Unraveling medieval lives with isotopic analysis

The researchers examined the isotopic properties of their samples and were surprised to find strontium and oxygen ratios in the tooth enamel which indicated that some of the Cramond individuals were brought up hundreds of miles away.

In 1976, archaeologists from Edinburgh City Council’s Archaeology Service discovered an enigmatic collection of human remains at the Roman fort at Cramond, a coastal village on the River Almond. The partially disarticulated skeletons – representing nine adults and five infants – were found in the latrine of the fort’s bathhouse. As they were found under a layer of medieval midden material, the bones were initially interpreted as the 14th-century remains of people who had died of plague or as a result of a medieval shipwreck. More recently, however, John Lawson, City of Edinburgh Council archaeologist, initiated the radiocarbon-dating of eight out of the nine adult skeletons (thought to be five females and four males), which was carried out at the Scottish Universities Research Centre (SUERC). It revealed that these individuals had in fact lived much earlier, in the 6th to 7th centuries AD. Moreover, examination of the individuals’ crania and mandibles by Dr Angela Boyle (University of Edinburgh) has indicated that several members of the group had suffered trauma from interpersonal violence. But who were these people, where did they come from, and what led to their demise? A new isotopic analysis of the skeletons, published in the journal Archaeological and Anthropological Sciences (https://doi.org/10.1007/s12520-022-01509-2), has provided further clues.

Image: © University of Aberdeen.

The analysis of stable isotopes preserved in human remains (see CA 118 and 344) can yield important information about the migratory and dietary histories of people who may be otherwise untraceable in the historical and archaeological record. CA has reported on how the method has helped archaeologists to understand the childhood origins and eating habits of individuals buried across the British Isles from the Neolithic (CA 335) to the 17th century (CA 308). Only a handful of studies have been carried out on human remains from Scotland, however, prompting a group of researchers based at the University of Aberdeen, the University of Edinburgh, and Edinburgh City Council to take samples of adult cranial bone and tooth enamel from the remains found at Cramond, in order to find out more about the individuals’ origins and life-styles. As Professor Kate Britton, a lecturer in archaeological science at the University of Aberdeen and senior co-author of the new paper, explained: ‘Food and water consumed during life leave a specific signature in the body which can be traced back to their input source, evidencing diet and mobility patterns. Tooth enamel, particularly from teeth which form between around three and six years of age, act like little time capsules containing chemical information about where a person grew up.’

The researchers examined the isotopic properties of their samples and were surprised to find strontium and oxygen ratios in the tooth enamel which indicated that some of the Cramond individuals were brought up hundreds of miles away. ‘When we examined the remains, we found six of them to bear chemical signatures consistent with what we would expect from individuals growing up in the area local to Cramond, but two – those of a man and a woman – were very different,’ Kate said. ‘This suggests that they spent their childhoods somewhere else, with the analysis of the female placing her origins on the West Coast. The male, instead, had an isotopic signature more typical of the Southern Uplands, Southern Highlands, or Loch Lomond area, so it is likely he came to Cramond from an inland area.’

Moreover, despite Cramond’s coastal and riverine location, analysis of collagen extracted from the bone samples (above) revealed carbon, nitrogen, and sulphur signatures indicative of a local land-based diet including meat and dairy but little-to-no fish, similar to that consumed in other areas of early medieval Britain. Additionally, no variability in diet was detected between the individuals identified as local to Cramond and those who came from further afield, which suggests that those born elsewhere had been accepted into the area. The results of the study thus indicate that there were community connections across Scotland in the early medieval period, when the country was roughly divided between Scotti (in Dál Riata, to the west), Picts (in most of northern Scotland), and Britons (in the south). As Dr Orsolya Czére, post-doctoral researcher at the University of Aberdeen and lead author of the study, commented: ‘This was a politically and socially tumultuous time. In Scotland, particularly, evidence is scarce and little is known about individual movement patterns and life histories. It is often assumed that travel in this period would have been limited without roads like we have today and given the political divides of the time. The analysis of the burials from Cramond, along with other early medieval burial sites in Scotland, is revealing that it was not unusual to be buried far from where you had originally grown up. Previous studies have suggested that those buried here were of high social status, even nobility. What we can say from our new analyses was that these were well-connected individuals, with lives that brought them across the country.’

The paper’s authors note that Cramond fort was strategically well-situated, with good connections to a tidal island in the region of various territorial borders across which conflict could have erupted. As for the identity of the individuals and their mysterious fate, however, the jury is still out.