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One of the greatest mysteries of the human experience on Earth—if not the greatest mystery of all—is the appearance, around 32,000 years ago, of magnificent paintings, drawings, and engravings of animals inside deep and often almost inaccessible recesses of large Ice Age caverns in France and Spain (and a small number of cases in southern Italy). The art seems to have followed very specific norms: It almost exclusively featured animals; there were only a few humanlike figures, never portrayed in as much detail as the animals. There was absolutely no terrain—no trees, no rivers, no mountains, no ground whatsoever; the animals appear to be floating in space, and their images often overlap.

Stunningly, this specific practice had remained perfectly unchanged for 20,000 years—from 32,000 years ago until around 12,000 years ago; the art found in all of the decorated caves followed this exact format. Then, around 11,500 years ago, the fecund artistic activity in deep caves inexplicably came to an abrupt end. The mystery of cave art is the question “Why?”

Why would the Cro-Magnon hunter-gatherers of Europe expend so much time, effort, and resources to penetrate into deep, dark, and dangerous caverns, where they might encounter cave bears and lions or get lost and die? Why would they often crawl on all fours for distances of up to a mile or more underground, over mud and sharp stones, through narrow jagged fissures in the stony entrails of caves, aided only by the dim glow of animal-fat-burning stone candles, to paint amazing, haunting images of animals?

The discovery of the first decorated caves in the 1870s shocked the world. Attempts to solve the mystery of the purpose, the meaning, and perhaps the hidden symbolism of Upper Paleolithic cave art in Europe began after the first decorated caves were discovered in the late nineteenth century—but these attempts were made only when people became convinced that the art was authentic. (The Paleolithic is the “Old Stone Age,” lasting from about 2.5 million years ago, roughly when stone tools appear—although some are even earlier than those and were made by early hominids—to about 11,000 years ago. The latter part, from 45,000 to 11,000 years ago is called the Upper Paleolithic, a period from 45,000 to around 11,000 years ago. Then comes a short intermediate period called the Mesolithic, and it is followed by the Neolithic, or the “New Stone Age.”) For a long time, they assumed that it had been produced by modern-day artists, perhaps as forgeries made to appear ancient.

The first explanations of cave art were logical deductions people made by extrapolating from beliefs and practices of present-day hunter-gatherer societies, such as the magic of the hunt, shamanism, and “sympathetic magic,” or drawing animals as a way to induce them to be captured. These early hypotheses were prompted by observations of modern-day hunter-gatherer societies in Africa, Australia, and the Arctic and were supported by the finding that some of the animals depicted in caves (although not many) appeared to be wounded. In addition, in very few cases, the humanlike beings drawn in caves appeared to be wearing animal masks or to have features with animal characteristics, and this reminded scholars of the shamanistic practices of some modern-day societies.

Yet it soon became clear that there must have been some mysterious and much deeper reason for the art, because the animals most often depicted in caves were not the most frequently consumed game. And the art was accompanied by strange, undecipherable signs, whose meaning was assumed to have something to do with the purpose behind this whole enterprise. Scientists were baffled; many proposed theories to explain the phenomenon, but all of these attempted explanations were found to have limitations.

I became captivated with European cave art when I visited my first cavern: the famous cave of Niaux in the French Pyrenees a few years ago. Thereafter, I pursued an extensive effort aimed at solving the mysteries of this ancient artistic activity. After years of research and visits to most Paleolithic caves that are still open to the public, I became convinced of the power and depth of Leroi-Gourhan’s remarkable theory, even though his writings on cave art have been criticized by some who came after him.

But later is not always better. I believe that this French expert, who wrote in the 1950s, had it right, whereas those who came after him got it wrong. It’s unusual in science that a later theory should be seen as less correct than an earlier one; what is new usually supersedes the old way of thinking. But in the case of European Paleolithic cave art, I believe that what happened here bucks the trend, thus making it an even more interesting story.

I am very grateful to my agent, John Taylor (“Ike”) Williams of Kneerim & Williams in Boston, for his unwavering support throughout this and many previous projects, and my deep gratitude also goes to Hope Denekamp of Kneerim & Williams. I am especially indebted to my editor at John Wiley & Sons, Stephen Power, for all of his help, suggestions, and insights into the mystery of Paleolithic cave art. I greatly appreciate the help given me by Ellen B. Wright at the editorial department of Wiley. I also thank very much the production editor, Lisa Burstiner, for her superb editing of the book.

When my wife and I visited Niaux, waiting was hard, but we knew we didn’t have a choice. Being allowed to see this cave was a great privilege, one that might some day cease to be offered. The cave’s treasures are too fragile to expose long term to human beings and the carbon dioxide they invariably bring with them, along with body heat and bacteria. All of these are injurious to this pristine environment, which for millennia has been sealed off from the outside world. To be allowed the privilege of entry, you must apply weeks in advance and await your turn.

So we waited in the beautiful countryside of southwestern France, enjoying this peaceful part of the world, with its small tradition-following towns and picturesque villages perched on hilltops. The French Pyrenees are a rustic, heavily forested mountain region where wild game is served in rural inns, along with regional wines made in small family vineyards on the foothills of these mountains.

This is the region of the Cathars, a secretive religious sect that split from mainstream Catholicism in the Middle Ages. Its members were brutally persecuted by the Inquisition and found refuge in inaccessible chateaus they built on desolate mountain-tops in the twelfth century. These ruins can still be seen today, dotting the lower reaches of the Pyrenees.

What is amazing about this land is the antiquity of its habitation: people have lived on the lower slopes of these mountains almost ever since our Homo sapiens ancestors first arrived in Europe from Africa by way of the Middle East. The oldest finds in caves in the craggy mountain slopes date from 30,000 years ago. The cave of Niaux, however, is only half as old; it was decorated by prehistoric artists about 14,000 years ago.

We were a small group, since only a handful of people are allowed each day to enter this primeval cave. There was a Dutchman, middle-aged and attentive; a young French couple in their twenties who wouldn’t give up their cigarettes until the last moment; and then there was George, an Englishman in his seventies who had introduced himself to me at the gift shop, accompanied by his daughter and a grandson. I worried about George, since I already had an idea about what our guide would say next.

“So, remember,” she told us, “you have to walk fast. We have a very long way to go underground: eight hundred meters [half a mile]. And it is on rocks and sand, and up and down. And the rocks are very, very slippery. And you cannot see very well inside the cave. Every day, somebody falls. Do you want to be that somebody? No? Then you must be careful. And do not get behind. If you do, you fall or even get lost and we never find you.”

We looked at one another. Some smiled, others shrugged their shoulders. Then we turned on our lights and filed, one by one, through the narrow, jagged cave entrance. I had a feeling that our guide was not exaggerating. “Remember,” she continued once we were all inside the cave, “you are not allowed to touch anything. Never ever touch the cave walls—even if you are about to slip and fall. These walls have been here millions of years, and if you touch them, you give them bacteria that can destroy the art. Okay? So let’s move.”

Water was slowly dripping from the stalactites above onto the cave floor, and we all started to slip here and there, barely catching ourselves from falling as we progressed ever deeper into this dark cavern. The lanterns did not provide enough light to see everything in front of us. If you focused your attention too much on the ground, you might not see a sudden lowering of the cave ceiling in front of you in time to duck and avoid smashing your head.

About fifteen minutes into our brisk march through this tortuous, dark, and narrow rocky corridor, our guide suddenly stopped. The French couple, my wife, and I were right behind her, but the Dutchman and George and his family were somewhere behind. The Dutchman finally appeared, but no Britons. I feared that perhaps George couldn’t walk as fast as required, and his daughter and grandson had to stay behind with him. Tense moments passed: had they inadvertently taken a wrong turn?

This was a very tricky underground trail. Few people traverse it, and there are no aids to finding your way: no cleared paths, no steps or pavement, no electric lighting—aids that almost all caves that are open to the public now have. There were several branching points along the trail, leading to distant dead-ends, and you could walk or crawl for miles only to realize that you were completely lost. (Judith Thurman, in an interesting article about cave art in the June 23, 2008, issue of the New Yorker, described an experiment in which the guides who have been working at Niaux for years tried to see if they could find their way out of the cave without light; not one of them could.) In addition, it was cold: a constant 51 degrees (outside, it was in the mid-80s). We had all been instructed to bring sweaters and other warm clothing, as well as good walking shoes, or else we would not be allowed to enter. The dampness, the constricted space, and the nearness of forbidding cave walls made it feel even colder than the actual temperature. I could see that some in our group were shivering.

Finally, we saw a dim light turning a corner in the pitch darkness of the cave. It was George with his daughter and grandson, and nobody had fallen. We were all relieved. We continued but grew increasingly tired from the exertion of constantly watching where we stepped and worrying about the changing ceiling level on this dark and narrow way. Claustrophobia was setting in: how deep underground were we now? The terrain changed frequently as we descended on a trail that was once an underground river fed by ice from the melting glaciers that engulfed these mountains in the Ice Age. Then we found ourselves walking on silt and sand that was once the bottom of an ancient underground lake.

“We must go, we must go!” urged our guide. “We have a long way still.” We staggered on for what seemed an eternity, checking our every step: nobody wanted to fall and break a leg deep inside this mountain. No cell phone worked here, and I remembered the sound made by the heavy steel entrance door when it was locked behind us as soon as we had all entered this cave. It would be almost impossible to find our way back without a guide.

Our guide stopped once again to wait for the laggards, but this time she just stood in the darkness, not saying a word. When everyone finally arrived, she moved forward again and after another ten minutes suddenly stopped. “This is the entrance to the Black Salon,” she said, motioning with her light forward and to the left. “Be careful, you have to turn here sharply, and at the same time walk steeply uphill. And bow your heads—it is very low and narrow here.” The rocks here were very slippery, and we continued slowly. Then the path rose sharply, and the walls widened all around us. Our narrow, low, and uneven passage had given way to an unexpectedly large underground hall.

Our guide stopped. “Everyone come together,” she said. “Get closer.” Once we congregated around her, she turned off her light and said, “All lights off now.” Reluctantly, we did as she commanded. It was the most eerie moment of my life—and probably in the lives of my companions. We stood there, half a mile deep inside a mountain, now connected to the outside world through an impossibly intricate system of narrow rocky passageways, in a darkness none of us had ever experienced. It was as if we had gone blind. We stood there in complete stillness; nobody said a word or dared to move for fear of losing his or her balance.

What we now saw stunned us. The light revealed beautiful and detailed charcoal drawings of Ice Age bison, horses, deer, and ibex. The stark cave wall seemed to teem with life. Images overlapped: a horse and a deer shared the same eye; a bison’s tail became part of a horse’s belly. And each animal had been drawn in such perfect detail that it really came alive. These drawings looked as if they had just been completed by a gifted modern artist. In fact, radiocarbon dating has indicated that they were made 14,000 years ago. Plate 1 shows the drawing of a Pyrenean ibex from the wall of the Black Salon in Niaux.

Our guide pointed out details we could not at first observe. By turning her light sideways on the drawings, she made them appear three-dimensional. A bison’s tail seemed to emerge out of the stone wall in front of us, and a deer’s ear looked as if the animal had just turned it toward the visitor. “Notice how they used the cave’s surface—the horse’s hooves are placed exactly on the line where the cave wall curves outward.”

“Why did they do it? Why did they come so far inside the cave?” she asked. “And they had to cross the lake, you know. It was still there when they were here, these Magdalenians. We know that, because their footsteps disappear when we get to the edge of what was once the lake.” Then she said, “And imagine—they did all of this without flashlights: only carved-out little rocks into which they had melted animal fat to burn. How could they see so well to draw in such detail? And why? Why did they make these drawings?” She waited. But none of us would even venture a guess. “Nobody knows,” she concluded. We stood there in the darkness for many moments, looking at these startling drawings. Then our guide turned briskly and said, “There is more—come along.” We continued, past a narrow exit from the Black Salon, walking very slowly. After another hundred yards, our guide stopped before a widening of the passageway. She shone her light on the cave wall, and what we saw there was incomprehensible.

We faced an array of bizarre symbols: rows of red dots, black lines, and designs that looked like lines with half-circles joined to them. Finally, there were what appeared to be spear-heads. “We have no idea what these signs mean,” our guide informed us. “People have tried to analyze them for a hundred years now—since this cave was first discovered in 1906. Nobody has a clue.”

As we turned back to begin our long, slow return to the outside world, I took one last look at these signs. I was very tired now, exhausted—as were all of us—and it seemed to me that my weary, twenty-first-century male imagination was playing tricks on me: that last sign on the left looked to me like a drawing of a vulva. I must be losing my mind, I thought.

We finally staggered out of the cave, squinting in the bright sunlight. We had all survived this experience. Nobody had fallen or gotten hurt, and no one was lost. The following weeks were bewildering: my wife and I continued to be haunted by the images from the cave of Niaux. We spent much of our time pondering what we had seen: the drawings and the strange signs. We knew that Niaux was not the only prehistoric cave; there were many ancient drawings inside caves in France and Spain, mostly found within the deepest, most hidden and inaccessible parts of the caverns. The drawings and the signs were all that such caves contained: there were no indications of any permanent habitation inside these deep grottos, such as bones or stone tools (very few tools have been found, perhaps dropped by accident) or any remnants of hearths. Such signs of human occupation have been discovered only in shallow caves or rock shelters, which contained no art, and in which the Magdalenians (Cro-Magnon peoples who lived in Europe around 18,000 to 11,500 years ago) and earlier Cro-Magnons had lived.

The cave drawings always followed the same pattern: they represented animals with no surroundings or landscape, with no apparent connection to actual terrain, and rarely in relation to any human presence. These animals were often drawn on top of one another, appearing as if they were floating in space. And the varieties of animals, their positions, and their proportions seemed to be governed by arcane rules that were always roughly the same, as were the accompanying abstract symbols in caves from Cantabria, in northwest Spain, to France’s Dordogne region, the Ardèche, and the Pyrenees, to a couple of isolated sites in Italy. These drawings spanned thousands of years without any noticeable change in style or subject matter. The earliest date from around 32,000 years ago (the Chauvet cave in France), and the latest are about 12,000 years old.

After our trip, my wife and I purchased a scholarly treatise on the prehistoric cave art of France and Spain. The book contained a display of the drawings and the signs found at Niaux, Lascaux, Chauvet, and many other caves. Leafing through its pages, I suddenly came upon a photograph of that last sign I had seen inside Niaux: the one I thought I somehow understood but later dismissed as a figment of my imagination. To my great surprise, I found it displayed together with many similar—and even more explicit—signs of the same kind. Such symbols had been discovered in great abundance in prehistoric caves. And there was a two-word caption in French below the photographs of these signs: “Symboles Sexuels.”

The prehistoric European cave drawings represent the first evidence of our ancestors’ ability to think symbolically. These fabulous paintings of very specific animals with no background and no apparent connection to terrain or context are presumed to be symbols. But nobody knows for sure. And these totemic animals are almost always accompanied by very specific stylized signs: arrows, pairs of lines, sets of dots, and what appear to be sexual symbols. The signs may represent the very root origin of language and communication, even though we do not know how to interpret them. Their meaning is the oldest unsolved mystery of the human experience.

The enigmatic practice of creating art in deep and dangerous caves—besides the physical hazards, there were bears and lions in many caverns—lasted for 20,000 years. And then, around 12,000 years ago, as the reindeer, the bison, and the mammoth herds of the Ice Age vanished with the melting ice and the drastically changing climate, the cave art activity came to an abrupt end. Cro-Magnon societies gave way to civilization, beginning with agricultural communities and the domestication of animals in the Neolithic Revolution. The earliest writings appeared several thousand years later, and then came the copper, bronze, and iron ages. Prehistory, as we define it, ends with the invention of writing some 5,000 years ago in Mesopotamia.

Niaux is one of the most important decorated caves in the world. It was not the first to be discovered—some cave art was found as early as the 1870s, such as the famous “Ceiling of the Bulls” in the cave of Altamira, in the Spanish region of Cantabria. In the case of Niaux, the first “gallery” of cave drawings, the so-called Black Salon, which we visited, appears half a mile deep inside the cavern. For this reason, although the cave had been known for centuries, perhaps only one person (who left his mark in the cave) had ventured all the way into its depths from the time the cave was abandoned some 13,000 years ago until the beginning of the twentieth century. Hundreds of graffiti have been found in this cave, but all of them were made around the entrance to the cave and certainly no more than a hundred yards inside it. The oldest dated graffito at the cave’s entrance bears the year 1602.

But in 1660, a visitor named Ruben de la Vialle carved his name and the date all the way inside the Black Salon, half a mile deep inside this cavern, right next to the drawings of the animals. Did de la Vialle realize how ancient the drawings were? We do not know, and there is no evidence that anyone else had penetrated the cave to this depth. De la Vialle must have lighted his way in with fire, using a candle or a torch not much different from the kind the Paleolithic artists who decorated this cave had used.

But somehow, Ruben de la Vialle made it alone all the way in. He saw this great art, and he made it back out of the cave. His footsteps have been found in the cave, showing his way in and out. There are also footsteps of the Paleolithic people who made the art and those of ancient visitors who entered the cave still in the Ice Age, a couple of thousand years after the artists had left. These Ice Age visitors were two women and two young children, as revealed by an analysis of their footsteps. They, too, made it all the way to the Black Salon. We know this because the cave environment was undisturbed by wind or fire or much geological erosion, and therefore ancient footsteps inside remained intact for millennia.

On September 21, 1906, the Paleolithic treasure hidden in the depth of Niaux was rediscovered. That day, two young brothers, Paul and Jules Molard, were hiking in the woods with their father, known only as Captain Molard, in the rural region of the lower central Pyrenees. The boys and their father were in the habit of spending their time leisurely exploring the countryside around their vacation home in the nearby hamlet of Sabart. By late September, they had discovered several previously unknown cavities in the rough terrain of these steep hills, often by climbing with ropes on cliffs that were very difficult to reach.

On the morning of the twenty-first, they were hiking near the entrance to Niaux and entered the cave to find the graffiti in the first hall. This part of the cave had been known for many decades. But the three explorers decided to venture farther in. Rocks covered the entrance to the corridor that continued into the depth of the cavern, and they removed them, one by one, and filed through the very narrow entrance they had made. Excitedly, the two boys continued and reached the dry bed of the ancient lake, where only the Magdalenians and Ruben de la Vialle had tread, and came to the second narrowing of the cavern. Their father followed a few dozen yards behind. They climbed up through this last hurdle, and when they shone their lights on the face of what we now call the Black Salon, they were stunned to find it covered with spectacular drawings of bison, horses, and ibex.

That evening, Capitain Molard went over to his neighbor’s house. This neighbor was the well-known French prehistorian Félix Garrigou. The latter, too old and frail to venture into the cave his friend had just described to him, immediately wrote a letter to Professor Émile Cartailhac, a prehistorian at the University of Toulouse. Cartailhac, on receipt of the letter with the exciting news about the discovery, rushed to the site of Niaux, bringing with him a prominent expert on Paleolithic art, the French scholar Abbé Henri Breuil (1877-1961). The pair of experts authenticated the drawings as Paleolithic (rather than present-day or at most a few hundred years old), and Breuil, who was a good artist, copied many of the drawings, which were published and roused much interest among prehistorians and the general public.

But the custom of hiding extraordinary art in the deepest parts of caves, accompanied by marginal art in the periphery, and painting signs at specific locations within a cave, appears in every important decorated cave in the Franco-Cantabrian region, which comprises Cantabria and the French Dordogne (also called Périgord), Lot, Ardèche, and the Pyrenees. In the following chapters, we will explore many of these caves and will consider the theories that have been proposed to explain the riddle of why ancient peoples decorated deep caves.

I had been visiting lan—a world expert on prehistoric cave art—to discuss the meaning of the stunning paintings and drawings found in European caves and dating back tens of thousands of years. We had a long, leisurely conversation in his office, drinking a rustic red Sicilian wine and sampling goat cheese as we discussed this beguiling art. Ian summed up our discussion by saying that the meaning of this art still remains the greatest mystery in all of anthropology. After decades of intensive research, we simply don’t know why ancient artists made their way—often crawling for miles—into the depths of caves, with only the light from stone candles burning animal fat to guide them through the tricky and dangerous underground labyrinths, finally to reach the deepest hollows, where they indulged their need to paint or engrave animals.

In fact, Ian begins his marvelous 1998 book about human evolution and human origins, Becoming Human, with the story of the enigmatic art found in one such Paleolithic cavern, the cave of Combarelles. He writes:

A leisurely half hour’s stroll outside the sleepy southwestern French town of Les Eyzies de Tayac, a narrow fissure penetrates deep into a limestone cliff face. The path of an ancient underground stream, this tortuous subterranean passage is the cave of Combarelles I. At its entrance, a guide unlocks an ancient iron grille and swings it open ... you proceed a hundred and fifty yards along this somber passage, wondering why on Earth you have come to this cramped, forbidding place.... Under the oblique light of filtered lamps, the walls of the cave suddenly come alive with engravings, some of them almost obscured by a calcite coating deposited on the cave walls over the millennia. Horses, Mammoths, reindeer, bison, mountain goats, lions, and a host of other mammals cascade in image along the cave walls over a distance of almost a hundred yards.... Leaving the cave, you are consumed with the question “Why?” Why wriggle and struggle along a constricted, choking, dark, uncomfortable, and potentially dangerous passage that dead-ends deep in the rock with barely room to turn around? Why create art that could only be revisited with the greatest of difficulty? Why virtually ignore the outer part of the cave, executing your art only in its far interior recesses? Why engrave image over image, and intersperse those lifelike renderings with geometric designs and a profusion of obscure and apparently superfluous markings? And, quite simply, why the art at all? Frankly, we will never certainly know the answer to any of these questions.¹

But I was determined to try to solve this great mystery. And I knew that Ian did have his own theory about cave art. He firmly believes that Paleolithic cave art is the result of the development of the human brain achieving a point of no return, a “tipping point,” as one might describe it in the popular jargon: a point at which our developing brain has made a discontinuous, giant leap forward.

Ian Tattersall is an anthropologist and also an expert on primates, particularly lemurs: cute, furry, large-eyed prosimians that live on the island of Madagascar. He has spent many years studying these ancestors of monkeys, and his research has led him to important results in the evolution of humans and other primates. Ian looks at cave art from the strong perspective of evolution.

He believes that the human brain is the outcome of brain evolution that had taken place over millions of years, and that none of the hominids that came before us—Australopithecus, Homo erectus, Neanderthals—had reached a level of symbolic thinking. According to Ian’s theory, when our Cro-Magnon European ancestors, members of the species Homo sapiens like us, reached the developmental point at which they could think symbolically, they celebrated their amazing new ability by creating art in deep caves.

At some point in the distant past, perhaps not much earlier than 35,000 years ago—the upper limit to the time span going back into the past when the very first artistic inclination by our species manifested itself—Stone Age people realized that they could capture the image of a living thing: an animal or another human. They realized—and this must have happened very suddenly—that they could symbolically recreate the image of such a living organism.

This could have been an extension of the activity of making a stone tool. Instead of making a stone ax, the first artist of prehistory worked the stone into the shape of a human being: making a statuette (the “Venus statuettes,” which I will describe later). Others may have had the idea of capturing the image of an animal on a cave wall. To celebrate this great ability, early humans created more and more such art. They reveled in their newfound ability to capture images and continued to do so for thousands of years.

It’s an appealing theory, and it relies on the assumption that although the human brain has been fully developed for perhaps 150,000 years (we know this from an analysis of the cranial shape and capacity of early Homo sapiens fossil skulls found in the Middle East), something “clicked” in the human brain—some connection of neurons that allowed these people to think symbolically. Once this happened, it was a point of no return for human consciousness. At that moment, we became who we are today.

Ian and I discussed the mysterious cave of Combarelles and compared our impressions of the art found there. Right next to it is another cave that is very different from it. While Combarelles has only engravings, the nearby cave of Font-de-Gaume has multicolored paintings. Both caves were discovered by the French cleric and prehistorian Abbé Henri Breuil, affectionately known in his country as the “Father of Prehistory” (or sometimes even the “Pope of Prehistory”) because, in a career that spanned more than half a century, he made so many important contributions to our understanding of our ancestors and the art they created on the walls of deep caves and on rock faces in the open air.