It is known that when a person is born, he has 350 bones, but by adulthood this number decreases to 206. So why is it so, if according to the idea everything should be exactly the opposite?

The fact is that the change in the number of bones in the skeleton is related to the process of human evolution. For example, children have milk stitches, or soft areas, on their skulls. Over time, these stitches close, resulting in a strong skull.

Ossification is the main factor associated with the decrease in bone number. In other words, it is a process in which soft tissue eventually turns into bone. This happens in newborns. It consists of cartilaginous formations, some of whose elements later turn into bone.

As the child grows, some bones also grow. This happens, for example, in the spine. The same applies to arm and leg bones. Therefore, the skeleton of an adult becomes less mobile than the skeleton of a child. Source