Fossilized circles in the sand on South Africa's coast may be artwork by our early ancestors

If you have walked on a dune surface after windy conditions have settled, you may have been privileged to recognize one of Nature's wonders: scratch circles. These are structures formed when the end of a tethered object is passively rotated into the surrounding sediment. In other words, a flimsy frond or blade of grass that is attached to the ground will blow in the wind, and its loose end will inscribe a perfect circle or perfect arc, with the point at which it is attached becoming the center of the circle or arc.