Summary | Introduction | Method of Analysis | Sample for analysis | Results of the functional analysis | Analysis of the functional results | Statistical analysis of use-wear data | Ethnographic data | Users | Change in edge angles | Relations between the four phases | Discussion

6.2 Method of analysis

Methods in micro-wear analysis (200x magnifications and over) can be separated into two groups; the polish-only group and the multi-dimensional group. These two methods have been described many times (e.g. Keeley 1980; Grace 1989; Unrath et al. 1986; Newcomer et al. 1986).

The polish-only method (e.g. Keeley 1980) concentrates mainly on the polish which forms on a tool's edge during use. Users of this method maintain that it is possible for individuals, through repeated and prolonged exposure to polish types observed under a microscope at between 200–400x magnifications, to train themselves to recognise mutually exclusive polish types which correspond to different classes of worked material such as wood, hide, bone, etc.

The multi-dimensional approach, many versions of which have been developed by different researchers (e.g. Finlayson 1990; Grace 1989; Gutierrez Saez 1993), does not work on the premise of mutually exclusive polish types. It aims to examine every aspect of the used edge and indeed the whole artefact, any feature of which may have been important or related to its function. This method, which is eliminatory and deductive, reduces possible uses to a few and, finally, one most probable use. The main advantages in the multi-dimensional approach are that it is relatively quick and easy to learn, relatively fast to use and finally, and most importantly, it is quantifiable – results can be checked and compared as each aspect of the method is based upon measurable variables. In this study the multi-dimensional approach was followed and tested, using the data collected.

Use-wear analysis is one way of gaining new insights into tool use. While traditional lithic analysis techniques are a useful mechanism for understanding raw material use and technological aspects, they are not able to determine artefact use. Use-wear analysis can determine which artefacts were used, the way they were used (for example Hardy in press; forthcoming a; forthcoming b; Finlayson and Mithen 2000), and what raw materials they had probably been used on (e.g. Grace 1992). This information is useful, both at the level of individual sites and to examine craft activities, subsistence and early agriculture (e.g. Juel Jensen 1994; van Gijn 1998; Owen 2000).

One of the ways in which the effectiveness of experimental archaeological methods has been tested is through the blind test examination of experimentally made and used artefacts. As with all archaeological experimental work, blind test data has always been based upon manufacture and use of replicas of archaeological artefacts. These analogues are made and used by archaeologists or local people (Hayden 1979; Lewenstein 1987; Newcomer et al. 1986) trying to replicate the way in which a prehistoric user may select and use a tool.

While this is an effective way of reproducing consistent use-wear traces, modern users learn as an intellectual activity rather than as a motor action (MacKenzie 1991). They do not have the same feel for the craft as someone who has learnt, by observation and imitation, from a very early age. The 'real' users are therefore likely to make and use their tools in a more natural way than those who have learnt as adults.

Only rarely have real stone-tool users been observed and studied actually selecting and using tools and, as far as we know, no blind tests have been carried out using stone tools such people have made and used. This assemblage offered a unique opportunity for an archaeologist to carry out such a blind test. The documents relating to the use of the artefacts were retained by one of us until the other had completed the functional analysis.

In addition, the difference between used and unused edge-angle measurements were evaluated and a comparison between the low-power and high-power analyses was made to assess the extent to which the high-power variables increase the information gained. Results and records of the use-wear traces are described relative to each other.

The artefacts were collected and bagged by the ethnographer directly they had been discarded. No cleaning was carried out, either on the new assemblage or the bought pieces. As this assemblage was being made for the ethnographer, who collected the assemblage as soon as it had been knapped and used, there was no opportunity to observe the selection of pieces that might have been stored or cached. The microscopic analysis was done first and with a minimum amount of handling so that the use-wear traces would remain relatively free of contamination. Used artefacts were then measured and macro observation of them was carried out using a 10x hand-held magnifier.

After numbering, the artefacts were washed. They were soaked overnight in plastic containers with warm water and detergent. Most of them were clean following this treatment, although some retained stubborn dirt on their edges. These were rubbed with a thumb while still wet, then rinsed and left to dry. This removed the dirt on most artefacts. A number of artefacts retained staining and no amount of washing could remove it. These were the largest wide-edge-angled pieces; the staining was always the same and appeared to have been made by the same raw material. Later, after identifying the uses of the individual artefacts from the ethnographic notes, it was found that all of the large artefacts had been used to pare down either wood arrow points or wood axe handles. Finger grease was removed before analysis by wiping the surface with a cotton bud soaked in alcohol (procedure after Grace 1989).

One of the problems with micro-analysis of light-coloured raw materials, such as many cherts, is that it is difficult to detect clearly the surface polish with the incident light needed for identification of edge damage like fractures, topography and striations. Incident light, which comes from above at an angle of approximately 45°, is reflected by the surface and is excellent for detecting irregularities in the surface and on the edge of the artefact, but it does not, except very faintly, reveal the presence and location of polish. Incident light can also detect polish on the surface of a dark raw material, such as Brandon flint, but this method of detection becomes more difficult for detailed analysis on any lighter raw material.

The sample was analysed using a petrological microscope, (model Olympus BH2), with transmitted and incident illumination facilities. The polish was examined both with incident light and between crossed polarisers using transmitted light. This enabled the polish to be clearly detected by showing it up as very bright, shiny, patches along the used edge. The reason for this is that unpolished birefringent, crystalline materials, such as flint and chert, scatter light such that their surface appears dull and dark through the microscope. When light emerges through polished surfaces, it does not scatter resulting in these areas appearing brightly illuminated in contrast to surrounding dark, unpolished surfaces.


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Last updated: Wed Oct 8 2003