A simple form of stone cutting tool, the oldest type of tool made by forerunners of modern humans. The tool consists of a rounded stone struck a number of blows with a similar stone used as a pounder, which created a serrated crest that served as a chopping blade. The core is only slightly altered by striking off a few small flakes. The most typical are choppers and chopping tools. These tools could be used as crude hunting knives, to grub roots, and for other purposes. The oldest examples are perhaps 2 to 2 1/2 million years old, from sites like the Omo Valley and Hadar in Ethiopia. Those found in large numbers in Olduvai Gorge, in Tanganyika, are universally accepted as eoliths, dating back man's history to 1,000,000 years ago. By a process of refinement these pebble tools developed into the handaxes of Africa, Europe, and southwest Asia, and into the chopping tools of the Far East.