Prehistoric tools are often difficult to distinguish from natural debris because of their simplicity. It is not only that the techniques of tool-making developed gradually; so too did the conceptual range of tool types develop gradually. Today, hammers, wrenches, screwdrivers and saws are all clearly distinguished from each other by large differences in appearance; stone age tools, by contrast, are very similar to each other in appearance, even when they served different functions. Manufactured prehistoric tools are only distinguished from naturally-occurring gravel by the signs of consistent modification.
This is an important observation because, in the final analysis, any natural object can be utilized as a tool if it serves a need, and not only by humans. Chimpanzees have also been observed in using sticks and flat rocks as tools; surely, early humans did the same thing, even after early tool-making technologies had been developed. Most impromptu tools will never be identified; some, such as sticks, are made of perishable materials, while durable tools of this sort, such as flat rocks, are indistinguishable from rocks that have never been used in this manner. Only tools that have endured physical modification to suit human purposes can be identified.
Most of these manufactured tools are made of stone, and the earliest of these go back some two million years. Prehistoric stone tools were created by a process that is still practiced today, known as flintknapping. In this process, hard, brittle rocks like flint, obsidian and quartz are struck at oblique angles by another rock in order to knock off chips and flakes. This process serves both to shape the rock and to give it a cutting edge. Skillful flintknappers are good at guiding the final shapes of their tools, but the process is not perfect; internal flaws in the rock sometimes cause the primary piece, known as a core, to break apart in unexpected shapes. Early humans were likely opportunistic, using the larger pieces and the smaller chips alike, depending upon their needs.
In the earlier phases of stone age development, the dominant style of manufactured tool is the hand axe or hand chopper, a vaguely leaf-shaped piece knapped fairly flat with sharp edges on both sides. It was probably used in a variety of ways, being capable of slicing meat, scraping it off bones, cutting hides, and so on. Later, in the Upper Paleolithic and moving into the Neolithic, smaller and more carefully shaped flakes were prepared, presenting distinct patterns such as points, scrapers and burins.
Distinguishing these types from each other can be difficult for a layman; what is essential in identifying these pieces as manmade is the faceted surface that is created when chips are knocked off the primary piece. Naturally-broken rocks may have chips missing on one side, or in a random configuration, while manufactured tools show a systematic effort to remove flakes, often including dozens of tiny chips along the edges where a cutting blade was intended.
Stone is not the only durable material that was used in the Stone Ages to create tools. Bone and similar materials (teeth, ivory, and antlers) have also been utilized. These are softer, and therefore more easily carved. Moreover, bones begin with standard, recognizable shapes, and so modification of shape is more clearly identifiable. At the same time, one must remember that bones can break naturally; the discovery of a broken animal fibula with a sharp point at one end does not conclusively prove that it was made or even used by early humans. In an article in Burenhult 1993 (page 60 f), Peter Rowley-Conwy pointed out that even experts have hotly disputed some of these examples, with some scholars arguing persuasively that bones found with signs of cutting were actually the result of damage caused by the teeth of predators, rather than the tools of humans.
Unambiguous evidence of human manufacture in bone-type objects consists of two possible characteristics, either or both of which might be found in a given object: radical transformation or decoration. Radical transformation refers to the removal of a significant amount of material to create a shape determined by human planning rather than the natural form of the piece. A length of bone broken at one end, revealing a sharp point, has not been transformed and may not be the result of human action. A Neolithic sewing needle, however, created by whittling down a sliver of bone is clear evidence of human activity. Decoration is an obvious sign of human activity when it is found on a piece of bone or ivory, whether it consists of representational or abstract art.
The key to recognizing prehistoric stone age tools lies in awareness of the kinds of procedures that were used in creating them. Tools that are definitively identified as manufactured tools show signs of systematic manipulation and transformation that could only be performed by humans. Marginal cases surely exist where a minimal amount of modification was performed before the tool was used, and to modern eyes, there is nothing to distinguish these pieces from bones or rocks that were broken by natural processes. Perhaps tests may one day be discovered to distinguish these cases more thoroughly. For the layman, however, the criteria outlined above are currently the best ways to distinguish prehistoric tools from naturally-occurring debris.
Sources:
Burenhult, Goran, ed. The First Humans: Human Origins and History to 10,000 BC. Harper San Francisco, 1993.
Midant-Reynes, Beatrix. The Prehistory of Egypt: From the First Egyptians to the First Pharaohs. Blackwell, 1992.
Wright, Edmund, ed. The Desk Encyclopedia of World History. Oxford, 2006.
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