Stable C & N isotopes in 2100 Year-B.P. human bone collagen indicate rare dietary dominance of C4 plants in NE-Italy

C4 plants (e.g. maize, millet), part of our current diet, are only endemic of reduced areas in South-Europe due to their need of warm climates. Since the first vestiges of agriculture in Europe remains of C4 plants were recorded but their overall proportion in the human diet remains unknown. Therefore, isotopic (δ13C and δ15N) composition of bone collagen from the skeletal remains (human and animals) of a Celtic population, Cenomani Gauls, from Verona (3rd to 1st century BC) in the NE Italy provide a new perspective on this matter. The δ13C collagen values of 90 human skeletal individuals range between -20.2‰ and -9.7‰ (V-PDB) with a mean value of -15.3‰. As present day C4 plants have δ13C values around -11‰, which is equivalent to -9.5‰ for samples of preindustrial age, the less negative δ13C values in these individuals indicate a diet dominated by C4 plants. This palaeodietary study indicates that some European populations predominantly consumed cultivated C4 plants 2100 year B.P. This is supported by the paleobotanical records and ancient Roman sources (e.g. Pliny the Elder), which indicate that millet was a staple food in South-Europe.