The invention of the wheel represented a major turning point in human civilization. The first wheels, disks carved from solid wood, may have been built as early as 3500 BC. The earliest use of this device was the potter's wheel, used to spin and shape clay pottery. It was not long before the true potential of the wheel was discovered, and wheeled carts soon replaced the sledge as a means of transportation. Rapid developments, such as wheels consisting of a ring with radial spokes, made the wheel even more practical by reducing its weight. By using the wheel, mankind gained the ability to work more efficiently and travel more quickly. Besides its use in transportation, the wheel went on to become the basic principle behind almost every mechanical device.