“The general sequence of friction-reducing inventions is thought to have been runners, rollers, rollers held in place by guides, rollers held in place by guides and thickened on the ends to make them roll straighter, the wheel and axle. The wheel appears to have been first used in Sumer around 3500 BC, whence it spread across Europe, Asia, and North Africa. This orderly diffusion pattern makes it conceivable that all the wheels in use today are directly descended from the invention of a single gifted individual."
— Cecil Adams

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