6. Use-wear Methodology

The use-wear method applied in this research is based on the combination of four kinds of features: a) edge rounding; b) edge-scarring or edge damage; c) micropolish; and d) striations (Keeley 1980; Mansur 1999). Each feature includes clusters of attributes that are considered as a whole in order to interpret the worked material, the kinematics and the use-time. Of all the features, micropolish traces can be used with the most confidence to determine the worked material (see discussion in Juel Jensen 1988). For the purpose of this study, the pieces from March Hill were examined with an incident-light microscope and a stereomicroscope. The incident-light microscope was a Nikon model with magnifications ranging between x50 and x500. The stereomicroscopes are useful when three-dimensional observation and perception of depth and contrast is critical to the interpretation of sample structure. Therefore, they are suitable for observing edge-scarring and edge-rounding. In contrast, the advantages of reflected-light microscopes rely on their resolving power and bright field illumination technique that provides bright light evenly dispersed across the plane of the field of view of the focused sample, appropriate for observing micropolishes and striations.

Perhaps the main problem encountered when undertaking micro-wear analysis of the March Hill lithic assemblage was that the finds had been labelled on the ventral face and varnished, with varnish sometimes extending across the entire artefact, obscuring observations of the surface (see Figs 5, 6 and 7). The varnish could not be removed and consequently 45% of pieces (N=804) could not be used in the study. The remaining pieces were studied following the aforementioned procedures. Before observation was undertaken the pieces were cleaned with mild soap and water and then wiped with alcohol.

Figure 5 Figure 6 Figure 7

Figure 5: (left) Lithic artefacts covered with varnish. Magnification x200
Figure 6: (middle) Lithic artefacts covered with varnish. Magnification x200
Figure 7: (right) Lithic artefacts covered with varnish. Magnification x200

6.1 The morphotechnical analysis

The analytical proposal created by Georges Laplace (analytical and structural typology) was applied to the March Hill assemblage (Laplace 1956; 1972; 1974; 1981; Laplace and Livache 1975; Laplace and Sáenz de Buruaga 2000). His structure offers the possibility of creating new variables without breaking the whole coherence. And, at the same time, it is a multi-scale method: it is possible to adjust the dimension of the analysis for each variable, each piece, each assemblage, etc. Insofar as the different applications of the method share the structure as well as the variables, it is possible to compare assemblages.

Through the concrete application of this approach, developed by A. Vila (1981; 1986), comes the analytical and structural typology that allows us to recognise and quantify the pieces as products of labour, and of the variables resulting in different edge morphologies. This sequence, which follows a relational formula through a specific syntax based on specific rules, represents the inter-relation of the variables that make up the edge; on a greater hierarchical level, the correlation between the different edges can be achieved. In this way, the morphology can be represented in a unique formula including qualitative and quantitative variable values. Thus, each piece is analysed at two levels: a broader level (which includes the inter-relations already mentioned) and a specific level according to its own traits. The analysis includes all the edges of an artefact, based on the calculation of every one of the morphological variables and their inter-relationships. These variables are (Briz 2004):

Type of edge. Retouched; angle, for unretouched edges; fractured, etc.
Mode. Edge-angle: abrupt, simple, etc.
Amplitude. (Only for retouched artefacts). Level of invasiveness of the retouch on the faces of the piece: marginal, profound.
Direction. Surface where the retouching occurs: direct, inverse, etc.
Alignment. Morphology of the global edge-shape: rectilinear, convex, etc.
Orientation. Direction of the edge in relation to the axis of the piece: convergent, divergent, etc.

For example, an edge formed by a simple, sinuous angle, that tends to converge with the axis of the piece, would express itself at the level of a codified formula in the following way:


The 'a' indicates the presence of a 'natural' edge without fracture or retouch. 'S' designates the angle measurement: between 30 and 44°. 'Sin' means that the edge is aligned (in relation to the percussion axis of the artefact) with a series of approaches and separations. Finally, 'cvg' indicates the general orientation of the edge: convergent in relation to the percussion axis of the artefact.

If the piece (a flaked stone) continues with an abrupt, rectilinear, transversal distal fracture followed by a plane, divergent, rectilinear angle on the right edge, the complete formula would be the following:

[aSsincvg+ fArecttrans+aPrect div]

If distal edge is abrupt, profound, direct, convex, transversal retouched of the previous example, the result would be:

[aSsincvg+rApdcxtrans+aPrect div]

6.2 Form-function relationships: dynamics of the structural sequence

In contrast to other attempts to analyse the form-function correlations following the traditional lithic typologies (for example, and from different archaeological contexts, Barton 1990; Calvo 2002; Dibble 1987; Finlayson and Mithen 1997; Knecht 1988; Kuhn 1992; Meltzer 1981; for a general compilation, Juel Jensen 1988), the aim was to move away from the assumptions of typological reasoning. The data were structured by employing the defined dimension of the context of use: they are the referential elements to contrast the hypothesis of significant association. The steps consist of: a) selecting the cases of a specific production process (for example, bone cutting); b) quantifying all variables already mentioned.

The algorithm employed (Laplace 1974; 1975; 1978; 1981) calculates the levels of homogeneity and the internal dynamic of the structure of the morphological groups that make up an archaeological lithic assemblage (for example: Sáenz de Buruaga 1991; Laplace and Sáenz de Buruaga 2000).

The method links the hierarchical recognition of different groups based on the number of individuals that form them and then analyses the mathematical significance of the existing differences between these groups, employing the distance from X2 (or Pearson's reduced quadratic deviation) as a meaningful reference. The final result is an evaluation in relation to the empirical appraisal of the whole assemblage analysed. The identification of differences is obtained and the calculation of their significance: the identification of ruptures significant enough to break the homogeneity of the assemblage. As they break off we can see the significant groups that exist in relation to the global whole, and we identify their relationship in respect of the total and the rest of the groups. We can then recognise the existing internal hierarchies: that is the articulation of the structural sequence (Laplace 1974).

The structural sequence offers us a representation of the variability of a given morphological trait; it expresses how this trait is articulated in the assemblage: it identifies the presence of predominant traits, and the intensity of its difference. For example, in Figure 8, we can see five hierarchical levels:

Figure 8

Figure 8: Results for type of edges used for faunal material processing from Túnel VII site, Tierra del Fuego, Argentina (Briz 2004). Edge types: A: Angle; F: Fracture; MX: Mixed edges; TDA: Angular tendency. XAR: Overhang (in the distal portion of the flake); A0: angle 0. In the graphic (Vila 1986) the interruptions are represented by the symbol '/' and the repetitions indicate an increase in their intensity. The symbol '____' indicates continuity.

The algorithm is also designed for the recognition of existing dynamics between different groups: under the same parameters of mathematical calculation, the change, the movement and its intensity can be observed. Organised under context of use criteria that act as independent variables (every work process), the absence of movement indicates an absence of inter-relation: the hierarchisation recognised is not a product of the selected functional variable. The following example (Fig. 9) correlates the types of cutting edges and the material worked:

Figure 9

Figure 9: Table of the dynamic of the structural sequence. Túnel VII site, Tierra del Fuego, Argentina (Briz 2004)

In this inter-relation, the only significant interruption is not relevant enough. Consequently, there is no significance in the selection of the types of cutting edge to the function of the worked material. The null hypothesis is the correct one.

This procedure will be repeated with each morphological variable, recognising the dynamics of the whole assemblage by ranking them. These diverse and complex dynamics can be near or far from a morphological specialisation.


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