The Age of the Coa Valley (Portugal) Rock-Art: Validation of Archaeological Dating to the Palaeolithic and Refutation of 'Scientific' Dating to Historic or Proto-Historic Times
Zilhao, Joao, Antiquity
The dating studies of the `modern rock-art scientists', when critically examined, are found not to show that the Coa valley petroglyphs are of recent age. Their Upper Palaeolithic characteristics, and therefore their likely late Pleistocene age, are consistent with their archaelogical context.
Results of EDP's project
For the most part, the thousands of petroglyphs recently found in the Coa valley have been unanimously attributed to the Palaeolithic, on stylistic grounds, by archaeologists and rock-art experts from all over the world (Bahn EDP (Electricidade de Portugal), the state-owned electricity company building the dam that threatens to submerge and destroy the site, however, decided that stylistic analysis was not enough to establish the age and relevance of this art. They organized a `direct dating project' aimed at obtaining `scientific' chronological estimates and hired two Australian (Alan Watchman and Robert Bednarik) and two American (Fred Phillips and Ronald Dorn) dating professionals to carry out these studies.
The four researchers are. supposed to have worked independently, in a `blind test' experiment. Although EDP (Electricidade de Portugal) and the Minister for Industry have used their reports as the basis for policy, they have not made them public. The authors have refused to make them directly available to Portuguese archaeologists, although a copy of Bednarik's report was obtained through independent channels.
Evaluation of EDP's `direct dating project' therefore relies on the following:
* The results reported by O Independente (Sa & Ferreira 1995);
* Bednarik's (1995b) report;
* Dorn's (1995) table of minimum ages, given to the press by the office of the Minister for Industry,
* Watchman's (1995a) `Executive Summary', also given to the press by the office of the Minister for Industry;
* Watchman's statements to the Portuguese newspaper Publico (Salema 1995);
* Watchman's statements to Science (Fischman 1995);
* Abstract of Watchman's (1995b) paper at the September 1995 International Rock Art Congress of Turin (Italy).
Figure 1 shows the location of the Coa valley art-sites known to contain stylistically Palaeolithic petroglyphs. The first 6.5 km upstream from the river-mouth have been partially flooded since the early 1980s by the Pocinho dam on the Douro. The engravings presently visible in localities 3-6 of Figure 1 represent just the tip of an artistic landscape now submerged under a few metres of water most of the year. The Foz Coa dam would drown these sites to a depth of more than 100 metres.
According to EDP (1995), all four researchers worked on the same three panels, at Canada do Inferno (Figure 1.4), Ribeira de Piscos (Figure 1.8), and Penascosa (Figure 1.11). As other illustrations in this paper, the tracings of these three panels (Figure 2) are partial and preliminary, intended only for independent stylistic evaluation by the readers, a purpose for which they are considered accurate enough. Systematic tracing and analysis of the Coa rock art is now under way by a government appointed team led by Portuguese rock-art researchers A.M. Baptista and M.V. Gomes.
Phillips, Chlorine-36 dating
Fred Phillips used Chlorine-36 studies to attempt a direct dating of the age of exposure of the engraved rock surfaces, that is, to obtain a maximum age for the petroglyphs.
Sa & Ferreira (1995), published on 7 July, report that Phillips obtained a maximum age of 3000 years for the Canada do Inferno panel. In a letter to the present author, dated 20 July, Bednarik mentioned Phillips' results as part of the `proof' that the three panels were post-Palaeolithic; he repeated this in oral presentation to the Turin congress. But a letter by Monty Flinsch, a collaborator of Phillips, dated 7 July and distributed at a press conference held by the EDP on 13 July, stated that it had not yet been possible to process the Coa samples, and that it would not be possible to do it until late August. …