Subsistence change in Iron Age to Tubo-period western Xizang: A stable isotope study from Phiyang Dunkar

• Human and fauna remains from Phiyang Dunkar cemetery were analyzed. • Stable isotope analysis reveals human relied on C 3 -based resources and animal protein consumption. • Increased dependence on C 3 foods and reduced animal protein intake after 7th centuries CE. • Dietary shift driven by intercultural exchange, climatic variability, and political change. The Phiyang Dunkar cemetery in western Xizang was in use from approximately 8th century BCE to the 10th century CE. Human skeletal remains from this site provide crucial evidence for understanding subsistence strategies in this high-altitude environment. We conducted stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope analysis on bone collagen from 16 human and 23 fauna remains, spanning four chronological phases: Phase I (8th-4th centuries BCE), Phase II (4th-1st centuries BCE), Phase III (1st-6th centuries CE), and Phase IV (7th-10th centuries CE). Results show that both humans (mean δ 13 C: −17.4 ± 0.4‰) and animals (mean δ 13 C: −17.8 ± 0.9‰) relied primarily on C 3 -based resources, while elevated human δ 15 N values indicate significant animal protein consumption. While dietary patterns remained stable from Phases I to III, a marked shift occurred in Phases IV, characterized by lower δ 13 C and δ 15 N values, signaling increased dependence on C 3 foods and reduced animal protein intake. By integrating isotopic data with paleoclimatic, mortuary, and historical evidence, we propose that this shift was driven by a combination of intercultural exchange, climatic variability, and political change. During Phase IV, communities supplemented their traditional pastoral and foraging economy with intensified crop cultivation, demonstrating the adaptive capacity of high-altitude societies to ecological and sociopolitical pressures.