For more than 17,000 years, the bestiary of the Lascaux cave in southwestern France survived the ravages of history, unseen and undiscovered. . . But despite its robust longevity, Lascaux is surprisingly fragile. Five years ago, after the ill-conceived installation of new climatic equipment, Lascaux suffered a fungal infection that threatened to destroy in a few years what thousands of years had left largely unscathed. The cave's custodians are still struggling to eradicate this scourge, a nasty fungus called Fusarium solani . . .

. . . to keep the fungus in retreat, a team of restorers enters the cave every two weeks--dressed, as everyone who enters now must be, in hooded biohazard suits, booties and face masks--to remove filaments from the walls. "They tell us the cave's condition is stable," says a member of the Scientific Committee of Lascaux Cave, which the French Ministry of Culture set up in 2002 to deal with the problem. "But that's what they say about Ariel Sharon."