Biting into the truth: Connecting oral pathology and stable isotopes through the paradigmatic example of a hyper-specialized marine diet in Medieval Pontevedra (NW Iberia)

Human feeding patterns have been reconstructed in Archaeology by analysing either oral pathology or stable isotope ratios in human skeletal remains. However, no clear agreement has been developed between these two methodologies. The main objective of this study is to determine if we can establish a link between them when analysing a population with a hyper-specialized diet, in this case marine resources (and millet/maize). To reach this goal we developed a conjoined multi-isotope analysis using collagen and bioapatite (δ¹³C_col, δ¹⁵N_col and δ¹³C_car) and a detailed study of oral health (caries, antemortem loss, periapical lesions, periodontal disease, calculus, and wear). All available skeletons with at least one preserved tooth from two cemeteries of the medieval town of Pontevedra (n = 34) were studied. The buried individuals belonged to the guild of fishers and artisans, professions which were dominant among the families of medieval Pontevedra. A detailed FTIR-ATR study of extracted bone bioapatite showed a high correlation between bioapatite carbonate content, carbonate typical vibrations, and FTIR-ATR indices related to bone diagenesis, which is in line with previous research. No significant correlations were found with bioapatite yield and isotopic composition (δ¹³C_car and Δ¹³C), ruling out possible diagenetic effects. The diet was based on marine fish protein with contributions of millets (e.g., δ¹³C_car -11.9 ± 1.8‰) that seems to be slightly higher in individuals linked to artisanal guilds. The oral pathology study shows severe dental wear from an early age (Grade 2–4 in permanent dentition for 20% of infants and 60% of juveniles in M1), as well as moderate-high presence of caries in permanent dentition (64%, 22/34) and dental calculus (72%, 24/33). Both the oral pathology and the isotopic signal differ from that observed in other areas of the Iberian Peninsula. This study points to the existence of connections between findings of the two methodologies, and specifically an association between intense dental wear and high consumption of marine resources and millet. At the same time, this analysis implies the necessity of caution in estimation of age by dental wear in populations linked to the sea.