Stable carbon and nitrogen isotope evidence of human and pig diets at the Qinglongquan site, China

Abstract

Previous studies on the Rice-Millet (foxtail millet and common millet) Blended Zone in Chinese Neolithic have not clearly addressed such questions as the importance of primitive rice-millet mixed agriculture to human lifestyle and livestock managements within this region, the relationship among the development of the agriculture, paleoenvironment, and cultural interactions, and so on. Here stable carbon and nitrogen isotope analysis of human and pig bones from the Qinglongquan site was conducted, covering two cultural phases, namely the Qujialing Culture (3000 BC to 2600 BC) and the Shijiahe Culture (2600 BC to 2200 BC). Based on this analysis, we further discussed the diets of ancient humans and pigs in the site, investigated the importance of rice-millet mixed agriculture to human and pig diets, and explored the relationship among the primitive rice agriculture and millet agriculture, cultural interactions, and paleoenvironment. The δ13C values of human bone collagen (−16.7‰ to −12.4‰, averaging −14.6‰ ±1.3‰, n=24) revealed that both C3 and C4 foods were consumed, probably from the contribution of rice (C3 plant) and millets (C4 plants) due to the coexistence of these crops at this site. In addition, the human mean δ13C value suggested that millet agriculture was only minor in human diets. The human δ15N values (6.6‰ to 10.8‰, averaging 9.0‰ ±1.2‰, n=24) showed that animal resources played a significant role in human diets, and varied greatly. The mean δ13C value of the pigs (−14.3‰ ±2.5‰, n=13) was quite similar to that of the humans, but the mean δ15N value of the pigs was slightly less (1.3‰). The similar δ13C and δ15N values between humans and pigs suggested that the pigs consumed a lot of humans’ food remains. No correlations of the δ13C and δ15N values between humans and pigs showed that both human and pig diets were based mainly on plant foods, which might be related to highly developed rice-millet mixed agriculture at that time. In comparison with the human and pig diets between the two periods, millet agriculture contributed more than 10% in the Shijiahe Culture, if a simple mixing model was used. This apparent dietary shift matched the climatic variation and agricultural development through the time. In warm and humid climate with the expansion of the Qujialing Culture northwards, rice was widely cultivated. However, when the climate was cold and arid, northern culture was expanding southwards. Thus, millet agriculture became more important.