Mercury and Stable Isotope Analysis of Human Bone from a Late Neolithic/Chalcolithic Ditched Enclosure at Perdigões, Portugal

Numerous ditched enclosures of late Neolithic and Chalcolithic ages have been documented throughout Europe including the Iberian Peninsula.  The large enclosure at Perdigões, south-central Portugal, includes at least eight funerary features (pits, ditches and tholoi tombs). Here, 21 samples of human bone were analyzed for total mercury and produced a high variation in mercury content, ranging from 0.057 to 115.62 ppm. The most likely explanation for high mercury levels is from diet with individuals feeding at higher trophic levels being more exposed via biomagnification.  However, stable isotope analysis (δ¹³C and δ¹⁵N) of the same 21 bone samples revealed a weak negative relationship with δ¹⁵N.  Mercury was lowest in individuals with the highest δ¹⁵N values indicating no relationship with a high trophic diet.  Instead, these results imply a possible age and/or sex bias in exposure to mercury, possibly through the use of cinnabar as a pigment or for other cultural uses.