Up till now, it is still a mystery as to who invented the wheel and when the wheel was invented. According to archaeologists, it was probably invented in around 8,000 B.C. in Asia. The oldest wheel known however, was discovered in Mesopotamia and probably dates back to 3,500 B.C.
This wheel was believed to have been made by the Sumerians. It was made of planks of wood joined together. The picture below briefly describes the stages of development of the wheel.
Stage one: Early men placed rollers beneath heavy objects so that they could be moved easily.
Stage two: Early men began to place runners under a heavy load, which they discovered would make it easier for the load to drag. This was the invention of the sledge.
Stage three: Men began to combine the roller and the sledge. As the sledge moved forward over the first roller, a second roller was placed under the front end to carry the load when it moved off the first roller. A model of a sledge with such rollers is in the Smithsonian Institution.
Stage four: Soon, men discovered that the rollers which carried the sledge became grooved with use. They soon discovered that these deep grooves actually allowed the sledge to advance a greater distance before the next roller was needed to come on!
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