Ancient throwing dart reveals first archaeological evidence of castoreum

[Display omitted] •Red-orange residue was observed on a 6000-year-old throwing dart from Yukon.•Residue contains substituted phenols, phenolic dimers, coumarins and xanthanes.•Residue composition matches castoreum from castor sacs of beavers.•Castoreum residue was associated with sinew and wood components.•Finding represents earliest evidence of castoreum in weapon fabrication. Alpine ice patches were caribou and sheep hunting territories for southern Yukon First Nations people for thousands of years. With increasing global temperatures, well-preserved projectile weapons that were frozen for centuries are now melting out of the ice. The study of organic residues on recovered projectiles is part of a larger effort to learn about traditional hunting technology. Here we identify the residue on a recently recovered, 6000-year-old throwing dart as castoreum, harvested from the castor sacs of butchered beavers. FTIR spectroscopy and pyrolysis-GC-MS analysis of the residue indicated substituted phenols, phenolic dimers, coumarins and xanthenes as well as cholesterol derivatives and traces of protein. Comparative analysis of reference material extracted from the castor sacs of recently trapped beavers confirmed the identity of the residue as castoreum. This finding represents the earliest evidence of castoreum use in the fabrication of weaponry and the first chemical identification of this material in the archaeological record.