ISRAEL: Hand-size stone balls have been found at numerous early Paleolithic sites around the world, but their exact purpose has baffled experts. Microscopic analysis of wear patterns and bone residues on the surface of examples found in Qesem Cave has indicated the spheres may have been shaped and used by humans between 400,000 and 200,000 years ago to crack open animal bones. Experimental trials using replicas demonstrated just how efficient these tools would have been at accessing bone marrow, which was nutrient-rich and much sought-after.