Assessment of artifact use is only appropriate through use of microscopic examination. There are several main reasons that some form of magnification is necessary. The use of “functional types” of artifacts (e.g., scraper, projectile point, etc.) is common in archaeology. These terms are functionally loaded names and many times are not based on empirical evidence. As Ahler (1971) demonstrated a number of years ago, artifacts in the same morphological class (projectile point) were actually used for a variety of prehistoric uses (cutting, boring, projectile tip, etc.). Form does not equate with function. Further, as a study by Young and Bamforth (1990; also see Odell 1996:24 for similar comments) demonstrated, without the aid of magnification, identifying between used and non-used specimens from an experimental collection was highly prone to error (average 25% correct classification for nine different individuals). In addition, scarring on tools used on soft resistance materials (e.g., plant and animal materials) does not show evidence of use except under higher magnification, often in excess of 40x. Scarring produced through post depositional processes (e.g., trampling, screen wear, excavation damage, etc.) may often be indistinguishable from that produced during the use of the tool except with the aid of higher magnification (greater than 10x).
The following two main forms of microwear analysis are common in the analysis of lithic implements: low magnification (e.g., Odell 1977, 1979, 1996; Odell and Odell-Vereecken 1980; Tringham et al. 1974) and high magnification analyses (e.g. Keeley 1980). The low magnification method is used at Cultural Resource Analysts, Inc.
In the low magnification microwear approach, micro scarring on the edges of lithic implements is examined to determine
- If the implement was used
- The area of use
- The material being worked
- The motion of use relative to the working edge
The specific methods used for this analysis follow that of other practitioners of the approach (e.g., Odell 1977, 1979, 1996; Odell and Odell-Vereecken 1980; Tringham et. al 1974). Cultural Resource Analysts, Inc., employs a Wolfe stereoscopic microscope with a reflective light source for such purposes. The microscope is fitted with 20x eyepieces and 4.5x paired objectives. The magnification is continuously variable and ranges between 14x and 90x. Implements are generally scanned for evidence of wear at 20x. Magnification is then increased or decreased as needed to view any observable edge damage more clearly.
In the low magnification approach, worked materials are categorized as to resistance of the material (i.e., hard, medium, or soft). Hard resistance materials consist of materials such as bone, antler, and stone. Medium resistance materials consist of materials such as wood. Soft resistance materials include such materials as meat, hides, and vegetal matter. The advantage of the low magnification approach (over the high magnification approach) is that it is less time consuming so a greater number of specimens can be examined.
The determination of what the observable wear represents in terms of prehistoric use is made through the combination of attributes. Variables such as scar form and size and edge shape are useful for determining the resistance of the worked material. Rather than specify what activity created the wear (e.g., cutting, scraping, etc.), edges of the implement in question are examined to determine the motion of the tool in relation to the worked material. In other words, it may be determined that a tool was used in a motion longitudinal to the working edge. This motion includes such activities as cutting, sawing, and slicing.
Each instance of wear is recorded separately to allow for cases of tools being used for multiple purposes. In addition, the microwear database can be linked to the modified artifact database to investigate such questions regarding technology and use.