Journal of Archaeological Science (2002) 29, 65–75 doi:10.1006/jasc.2001.0702, available online at http://www.idealibrary.com on An Index of Invasiveness for the Measurement of Unifacial and Bifacial Retouch: A Theoretical, Experimental and Archaeological Verification Chris Clarkson School of Archaeology and Anthropology, Australian National University, Canberra, ACT 0200, Australia (Received 13 September 2000, revised manuscript accepted 2 March 2001) Archaeologists are increasingly in need of quantitative measures of stone artefact retouch. Existing techniques fail to provide a generic measure of retouching for all chipped stone artefacts. A fast and reliable index is proposed which measures retouch in terms of the invasiveness of flake scars on the surfaces of complete stone artefacts. Unlike other measures, the index of invasiveness is well suited to the analysis of bifacially worked artefacts such as bifacial points and bifaces. Experimental tests demonstrate a strong correlation between the index and measures of reduction based on diminishing flake weight and numbers of retouch blows. Inter-observer reliability is also demonstrated through the use of a blind test. Limitations of the method are discussed, although potential techniques for surmounting problems are identified. An archaeological application of the index demonstrates the utility of the method in the context of regional assemblage variability in northern Australia.  2002 Academic Press Keywords: STONE ARTEFACTS, CURATION, BIFACIAL TOOL REDUCTION, EXPERIMENTAL FLINTKNAPPING, NORTHERN AUSTRALIA. Introduction A rchaeologists are increasingly asking questions concerning the extent to which different stone artefact assemblages have been curated. This is because assessments of relative curation are useful in testing models of changing mobility, land-use, economy, and technological organization, as well as in defining the relationships between tool design, labour investment and morphological standardization (for discussion of the value of the curation, tool design and use life concepts in addressing these questions see Ammerman & Feldman, 1974; Bamforth, 1986; Binford, 1979; Bleed, 1986; Close, 1991; Davis & Shea, 1998; Dibble, 1984, 1995a, 1995b; Gordon, 1993; Hayden, Franco & Spafford, 1996; Hiscock, 1994, 1996, 1998; Kelly, 1988; Kelly & Todd, 1988; Parry & Kelly, 1987; Holdaway, McPherron & Roth, 1996; Kuhn, 1990, 1992, 1995; Nash, 1996; Neeley & Barton, 1994; Nelson, 1991; Odell, 1996; Shott, 1989, 1996; Roland & Dibble, 1990; Torrence, 1983, 1989). Our ability to address such questions adequately relies on having effective quantitative measures of stone artefact reduction, curation and use-life. It has been argued (Barton, 1988; Kuhn, 1990; Davis & Shea, 1998; Dibble, 1984, 1995a, 1995b) that measurement of the amount of retouching present on tools provides one such means of addressing the relative curation and use-life of artefacts in different archaeological contexts. Generating such a metrical index of stone tool reduc- tion for each artefact in an assemblage would provide the necessary data for making comparisons of relative retouch intensity and tool curation in different spatial and temporal contexts. In addition, metrical data in the form of a reduction index would allow the comparison of not only the level of reduction of different assem- blages, but also provides a measure of the degree of variation in retouching within and between assemblages. Finding appropriate measures of variation allows for better integration of emerging theoretical concerns for the characterization of variability within and be- tween populations, with the types of archaeological materials under analysis (O’Brien, 1996; Maschener, 1995; Telster, 1995; Barton & Clark, 1997). The index of invasiveness outlined in this paper provides one such means of quantifying variation in artefact retouch and reduction that is quick, versatile and relatively robust. This paper first examines the limitations of several existing measures of artefact retouch before explaining various theoretical and methodological aspects of the index proposed here. Theoretical expectations are then verified against experimental data derived from the hard-hammer retouching of 30 flakes of varying size, shape and raw material type. This experiment success- fully demonstrates a correlation between the index of invasiveness, amount of retouch and flake weight. Inter-observer error is then examined using a simple 65 0305–4403/02/010065+11 $35.00/0  2002 Academic Press