Stable isotopic analysis of human bones from Jiahu site, Henan, China: implications for the transition to agriculture

We have investigated change in subsistence during the transition to agriculture in the site of Jiahu, Henan Province, China, using stable isotopic analysis of collagen and apatite in human bones. Millet agriculture is well documented at drier high latitudes of the Yellow River Valley, while rice agriculture predominated at wetter lower latitudes of the Yangtze Valley region. The early Neolithic site of Jiahu lies near the boundary between the drier north and wetter south. Archaeobotanical evidence shows that rice was a significant component of diet at Jiahu, but its δ¹³C value is similar to that of other foods, and therefore cannot be conclusively identified by carbon isotope analysis. Foxtail and broomcorn millets are the only C₄ crops known for the Chinese Neolithic. Because of their high δ¹³C values, their consumption can be evaluated by stable carbon isotope analysis of human bone. Collagen reflects mainly the δ¹³C value of dietary protein, and apatite accurately records that of the whole diet. Isotopic analysis of 15 well-preserved samples from three periods shows that collagen δ¹³C values were very low for almost all individuals, suggesting C₃-based foods dominated their diets. However, apatite carbonate δ¹³C values and δ¹³C spacing between collagen and apatite (Δ¹³C_ap-co) indicate that millet may have been a minor component of the diet in this region. Individuals, who consumed the smallest amounts of animal protein, as indicated by low δ¹⁵N, generally had the highest apatite δ¹³C values. Archaeobotanical evidence for millet at Jiahu is needed to support this interpretation. Higher rainfall during the early Holocene may have favored rice agriculture, and the drier climate of the middle Holocene may have favored millets cultivation. However, no clear diachronic trends were observed between 9000 and 7800 BP at Jiahu. Therefore larger numbers of individuals from each phase at Jiahu and other sites are needed to evaluate temporal trends in Neolithic diet, and their relation to climate change, and social factors.