The earliest knives were shaped by percussion flaking from rock, particularly water-worn creek cobbles made out of volcanic rock. During the Paleolithic era Homo habilis likely made similar tools out of wood, bone, and similar highly perishable material that has not survived. As recent as five thousand years ago, as advances in metallurgy progressed, stone, wood, and bone blades were gradually succeeded by copper, bronze, iron, and eventually steel. The very first stone tool assemblage in prehistory is called the Olduwan by anthropologists. Olduwan tool use is estimated to have begun about 2.5 million years ago, lasting to as late as 1.5 million years ago. It is suggested that its users comprised a number of species of hominina ranging from Australopithecus to early Homo, and passing its loosely categorized tool tradition between more than one genus.
