Morphological trend analysis of rice phytolith during the early Neolithic in the Lower Yangtze

The investigation of rice domestication process is important for understanding how agriculture evolved in China. In this paper, we studied samples of rice phytoliths from the Shangshan (around c. 11,000-9000 cal. BP), Kuahuqiao (around c. 8200-7200 cal. BP) and Hemudu (around c. 7000-6500 cal. BP) periods in the lower valley of Yangtze River. Using two different techniques it was demonstrated that rice phytoliths could be separated into wild rice and domesticated varieties. Through time the percentage of wild rice phytoliths decreases while the percentage of domesticated rice phytoliths increases. The changes in morphological characteristics of double-peaked glume cells and scale-like decorations numbers of cuneiform bulliform cells indicates that human intervention likely impacted rice during the Shangshan, Kuahuqiao and Hemudu Periods. Based on morphological characteristics when classifying the rice phytoliths into wild rice and domesticated rice varieties of double-peaked glume cells, a large percentage of phytoliths could not be assigned to either a wild or domesticated variety. The large percentage of the uncertain type indicates that early domesticated rice phytolith may be neither completely wild nor fully domesticated in morphology. The result of this study indicates the evolution from wild rice to domestic rice occur between 12,000 and 7000 cal. BP.