Invented during this period, it seems likely that the very first wheels were used in pottery making. Artisans would throw a lump of clay onto a horizontal plate balanced on an axle, then spin this to shape a round utensil - the same methods used by potters ever since.
The Sumerians were the first to think of flipping the potter's wheel on its side and adapting it for locomotion. The wheel enabled farmers to work land which was at a considerable distance from their village or town. An ox or a donkey hitched to a wheeled cart could pull three times the load the animal could previously carry on its back or drag on a flat-bottomed sledge. (When this idea reached the Pontic-Caspian steppe not too long later it revolutionised life there, creating a horseborne, chariot-riding elite which would sweep all other cultures before it in the form of the Indo-Europeans.)
As social stratification increased and villages grew, there emerged an early elite class. These probably formed a group of families who were linked to the village leader, or chieftain, and as the latter's power and influence grew, so did their status. Power came to be inherited and the seeds of later city states were laid down.