Revealing Coix lacryma-jobi var. lacryma-jobi (Job’s tears) in Han Dynasty burials with evidence from phytolith identification

Abstract Coix lacryma-jobi L. (Job’s tears, adlay, yiyi 薏苡in Chinese) is a tropical member of the Poaceae family which is widely grown in southeast Asia for its grain, as medicine and for beads. However, archaeobotanical evidence of Coix from macrofossils or phytoliths remains limited, and the varieties used in ancient China have yet to be identified through research. In this study, the remains of involucral bracts of Coix from two Han Dynasty tombs (2004CSX Tomb M110 and RNSM Tomb M1, dated to around 2,100 cal bp) in Xi’an, Shaanxi Province, China, were examined. Macrobotanical analysis suggested they were C. lacryma-jobi , and phytolith analysis further confirmed their identification as C. lacryma-jobi var. lacryma-jobi . This is the first report to successfully identify ancient remains of this plant to variety level from phytoliths. The findings provide new insight into the cultural significance of Coix in Han Dynasty funerary customs and demonstrate the potential of phytolith analysis for the identification of taxa from archaeological contexts to variety.