A multi-isotope investigation of diet and subsistence amongst island and mainland populations from early medieval western Britain

ObjectivesThis is the first investigation of dietary practices amongst multiple early medieval populations (AD 500-1000) from Wales and the Isle of Man using carbon, nitrogen, and sulphur isotope analysis. The analysis will illuminate similarities or differences between the diets and subsistence strategies of populations occupying different geographical regions, specifically those living in marginal coastal regions in comparison to inland populations well-connected to ecclesiastical centres and high-status settlements. Materials and MethodsOne hundred and two human skeletons were sampled for carbon and nitrogen isotope analysis, and 69 human skeletons were sampled for sulphur isotope analysis from nine cemetery sites from western Britain (Isle of Man=3, southwest Wales=4, southeast Wales=2). Thirteen faunal skeletons from St Patrick's Chapel (southwest Wales) were sampled for carbon, nitrogen, and sulphur isotope analysis. ResultsHuman C-13 values range from -19.4 to -21.2 parts per thousand (C-13 mean=-20.4 +/- 0.4 parts per thousand, 1 sigma, n=86), and N-15 values range from 9.1 parts per thousand to 13.8 parts per thousand (N-15 mean = 10.8 +/- 0.9 parts per thousand, 1 sigma, n=86). S-34 values range from 1.2 parts per thousand to 18.4 parts per thousand (S-34 mean = 11.6 +/- 4.5 parts per thousand, 1 sigma, n=66). Significant differences were noted between the mean C-13, N-15 and S-34 values according to geographic region: Isle of Man (C-13=-20.7 +/- 0.4 parts per thousand, N-15=11.4 +/- 0.6 parts per thousand, n=13/86; S-34 mean=17.1 +/- 0.6, n=4/66), southwest Wales (C-13=-20.5 +/- 0.4 parts per thousand, N-15=11.0 +/- 1 parts per thousand, n=32/86; S-34=16.1 +/- 2.1, n=21/66), and southeast Wales (C-13 =-20.3 +/- 0.4 parts per thousand, N-15=10.4 +/- 0.7 parts per thousand, n=41/86; S-34= 8.8 +/- 3 parts per thousand, n=41/66). Faunal C-13 values range from -23.1 parts per thousand to -21.2 parts per thousand (C-13 mean= -22.1 +/- 0.5 parts per thousand, 1 sigma, n=13), and N-15 values range from 6.3 parts per thousand to 9.8 parts per thousand (N-15 mean = 7.3 +/- 1.1 parts per thousand, 1 sigma, n=13). S-34 values range from 4.7 parts per thousand to 18.4 parts per thousand (S-34 mean= 16.3 +/- 3.6 parts per thousand, 1 sigma, n=13). ConclusionsThe data reveal a reliance on terrestrial protein, however differences are observed between the resource consumption of populations from southwest Wales and the Isle of Man in comparison to the populations from southeast Wales. Populations from the west coast have a marine sulphur signature that reflects their coastal proximity and may also include a reliance on seaweed as a fertiliser/food source. Populations in the southeast were connected to ecclesiastical centres and high-status settlements and had access to inland-grown produce. The data add support to the suggestion that S-34 can be used as a mobility indicator.