‘Big Isotopic Data’ link millet consumption under Lombard rule in early medieval northern Italy

Archaeobotanical and biomolecular evidence from northern Italy has highlighted a significant increase in millet cultivation during the early medieval period. This study applies Bayesian spatiotemporal modelling to the Isotòpia and CIMA databases, which collected isotopic measurements on bioarchaeological remains from ancient and medieval Europe, respectively, to investigate a debated historical link between this agricultural shift and the Lombard rule in northern Italy (568-774 CE). Results confirm that this period coincides with an increased reliance on millet, particularly in regions associated with the Po Valley. This shift is primarily attributed to the need for food security in a politically fragmented and unstable environment, with millet offering reliable yields due to its phenotypic traits for tolerance. While political agenda and environmental factors appear to impact millet cultivation to varying degrees, specific links with social or ethnic affiliations remain largely unclear and require additional research. The approach used in this study demonstrates the potential for ‘Big Isotopic Data’ to identify major historical trends.