The Ocucaje Desert holds some of the most important fossils in the world. And their only defender is a renegade guide with an eye for shark teeth.

I am investigating the skull of a huge toothy beast on the rocky slope of a dun mountain when I hear Roberto cry out. I look over to see him doing a shuffle in the dust, tan arms held above his head—the lone spot of motion on the mountain’s stony face. He gathers us around so that we can all see what he has found: the fossilized tooth of a megalodon shark, one of the most fearsome killers in the planet’s history. The tooth is a six-inch dagger, gleaming white.

It’s our second day deep in the Ocucaje Desert in the Ica region of southern Peru. Photographer Morgan Stetler, Sergio Tueros Grimaldo (a 17-year-old spending his summer vacation studying extinct sharks), and I have traveled here with our guide, Roberto Penny Cabrera, in search of fossils.

For eons, this land was the bed of a shallow bay off the coast of South America. The water teemed with life: whales, dolphins, giant penguins, crocodiles, and the megalodon, a 45-foot-long whale-eating shark, which disappeared some 1.5 million years ago. As the Andes rose, they pushed the land out of the water. A million years ago it stopped raining. Now the landscape looks like Mars. Wind-formed hills of crumbling stone and dunes of fine sand enclose basins of shiny polished pebbles that appear to have been sorted by size: small ones here, larger ones over there. And the remains of all the creatures that once swam now lie buried in the stone.

The fossils, particularly those of the megalodon, make the region one of the most important paleontological areas in the world. And yet the Peruvian government offers the desert no legal protection. Most of the land is available for mining, but fossils—taken by unscrupulous scientists and local scavengers and sold to collectors and museums—have become lucrative exports.

Our guide, Roberto, sees himself as the desert’s only protector, and for the most part he’s right. Behind the wheel of Hermelinda, his trusty black-and-olive ’83 Datsun diesel pickup, he cruises the trackless desert sands like one of the lonely, indefatigable desert foxes that live there.

Roberto is a descendant of Capitán Doctor Jerónimo Luis de Cabrera y Toledo, a conquistador who, in 1563, founded the city of Ica on the banks of a river 160 miles south of Lima. Roberto favors desert fatigues, a khaki shirt, and tan boots. He has a thick gray moustache, and over his shirt he wears a steel-ribbed tan corset that he cinches tight each morning to keep his back straight. A broad-brimmed hat shades his blue eyes, and he is never without the knife on his wide leather belt or the cell phone strapped to his thick wrist. At 54, he maintains the natural good looks of a rakish man of action: a Burt Reynolds or a Douglas Fairbanks Jr.

We had begun our trip at Roberto’s home in Ica’s city center. He lives on the main square, in the thick-walled yellow mansion built by his grandfather a century ago. From the facade of the house, under the Cabrera coat of arms, two huge, dark doors swing into a courtyard. Inside, the bustling traffic in the plaza fades to a distant echo. In narrow, dim hallways with dark wood wainscoting, cracks in the plaster snake off into the gloom. A piano sits askew in the middle of a room, where an earthquake shoved it. In a grand dining room, a massive mahogany table is set for a feast of dust. In the rear courtyard, the entire back of the house has collapsed.

The front rooms of the mansion, facing the plaza, house the Museum of the Engraved Stones of Ica. The stones were collected by Roberto’s late uncle, Javier Cabrera Darquea. A prominent physician in the 1960s and ’70s, he spent his later years taking trips to the desert. He came back bearing rocks engraved with images of people of, as he told it, extraterrestrial origin, commingling with dinosaurs. Above Javier’s desk is a framed photo of him presenting a black, carved stone to actress Shirley MacLaine.

This is Roberto’s birthright: The Cabrera name is equal parts proud legacy and burden. The family is given to big ideas both practical (bringing irrigation to the valley; planting the first olive trees in the area) and eccentric (communing with aliens; ranting in the public square, as one of Roberto’s brothers has been known to do). For every noble event commemorated in the bright oil paintings hung above Javier Cabrera’s stones, the clan hides a darker tale. When I told our cab driver we were going to the Cabrera mansion, he looked at me over his shoulder and said, “They’re all crazy.”

After walking us through the house, Roberto leads us up to the flat adobe roof. Pigeons roost in the crumbling steeples of the cathedral next door. Below, minibuses zip around the plaza’s perimeter. Massive sand dunes loom at the edge of town. This is where, as an 8-year-old, Roberto discovered who he could be in the desert: “You go up to the top of the dunes,” he says, gazing past the garish billboards for chicken burgers, computer classes, and plastic surgery, “and you feel free.”

Back inside the decaying mansion, Roberto’s single room feels like a campsite. A mattress lies on the floor, covered in camouflage sheets; even the easy chair is upholstered in camo. The air has the close smell of late-night cigarettes. Massive satellite maps of the region cover one wall. Along another wall are glass cases holding Roberto’s collection of fossil shark teeth.

A legion of small-scale entrepreneurs in Ica collect fossil shark teeth for sale to tourists, but to Roberto they are valuable only as trophies, testaments to his skills. “It is the hunt that I like,” he says. “The finding.”

The next day we load Hermelinda with gear and supplies and head south on the Panamerican Highway. We halt at the windblown truck stop where Roberto always pauses before entering the desert—for a cup of coffee and to pay our respects to the roadside shaman who lives there. Then we leave the paved road and head straight into the desert.

From the back seat, crammed between two knobby spare tires, I can see we’re following a track across the plain toward a wall of tan mountains. We’re traversing one of the driest places on earth, an arid zone that stretches more than a thousand miles across Peru and Chile. Hardly anything lives in the landscape flowing by. It would be days before I’d see my first lizard, a ghostly creature living on an excrescence of rock salt.

One of the first things Roberto stops to show us is a whale skull worn open by the wind. The brain that once pondered whalesong has turned to stone and glows milky white in the hot sun. “I collect brains,” Roberto says. “But not that one. It is in the ground. I do not take from the ground.”

Roberto’s ethic is simple: He takes only fossils that have been fully freed by the wind, figuring that these will soon be worn away to join the dust. Everything else he leaves, set like gems in the rock. The desert and all it contains—fossils, pre-Columbian relics, minerals, meteorites—form an inviolable, pristine whole.

To Roberto, fossils are better company than people. “I first came here for solitude,” he tells me as we sit on folding chairs at our first campsite, observing a broad valley rising to a rounded gray mountain. He was 18 back then, riding a motorcycle over the dunes and through nameless canyons. “I went around and around and around, and I found fossils.”

After a stint in Naval College (he was kicked out for going AWOL) and some time heading up road-building operations for a U.S. mining company in the Andes (where he learned English and, crucially, geology), Roberto returned to the Ocucaje Desert to run his own small mining business, extracting minerals used as fertilizers. To move the minerals out of the desert, he would drive his truck over a bridge that spanned the Ica River. About 15 years ago, a flood washed away the bridge. It ruined him. His business, then his marriage, disintegrated. But he still had Hermelinda, so he started bringing travelers to the desert.

His geological training and years of experience allow Roberto to read the desert in a way few can. “Roberto’s skills are amazing,” says Jürgen Kriwet, head of the Fossil Shark Research Lab at the Staatliches Museum für Naturkunde in Stuttgart, Germany. “He is one of the best finders of fossils I have ever met.”

Finding shark teeth is a subspecialty of its own. Roberto favors morning light, when the low sun glints off the smooth fossil enamel, distinguishing it from the matte ground. Early in the morning of our second day in the desert, he stands pointing out teeth in the distance: “There is one. And there. And another one there.” We investigate, and that’s when he finds the six-inch dagger of a tooth that makes him dance his megalodon shuffle. As he moves on to continue his search, I notice a dolphin skull that had been watching us from a few feet up the slope.

The area’s fossils have been crucial in understanding the evolutionary history of modern sharks. Fossilized shark teeth can be found in many parts of the world, but Peru’s desert—specifically a geological area known as the Pisco Formation—hides entire fossilized shark skeletons, which are much rarer and much more informative for paleontologists. “Nowhere else in the world has this quality of fossils,” says Kriwet. “This is unique.”

Laws protect important fossil beds in other countries, but Peruvian politics and bureaucracy are notoriously opaque. Due to a turf war between agencies in Lima and Ica, even highly regarded paleontologists such as Kriwet have a hard time figuring out what permits they need to work there. In the absence of official clarity, says Vera Alleman Haeghebaert, a paleontologist at Lima’s Ricardo Palma University, “anyone can go into the desert. There are no official guides. There are abuses. Nothing is organized.”

The bone hunters, tooth collectors, and other guides follow Roberto’s tracks. Not long after he started leading trips, Roberto brought a group to the site of one of his favorite fossils—a rare complete fossil shark, seven feet long—only to find an empty hole in the ground. The skeleton had been taken. Now Roberto is careful about whom he takes. Some places are so special he never returns, lest his tracks give them away.

Both Roberto and Peruvian law insist that relics from the ground belong to the region in which they are found, but Ica has no suitable museums. In the meantime, unregulated fossil hunters comb the area, limited only by their equipment (most use motorcycles, which cannot go very far into the desert) and their lack of specialized knowledge. Roberto relishes foiling them: “When I understood that they are not taking fossils to study, but are selling them, I became a hunter of the hunters.”

His efforts led to some high-profile busts. In 2007, Roberto led government agents to an unauthorized dig in progress, resulting in a French scientist’s expulsion from Peru. Subsequently, Roberto was deputized to monitor the area by Ica’s regional president, Vicente Tello, but when Tello’s term ended, Roberto’s role disappeared, and the fossils were left, once again, with no official protection.

Now Roberto’s plan is to team up with institutions from abroad to establish a museum and a national park in the region that, together, would preserve the desert while fostering scientific discovery and the local economy. “It’s so rich!” he says. “People here will find out that if they protect the area it will be good for them. Now it is the opposite: People are coming and taking the fossils out, and leaving very little money.”

Yet Roberto’s mercurial personality has a way of alienating those who could help him. “The universities are amateurs,” he says with disdain, even though their political connections could help protect the area. “There needs to be a law [to protect the desert],” he goes on, but again immediately dismisses his most likely ally: “The Congress is a house of witches.” (Both Kriwet and Alleman say they are still in discussions with Congress and other institutions in Peru and abroad to build a museum on the campus of Ica University.)

After our morning search for shark teeth, the four of us drive south, across a river and away from Ica, now 50 miles and countless valleys to our north, past a failed dam Roberto’s grandfather built, ever deeper into the desert and into total isolation. “You will see a place that has been untouched for 12 million years,” Roberto shouts over the din of Hermelinda’s motor. “The paleontologists cannot go there because it’s very dangerous. Very. You can’t get out of there walking.”

He turns the faithful truck toward a range of black mountains, and we climb a huge tongue of sand that falls from them like a dry glacier. It’s an exhilarating ride, the truck shimmying as it paws the uncertain ground along a precipitous vista. When he drives, Roberto is one with the truck, sensing every vibration. When something does go wrong—on this day with a snap and an ominous hiss—he acts without thinking. Instantly, the truck is in neutral and pulled into a safe position, and Roberto is under the hood reattaching the air hose.

We reach the crest and confront an awe-inspiring sight. In front of us stretches a plain of fine gray sand studded with fossilized whales. Hundreds of them. Rolling past them in Hermelinda is like a macabre whale-watching trip: Broad, iridescent skulls break the surface of ancient seas turned to sand. Complete skeletons 20 feet long lie with their huge vertebrae and fat rib cages, some with even their baleen and skin preserved. We come to a stop and Roberto cuts the motor. There is no sound but the howl of the wind. Fingers of fog cast shadows on the profoundly silent pod of whales.

We camp just around a bend, huddling behind a pre-Hispanic shelter—a crescent of flat boulders set on edge atop a low dune. There is no need for a roof on this rainless promontory. The boulders block the wind, and we are warm and happy. As Roberto sets up an ingenious open-sided tent of his own design, he says, “I have done the same—I learned from those before us.” He lights a fire and sits on the ground smoking and looking across a broad swale of sand to even higher mountains. Tufts of gray hair and sideburns wildly asunder, stubble glinting on his tan cheeks, he slumps in his corset.

As night closes in, so does the fog, confining our world to the tent and a patch of sand surrounded by impenetrable murk. “If I die here,” says Roberto, his voice gravelly, “take my phone, go to a mountaintop, and call the last number I called. Tell him, ‘Roberto is dead.’”

We are all still alive the next morning, so we climb aboard Hermelinda and skitter down falling dunes, past strange rock outcrops and through trackless valleys of dust and sand, until we come to a long slope of fine sand coated in a thin layer of dark pebbles. When we leap from the truck, I can see fossil fragments that have drained down in streams from layers of rich beds above. “He is here, Gregory, he is here,” Roberto says, looking deep into my eyes. “Megalodon—the biggest one!”

Somewhere above us a giant shark has lain for 10 million years. Of late, it has been giving up massive teeth. If Roberto can find the whole jaw, that would be a paleontological prize big enough to bring global attention to the area—enough, perhaps, to bring about his plan for protecting the Ocucaje Desert. “I am waiting for this guy,” he says, scanning the ridgeline. “I know where he is.” Digging wouldn’t work—the location is imprecise, and besides it would violate his ethic—so he’s waiting, as patient as the wind.

We four become a swarm of little boys, gleefully strolling the hillside, picking up this tooth fragment and that knucklebone, a periwinkle here, a stingray spine there. I find a set of deadly sharp black and brown mako shark teeth, each bigger than those of anything in today’s oceans. When I look up, I see Roberto down the slope, standing stock still. He raises his arms above his head, then falls onto his back and lies in the dust.

I run over, wondering which of the nearby mountains is my best bet for phone service, but he is sitting up by the time I reach him, laughing softly at something in the sand next to him: a massive megalodon tooth. It is broken in two and missing its point, but it is clearly from a huge shark. “Another sign,” Roberto says softly. He had not even touched it, this small fragment of the immense landscape to which he has devoted his life. “What luck to have been born with a chance to see this place!” A

A Current Affair

The Humboldt ocean current is largely responsible for making Peru’s desert such a fascinating region. The current’s cold water and accompanying winds prevent rain clouds from forming and bring nutrient-rich waters from deep in the Pacific Ocean to the surface.

On land, the result is a desert that preserves not only fossils but also the remains of cultures that have inhabited the area. The most famous archaeological remains are the Nazca Lines, giant figures created by scraping away the top layer of soil. The meaning of the lines—which take the form of a monkey, a hummingbird, a spider, and other natural and abstract images—is still debated, but the latest research suggests that they were stages for religious ceremonies of the Nazca culture, which emerged around 200 BCE and lasted until between 500 CE and 600 CE. The Paracas culture, which preceded the Nazca, left its own geoglyphs in the desert, along with ceramics and mummies.

The waters off the coast of Peru and Chile produce up to 20 percent of the world’s seafood catch every year and are home to dolphins, seals, sea lions, turtles, and millions of birds. Those birds produce another valuable commodity: guano. For hundreds of years, birds such as cormorants and boobies have left their droppings on a series of small islands off the coast, where, with no rain to wash them away, they have built up in layers dozens of feet thick. Peruvian guano has long been coveted as a fertilizer and as an ingredient for explosives. In 1909, the Peruvian government established a Guano Administration to conserve its guano reserves. And in December 2009, it created the Guano Islands and Capes National Reserve, protecting some 350,000 acres of habitat all along the coast to help ensure that the birds keep dropping by.—JEREMY SAUM

Photos by Morgan Stetler. This story appeared in the July/August 2010 issue and won a bronze in environmental tourism from the Society of American Travel Writers Foundation.