Scientists are at loggerheads over whether or not to allow visitors into the caves of Altamira, one of the most prized prehistoric art sites in the world, because of the damage they could cause to its wall paintings.

The Altamira caves, in Cantabria in northern Spain, were closed to the public in 2002 due to concerns about the effect human visits might have on the famous depictions of bison and other animals which have made the site known as “the Sistine Chapel of prehistoric art”.

They were partially reopened in February of this year on a short-term basis, under strict guidelines. Groups of five people, chosen by lottery, were allowed to enter at a time for a short tour while wearing full body suits and with minimal torchlight.

Bacteria

“The risk threshold has already been surpassed,” says the document, which warns that Altamira could be heading the same way as the caves of Lascaux, in the southern France, whose wall paintings were damaged following mass visits.

The CSIC report’s findings, quoted by El País newspaper, have still not been published in full but are expected to be released soon.

However, another study, completed in September and led by the esteemed scientist Gaël de Guichen, came to the opposite conclusion.

“No cause-effect relationship has been detected between the presence of researchers and visitor . . . and the loss of pigment,” said his report, stating that any fading of colours on the paintings was a purely natural process, caused by condensation and other factors.

Altamira has long been the focus of admiration and scientific fascination. Its paintings were fully discovered in the late 1870s by amateur archaeologist Marcelino Sanz de Sautuola and his eight-year-old daughter. Initially dismissed as fakes, the artwork was not taken seriously within the scientific community until the beginning of the 20th century.

Experts believe humans inhabited the caves up to 35,000 years ago, with many of the paintings believed to be about 15,000 years old. The quality and quantity of the paintings and their relatively well-preserved state makes Altamira one of the pre-eminent sites of its kind in the world. A replica cave for visitors is located nearby.

Spain’s culture ministry must decide whether to reopen Altamira to regular visits. Yet beyond the scientific debate, political considerations may influence that decision.