“[Using] wheels to reduce friction while moving objects was one of the most important invention…”
Odis Hayden Griffin, Engineer
Most inventions do not appear out of thin air or from the ingenious brain of a brilliant scientist, but evolve from something already in existence. This is certainly true of the wheel and its attached axle, which developed from two different sources. The first was the revolving potter's wheel, invented in Mesopotamia in around 3500 B.C.E. Although not a tool essential to the potter's craft, the wheel did help in the faster production of better-quality pots. The second source was the sledge, a primitive but effective means of hauling large loads on parallel sleds or bars of wood. The sledge was ideal in icy and snowy conditions, and on hot sand, but not on hard, dry terrain, where great effort was required to pull it along.
Evidence that the use of the potter's wheel and the sledge came together in the invention of the wheel is found in some of the world's earliest picture-writing. Examples in Uruk, in Sumer, southern Mesopotamia, dating to around 3200 B.C.E., show various sledges, some with sleds, others with wheels. These first wheels were crude but effective: solid wooden discs made of two or three planks pegged together and then cut to form a wheel. When a pair of wheels was mounted on a fixed axle that enabled them to rotate together simultaneously, it was then but a short leap of the imagination to use the wheel-and-axle combination to carry a physical or human load in a cart, wagon, or chariot. Mesopotamia should not, however, claim sole deeds to this invention. Wheels were found in graves in the northern Caucasus, and wheels also appear on a clay pot from Poland; this earlier evidence dates to around 3500 B.C.E.
