Portuguese rock art raises ruckus.

Scientific and political controversy is raging around several clusters of engraved animal portrayals found in the Coa Valley of northeast Portugal. The fate of a major dam may hinge on the resolution of widely disparate estimates of the age of this rock art.

On the scientific front, two reports in the December 1995 Antiquity provide starkly contrasting estimates. One analysis suggests that the engravings date to no more than several thousand years ago; the other supports a much older, Late Stone Age origin for the figures.

An archaeologist hired by Portuguese authorities to conduct independent dating tests last spring contends that evidence gathered so far places most of the engravings at 3,000 years old or younger. Radiocarbon dates were obtained from thin mineral layers that formed on some of the engravings, says Robert G. Bednarik of the International Federation of Rock Art Organizations in Caulfield South, Australia.

In addition, a preliminary microscopic analysis of erosion on the engravings suggests that those classed initially as Late Stone Age works are, in fact, of quite recent vintage, Bednarik asserts. Finally, he adds, a number of engravings bear marks made by metal points. Farmers who inhabited the Coa Valley around 1,700 years ago may have carved some of these figures, he holds.

Stylistic comparison with other prehistoric art specimens in western Europe places the Portuguese finds squarely in the Late Stone Age, argues Joao Zilhao of the Institute of Archaeology in Lisbon, Portugal.

He also says that none of the data cited by Bednarik undermines the view that most of the Coa figures date to about 20,000 years ago. Radiocarbon dates obtained so far provide only minimum age estimates for several engravings, and the validity of microscopic analyses of rock art has yet to be demonstrated, the Portuguese archaeologist holds.

"I leave it to readers and, in time, to further work and to history to decide truths in the matter," writes Antiquity editor Christopher Chippindale of Cambridge University in England in an accompanying comment.

Construction of a hydroelectric dam in the valley came to a halt last year amid charges that the project would submerge what some archaeologists have deemed priceless examples of Late Stone Age rock art, between 30,000 and 10,000 years old. The situation grew particularly tense early in 1995. Information surfaced that the national utility company building the dam and Portuguese government officials had known about several engravings for at least a year before announcing their existence-2 months after the expensive project had begun.