Why is the prehistoric period called the stone age

The prehistoric period is not necessarily the same thing as the stone age.Prehistoric means before writing, and the classification of the past according to what materials were available is not looking at precisely the same thing.In the stone age, only stone and some natural materials like bone and wood were available to make tools and weapons.It was followed by the bronze age, and then the iron age.Precise dates cannot be given because societies evolved at different speeds in different parts of the world.