The study of the skull and teeth of primitive people showed that although the occlusal and adjoining surfaces of the teeth of primitive people were severely worn out, there was basically no crowding, which was mainly due to the abrasion of the teeth by eating rough foods to offset the wedge-shaped force of the occlusal force on the front teeth, and it was deduced that modern people should eat more rough foods such as corn, sorghum rice, raw vegetables and fruits to aggravate some dental Abrasion can avoid the crowding of the front teeth caused by the occlusal force of the teeth. Secondly, the evolutionary trend of human is inevitable: the nervous system is more and more developed, the motor system is more and more degraded, in the degradation of the motor system, the soft tissue degradation is the fastest, the harder the tissue degradation is slower. In the oral cavity is the most muscle degeneration, followed by bone degeneration, teeth degeneration is the slowest. In other words: the musculoskeletal formation has less and less capacity to accommodate the teeth, and the teeth erupt and cover each other because there is not enough space to arrange them, and crowding does not occur. In this case I also recommend that you let your child eat more food that requires more chewing to stimulate the bones and muscles to increase the space and ability to accommodate the teeth. Some of you may say that this degeneration can be resisted? It is the degeneration of the human race. I can happily tell you that the results I found out are that this degeneration can be changed in one generation. So everyone consume less fine food will be good for the mouth to other organs of the body.