Man is the only vertebrate with an arch, and the existence of the arch is not only a characteristic of man, but also a sign of human evolution. The human ancestors lived in the forest and lived an arboreal life. There was no clear division of labor between the functions of their upper and lower limbs, and they were all based on climbing and grasping, so their hands and feet were similar, with no arch, a well-developed forefoot, long and flexible toes, and a non-weight-bearing heel, which was smaller. At this time, the posture of the foot, the forefoot rotated inward, the inner edge of the foot depression, the outer edge of the convex. When human evolution, since the arboreal life moved to the plains, more important and decisive is the development of upright life, hands and feet have a clear division of labor. The hands were mainly engaged in labor production, while the feet were specialized in weight-bearing walking. For this reason, the structure and morphology of the foot has also changed accordingly.
(1) upright life on land, both feet bear the weight, so the heel bone developed and grew, becoming the largest bone of the foot.
(2) Standing and walking, the foot is required to have elasticity and forward propulsion, so the navicular bone and the medial cuneus are raised upward to form the longitudinal arch of the foot.
(3) The original in order to grasp the convenience of the thumb, the thumb is slender and left with the second toe, forming a certain angle, flexible activities similar to the thumb. In order to walk upright requires weight-bearing stability, so the bunion and the second toe are close to parallel, no longer abducted into an angle, and there are ligaments associated with it, the activity is reduced because of it.
(4) Due to the formation of the arch of the foot, the ligaments of the foot develop and grow in order to maintain this arch-shaped structure. Then because the foot is no longer engaged in grasping action, so the foot intrinsic muscle atrophy degeneration.
Our Fang Xianzhi believes that the height of the human foot arch is not uniform, and does not represent the strength of the foot function. For example, in patients with high arches after poliomyelitis, the arches are high but inelastic, and the walking gait is ugly. Another example is the ballerina, who has a flatter arch, but because of the robust development of the intrinsic muscles of the foot, her gait is light, beautiful and elastic. Therefore, Fang believes that the formation of different arch heights, and people’s lives, customs and the environment in which they live. In the past, farmers in southeastern China, more barefoot labor throughout the year, at most, only wear grass tracks in the field, the environment is mostly mud, soft for the arch has a supporting role. Such a foot, not with shoes and socks, no restraint, can move freely, maintaining the original muscle ligament tension and elasticity, no factors leading to soft tissue contracture, followed by days of field work, the foot inside and outside the muscle have been exercised, muscle development is good, can play a protective role for the arch. These farmers rarely have the occurrence of flatfoot syndrome.