Were they actually local? Strontium isotope analysis of individuals from the Roman cemetery of Lucus Feroniae (Rome, Italy)

The town of Lucus Feroniae (I-III century CE) was inhabited, according to the archaeological record, by local people, war veterans and liberti (freed slaves). The study of this community makes it therefore possible to shed light on individuals whose lives are often not reported by classical literary sources. In particular, to understand from which other parts of the Roman Empire the liberti and veterans came from. In order to answer this question, this research couples skeletal evidence and isotopic analyses. The former has highlighted six individuals from the necropolis of Lucus Feroniae who display skeletal features associated with a harsh quality of life, in particular fractures on the skull and postcranial bones, which in turn might be associated with the consequences of being a slave or a labourer. Strontium isotopic analysis has then been performed on such individuals to explore their geographic origin. Analysing the dental enamel of the first molar, it was possible to gain information about their first decade of life, approximately. A baseline was created to look at the local range of strontium isotopic ratio using bones and teeth of archaeological animals, focusing on animals that lived, supposedly, in confined areas, rather than free-ranging ones. Soil samples have also been collected for this purpose. However, in several instances local strontium ratios are similar among very distant areas. It is therefore difficult to tell whether an individual spent her/his first years of life in Lucus Feroniae or came from further-away areas. Despite the diversified geological background of Italy that might appear promising for strontium isotope analyses, our results hold up as a cautionary tale about the use of these data.