Shell fragments. Close-up of a mound of shell fragments found along the shore near the entrance to the Blombos cave site in South Africa. This site was made famous by the discovery of pieces of ochre engraved with abstract designs, 75000-year-old beads made from Nassarius shells, and bone tools thought to be around 80,000-years-old. These fragments indicate that seafood was a significant component of the diet for occupants of the cave over many millennia.