This belief is based on the fact that the remains peculiar to rice were found in the blade area of the excavated ishi-bocho in the past, while the remains of plants and animals that were thought to be ate at that time were not found.
これは過去に発見された石包丁の刃部分より、稲固有の残留物は見つかったものの、それ以外の当時食用にされていたと見られる動物や植物の残留物がみられなかったためである。