Abstract: The Han Dynasty marked a pivotal phase in the transformation of wheat from an exotic crop to a core staple grain in northern China. However, there is a lack of direct dietary evidence regarding the actual utilization of wheat by the early inhabitants of the Beijing area. This study analyzed the carbon and nitrogen stable isotopes of 54 human bone samples from the Luxian County, dating to the Han Dynasties, to explore the evolution of local dietary structure. The results showed that during the Western Han Dynasty, the diet of the local people was mainly based on C₄ foods (with an average δ^¹³C value of -11.5‰), while in the Eastern Han Dynasty, it shifted to a mixed C₃/C₄ diet (with an average δ^¹³C value of -14.4‰), based on archaeobotanical research conducted at this site, the significant increase in the proportion of C₃ foods is likely attributable to wheat consumption. There was no significant difference in the average δ¹⁵N values of human bones from the Western and Eastern Han Dynasties (8.6‰ to 9.0‰), indicating a stable protein intake structure. Compared with other northern sites, an increasing trend in the consumption of C₃ foods was observed throughout northern China during the Han Dynasties, but there were regional differences in nitrogen isotope changes. This study directly confirmed the increasing dependence of the early inhabitants of the Beijing area on C₃ foods during the Han Dynasties, providing key isotopic evidence from human bones for revealing the spatiotemporal process of the large-scale promotion of wheat in northern China.

Key words: stable isotopes, Han Dynasty, Luxian County, wheat