This dating approach seems to be borrowed from art history, where historically documented art styles can assist in dating artworks. Nevertheless, the validity of extending this practice to traditions that are beyond ethnographic or historical access has not been demonstrated, nor can this procedure be said to be universally valid in art history itself. Stylistic conventions can be no more than social language forming a transmission system of differential messages (Ucko 1987). Individual artists may use different styles at different times (of their lives, or for different purposes; cf. Whitley 2001: 25), and reliable ethnographic work with contemporary producers of rock art provides no evidence that the artists of a specific group (clan, language group, even family) necessarily share a common distinctive style (see Mulvaney 1995; Novellino 1999, for pertinent ethnographic examples). Two closely related Aboriginal artists from the same family group and generation, living in the same locality, may depict the same object quite differently. Imagery relating to totemic ancestors, sorcery figures and secular meanings, produced by members of a common cultural tradition, can be distinguished by very different styles (Layton 2001: 315). While cultures do exhibit certain preferences in the genres of art they produce, there is nevertheless considerable scope for individual variation. Intra-cultural variability is almost never of a more narrow range than intercultural stylistic variability. Styles do exist, but to correctly identify them and their meaning and underlying rules, the 'visual grammar' needs to be known (Layton 1991). We have some understanding of this concerning Historic arts, but we lack it for pre-Historic art traditions.
The dependence of archaeological claims upon stylistic premises is by no means limited to palaeoart, it permeates every aspect of traditional archaeology. Practitioners construct the taxonomies of all forms of classes of material evidence on the basis of their own perceptions of reality. They invent categories of stone implements, spinning whorls, ceramic pots and whatever else they study, and then apply these pigeonholes (or 'egofacts', as they have been called; Consens 2000) to any further finds. Material that does not fit into the constructs so created is regarded as non-diagnostic or untypical, or is even viewed as irrelevant. The value of these tautological taxonomies needs to be questioned.
The classes of stone tools archaeologists are likely to invent and name do not coincide with those of the makers and users of such artefacts. The classifications of archaeologists are based on judgments about shape, form, working edge angle, ratios of dimensions and particularly on aspects of retouch. The experienced stone tool knapper tends to be sceptical of these well honed academic definitions, and the same applies to the researcher who uses lithics in replication experiments. The original users of stone tools are much more concerned about aspects such as the technological properties of the lithic material, even its colour, and with the function of the tools, at least in known ethnographic contexts. It would be judicious to regard the taxonomies of archaeologists, be they of stone tools or any other categories they define, with some healthy scepticism. They are usually not refutable constructs. Microwear analysis is a scientific method in replication work, but when applied to archaeological specimens does not necessarily provide secure evidence. Observed similarity between wear traces is not conclusive proof, and the confidence expressed by some students of microwear is not warranted (Derndarski 1997).
The difficulties with stylistic taxonomic constructs of stone artefacts and other classes of material evidence apply also to rock art, where they are in fact amplified by the almost exclusively non-utilitarian nature of the medium. After all, lithics are at least partly utilitarian. That their classification is based especially on their perceived non-utilitarian variables (i.e. those of style) is of concern, and these are probably much less accessible to the alien researcher than their utilitarian aspects. In the case of petroglyphs and pictograms, claims to intuitively 'know' the stylistic conventions of the alien arts resemble the belief that one can 'communicate' with the societies in question, perhaps through some imagined human universals. It must not be overlooked that these claims refer to essentially undated motifs or whole art traditions. They seem to be based on the beliefs of their advocates to possess some special powers of detecting which variables shared by two or more pictures express ideological Gestalts that are specific and unique to a particular culture. Since such claims are made about artefacts whose age or attribution is otherwise unknown, they are inadequate proof of age and need to be substantially corroborated by more reliable evidence.
Another difficulty with the circular reasoning of 'stylistic dating' of rock art lies in the reluctance of its practitioners to present the basis of their pronouncements in a repeatable and testable format. Science has a clear preference for experiments that are repeatable, and processes of discrimination that are transparent. Attempts to render stylistic pronouncements transparent seem to founder on the intractable problem of translating subjective proces-ses of perception into quantifiable, repeatable and thus testable entities.
Although numerous techniques have been used in producing rock art, most of them are repeated in various regions or periods. The possible techniques of making rock art, both as pictograms and petroglyphs, are necessarily limited - particularly those readily available to the peoples of early periods. The risks in using technique as a criterion of age or cultural provenience are therefore obvious. Nevertheless, such uses can be found in the literature.
There are two fundamental objections to this approach. First and foremost, there is the issue of recognising technique correctly. The technology of rock art has commonly been misjudged by archaeologists because of a combination of several circumstances: replicative experiments were rare and detailed scientific reports about them even more so; detailed studies of technology (especially by microscopy) were almost completely lacking; pronouncements about the technology of rock art were in nearly all cases made on the basis of subjective impression and superficial but uninformed examination; ethnographic evidence was in practically all such considerations ignored; and the few scientific comments made about the topic have been widely disregarded, even attacked. The judicious researcher will therefore disregard most published opinions about rock art technology.
Secondly, as already implied, identical treatment or technique guarantees no more cultural coherence than differences in technique guarantee the presence of culturally different traditions. The above observations about style apply even more to technique: individual artists may use different techniques at different times or for different purposes, while by the same token artists far removed spatially and chronologically may use an identical technique, because of the limited repertoire available to a hunter-forager. Simple logic offers a number of non-cultural explanations for continuity of technique. For instance, geological aspects of a region may be a major determinant of the kind of rock art found in it, and these are often strongly emphasised by taphonomic factors. The type of rock available for painting or engraving usually predetermines favoured techniques, much in the same way as the available lithic resources may determine stone tool types much more than cultural preferences do.
This is not to say that preferred or exclusive technique of rock art production may not be culturally determined. Certainly this may be the case, the problem is simply that the researcher must not base chronological claims on such an ambiguous variable. The use of these tenuous arguments is particularly misleading when they are offered together with one or more similarly weak hypotheses that are said to support the same finding. Confirmationist constructs drawing their support from two or more similarly slender arguments are particularly deceptive, in that they are designed to create confidence as if they were a substitute for solid or refutable evidence.
For instance no securely dated European Upper Palaeolithic petroglyphs have been made by impact, they are without exception engravings rather than percussion petroglyphs. This would seem to speak against the Iberian open-air petroglyphs on schist being of the Pleistocene, as many claim. But this argument, while probably quite correct, is still specious because we have no Palaeolithic cave art on schist, and the Palaeolithic artists could conceivably have used one method on one rock type, another elsewhere. Considerably more decisive evidence is needed in such reasoning.