Archaeological excavation. Close-up of a specimen bag containing fossilised shells found during excavations at 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 shells are thought to be around 77,000 years old.