Edible starchy cereal grain and the plant by which it is produced. The origin of rice culture has been traced to India. Rice culture gradually spread westward and was introduced to southern Europe in medieval times. Roughly one-half of the world population, including virtually all of East and Southeast Asia, is wholly dependent upon rice as a staple food. The earliest datable record is from Chirard in the Ganges Valley, before 4500 BC. By the third millennium it was widely grown in south China and it was likely domesticated at Hemudu by the eartly 5th millennium BC. Its original center of cultivation could lie anywhere between the two. The earliest cultivated rice may have been grown in natural swamps or middens, but by at least 2000 years ago many parts of southeast Asia were developing terraced or wet-field cultivation.