Who swung the first hammer stone? Early human ancestors may have hefted tools more than three million years ago, ancient hand bones suggest. That's roughly half a million years earlier than the oldest stone tools yet discovered. The hand-bone analysis, led by the United Kingdom'sMatthew Skinner of the University of Kent in Canterbury, compared the internal structure of hand bones from modern people, chimps, apes, Neanderthals, and early human species.