A tool is an implement or device used directly upon a piece of material to shape it into a desired form. The date of the earliest tools is extremely remote. Tools found in northern Kenya in 1969 have been estimated to be about 2,600,000 years old, and their state of development suggests that even older tools may remain to be discovered.
The present array of tools has as common ancestors the sharpened stones that were the keys to early human survival. Rudely fractured stones, first found and later “made” by hunters who needed a general-purpose tool, were a “knife” of sorts that could also be used to hack, to pound, and to grub. In the course of a vast interval of time, a variety of single-purpose tools came into being. With the twin developments of agriculture and animal domestication, roughly 10,000 years ago, the many demands of a settled way of life led to a higher degree of tool specialization; the identities of the ax, adz, chisel, and saw were clearly established more than 4,000 years ago.
The common denominator of these tools is removal of material from a workpiece, usually by some form of cutting. The presence of a cutting edge is therefore characteristic of most tools, and the principal concern of toolmakers has been the pursuit and creation of improved cutting edges. Tool effectiveness was enhanced enormously by hafting—the fitting of a handle to a piece of sharp stone, which endowed the tool with better control, more energy, or both.