Mysterious metal spheres measuring about an inch in diameter have been found in South Africa in rock dated to 2.8 billion years old, and some are etched with three parallel grooves. Fossils that seem out of place have also been found, including a human handprint in limestone estimated at 110 million years old and a possible human footprint from 300-600 million years ago. In 1938, an expedition in China discovered a cave containing hundreds of stone disks approximately nine inches in diameter with a central circle and spiral groove etched with tiny hieroglyphs describing a crash landing of spacecraft carrying beings called Dropa.