The tiny skeletal hand jutted from the sand as if beckoning the living to the long dead.
For thousands of years, it had lain unheeded in the most desolate section of the Sahara, surrounded by the bones of hippos, giraffes and other creatures typically found in the jungle.
A chance discovery by a team of American scientists has led to the unearthing of a Stone Age cemetery that is providing the first glimpses of what life was like during the still-mysterious period when monsoons brought rain to the desert and created the "green Sahara."
The more than 200 graves that have been explored so far indicate that, beginning 10,000 years ago, two populations lived on the shores of a massive lake, separated by a 1,000-year period during which the lake dried up.
Among the scientists' most surprising discoveries has been a poignant burial tableau of a woman and two children with fingers intertwined, a find that is putting a surprisingly human face on the little-known people who enjoyed a brief visit to Eden in what is normally one of the most forbidding places on Earth.
The first to settle the area was a group of tall, powerfully built hunters, gatherers and fishermen called the Kiffian, University of Chicago paleontologist Paul Sereno said at a news conference Thursday.
The group that followed the Kiffian was a physically smaller band of pastoralists called the Tenerian, who relied on fishing and hunting but also herded cattle, he said.
"They've managed to find these people," said archaeologist Anne Haour of the University of East Anglia in Britain, who was not involved in the research. "We've always suspected something was going on, but this is the first time it has been properly documented."
In addition to the graves, researchers found a massive collection of the remains of meals, tools, pots and other artifacts -- the detritus of everyday life.
"This is a real find . . . for a time period that is not very well documented in that part of the world," said archaeologist Kathy Schick of Indiana University's Stone Age Institute. "It's just a gold mine of information."
The new findings were published Thursday in the online journal PLoS One and in the September issue of National Geographic magazine.
The Sahara has been a desert for untold millenniums. But about 12,000 years ago, a faint wobble in Earth's orbit and some other factors caused Africa's seasonal monsoons to shift slightly north, bringing rains to the Sahara and greening it from Egypt in the east to Mauritania in the west.
About 8,000 years ago, the rains retreated, leaving the region arid once more and causing it to be abandoned. A thousand years later, the rains returned for two more millenniums, before again retreating.
The newly discovered site, called Gobero after the Tuareg nomads' name for the area, lies deep in Niger's Tenere Desert, a large region in the still larger Sahara. The site lay unobserved and untouched because it was literally "in the middle of nowhere," Sereno said. "There is absolutely no reason for anyone to go there."
Sereno had a reason: a nearby table of 110-million-year-old sandstone "that has more dinosaurs in it of high quality than any other rock in the continent of Africa."
In 2000, Sereno and a small group of colleagues were on one of their periodic forays in which they would load up a Land Rover and travel as far from their main site as they could in one day, looking for dinosaur bones.
"We were at the end of our rope," Sereno said, nearly out of water and ready to turn around, when he spotted a stone formation sticking up in the distance and decided to go a little farther.
When they got there, they found animal bones scattered on the surface, exposed by the weather. Photographer Mike Hettwer wandered off to a trio of small dunes, then rushed excitedly back to the group.
"I found some bones," he told them. "But they're not dinosaurs. They're human."
The hand, probably belonging to a child, stood out amid the flat landscape, its finger bones blackened but intact. The researchers saw parts of dozens of human skeletons, including jawbones with nearly full sets of teeth and skullcaps like serving dishes filled with sand.
The group "tiptoed in and saw a dozen skeletons" but didn't disturb anything, Sereno said. "I realized we were in the green Sahara."
They left the site alone for three years while Sereno continued his dinosaur excavations. He had originally intended to turn it over to archaeologists while he concentrated on more ancient discoveries, "but it turns out there were a lot of things calling to me from the site."
Eventually, he assembled a team and excavated for three seasons, before being kept out of the area in 2007 and 2008 because of clashes between the Tuareg and government troops.
One of the experts he took with him was archaeologist Elena Garcea of the University of Cassino in Italy, a pottery expert who has spent three decades working in northern Africa.
She immediately spied small potsherds inscribed with a pointillistic pattern characteristic of the nomadic Tenerian, who lived 6,500 to 4,500 years ago.
But she quickly found others that had a wavy, zigzag pattern characteristic of the Kiffian, who lived 10,000 to 8,000 years ago.
That dichotomy continued throughout the excavations. One group of graves contained individuals who averaged more than 6 feet tall, with some as tall as 6 feet 8. These individuals, the Kiffian, were folded in tight burial arrangements with their knees against their chests and arms at their sides, almost as though they had been buried in burlap bags.
Accompanying the graves were remains of elephants, giraffes, hartebeests, wart hogs and pythons, as well as abundant 6-foot-long, 300-pound Nile perch, which indicated the presence of a deep lake at the site during the period.
The team found harpoon points and fishing hooks as well as stone tools associated with the Kiffian. Their bodies were heavily muscled and robust, suggesting that they were active fishermen.
Bodies in the other graves were shorter and more slender, characteristic of pastoralists who did less fishing and more herding. The same animals, as well as a small number of cattle, were associated with them, but the fish were smaller catfish and tilapia, suggesting that the lake was shallower during their occupation.
Among the Tenerian graves was a heart-rending burial tableaux: A young woman was lying on her side. Pollen under her body suggested that she was placed on a bed of flowers. Lying on their sides facing her were two young children, their fingers interlocked with hers, leaving a tangle of bones.
One girl in another Tenerian grave had an upper-arm bracelet carved from a hippo tusk, the first such find on a female. A male was buried sitting on the shell of a turtle, and another was interred with his head resting on a clay vessel. Researchers can only speculate about the reasons for such ritualistic poses.
It is not clear how they died. Two arrowheads were associated with the woman buried with the two children, Sereno said, but there is no evidence of trauma on her skeleton. The team is running DNA tests to confirm whether they are mother and children.
Radiocarbon dates from the teeth indicate that the larger people were Kiffian, from the early greening period. Dates from the more gracile people indicate they were Tenerian, from the later period.
Haour didn't find it surprising that the same site was occupied at different times by such widely disparate peoples. "We repeatedly find that favorable locations are occupied time and time again."
Travel in time
View a video and photo gallery of the Sahara dig at