Lithic technologists are sometimes confronted with forms of stone tools which are hard to explain. To give an example from North America, the highly technical means used to flute Folsom projectile points resulted in failure rates of 20 per cent or greater (Amick 1999: 2) prompting archaeologists to lament that Folsom fluting "seems contrary to common sense" (Ingbar & Hofman 1999: 103). Some archaeologists have argued that the benefits in Folsom fluting were obtained in non-material, socio-religious ways (e.g. Frison & Bradley 1982: 211; Bradley 1993: 255-6; Ingbar & Hofman 1999: 106-7), while others take a material, "technofunctional" perspective (e.g. Ahler & Geib 2000).
A second example is provided by the famous "Tula Adze" of Australia which forms the subject of this paper--and here we have valuable historical sources to aid and check any interpretation. In Australia archaeologists have a myriad of ethnographic observations of tools in use and the benefit of Indigenous Australians' own explanations about socio-religious and/or technofunctional factors behind making and using stone tools. These accounts can be used to amplify and inform archaeological interpretation, at the same hopefully avoiding the problem of "ethnography retrodicting for 50 millenia" (Murray & White 1981: 258).
The tula adze is a woodworking tool consisting of a flake retouched across the distal end and hafted onto the end of a robust handle or shaft using strong, high-quality resin from desert plants such as spinifex grass (Triodia sp). Tulas were invented around 3600-2700 BE supplanting the unwieldy stone chopper of earlier times (Mulvaney & Kamminga 1999: 248-249). The adze's working edge, located opposite the platform, was progressively resharpened to a distinctive "slug" stage, then replaced. Adze slugs are a ubiquitous tool type on sites in central and northern Australia, and hence the stone adze is considered the signature stone tool of Australia's arid region (Gould 1978: 820).
Tula manufacture on the upper Georgina River at Camooweal, Queensland (Figure 1) is explored here in three parts. First, the ethnographic literature on tula adzes is summarised to provide an interpretive context for the tool. Second, a purely archaeological description of tula manufacturing technology is provided and its peculiar aspects described. And third, the methods of manufacture are studied experimentally. Drawing on these studies, the rationale for the manufacture and use of the tula adze is suggested.
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Ethnographic evidence for manufacture and use
The upper Georgina River is notable for its chert deposits. Nodules tip to 150 mm in diameter are distributed widely and in high densities due to the decomposition of the parent dolomite. This chert has long been exploited by Indigenous Australians to make various stone tools, including blades, bifaces, and tula adzes. Walter E. Roth observed tula-making among Camooweal inhabitants some 100 years ago. He described the flake blanks for tulas as "comparatively short" and stumpy" (Roth 1904 17). However, he offers little insight into tula flake production: "As to the causes limiting the shape of the flakes ... it is impossible for me to state anything definite ..." (Roth 1904: 16). Tula flake retouching occurred in several steps. During initial manufacture, the flake blank's edges were removed up to the margins of the bulb of percussion either by freehand percussion or percussion using anvil support. Once the perimeter of the bulb was reached, retouching was conducted more carefully, using a "comparatively small and light hammer-stone" (Roth 1904: 17). The retouched edge at this point "has a comparatively thick and serrated edge" (Roth 1904: 17). Next, the flake blank's platform was reduced by striking flakes down the tool's dorsal face from the dorsal platform edge. The final step involved regularising the working edge by halting the tula at a right angle to the handle and trimming the edge by soft hammer percussion using a boomerang (Roth 1904: 17) (Figure 2). …