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That's not to say that he or the cave's curator, the prehistorian Jean-Michel Geneste, could have been entirely surprised. The previous spring, workers had finished installing a $28,000 air-conditioning system beneath the stairs leading down to the cave. The new machine represented a major change in the way Lascaux's delicate balance of temperature and humidity had been regulated for more than three decades. The old system, installed in 1968 after years of minute studies of the cave's climate, relied on Lascaux's natural currents to pass air over a cold point and ensure that water condensed there, like it does on a beer can, rather than on the walls of the cave. This passive system was necessary only during the wettest periods of the year, when it worked as a functional replacement for the earth that for millenniums had absorbed excess water from the saturated air of the cave but was removed after the cave's discovery in 1940.
The new system was designed to automate the process and improve on it, using two massive fans to pull air toward the cold point. The intrusive approach scandalized those who had worked so hard to figure out a more modest solution to earlier problems in the cave. "Our idea was always to be as parsimonious as possible," says Pierre Vidal, a retired researcher who worked in Lascaux for decades. "This thing seemed more like a central air-conditioning system."
In most organizations, an individual or board has the last word on decisions, especially one this controversial. Yet nobody claims authorship of the decision to install the new machine--neither the curator nor the project's main architect. Technical advice was provided by Ingéni, an air-systems consultancy firm based near Paris, which had designed systems for supermarkets and museums but had no experience with caves. "We proposed a system, and that's what they chose," says the firm's managing director, Michel de la Giraudière. "I don't know why they favored an active system over a passive one, but I do know not everyone was of the same opinion. They wanted a certain efficacy, and the discussion was somewhat political."
The appearance of the mold soon after the new apparatus was put in place in April 2001 suggests it was not up to the task of maintaining Lascaux's equilibrium. By the end of that year, Geneste ordered the fans taken out altogether. "If we knew then what we learned later, we wouldn't have installed that machine," says Alain Rieu, the director of conservation for the region of Aquitaine, which ultimately signed off on--and paid for--the work. "But the old machinery was in a bad state of repair, and we all decided unanimously that we couldn't take the risk of doing nothing. It seemed like the least bad solution."
But the new machinery may not be what introduced the fungus to the cave. Isabelle Pallot-Frossard, director of the LRMH, says that the presence of formaldehyde--used for decades as a foot wash to prevent fungal infections--may have killed off many other organisms present in Lascaux that might have prevented the explosion of fusarium. "The fusarium strains we found in the cave are extremely resistant to formaldehyde, unlike strains from elsewhere," says Pallot-Frossard. "It didn't come from outside, but had been there all along. All it needed was a slight modification in climate to take off."