Ever since the wheel was first invented around 3,500 BC in Mesopotamia as a wooden disc with a hole in the middle for some form of axle, creative Sumarian minds were buzzing. They were, after all, already planting crops, herding animals, and had a pretty impressive social order. But getting the wheel contraption right took a bit of creative genius. The holes in the centre of the disc and at the ends of the axle had to be perfectly smooth and round in order for the wheel to fit and turn. Otherwise, too much friction would cause breakage.