A bison depiction in the Altamira Cave, discovered in the north of Spain and dated between 35,000 and 15,000 BC, and a bison living in Europe today.

A group of European tourism ministers check out a replica of the ancient caveman paintings in the Altamira caves in 2002. ((Victor Fraile/Reuters) )

A Spanish cave complex boasting prized prehistoric paintings will reopen after eight years of closure, despite scientists’ warnings that heat and moisture from human visitors will damage the site known as the Sistine Chapel of paleolithic art.

Spain’s Culture Ministry and the site’s board of directors said Tuesday that visits to the Caves of Altamira in the northern Cantabria region will resume next year, although on a still-unspecified, restricted basis.

The main chamber at Altamira features 21 bison painted in red and black, which appear to be to charging against a low, limestone ceiling. The site was declared a UNESCO world heritage site in 1985. The paintings are estimated to be 14,000 to 20,000 years old.

Discovered in 1868, the cave complex became a tourist magnet and by the 1970s received 3,000 visitors a day. Body heat and moisture from people’s breath were blamed for a gradual deterioration of the images, and from 1982-2002 only a handful of visits were allowed each day.

The cave was completely shut off to most visitors after scientists detected green mould stains on the paintings in the main chamber. A replica of the caves was built in a museum in 2001.

This 1985 photo shows a large male bison, a common figure in the Altamira cave in northern Spain. Spain’s Cultural Ministry said Tuesday that it has decided to reopen a cave complex featuring prehistoric paintings after eight years of closure. ((Pedro A. Saura/Associated Press))

In April of this year, the government’s main scientific research body, called the CSIC, recommended that the caves remain closed.

“The people who go in the cave have the bad habit of moving, breathing and perspiring,” CSIC researcher Mariona Hernandez-Marine wrote then.

The site’s board voted to reopen, however, calling the caves too valuable to keep closed. “Altamira is an asset we cannot do without,” the Cantabria region’s president, Miguel Angel Revilla, said.

He said he had had the misfortune of saying no to Jacques Chirac when the former French president once asked to see the caves, and more recently to the visiting president of Mexico, Felipe Calderon.

“The other day I suggested we could even invite [Barack] Obama. The important thing is that at least somebody can see this symbol,” Revilla said.

A committee has been appointed to set the new rules for how many people can visit the caves each day and will meet for the first time next week.