There is a postulate related to the origin of rice and continental drift. Based on the postulate, the
ancestors of common rices had evolved into cultivated rices and they have differentiated to several ecotyces of rices according as Gondwana land separated into sevral continents.
As a matter of fact, the issue where and when common rices were domesticated has been unsettled. De candolle postulated in his book that rice culture first occurred in China where historical records were the earliest. Vavilov considered that rice domestication occurred in India. Li as well as Sampath was inclined to consider the domestication of rice in Indochina.

According to Chang(1976), domestication of rice in Asia may have occurred independently at about same time in many places along a broad belt extending from the Ganges Plains below the eastern foothills of the Himalayas, across northern Burma, northern Thailand, Laos and Vietnam, to Southwest and South China. Japanese analysis on variations in isoenzymic genotypes in native rice varieties showed that the center of genetic diversity exists in the area of Assam India and Yunnan China (Nakagahra and Hayashi 1977). Therefore They concluded that the area is the origin of cultivated rice and it was broadly accepted up to early 1990s. However Korean archaeologist Ahn Sung-Mo insisted in his book(1999) that middle and lower Yangtze river is the origin of cultivated rices based on the earliest archaeological evidences in China.