Science News goes deeper into a rock that bears a cross-hatch pattern made 73,000 years ago in a South African cave:
The discovery “helps round out the argument that Homo sapiens [at Blombos Cave] behaved essentially like us before 70,000 years ago,” says archaeologist Christopher Henshilwood of the University of Bergen in Norway.
His team noticed the ancient drawing while examining thousands of stone fragments and tools excavated in 2011 from cave sediment. Other finds have included 100,000- to 70,000-year-old pigment chunks engraved with crosshatched and line designs, 100,000-year-old abalone shells containing remnants of a pigment-infused paint and shell beads from around the same time.
The faded pattern consists of six upward-oriented lines crossed at an angle by three slightly curved lines, the researchers report online September 12 in Nature. Microscopic and chemical analyses showed that the lines were composed of a reddish, earthy pigment known as ocher.
The lines end abruptly at the rock’s edges, indicating that a larger and possibly more complex version of the drawing originally appeared on a bigger stone, the researchers say. Tiny pigment particles dotted the rock’s drawing surface, which had been ground smooth. Henshilwood suspects the chunk of rock was part of a large grinding stone on which people scraped pieces of pigment into crayonlike shapes.