Published: September 2008
Lost Tribes of the Green Sahara
How a dinosaur hunter uncovered the Sahara's strangest
Stone Age graveyard
By Peter Gwin
National Geographic Staff

On October 13, 2000, a small team of paleontologists led by Paul Sereno of the University of Chicago clambered out of three battered Land Rovers, filled their water bottles, and scattered on foot across the toffee-colored sands of the Ténéré desert in northern Niger. The Ténéré, on the southern flank of the Sahara, easily ranks among the most desolate landscapes on Earth. The Tuareg, turbaned nomads who for centuries have ruled this barren realm, refer to it as a "desert within a desert"—a California-size ocean of sand and rock, where a single massive dune might stretch a hundred miles, and the combination of 120-degree heat and inexorable winds can wick the water from a human body in less than a day. The harsh conditions, combined with intermittent conflict between the Tuareg and the Niger government, have kept the region largely unexplored.

Sereno, a National Geographic Society explorer-in-residence and one of the world's most prolific dinosaur hunters, had led his first expedition into the Ténéré five years earlier, after negotiating agreements with both the leader of a Tuareg rebel force and the Niger Ministry of Defense, allowing him safe passage to explore its fossil-rich deposits. That initial foray was followed by others, and each time his team emerged from the desert with the remains of exotic species, including Nigersaurus, a 500-toothed plant-eating dinosaur, and Sarcosuchus, an extinct crocodilian the size of a city bus. The 2000 expedition, however, was his most ambitious—three months scouring a 300-mile arc of the Ténéré, ending near Agadez, a medieval caravan town on the western lip of the desert. Already, his team members had excavated 20 tons of dinosaur bones and other prehistoric animals. But six weeks of hard labor in this brutal environment had worn them down. Most had mild cases of dysentery; several had lost so much weight they had to hitch up their trousers as they trudged over the soft sand; and everyone's nerves had been on edge since an encounter with armed bandits.

Mike Hettwer, a photographer accompanying the team, headed off by himself toward a trio of small dunes. He crested the first slope and stared in amazement. The dunes were spilling over with bones. He took a few shots with his digital camera and hurried back to the Land Rovers.

"I found some bones," Hettwer said, when the team had regrouped. "But they're not dinosaurs. They're human."

Heat, thirst, and, for the moment, dinosaurs were forgotten as the team members followed Hettwer back to the three dunes and began to gingerly survey their slopes. In just a few minutes they had counted dozens of human skeletons. Parts of skullcaps pushed up through the sand like upturned china bowls; jawbones clenched nearly full sets of teeth; a tiny hand, perhaps a child's, appeared to have floated up through the sand with all its finger bones intact. "It was as if the desert winds were pulling them from their final resting places," said Hettwer. Insinuated among the human bones was a profusion of clay potsherds, beads, and stone tools— finely worked arrowheads and axheads and well-worn grindstones. There were also hundreds of animal bones. In addition to antelope and giraffe, Sereno quickly recognized the remains of water-adapted creatures like crocodiles and hippos, then turtles, fish, and clams. "Everywhere you turned, there were bones belonging to animals that don't live in the desert," said Sereno. "I realized we were in the Green Sahara."

For much of the past 70,000 years, the Sahara has closely resembled the desert it is today. Some 12,000 years ago, however, a wobble in the Earth's axis and other factors caused Africa's seasonal monsoons to shift slightly north, bringing new rains to an area nearly the size of the contiguous United States. Lush watersheds stretched across the Sahara, from Egypt to Mauritania, drawing animal life and eventually people.

Archaeologists have inventoried the stone tools used by these early inhabitants and the patterns inscribed on their ceramics. They have also identified thousands of their rock engravings, which depict herds of ostriches, giraffes, and elephants. Some of the images suggest that along the way the people of the Green Sahara learned to domesticate cattle. But they remain veiled in mystery. Did they arrive here from the Mediterranean coast, central African jungles, or Nile Valley? Were they nomads, or did they stake out territories and build settlements? Did they trade with each other and intermarry, or did they wage war, or both? As the monsoons began to recede, how did they cope with a drying landscape? The only part of the story that then seems clear is that by some 3,500 years ago the desert had returned. The people vanished.

Seeking answers to such questions is normally the domain of anthropologists and archaeologists—not dinosaur hunters. But Sereno had become transfixed by the discovery. "There is something soul stirring about looking into the face of an ancient human skull and knowing this is my species," he said. Whenever he could steal a moment from his paleontological work, he pored through every scholarly publication he could find on the Green Saharans, tracked down the authors and badgered them with emails full of questions. Sometimes he would read all night before downing a cup of coffee and heading back to his lab. In 2003, during another dinosaur expedition in Niger, he took three days off to revisit the dunes and survey the site, counting at least 173 burials. To dig any deeper, however, would require more time, money, and expertise.

In the spring of 2005 Sereno contacted Elena Garcea, an archaeologist at the University of Cassino, in Italy, inviting her to accompany him on a return to the site. Garcea had spent three decades working digs along the Nile in Sudan and in the mountains of the Libyan Desert, and was well acquainted with the ancient peoples of the Sahara. But she had never heard of Paul Sereno. His claim to have found so many skeletons in one place seemed far-fetched, given that no other Neolithic cemetery contained more than a dozen or so. Some archaeologists would later be skeptical; one sniped that he was just a "moonlighting paleontologist." But Garcea was too intrigued to dismiss him as an interloper. She agreed to join him.

"I was impressed that he hadn't just ignored the burials and continued looking for dinosaurs," she told me.

They arrived at the site six months later. Clad in a salt-stained T-shirt and jeans, Sereno, vibrating with energy, powered up the first of the three dunes, identifying animal bones with nearly every stride—giraffe vertebra … hippo ulna … gazelle humerus. Garcea, a petite woman in unwrinkled chinos and a tennis hat, followed at a more measured pace, bending at the waist to scrutinize each item.

At the top, they surveyed a macabre scene. Around them lay dozens of human skeletons in various degrees of completeness, far more than Garcea had seen at all her other digs combined. Nonetheless, she seemed more interested in what looked to me like tiny gray chunks of gravel. "They're potsherds," she said, and held up one inscribed with a pointillistic pattern. She identified the markings as belonging to a people known to scholars as the Tenerian, a nomadic herding culture that lived during the latter part of the Green Sahara era, 6,500 to 4,500 years ago. Then she picked up another piece. She studied it for a moment, looking perplexed. Instead of little dots, this sherd was decorated with wavy lines. She picked up another like it, then another. "These are Kiffian," she said, her voice rising with excitement.

Garcea explained that the Kiffian were a fishing-based culture and lived during the earliest wet period, between 10,000 and 8,000 years ago. She held a Kiffian sherd next to a Tenerian one. "What is so amazing is that the people who made these two pots lived more than a thousand years apart."

Over the next three weeks, Sereno and Garcea—along with five American excavators, five Tuareg guides, and five soldiers from Niger's army, sent to protect the camp from bandits—made a detailed map of the site, which they dubbed Gobero, after the Tuareg name for the area. They exhumed eight burials and collected scores of artifacts from both cultures. In a dry lake bed adjacent to the dunes, they found dozens of fishhooks and harpoons carved from animal bone. Apparently the Kiffian fishermen weren't just going after small fry: Scattered near the dunes were the remains of Nile perch, a beast of a fish that can weigh nearly 300 pounds, as well as crocodile and hippo bones.

Garcea suspected that the Tenerian had made most of the stone tools. Nearly three-fourths of them were hewed from a strange green volcanic rock that bore a glasslike sheen and yielded razor-sharp edges when fractured. The abundance of green flakes on the dunes indicated that the Tenerian spent long periods of time at Gobero making and sharpening their tools. "But it's possible they lived part of the time at the place where they quarried the green rock," said Garcea. One of the Tuareg said he had seen big boulders of it in the Aïr mountains, some hundred miles to the northwest.

At dusk the heat gave way to the cool evening air, and the camp divided into three groups. The soldiers, dressed in threadbare fatigues and combat boots with no socks, gathered around their fire, speaking Hausa, Niger's dominant language. At the Tuareg fire, the guides removed their linen chèches, which they kept neatly wound around their faces during the day. They reclined on foam mattresses, served each other strong, sugary tea, and quietly discussed Niger's restive politics in their native Tamashek. Meanwhile, the dig team cooked couscous and freeze-dried vegetables on a propane stove, eating by the light of their headlamps. Their conversations focused on the stark differences in the burials. Some appeared to be little more than a tight bundle of bones, as if the body had been bound or squeezed into a basket or a leather bag, which had long since decomposed. These compact burials belied the fact that some of these individuals were surprisingly large—as much as six feet eight inches tall, with thick bones suggesting they had been well muscled.

By contrast, other skeletons belonged to much smaller people, about five-and-a-half feet tall. They were buried on their sides in relaxed positions, as if they had fallen asleep and drifted into death. Some of their graves contained beads, arrowheads, or animal bones. But since no potsherds were found in the burials, it wasn't clear which were Kiffian and which were Tenerian. Until the age of the bones could be determined, no one could say for sure. And what had led the Tenerian to bury their dead in the exact same spot as the Kiffian had laid theirs to rest, thousands of years earlier?

"Perhaps the Tenerian found the Kiffian burials and recognized this place as sacred," Garcea offered. "It's possible they thought these bones belonged to their own ancestors."

The search for answers could not wait long. Gobero held at least 200 burials, which would take several field seasons to excavate. But the constant desert wind was eroding the site year by year, scattering the bones down the sides of the dunes. An even more dire concern was looters. Officials in Niger have identified close to a hundred Stone Age sites in the T�n�r� and report that nearly all were looted before they could be excavated. Often Tuareg traveling in camel caravans find the sites and scavenge artifacts to sell to dealers in Agadez, who in turn sell them illicitly to tourists. Though the Niger government has outlawed the sale of antiquities, only Gobero and one other site remained unlooted.

Members of the dig team suspected that a few of the soldiers were picking up artifacts as they patrolled the site's perimeter. When confronted by Sereno, they denied it. One night by the Tuareg fire, I asked one of the guides whether he thought anyone might pilfer artifacts. He shrugged. "When you are hungry and your children are hungry, what can you do?" Another confided to me that over the years he had collected a small number of artifacts during his travels in the desert. He produced a leather pouch that held an array of gemlike arrowheads and a beautiful knife chipped from the strange green stone. "These are not for sale," he said. "They are for my children. It is their history. I want them to see it before it is all gone."

SERENO FLEW HOME with the most important skeletons and artifacts and immediately began planning for the next field season. In the meantime, he carefully removed one tooth from each of four skulls and sent them to a lab for radiocarbon dating. The results pegged the age of the tightly bundled burials at roughly 9,000 years old, the heart of the Kiffian era. The smaller "sleeping" skeletons turned out to be about 6,000 years old, well within the Tenerian period. At least now the scientists knew who was who.

In the fall of 2006 they returned to Gobero, accompanied by a larger dig crew and six additional scientists. Garcea hoped to excavate some 80 burials, and the team began digging. As the skeletons began to emerge from the dunes, each presented a fresh riddle, especially the Tenerian. A male skeleton had been buried with a finger in his mouth. Another had been interred inside a frame of disarticulated human bones. Among the strangest was an adult male buried with a boar tusk and a crocodile ankle bone and his head resting on a clay pot. Parts of the skeleton appeared to have been burned, hinting that an elaborate ritual had accompanied his burial.

Garcea paid close attention to these details. In lieu of a written language, such clues are critical to understanding what she described as a culture's "software"—its traditions, value system, and beliefs about the supernatural. The very act of burial contains a message, Garcea told me as she delicately brushed dirt from another Tenerian skeleton. "By infusing the land with the remains of your people, you claim it."

Unlike the Tenerian burials, the bundles of Kiffian bones came with few artifacts to shed light on their culture. But bones and teeth alone can say a lot about the daily lives of a vanished people. Their appearance can reveal an individual's sex, age, and general health, and they hold chemical signatures that, analyzed in a lab, can reveal the kinds of food a person ate and the location of the water sources he drank from.

Even at the site, Arizona State University bioarchaeologist Chris Stojanowski could begin to piece together some clues. Judging by the bones, the Kiffian appeared to be a peaceful, hardworking people. "The lack of head and forearm injuries suggests they weren't doing much fighting," he told me. "And these guys were strong." He pointed to a long, narrow ridge running along a femur. "That's the muscle attachment," he said. "This individual had huge leg muscles, which means he was eating a lot of protein and had a strenuous lifestyle—both consistent with a fishing way of life." For contrast, he showed me the femur of a Tenerian male. The ridge was barely perceptible. "This guy had a much less strenuous lifestyle," he said, "which you might expect of a herder."

Stojanowski's assessment that the Tenerian were herders fits the prevailing view among scholars of life in the Sahara 6,000 years ago, when drier conditions favored herding over hunting. But if the Tenerian were herders, Sereno pointed out, where were the herds? Among the hundreds of animal bones that had turned up at the site, none belonged to goats or sheep, and only three came from a cow species. "It's not unusual for a herding culture not to slaughter their cattle, particularly in a cemetery," Garcea responded, noting that even modern pastoralists, such as Niger's Wodaabe, are loath to butcher even one animal in their herd. Perhaps, Sereno reasoned, the Tenerian at Gobero were a transitional group that had not fully adopted herding and still relied heavily on hunting and fishing.

The twilight of the Green Sahara around 4,500 years ago might have been the perfect time to be hunting at Gobero, said Carlo Giraudi, the team's geologist. As water sources dried up throughout the region, animals would have been drawn to pocket wetlands, making them easier to kill. Four middens found on the dunes and dated to around that time included hundreds of animal remains, as well as fish bones and clamshells—not usually part of a herder's diet. "The Green Sahara's climate was rapidly changing," said Giraudi, "but just before the lake dried up, the people at Gobero would have thought they were living in a golden period."

Then they were gone, leaving only bones and a few artifacts to bear witness. On my last day at Gobero, Sereno and his colleagues began excavating a particularly poignant burial containing three skeletons. Several members of the dig team interrupted their own work to watch. Soon a few of the Tuareg abandoned their late afternoon tea and wandered over, and a couple of soldiers joined the group. Evening breezes began to sweep away the desert's intense heat. As the sand was carefully brushed away, a petite Tenerian woman came into clear relief, lying on her side. Facing her were the skeletons of two children. Their molars suggested they were five and eight years old when they died. Each child reached tiny arms toward the woman. Her fragile arm bones reached back to them. Between the skeletons lay a cluster of disarticulated finger bones, implying the deceased had been laid to rest holding hands.

Was this a mother and her children? Had a grieving father posed his family in this gesture of love before covering them with sand? The questions rippled around the graveside in English, French, Tamashek, and Hausa. The skeletons exhibited no clear signs of trauma, though four arrowheads turned up near the bones, perhaps part of a burial ritual. But if their deaths weren't violent, how did they all die at the same time? If it was a disease or a plague, who would have been left to bury the bodies in such an elaborate fashion? Maybe, someone suggested, they drowned in the lake.

Back in Arizona, Stojanowski continues to analyze the Gobero bones for clues to the Green Saharans' health and diet. Other scientists are trying to derive DNA from the teeth, which could reveal the genetic origins of the Kiffian and Tenerian—and possibly link them to descendants living today. Sereno and Garcea estimate a hundred burials remain to be excavated. But as the harsh Ténéré winds continue to erode the dunes, time is running out. "Every archaeological site has a life cycle," Garcea said. "It begins when people begin to use the place, followed by disuse, then nature takes over, and finally it is gone. Gobero is at the end of its life."

In February of 2007, as the team was making plans to return to Niger, hostilities broke out again between some of Niger's Tuareg groups and the government. By December, Human Rights Watch had reported scores of soldiers and civilians had been killed or injured in clashes and by land mines. The government declared emergency rule in the region, prohibiting foreigners from traveling to the Ténéré. Sereno and Garcea were forced to cancel the 2007 and 2008 dig seasons. Meanwhile, the wind blows across Gobero, and the desert continues to consume the last remnants of the Green Sahara.