Early medieval reliance on the land and the local: An integrated multi-isotope study (87Sr/86Sr, δ18O, δ13C, δ15N) of diet and migration in Co. Meath, Ireland

• Published in: Journal of archaeological science 2018-10, Vol.98, p.59-71
• Main Authors: Ryan, Saskia E., Reynard, Linda M., Crowley, Quentin G., Snoeck, Christophe, Tuross, Noreen
• Format: Article
• Language: English
• Subjects: Diet; Early medieval; Geographical discrimination; Ireland; Migration; Stable isotopes; Strontium isotopes
• ISSN: 0305-4403; 1095-9238
• DOI: 10.1016/j.jas.2018.08.002

Three early medieval Irish communities within a 30-km radius in Co. Meath, Ireland, have been examined using multiple isotopes (87Sr/86Sr, δ18O, δ13C, δ15N) to elucidate human and domesticated animal subsistence and provenance. Existing 87Sr/86Sr data from geochemical mapping of contemporary soils, plants and streamwater were compared to human and animal tooth enamel 87Sr/86Sr to assess potential past human migration, in combination with δ18O from bone collagen. Oxygen isotope (δ18O) values of human bone collagen are notably invariable, 10.0 ± 0.6‰ (n = 36), for the three archaeological sites: Collierstown, Johnstown and Raystown. Fauna (sheep, pigs, cats and a dog) δ18Ocollagen from Raystown are distinctly grouped between and among certain species, the first instance to our knowledge of such a result. The aggregate faunal data demonstrate that δ18Ocollagen values of faunal remains should not be used to infer local δ18O ranges for humans. Nitrogen isotope (δ15N) values for both domesticated animal (9.8 ± 1.7‰) and adult human (12.0 ± 0.8‰) bone collagen are tightly constrained suggesting a similar source of protein in the diet of humans. A mean carbon isotope (δ13C) value of −21.0 ± 0.4‰ for adult humans indicates overwhelming terrestrial sources of foodstuffs. Strontium isotope ratios (87Sr/86Sr) from human dental enamel range from 0.7085-0.7110 (n = 25). Two individuals (R841 and R854), both from Raystown, are statistical outliers based on their 87Sr/86Sr and δ13C values and are likely migrants to the locality where they were buried. We note that one of these putative migrants met a particularly violent end. •Isotopes (87Sr/86Sr, δ18O, δ13C, δ15N) of three early medieval Irish sites are presented.•Two individuals are outliers based on 87Sr/86Sr and δ13C and are likely migrants.•Oxygen isotope (δ18O) values of human bone collagen are invariable, 10.0 ± 0.6‰.•Fauna (sheep, pigs, cats and a dog) δ18Ocollagen group between and among species.