What is on the menu in a Celtic town? Iron Age diet reconstructed at Basel-Gasfabrik, Switzerland

The late Iron Age (150-80 BC) proto-urban site of Basel-Gasfabrik, Switzerland, yielded numerous human skeletal remains, with individuals of all ages and both sexes being found in two cemeteries and in various features of the settlement itself. About 200 inhumations and two cremation burials as well as isolated skulls and bones attest to complex mortuary practices. Stable carbon and nitrogen isotope analyses of 90 human, 48 faunal, and seven cereal samples provide a rich database for dietary reconstruction. The results point to a diet that was largely based on C3 plants with a limited contribution of herbivore or pig meat and/or dairy products. Divergent isotope ratios can be attributed to the consumption of chicken meat/eggs or seasonally available salmon. Moreover, the contribution of C4 plants, supposedly millet, to human diets is well documented at Basel as well as at other central European Iron Age sites. We found no significant dietary distinctions between males and females. In children, indications for breastfeeding terminate between 1.5 and about 4 years of age, with isotopic differences emerging with regard to the investigated skeletal elements. The stable isotope data from different burial contexts, forms of mortuary practice, and presence or type of funerary objects overlap widely, providing only tentative indications for dietary differentiation within the living population. These findings distinguish Basel-Gasfabrik from other Iron Age sites and call for further integrative studies for deciphering the complex mechanisms behind the highly differentiated mortuary practices in the late Iron Age.