Rice is mainly distributed in tropical and subtropical areas of Asia and Africa. The history of rice cultivation can be traced back to Hunan, China, about BC 12000 ~ 16000. 1993, a joint Chinese-American archaeological team discovered the world's earliest ancient cultivated rice in Yuchanyan, Daoxian County, about 14000 ~ 18000 years ago. After being widely planted in China, rice gradually spread westward to India, and was introduced to southern Europe in the Middle Ages.
Archaeological discoveries in Daoxian County, Hunan Province and Wannian County, Jiangxi Province show that human beings began to grow and eat about 13000 years ago. Before the Neolithic Age, humans should have chewed the whole rice with their mouths.
Hemudu culture in the middle and lower reaches of the Yangtze River entered the Neolithic Age about 7000 years later, and Chu Jiu's invention was applied. People know how to clean and separate inedible chaff and rice bran. Soon, it should be found that water elutriation is a more effective impurity removal and cleaning process. The effective effect of rice washing to remove bacteria, oxidized chaff and dust is still in use today, and the rice manufacturing equipment in Chu Jiu was used until 1970s.