Transhumance pastoralism of Roccapelago (Modena, Italy) early-modern individuals: Inferences from Sr isotopes of hair strands

Objectives. In this work, we use Sr isotopes to analyze human hair and determine short-term movements of a contemporary human traveler and of Early-Modern individuals from an archaeological site (Roccapelago, Modena, Italy, 16th-18th century). Materials and Methods. Analyses were performed using a Neptune MC-ICP-MS. We first set up and tested the procedure on scalp hair of a contemporary human, who spent some time between Brazil and Italy. We then analyzed the 87Sr/86Sr ratios of 8 exceptionally well-preserved archaeological hair specimens associated with human mummies from Roccapelago. Trace elements were analyzed by LA-ICP-MS on single-hair specimens to check the preservation of the archaeological samples. Results. The strontium isotope composition of modern human hair varies from 0.7087 to 0.7093. The 87Sr/86Sr ratios of the Roccapelago hair strands range from 0.7082 to 0.7137, with an average of 0.7093 ± 0.0031 (2σ), revealing also intra-individual differences in isotopic composition along the length of the hair shaft. Data were compared with local archaeological rodent bones and teeth and with published isotopic values of water and outcropping rocks. Trace element abundances of archaeological and modern human hair are similarly low in terms of Rare Earth Element (REE) and metal contents, in particular after HNO3 leaching. Discussion. The variable modern human hair 87Sr/86Sr ratios show that high-resolution hair sampling tracks the movements of this individual between the two continents. The Sr isotope composition of the mummy hair is consistent with sub-annual human movements from Roccapelago to an area with different 87Sr/86Sr ratios. Historical sources indicate that individuals from Roccapelago travelled with their herds to Tuscany for transhumance pastoralism practices. The high radiogenic 87Sr/86Sr ratios (> 0.71) found in some of the hair are possibly consistent with the Tuscan Magmatic Province and the Tuscan Metamorphic Complex isotope signature. To our knowledge, this is the first study in an archaeological context where the Sr isotope evidence of mobility is corroborated by historical documents.