Valladas says she and her colleagues encountered just such problems when they attempted to compare and crosscheck U-series and radiocarbon dating results from prehistoric cave paintings in Borneo back in 2003.Other researchers say the jury is out on whether prehistoric European cave art became more sophisticated over time.The French dating team at Chauvet is disdainful of such a conclusion."The dating at Chauvet has been confirmed over time" by numerous studies, says Gilles Tosello, an archaeologist at the University of Toulouse in France who has worked at the site since the late 1990s.By measuring the ratio of thorium-230 and uranium-238, daters can estimate how long ago the calcite was laid down.Using a blade or an electric drill, the team took 50 small samples from calcite that directly overlay either paintings or engravings in 11 caves in northwest Spain.The basic questions about early European cave art—who made it and whether they developed artistic talent swiftly or slowly—were thought by many researchers to have been settled long ago: Modern humans made the paintings, crafting brilliant artworks almost as soon as they entered Europe from Africa.
The team argues that the new dating, along with similar dates from sites such as Abri Castanet in France, where archaeologists recently dated depictions of female genitalia to at least 37,000 years ago, suggests that the earliest European artists "were less concerned with animal depictions" and more interested in simpler motifs such as "red dots, disks, lines, and hand stencils," as they put it in the paper.
The results, if correct, include the earliest ever reported date for cave art: A red disk from El Castillo Cave, on the Pas River in northern Spain, clocked in at a minimum of 40,800 years.
The disk, part of a larger composition that includes dozens of other disks and some 40 stencils of human hands, could be older, depending on how soon after it was painted the calcite layer formed.
The dating of the Spanish caves leaves many gaps in a supposed sequence of increasing stylistic complexity, say archaeologists Iain Davidson of the University of New England in Armidale, Australia, and Nicolas Teyssandier of the University of Toulouse.
Higham says that "more work is required," but adds that the U-series technique may now allow testing of such hypotheses.