Carbon and nitrogen isotopic variability in bone collagen during the Neolithic period: Influence of environmental factors and diet

Studies on Holocene periods in France and Liguria over the past 15 years provide an important isotopic database (δ13C and δ15N) on human and animal bone collagen during the Neolithic period (ca. 5500-3100 BC cal.; n = 573). The distribution of archaeological sites (n = 30) along a latitudinal transect from the Mediterranean to the Channel offers a broad data base reflecting a variety of environments and potential cultural practices. We propose a new insight into δ13C and δ15N data to understand the variability in both environment and human diet at the onset of farming. Statistical comparisons highlight significant geographical variation in both δ13C and δ15N ratios in most of the examined species and particularly in wild herbivores (Δ13C = 3.8‰; Δ15N = 8.5‰). Higher δ15N and lower δ13C ratios are found in samples from northern France. Conversely, lower nitrogen and higher carbon isotopic ratios are present in samples from the Mediterranean area. Results indicate the probable strong influence of natural factors impacting soil and plant isotopic ratios and passing this variation further on into the whole food chain. Our data indicate that the isotopic baseline depends on the local environmental particularities which must be taken into account in reconstructing human palaeodiets.