Strontium and stable isotope evidence for diet and mobility in Roman Gloucester, UK
Introduction
Britain under Rome was a multi-cultural society, with historical and epigraphic evidence recording the voluntary and forced migration of Gaulish, Germanic and North African individuals into the British provinces (Birley, 1979). This paper presents the results of an isotopic investigation of population and dietary diversity in Roman Gloucester, focusing on individuals found in a late 2nd century mass burial pit at London Road, and comparing them to those found in nearby discrete burials.
Mass burials are rare in the archaeological record, but offer potential for the investigation of specific events and cultural behavior within a narrow time frame. Mass burials are often explained in terms of casualties of war and small scale conflicts, or ethnic cleansing (Fiorato et al., 2007, Wahl and König, 1987); epidemics (Grainger et al., 2008, Shoesmith and Stone, 1995); or for the disposal of the community's poor. For example, outside the City of Rome, ‘puticuli’ – or grave pits containing the bodies of slaves and paupers, are attested (Toynbee, 1971: 49).
The 2nd century mass burial from Roman Gloucester (Glevum) offers the opportunity to test, whether it was the result of a catastrophic event, possibly a disease, affecting all members of the community. Alternatively, if the individuals within the pit were different to the ‘regular’ inhabitants of Gloucester, in their geographic origin or diet, other explanations for their mode of burial would have to be sought. More generally and as part of a larger project exploring diversity in Roman Britain, this study also allows us to explore diet and mobility at one of Britain's four colonia towns.
Various recent studies have combined strontium (87Sr/86Sr) and phosphate oxygen isotope (δ18Op) analysis of tooth enamel to characterize the local and non-local components of cemetery populations (e.g. Müller et al., 2003, Budd et al., 2004, Evans et al., 2006a, Evans et al., 2006b). However, these methods depend upon our ability to characterize ‘local’ isotope values which is not always straightforward (see Bentley et al., 2004). In order to achieve this and given the complex geology of the Gloucester area, we have conducted a survey of biosphere 87Sr/86Sr values within a 30 km radius around the city, using modern vegetation samples.
Section snippets
Roman Gloucester (Glevum)
The city of Gloucester is located in SW England on the east bank of the river Severn, near the Welsh border (Fig. 1). Roman activity began around AD 49, with the construction of a fortress at Kingsholm (Hurst, 1985), located next to a thriving pre-Roman settlement (Hurst, 1999). In the mid to late 60s AD, a new legionary fortress was built 0.5 km to the south, which eventually became a colonia, a settlement designed for retired legionaries and their families, at the end of the 1st century AD (
Isotopic analysis of human remains
The main principle of isotope analysis of human remains for reconstructing residential mobility or diet is that the natural abundance of different isotopes in items of food or drink varies systematically, according to the environments they are produced in. These “isotopic signatures” contained in food are incorporated into the skeletal tissues of consumers which, on analysis, allow the reconstruction of main dietary sources and, provided that foodstuffs are predominantly sourced locally and not
Bone and tooth sample preparation
The London Road site comprised 64 individuals from inhumation graves in the main cemetery, and a minimum of 91 individuals in the mass burial pit. Of these, 73 were articulated skeletons (Márquez-Grant and Loe, 2008). Fifty human bones (rib or long bones) and 11 faunal remains were sampled for carbon and nitrogen isotope analysis. Dentinal collagen, usually from the root immediately below the cemento-enamel junction, was also extracted from the teeth sampled for oxygen and strontium isotope
Results
Isotopic measurements for bone and dental tissues of humans and animals are presented in Table 1, Table 3. Strontium isotope data for the biosphere plant samples are given in Table 2. All individuals with sample numbers greater than 1500 are from the mass burial pit.
Purpose of the mass-grave
Statistical analyses revealed no differences between mass-grave and cemetery burials, age or sex for any of the isotopes tested, suggesting that the individuals in the mass-grave were a random sample of the population of Roman Gloucester. Our results are therefore consistent with the conclusions drawn by Simmonds et al. (2008) based on osteological evidence, that the mass-grave was constructed after a catastrophic event, such as an epidemic.
Historical sources report a number of epidemic
Conclusions
Strontium and oxygen isotope analysis for reconstructing geographic origin are relatively new techniques and applying them to the Roman period, where it is known that not only people but also foods moved over large distances, and in an area of significant geological diversity like Gloucestershire, is certainly ambitious. Our case-study has not only provided new evidence for diet and population composition at Roman Gloucester, but has also highlighted important issues regarding the
Acknowledgements
This project was carried out as part of an AHRC “Diasporas, migrations and identities” research programme (AH/E58758). Samples and background information were kindly provided by Oxford Archaeology and we thank especially Drs. Louise Loe and Nicholas Márquez-Grant for their help. We thank Dr Mark Cave (British Geological Survey) for statistical advice and Dr Janet Montgomery (University of Bradford) for constructive comments.
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