Wet-rice fields couldn't be found in northern Korean until the recent period and the oldest carbonized rice found on the Korean peninsula which can't be traced back to rice found in the Japanese archipelago was from 2000 B.C.; therefore, one theory suggests that the rice cropping was introduced to the Korean peninsula through the Japanese archipelago.
また朝鮮北部での水耕田跡が近代まで見つからないことや朝鮮半島での確認された炭化米が紀元前2000年が最古であり、日本列島のものを遡れないことなどから、稲作は日本列島から朝鮮半島へ伝播した説も出ている。