Use-wear traces and plant micro-remain analysis reveal the function of perforated shell tools from the Xianrendong and Diaotonghuan sites in the middle reaches of the Yangtze River, China

Shell remains are common cultural relics recovered from the late Paleolithic to the historical-age sites in China. Archaeological evidence shows that the number of perforated shells gradually increased at the transition from the Paleolithic to Neolithic age, a time period that coincides with the beginning of farming activities. Usage traces and plant residues from prehistoric perforated shells are often used to interpret tool function. In this study, we analyzed use-wear traces and recovered ancient starches and phytoliths from both the ventral and dorsal margin of twelve perforated shells from the Xianrendong and Diaotonghuan sites (30,000-12,000 cal. Y BP). These sites are well-known for the earliest pottery and the earliest cultivated rice micro-remains in the world. We found that: (1) all the twelve shells had scars and use wear, and that these use traces occurred on the edges of the shells; (2) an assemblage of 83 identifiable starch grains were recovered from the twelve perforated shells, including remains of starches from acorns, Panicoideae and the tribe Triticeae, tubers and roots; (3) only six phytoliths from the stems and leaves of grass taxa including Panicoideae and Bambusoideae were recovered from four shells. The meta-analysis of the use-wear and plant micro-remain analysis indicate that the functions of perforated shells were nearly identical from the late Paleolithic to early Neolithic periods. These functions include processing, harvesting or cutting grasses from the Panicoideae, Bambusoideae, and the tribe Triticeae, processing acorns or/and their starchy products, in addition to digging up and scraping tubers and roots. The digging and scraping of tubers and roots increased in intensity with the increase in rice cultivation during the period between 20,000 and 12,000 cal. Y BP.