On the use of trace elements in ancient necropolis studies: Overview and ICP-MS application to the case study of Valdaro site, Italy

The cross-cutting study of archeological human remains is an important tool for improving the knowledge of the past civilities. Bones are actually bio-archives, storing information about the lifestyles of the individuals, the place where they lived, and their migration habits. In particular, some peculiar trace elements (such as strontium and zinc) are considered indicators of the so-called paleodiet, i.e. whether characterized by vegetables, cereals or meat. A complete overview of the concerning literature is the starting point of this work. A straightforward optimized methodology for the study of ancient bones is proposed coupling for the first time trace element determination by ICP-MS (Mg, Mn, Cu, Zn, Sr and Pb were investigated) and statistical data analysis. The protocol was applied to samples coming from a necropolis (dated from Neolithic to Bronze Age) found in Northern Italy including ‘The Valdaro Lovers’, a rare double burial where the two skeletons were facing each other with their arms wrapped around in an enduring embrace. Principal Component Analysis and Discriminant Analysis permitted to correctly classify individuals by the historical period in which they lived according to the archeological and anthropological information. The results were compared with those found in the literature and a critical discussion on the use of trace metals in this case study is given.