"Celts" up the Alps. Patterns of territorial mobility and funerary variability in Switzerland during the Late Iron Age

The European Late Iron Age (ca. 5th-1st centuries BCE) is characterized by significant economic, social, and cultural transformations, including the development and intensification of cultural and economic networks. These features make the last centuries BCE relevant for the study of human territorial mobility and its demographic and social correlates. In this study, we investigate the frequency and nature of human mobility during the Late Iron Age in one of the central regions of the La Tène cultural sphere, the area that is now Switzerland. We further address the cultural factors that may have influenced the mobility patterns. Therefore, we analyze strontium (⁸⁷Sr/⁸⁶Sr), oxygen (δ¹⁸O) and sulfur (δ³⁴S) isotopic ratios from dental enamel and bone collagen in a human skeletal dataset (N⁸⁷Sr/⁸⁶Sr = 101; N δ¹⁸O = 90; N δ³⁴S = 121) representing various Swiss contexts dating to the last five centuries BCE. These isotopic data are contextualized using faunal and vegetation baselines and further explored for any demographic and funerary patterns. Results reveal spatial heterogeneity in the frequency of nonlocal individuals, suggesting that both long- and short-distance residential changes were influenced by regional political and economic differences across contexts. The absence of a correlation between geographic origin and sex suggests that specific residential rules may not have been prevalent in these communities. The lack of an association between isotopic variability and funerary treatment suggests that geographic origin held limited social significance compared to sex, socioeconomic status, and community membership. These findings enhance our understanding of the demographic and cultural processes in this geochronological region highlighting the complexities and challenges of estimating past mobility patterns and geographic origin using isotopic data.