Bone collagen hydrogen isotopes as tracers of local palaeoclimate: The Aurignacian from Isturitz cave (France) as a case study

Hydrogen stable isotopes (δ ² H) preserved in bone collagen have been proposed as a promising proxy for palaeoclimatic reconstruction, though empirical applications remain limited. To evaluate the reliability and scope of this approach, we performed a multiisotopic analysis (δ ¹³ C, δ ¹⁵ N, δ ³⁴ S, and δ ² H) on 50 herbivore bone samples collected from three archaeostratigraphic layers spanning the Aurignacian sequence of Isturitz Cave (France). This archaeological well-preserved, dated and studied site provides a robust framework for testing isotopic proxies across temporal and taxonomic gradients. Our results reveal a progressive δ ² H depletion over ∼3000-year interval, consistent with predicted increasing aridity. We also identified species-specific δ ² H differences, underscoring the need for taxonomic resolution in future applications and in general palaeoclimatic interpretations. While these samples reflect faunal remains accumulated through human activity—introducing potential ecological and sampling biases—they nonetheless provide valuable records of past local conditions. Overall, our findings support the potential of bone collagen δ ² H as a sensitive indicator of past hydrological conditions and a complementary tool for reconstructing both climatic trends and humanenvironment dynamics.