The make-up of skeletons to make-up a city

During the high medieval period (12th-13th c.), the city of Ypres in present-day Belgium turned into one of the largest in North-western Europe, benefiting from the success of its cloth industry and international trade relations. Yet, what was the composition of its population remains poorly documented. In this period, the city experienced challenges including a rapidly expanding number of inhabitants, the political unrest of popular revolts, and natural disasters like pandemics and famines. Multi-isotope analyses on human remains have been used for decades to understand the human past and provide information on people’s environment, health, movements, and social interactions. However, possible behavioural changes following these factors are missed as multi-intra-skeletal sampling is not often done on larger groups of individuals from a single population, which is needed before conclusions can be made at the scale of a population. Especially since the comparison of isotope values obtained from different skeletal elements is sometimes debated, resulting in a limitation of intra- and interindividual comparisons. How do we link information between different bones and teeth, and how can this information be applied in order to not just understand this population, but also to improve future sampling strategies to best answer historical questions? To overcome these limitations, over 1,200 analyses for carbon, nitrogen, oxygen, and strontium isotopes are measured on 150 individuals from high medieval Ypres. Additionally, statistical analyses made intra- and interindividual comparisons possible, providing answers to a larger variety of questions ranging from the more methodologically oriented, like the existence of intra-tissue differences, to historical ones; for example sex based divisions in mobility in medieval Ypres. The implications of these findings are not only relevant for the medieval population of Ypres, but also for isotope analyses studies in general.