What is the significance of the bends of the spine, the wide pelvis of the modern man firmly articulated with the sacrum?

These are the features of the human skeleton associated with upright posture and labor. Man is characterized by the vertical position of the body, leaning only on the lower limbs. The spine of an adult has bends. During fast, sharp movements, the bends spring and soften the tremors. In mammals, animals that rely on four limbs, the spine does not have such bends.
The human chest in connection with upright posture is expanded to the sides. In mammals, it is laterally compressed.
In connection with the vertical position of the human body, the belt of his lower extremities is very wide and looks like a bowl. It serves as a support for the internal organs of the abdominal cavity. In mammals, the pelvis is much narrower than in humans.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.