of females were weaned earlier but had access to greater amounts of meat, suggesting they were more involved in animal husbandry and/or production of animal products (e.g., cheese, yoghurt) outside the house. By contrast, the other half of females were weaned later in childhood, but ate significantly more plant foods, suggesting they were more involved in tending gardens and producing crafts and/or plant-based foods within the house, where they had greater access to breastmilk.