Feeding the first centralized empire: dietary shifts and the rise of the Qin Empire through stable isotope analysis from the Yijia site (Shaanxi, China)

The Qin state, which later established the first unified empire in China, has long been studied for its political and military strategies. However, the role of dietary patterns and agricultural practices in its ascendancy remains underexplored. This study combines new stable isotope analysis of human remains from the Yijia site (陕西西安宜家遗址) (n = 77) with a systematic review of published Qin period data (n = 626), aiming to investigate subsistence strategies during its expansion. Individuals from the Yijia site exhibited δ 13 C values ranged from −13.2‰ to −8.4‰ (mean ± SD; −10.4 ± 1.1‰), indicating dietary diversity with a predominant consumption of millet. The δ 15 N values ranged from 7.6‰ to 11.1‰ (mean ± SD; 9.1 ± 0.7‰), suggesting diverse intake of animal protein, with a predominance of consumption from pigs. A phased analysis of the Yijia site allowed further investigation into the differences in C and N values by period, gender, and burial type. Additionally, a systematic review of published Qin-period stable isotope data (n = 626) indicates a shift in δ 13 C values from a diversified diet in the early (–23.3‰ to −7.1‰, −12.6 ± 3.8‰, n = 52) and mid-Qin periods (−14.6‰ to −7.5‰, −10.2 ± 1.3‰, n = 123) to a predominantly millet-based diet during the late-Qin (−20.6‰ to −7‰, −9.9 ± 2.4‰, n = 451). This transition reflects the intensification of millet agriculture, which likely played a growing role in the Qin’s unification of China. Concurrently, advancements in livestock husbandry and millet-based agriculture provided a robust material foundation for the rise of the Qin state. These changes indicate that the increased reliance on millet and the expansion of millet-based agriculture were pivotal in establishing the economic base that supported the Qin’s ascent.