The abscission layer formed on a pedicel situated at the basal part of a short rachilla is an important characteristic for discriminating between wild,japonica,and indica rice.The short rachillae of paddy rice grains excavated from the Kuahuqiao,Luojiajiao,and Tianluoshan sites,located in the lower eaches of the Yangtze River and dating to 7000 years old,were observed.The results showed that the short rachillae could be divided into two types:a wild type and japonica type.These results indicated that the rice had been domesticated,but was a primitive cultivated rice that retained some of the characteristics of wild rice.The results also suggested that the rice was changing to resemble japonica type rice.Based on the ratios of wild and japonica types,it was inferred that rice domestication began 10000 years ago.