The archaeological record over such parts of the world as have been extensively dug up shows roughly the following sequence: Lowest, hence earliest are crude bits of chipped stone. These were used as tools, along with pieces of wood and bone that have generally perished. This Old Stone Age (Palaeolithic) made several very slow advances over a hundred thousand years or more in the technique of stone-tool chipping. It was ultimately succeeded by the age of polished stone tools (Neolithic). In between the two came what was called the Mesolithic Age, a term not now in fashion; its extent and duration are indeterminate. These underlying strata, bearing tools only of stone (and presumably of bone, wood, and horn) were covered in time by other layers with remains of metal tools and metal weapons.