The oldest wheel found in archeological excavations was discovered in what was Mesopotamia and is believed to be over fifty-five hundred years old.
Development of a Functional WheelThe following steps and developments took place to invent a functioning wheel, more or less in this order:
This is HeavyHumans realized that heavy objects could be moved easier if something round, for example a fallen tree log, was placed under it and the object rolled over it.
The SledgeHumans also realized a way to move heavy objects, with an invention archeologists call the sledge. Logs or sticks were placed under an object and used to drag the heavy object, like a sled and a wedge put together.
Log RollerHumans thought to use the round logs and a sledge together.
Humans used several logs or rollers in a row, dragging the sledge over one roller to the next.
Inventing a Primitive AxleWith time the sledges started to wear grooves into the rollers and humans noticed that the grooved rollers actually worked better, carrying the object further. This was simple physics, if the grooves had a smaller circumference than the unworn parts of the roller, then dragging the sledge in the grooves required less energy to create a turning motion but created a greater distance covered when the larger part of the log roller turned.
The log roller was becoming a wheel, humans cut away the wood between the two inner grooves to create what is called an axle.
First CartsWooden pegs were used to fix the sledge, so that when it rested on the rollers it did not move, but allowed the axle to turn in-between the pegs, the axle and wheels now created all the movement. These were the first carts.
Improvements to the cart were made. The pegs were replaced with holes carved into the cart frame, the axle was placed through the hole. This made it necessary for the larger wheels and thinner axle to be separate pieces. The wheels were attached to both sides of the axle.
Fixed Axles Make a Functional & Successful WheelNext, the fixed axle was invented, where the axle does not turn but is solidly connected to the cart frame. Only the wheels did the revolving by being fitted onto the axle in a way that allowed the wheels to rotate. Fixed axles made for stable carts that could turn corners better. By this time the wheel can be considered a complete invention.
The rest is history...