Exploring Shifting Roman Subsistence Practises through a Bayesian Meta-Analysis of Isotopic Data

In our presentation we explore the interplay between shifting human subsistence practises and the expansion, apogeum and final collapse of the Roman Empire. To achieve this aim, we introduce Isotópia, a collection of human, animal, and plant stable isotope data (δ13C, δ15N, δ18O, δ34S, 87Sr/86Sr) measured on archaeological material dated between 800 BCE and 500 CE and set within the geographical extension of the Roman Empire. The collection of large volumes of archaeological data has been and still is a major topic in this decade’s archaeology. Much has been recently done in isotopic archaeology, where the diffusion of standard laboratory protocols and the consequent increasing publication of new datasets across varying historical periods and geographical locations have enhanced the creation of independent isotopic databases. Once amassed and curated, also including historical, archaeological and biological meta-data, large assemblages of isotopic data represent a palimpsest of information providing for new insights on past human behaviours and lifeways at different scales and resolutions. Many of these collections are part of the IsoMemo initiative that brings together a network of isotopic databases and pursues an open-access and collaborative spirit acknowledging each collector’s efforts. This initiative, based at the Max Planck Institute - Science of Human History, also includes access to modelling tools to model spatio-temporal archaeological and historical phenomena. Isotópia is part of this isotopic network and, in combination with other databases (e.g. the CIMA database on medieval Europe) can now allow for broader meta-analyses of data aiming to explore temporal shifts in the lifeways of past human populations over more than two millennia. Here, we employed spatio-temporal modelling tools to focus on dietary shifts and changes in crop and animal management practises in populations that faced Roman domination. Britain and Italy are two of the regions that present the highest amount of isotopic measurements and preliminary results from the meta-analysis suggest a general increase in both δ13C and δ15N during the imperial period. An overall increase in marine protein consumption, imports of 15N-enriched cereals from north Africa and more intensive crop manuring and animal husbandry are the main reasons suggested to explain this phenomenon. A following decrease of δ13C and δ15N values during the Late Antiquity/Migration Period (c. 300-600 CE) could be then connected with the political and economic collapse of this system, depopulation processes and different cultural traditions on food consumption derived from incoming populations. 69 Overall our results illustrate the research potential of large-scale meta-analyses of bioarchaeological data and obtained preliminary results reveal clear links between historical developments and human lifeways in pre-Roman, Roman and Post-Roman Europe and the Mediterranean.