The invention of the wheel has probably had more conversations & debates than any other invention. Think about it! How many things do you know evolved from the wheel? Carriages, cars, planes, cogs, etc……With all of the different applications of the wheel and for the length of time from it’s “perceived” origination there is no doubt controversy behind it. 
However, according to the paleoanthropologists the wheel was not invented by the caveman. As posted on Answers.com, the wheel was invented in the 5th millennium BC in Mesopotamia (Neolithic era and close to modern day Iraq) and the cavemen lived during the Paleolithic era, before the 10th millennium BC.
From Wikipedia, looking back even further, it is of some interest that although paleoanthropologists now date the emergence of anatomically modern humans to ca.150,000 years ago, 143,000 of those years were “wheel-less”. That people with capacities fully equal to our own walked the earth for so long before conceiving of the wheel may be initially surprising, but populations were extremely small through most of this period and the wheel, which requires an axle and socket, and must be made round to actually be useful, is not as simple a device as it may seem.
So now that the Geico stereotypes have been resolved here is a simple yet effective definition of the wheel from Wikipedia:
A wheel is a circular device that is capable of rotating on its axis, facilitating movement or transportation while supporting a load (mass), or performing labour in machines. Common examples are found in transport applications. A wheel, together with an axle overcomes friction by facilitating motion by rolling. In order for wheels to rotate, a moment needs to be applied to the wheel about its axis, either by way of gravity, or by application of another external force. More generally the term is also used for other circular objects that rotate or turn, such as a ship’s wheel, steering wheel and flywheel.
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Without question, the greatest invention in the history of mankind is beer. Oh, I grant you that the wheel was also a fine invention, but the wheel does not go nearly as well with pizza.
~ Dave Barry
Where would we be without it?