On September 12, 1940, four Dordogne teenagers followed a dog named Robot into a hole torn open by a fallen pine and slid down a shaft into a chamber sealed since the Ice Age; the horses and aurochs on its walls had gone unseen for roughly seventeen thousand years.

Marcel Ravidat's dog Robot was not supposed to find anything. He had gone missing down a hole in the woods above Montignac, in southwestern France, where a storm had recently torn a pine tree out by its roots. He was not lost long, and the hole he vanished into led nowhere in particular, as far as anyone could tell that afternoon.

Four days later Ravidat came back with a lamp, a rope, and three friends.

What sent four teenagers into a hole in the woods

A rumor, mostly.

Ravidat, an eighteen-year-old apprentice mechanic, had heard that a tunnel somewhere in these hills led to the ruined manor of Lascaux, and that treasure was hidden along the way. On September 12, 1940, he returned to the tree hole with Jacques Marsal, Georges Agnel, and Simon Coencas, widened the opening with a knife, and dropped in feet first. He slid down a scree slope to the bottom of a shaft. His friends followed.

By lamplight they walked roughly a hundred feet into a gallery and found the walls moving. Not literally: the flickering light on curved rock made painted animals seem to shift as the boys' lamp swung past them. Bulls the length of a car stood over horses painted in ochre and black. Nobody living had seen any of it in longer than recorded history reaches back.

Why the dog gets less credit than the story wants

Robot is the detail every account leads with, and it may not have happened quite that way.

Ravidat himself told versions of the discovery over the following decades in which the dog's role shifted, and some historians treat the falling-in-the-hole version as an embellishment that made a better story than "we heard a rumor and went looking." What is not in dispute is the storm-felled pine, the hole it left, and the date Ravidat returned to it with a rope. The French Ministry of Culture's own account of the discovery, drawn from the boys' contemporaneous statements, does not mention Robot at all.

Say plainly what that means: the dog is folklore riding along on a fact. The cave is not.

Who believed four teenagers about a painted cave

Léon Laval did, eventually.

The boys' schoolteacher went down into the cave on September 18 and came out convinced enough to write to the regional prehistory authority. Two days later the message reached Henri Breuil, a Catholic priest and archaeologist already known across Europe as the leading authority on Ice Age art (colleagues called him the Pope of Prehistory, not always kindly). Breuil arrived, examined the pigments, and pronounced the paintings genuine and ancient rather than a hoax, which had been a live possibility for any sudden cave-art discovery in France; a forged trove of prehistoric tools and inscriptions at Glozel, in central France, had been declared fraudulent by an international commission just over a decade earlier.

France in September 1940 had larger emergencies than a cave. The Wehrmacht had entered Paris three months before, and the country was six weeks into its division under the armistice with Nazi Germany. Lascaux was found in the unoccupied zone, and even so, word of an ancient painted gallery in the Dordogne moved through occupied Europe fast enough that German soldiers were among the early visitors, alongside French archaeologists working under a government that no longer fully governed.

What was actually on the walls

Roughly six hundred painted or drawn figures, and nearly 1,500 engravings, cover the walls of Lascaux's connected chambers: the Hall of the Bulls, the Axial Gallery, the Nave, and a narrow shaft where a single human figure appears, stick-limbed and falling, beside a wounded bison. Radiocarbon dating of charcoal from the site puts the paintings at roughly 17,000 years old, though estimates for individual panels have ranged as wide as 15,000 to 21,000 years depending on the method and the pigment sampled. Four of the four discoverers are long dead; the youngest, Simon Coencas, lived to 92, and did not learn until decades later that the cave he helped find had made him, however briefly, a wartime celebrity. His family was Jewish, and in 1942 the Germans arrested them and interned them at Drancy, the transit camp outside Paris; Coencas and his sister were released only after Red Cross intervention on account of their age, while other relatives were deported to Auschwitz and killed there.

From a farmer's field to 1,200 visitors a day

The cave opened to the public on July 14, 1948 (Bastille Day), with electric lighting installed and a turnstile at the entrance that had been a fox's den eight years earlier. Ravidat and Marsal, the two local boys, worked there as guides.

It was too popular for its own good. By the late 1950s the cave was drawing up to 1,200 visitors a day, and each one of them was breathing. The carbon dioxide, heat, and humidity that a crowd generates began to change the air chemistry of a chamber that had stayed close to equilibrium for millennia; green algae, nicknamed "the green sickness" by the staff who scrubbed it off the rock, spread across panels that had survived the actual Ice Age. André Malraux, France's culture minister, ordered the cave closed to the public in 1963.

The mold that came back after the visitors left

The next threat to the paintings came from something too small to see.

A new air-conditioning system installed in 2001 to stabilize the cave's climate instead triggered an outbreak of white fungus across the cave floor and lower walls. Fungicides and antibiotic compresses knocked it back, and black spots of a different mold, Ulocladium, turned up in its place not long after. One of the organisms identified during the crisis was new to science; researchers later named it Ochroconis lascauxensis, after the cave it was found trying to consume. An international scientific committee has monitored the site's temperature, airflow, and microbial load since 2010, on a schedule that would have meant nothing to Breuil in 1940; access today is limited to a handful of specialists a year, suited up and timed by the minute.

What replaced the real thing

Lascaux II opened in 1983 about six hundred feet from the original entrance, a hand-painted facsimile of the Hall of the Bulls and the Axial Gallery built by artists working from photographs and molds of the actual rock surface. A traveling version, Lascaux III, has toured internationally since 2012. Lascaux IV, a full-scale reproduction of the entire cave with a visitor center attached, opened in December 2016 about a quarter mile from the site the boys found. All three exist for the same reason: to let people stand in front of the paintings without becoming, themselves, the next thing the cave has to be protected from.

The original chamber is dark again, sealed behind an airlock most of the year, checked over by conservators who read its humidity the way a cardiologist reads a chart. Nobody expects it to reopen. The compromise Lascaux settled on (hide the real cave, build a convincing one beside it, let the crowds have that instead) has since become the template for painted caves everywhere, from Altamira in Spain to Chauvet, discovered in 1994 and never opened to the public at all, its own facsimile built from the start. Four teenagers with a rope and a rumor found something that outlived the Ice Age; keeping it there now takes an international committee and a building next door pretending to be it.

Sources

• Ministère de la Culture, "The discovery" and "The four discoverers," archeologie.culture.gouv.fr/lascaux
• Wikipedia, "Lascaux"
• History.com, "Lascaux cave paintings discovered"
• The Collector, "Why Was the Lascaux Cave Closed to the Public?"
• Time, "The Battle to Save the Cave" (archive)