The ochre hashtag drawing found in Blombos Cave. (Credit: Craig Foster) The hashtag is far more ancient than we think. In a South African cave, inscribed on a flake of rock, nine lines of red ochre inscribe a familiar crosshatched pattern. The find, dated to 73,000 years ago, is the oldest abstract drawing discovered to date, and it was made by ancient Homo sapiens in the area, say researchers writing Wednesday in Nature. Blombos Cave, on the country's southern coast about 190 miles from Cape Town, has already yielded a rich collection of Stone Age artifacts including pieces of ochre with engraved patterns carved into them and "tool kits" for drawing with the pigment. The latest find was uncovered in 2011, and recently analyzed by researchers from Europe and South Africa.