When a stone flake is used in specific applications, such as sawing or whittling, distinct wear patterns are formed. In addition, unique patterns are also formed by the surface on which the tool is used. Wood, meat, hide, and bone all leave dissimilar scars on a lithic device.
Modern archaeologists have devised a method, called use-wear analysis, in which attributes from archaeological remains are compared to modern examples whose function is known. This allows archeologists to determine the function of a prehistoric tool by its wear patterns. The purpose of this experiment is to note the wear patterns caused by sawing wood, and to ultimately decide if use-wear analysis is indicative of the function of past tools. A small obsidian flake would be used in this experiment.
It was approximately forty-eight millimeters long, thirty-four millimeters wide, and seven millimeters thick. From the ventral view, the left side was serrated. This seemed like the most appropriate side to use as a saw. A small round twig, a centimeter thick, from a local deciduous tree was used as the wood subject.
The exact species of the tree is unknown; however, it was a very hard wood and a light brown/tan color. Initially, medium pressure was used on the flake and it was moved in bi-directional strokes across the stick. After about thirty strokes, the use edge angle prohibited the flake from cutting further in to the stick. The cut was roughly three millimeters deep and three quarters millimeters wide. It could be determined that a tool, in this particular shape, could not be used as an effective saw. However, use-wear patterns could still be inferred.
The flake was moved to another portion of the stick and the same process was repeated. This time the cut was only about two millimeters deep, before termination. Also, small pieces of obsidian were left in the cut and many more small pieces were mixed with sawdust on the table. The flake seemed to be deteriorating quite quickly. In addition, the pressure required to make the second cut was far more than the force needed for the initial cut.
The gradual increases in pressure continued in this manner until nine cuts were made. After this, the saw had been dulled to the point of being ineffective. In all, the procedure required roughly four hundred strokes, and wore about four millimeters of the left side of the flake. The most prominent change to the flake occurred on the serrated edge. Not only had it lost nearly four millimeters, but also the serration was rounded and no longer sharp. Furthermore there were many places on the flake were fairly sizeable pieces had come off.
This is not surprising because obsidian is known for being brittle. Many of the pieces had fallen off do to the heavy pressure the flake was enduring, and were not a result of the sawing itself. What was most interesting about the wear patterns in this activity, though, was the progress nature of the deterioration. After about the third cut, the serration was already dull. More cuts just dulled the flake more and contributed to its loss of mass. The overall damage to the flake throughout the experiment seemed pretty consistent.
This was surprising, because as the experiment went on, more force was used to saw the wood, however the wear did not increase. This is most likely a result of the obsidian being thicker further from the edge, and therefore more resilient to the pressure. As stated earlier, the thickness of the flake made it a poor saw, past a certain depth. A narrower blade would have done a better job. This flake was an expedient tool and had an informal design.
Therefore it obviously could not perform the task as well as a formal tool. The physical dimensions of the flake prohibited alliteration of the shape, as far as thickness was concerned, and no sort of modification could make the tool work better. After the post-use measurements and drawings were done, the flake was blunted by pushing it against a hard object. The purpose of this procedure was to see if there was a difference between the simple blunting of the flake, and the erosion do to sawing wood.
The results were very clear. The blunting of the flake results in much different wear patterns than sawing. After sawing, the serration is rounded but still existent. Also the basic outline of the pre-use flake is preserved. Blunting eliminates the serration and smoothes out the flakes natural changes in width. There is a distinct difference in the wear patterns of sawing and blunting.
The two would be hard to mix up. This experiment was a macroscopic experiment, however, and did not allow for microscopic analysis. Therefore, it was not unexpected that tiny cuts made by the wood could not be seen in the flakes utilized edge. Nevertheless, the macroscopic wear patterns on the flake are convincing of this one fact: Use wear analysis can be accurately used to infer the function of prehistoric tools.
The unmistakable dulling of the serration and mass loss of the flake could not be confused with other activities. Whereas some activities such as whittling and scraping can produce similar wear patterns, this experiment has concluded that wear patterns resulting from sawing are strictly unique. However, the same cannot be said for the material on which the tool was used. It could be concluded that bone would leave similar wear patterns as wood on the flake. Perhaps, though, the bone would do it more quickly, in possibly two hundred strokes. In spite of this use wear analysis is still one of the foremost methods for determine the application of past tools, and with the right training, good archaeologists may find methods, perhaps microscopically, to learn on what material the tool was used and therefore transcend all limits of the experiment.