technology/unit11/Documents Never Go Away11.html
There are cultures that never applied the simple machine of the wheel to a problem. For example, Native American cultures rely heavily on the concept of a circle to explain the forces of nature and the passing of life, but, they never put a wheel on an axle as a mechanical solution to a problem. One explanation for this is that there are no wheels in nature. Your body is made up of a great many levers. People and animals role things down inclined planes all the time. The wedge is applied all over the natural world. But there are no natural wheels that do any real work. You might say, “ah, what about the example you just gave of rolling things down inclined planes?” Remember your physics. A machine applied a force to one place in the machine to overcome resistance at another place and something round rolling down a hill doesn’t do this until you put it on an axle and use the force the rotating motion creates. This application of the wheel doesn't exist in the natural world.
So when the wheel and axel was finally used to solve a problem, it was used, not in transportation, but in pottery. The later application of the wheel to transportation is unrelated, and neither application went very far very fast for a very long time. Three things were missing that would make the wheel the essential component of most every mechanical development since about the year 0.
A way to power the wheel. One reason that the Romans didn’t bother developing mills as quickly as they did centuries later in Europe is that they had slaves to do their grinding. Once again, if you have no real problem, in this case a shortage of labor, you have no need to develop a technology to change it.
A way to control the speed of the wheel. In the case of the water wheel, you can imagine how problematic a river speeded up by spring flooding might be if it necessarily speeds up the mill.
A way to change the direction of motion from going around, say, vertically to going around horizontally.
The water wheel is an example of a solution to the first problem. The second was solved by gearing and the final was solved by the cam.