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Stone-Age graveyard reveals life in a “green Sahara”

Aug. 14, 2008
Courtesy National Geographic Society
and World Science staff

Sci­en­tists in Ni­ger have found the Sa­hara De­sert’s larg­est known Stone-Age grave­yard, which of­fers an un­par­al­leled rec­ord of life when the re­gion was green, the Na­tional Ge­o­graph­ic So­ci­e­ty an­nounced Thurs­day.

Archaeologists work on a grave­site es­ti­mated as 10,000 years old in Go­be­ro, Ni­ger. (Image cour­tesy Nat'l Geo­gra­phic So­ciety) 


Uni­ver­s­ity of Chi­ca­go pro­fes­sor and Na­tional Ge­o­graph­ic Ex­plor­er-in-Re­si­dence Paul Se­re­no, whose team first hap­pened on the site dur­ing a di­no­saur-hunt­ing ex­pe­di­tion, un­earthed the ce­me­tery, ac­cord­ing to the or­gan­iz­a­tion.

Dat­ing back 10,000 years and called Gob­ero af­ter the Tua­reg name for the ar­ea, the site was brim­ming with skele­tons of hu­mans and an­i­mals in­clud­ing large fish and croc­o­diles, re­search­ers said. 

Gob­ero is hid­den away with­in Ni­ger’s for­bid­ding Ténéré Des­ert, known to lo­cal Tua­reg no­mads as a “des­ert with­in a des­ert.” The Ténéré is the set­ting of other dra­ma­tic sci­en­ti­fic find­ings in­clud­ing the 500-toothed, plant-eat­ing di­no­saur Ni­ger­saur­us and the enor­mous ex­tinct croc­o­dil­ia Sar­co­suchus, al­so known as Su­per­Croc.

The dis­cov­ery of the lake­side grave­yard—said to rep­re­sent two suc­ces­sive hu­man popula­t­ions di­vid­ed by more than 1,000 years—is re­ported in the Sep­tem­ber is­sue of Na­tional Ge­o­graph­ic mag­a­zine and the Aug. 14 is­sue of the re­search jour­nal PLoS One

As they ex­plored the site, re­search­ers said, they tip­toed among doz­ens of fos­sil­ized hu­man skele­tons laid bare on the sur­face of an an­cient dune field by the hot Sa­har­an wind. Jaw­bones still clenched nearly full sets of teeth; a ti­ny hand reached up through the sand, its fin­ger bones in­tact. On the sur­face lay har­poon points, pot­sherds, beads and stone tools. The site was pris­tine, ap­par­ently nev­er vis­ited.

“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.”

Two sea­sons of ex­cava­t­ion sup­ported by the so­ci­e­ty even­tu­ally re­vealed some 200 graves clearly be­long­ing to two suc­ces­sive lake­side popula­t­ions, sci­en­tists said. The old­er group, de­ter­mined to be Kif­fian, were hunters of wild game who left ev­i­dence that they al­so speared huge perch with har­poons when they col­o­nized the green Sa­hara dur­ing its wet­test per­i­od be­tween 10,000 and 8,000 years ago. Their tall stat­ure, some­times reach­ing well over 6 feet, was not im­me­di­ately ap­par­ent from their tightly bound bur­i­al po­si­tions.

The more re­cent popula­t­ion was the Tene­r­ian, a more lightly built peo­ple who ap­peared to have had a di­verse econ­o­my of hunt­ing, fish­ing and cat­tle herd­ing, ac­cord­ing to the re­search team. They lived dur­ing the lat­ter part of the green Sa­hara, about 7,000 to 4,500 years ago. Their one-of-a-kind bur­i­als of­ten in­clud­ed jew­el­ry or rit­u­al pos­es—a girl wear­ing an upper-arm brace­let carved from a hip­po tusk, for ex­am­ple, and a stun­ning tri­ple bur­i­al con­tain­ing a wom­an and two chil­dren in a poign­ant em­brace.

“At first glance, it’s hard to im­ag­ine two more bi­o­log­ic­ally dis­tinct groups of peo­ple bur­y­ing their dead in the same place,” said team mem­ber Chris Sto­janowski, a bioar­chae­o­lo­g­ist from Ar­i­zo­na State Uni­ver­s­ity. “The big­gest mys­tery is how they seemed to have done this with­out dis­turb­ing a sin­gle grave.”

Al­though the Sa­hara has long been the world’s larg­est des­ert, a faint wob­ble in Earth’s or­bit and oth­er fac­tors oc­cur­ring some 12,000 years ago caused Af­ri­ca’s sea­son­al mon­soons to shift slightly north, bring­ing new rains to the Sa­hara. From Egypt in the east to Mau­ri­ta­nia in the west, lakes with lush mar­gins dot­ted the form­erly parched land­scape, draw­ing an­i­mals, fish and even­tu­ally peo­ple. Sep­a­rat­ing these two popula­t­ions was an ar­id in­ter­val per­haps as long as a mil­len­ni­um that be­gan about 8,000 years ago, when the lake disap­peared and the site was aban­doned.

Dat­ing the sun-bleached bones of fos­sil hu­mans in the Sa­hara has was very hard, re­search­ers said. Us­ing a new tech­nique, the team re­ported it had ob­tained nearly 80 so-called ra­dio­car­bon dates from Gob­ero bones and teeth. Ra­dio­car­bon dat­ing is a meth­od of es­ti­mat­ing the age of bi­o­log­ical ma­te­ri­al based on changes in its con­tent of ra­dio­ac­t­ive car­bon.

Ar­chae­o­lo­g­ist El­e­na Garcea of the Uni­ver­s­ity of Cas­si­no in Italy helped iden­ti­fy the site’s poorly known cul­tures so well-pre­served at the site. Garcea, an ex­pert in an­cient pot­tery who has spent nearly three dec­ades dig­ging at Stone Age sites in north­ern Af­ri­ca, trav­eled with Sereno in 2005 to the site. She re­calls stand­ing there amazed, gaz­ing at far more hu­man skele­tons than she had seen in all her pre­vi­ous digs com­bined.

She quickly homed in on two dis­tinct types of pot­tery, one that bore a pointil­lis­tic pat­tern linked with the Tene­r­ian and anoth­er that had wavy lines and zigzags. “These are Kif­fian,” a puz­zled Garcea told Sereno. “What is so amaz­ing is that the peo­ple who made these two types of pots lived in the same place more than a thou­sand years apart.”

Over the next three weeks Sereno, Garcea and their team of five ex­cavators made a de­tailed map of the site. They ex­humed eight bur­i­als and col­lect­ed scores of ar­ti­facts from both cul­tures. In a dry lake bed near­by, they found doz­ens of Kif­fian fish hooks and har­poons carved from an­i­mal bone as well as skele­tal re­mains of mas­sive Nile perch, croc­o­dile and hip­po.

A year lat­er, a sec­ond round of ex­cava­t­ion turned up more rid­dles, re­search­ers said. An adult Tene­r­ian male was bur­ied with his skull rest­ing on part of a clay ves­sel; anoth­er adult male was in­terred seated on the shell of a mud tur­tle. 

One bur­i­al, how­ev­er, brought 2006 ac­ti­vity at the site to a stand­still: Ly­ing on her side, the ske­l­e­ton of a pe­tite Tene­r­ian wom­an emerged from the sand, fac­ing the skele­tons of two young chil­dren; their slen­der arms reached to­ward her and their hands were clasped in an ev­er­last­ing em­brace. Sam­ples tak­en from un­der the skele­tons con­tained pol­len clus­ters—taken as ev­i­dence the peo­ple had been laid out on a bed of flow­ers. The team em­ployed a range of new tech­niques to pre­serve this re­mark­a­ble bur­i­al ex­actly as it had been for more than 5,000 years.

Bioar­chae­o­lo­g­ist Sto­janowski an­a­lyzed doz­ens of in­di­vid­u­als’ bones and teeth for clues to the two popula­t­ions. “This in­di­vid­ual, for ex­am­ple, had huge leg mus­cles,” he said of ridges on the thigh bone of a Kif­fian ma­le, “which sug­gests he was eat­ing a lot of pro­tein and had an ac­tive, stren­u­ous lifestyle. The Kif­fian ap­pear to have been fairly healthy—it would be dif­fi­cult to grow a body that tall and mus­cu­lar with­out suf­fi­cient nu­tri­tion.” In con­trast, the fe­mur ridge of a Tene­r­ian male was barely per­cep­ti­ble. “This man’s life was less rig­or­ous, per­haps tak­ing smaller fish and game with more ad­vanced hunt­ing tech­nolo­gies,” Sto­janowski said.

Anal­y­sis of mea­sure­ments on Kif­fian skulls links them to skulls found across north­ern Af­ri­ca, some as old as 16,000 years, Sto­janowski said. The Tene­r­ian, how­ev­er, are not closely linked to these an­cient popula­t­ions. The team is con­tin­u­ing to an­a­lyze Gob­ero bones for more clues to the peo­ple’s health and di­et. A large-scale re­turn ex­pe­di­tion is planned to the site to fur­ther ex­plore the two popula­t­ions that coped with ex­treme cli­mate change.


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Scientists in Niger have found the Sahara Desert’s largest known Stone-Age graveyard, which offers an unparalleled record of life when the region was green, the National Geographic Society announced Thursday. National Geographic Explorer-in-Residence and University of Chicago Professor Paul Sereno, whose team first happened on the site during a dinosaur-hunting expedition, uncovered the site, according to the organization. Dating back 10,000 years and called Gobero after the Tuareg name for the area, the site was brimming with skeletons of humans and animals including large fish and crocodiles, researchers said. Gobero is hidden away within Niger’s forbidding Ténéré Desert, known to local Tuareg nomads as a “desert within a desert.” The Ténéré is the setting of some of Sereno’s key paleontological discoveries, including the 500-toothed, plant-eating dinosaur Nigersaurus that lived 110 million years ago and the enormous extinct crocodilian Sarcosuchus, also known as SuperCroc. The discovery of the lakeside graveyard—said to represent two successive human populations divided by more than 1,000 years—is reported in the September 2008 issue of National Geographic magazine and the Aug. 14 issue of the journal PLoS ONE. As they explored the site, researchers said, they tiptoed among dozens of fossilized human skeletons laid bare on the surface of an ancient dune field by the hot Saharan wind. Jawbones still clenched nearly full sets of teeth; a tiny hand reached up through the sand, its finger bones intact. On the surface lay harpoon points, potsherds, beads and stone tools. The site was pristine, apparently never visited. “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.” Two seasons of excavation supported by the society eventually revealed some 200 graves clearly belonging to two successive lakeside populations, scientists said. The older group, determined to be Kiffian, were hunters of wild game who left evidence that they also speared huge perch with harpoons when they colonized the green Sahara during its wettest period between 10,000 and 8,000 years ago. Their tall stature, sometimes reaching well over 6 feet, was not immediately apparent from their tightly bound burial positions. The more recent population was the Tenerian, a more lightly built people who appeared to have had a diverse economy of hunting, fishing and cattle herding, according to the research team. They lived during the latter part of the green Sahara, about 7,000 to 4,500 years ago. Their one-of-a-kind burials often included jewelry or ritual poses—a girl wearing an upper-arm bracelet carved from a hippo tusk, for example, and a stunning triple burial containing a woman and two children in a poignant embrace. “At first glance, it’s hard to imagine two more biologically distinct groups of people burying their dead in the same place,” said team member Chris Stojanowski, a bioarchaeologist from Arizona State University. “The biggest mystery is how they seemed to have done this without disturbing a single grave.” Although the Sahara has long been the world’s largest desert, a faint wobble in Earth’s orbit and other factors occurring some 12,000 years ago caused Africa’s seasonal monsoons to shift slightly north, bringing new rains to the Sahara. From Egypt in the east to Mauritania in the west, lakes with lush margins dotted the formerly parched landscape, drawing animals, fish and eventually people. Separating these two populations was an arid interval perhaps as long as a millennium that began about 8,000 years ago, when the lake disappeared and the site was abandoned. Dating the sun-bleached bones of fossil humans in the Sahara has was very hard, researchers said. Using a new technique, the team reported it had obtained nearly 80 so-called radiocarbon dates from Gobero bones and teeth. Radiocarbon dating is a method of estimating the age of biological material based on changes in its content of radioactive carbon. Archaeologist Elena Garcea of the University of Cassino in Italy helped identify the site’s poorly known cultures so well-preserved at the site. Garcea, an expert in ancient pottery who has spent nearly three decades digging at Stone Age sites in northern Africa, traveled with Sereno in 2005 to the site. She recalls standing there amazed, gazing at far more human skeletons than she had seen in all her previous digs combined. She quickly homed in on two distinct types of pottery, one that bore a pointillistic pattern linked with the Tenerian and another that had wavy lines and zigzags. “These are Kiffian,” a puzzled Garcea told Sereno. “What is so amazing is that the people who made these two types of pots lived in the same place more than a thousand years apart.” Over the next three weeks Sereno, Garcea and their team of five American excavators made a detailed map of the site. They exhumed eight burials and collected scores of artifacts from both cultures. In a dry lake bed nearby, they found dozens of Kiffian fish hooks and harpoons carved from animal bone as well as skeletal remains of massive Nile perch, crocodile and hippo. A year later, a second round of excavation turned up more riddles, researchers said. An adult Tenerian male was buried with his skull resting on part of a clay vessel; another adult male was interred seated on the shell of a mud turtle. One burial, however, brought 2006 activity at the site to a standstill: Lying on her side, the skeleton of a petite Tenerian woman emerged from the sand, facing the skeletons of two young children; their slender arms reached toward her and their hands were clasped in an everlasting embrace. Samples taken from under the skeletons contained pollen clusters — evidence the people had been laid out on a bed of flowers. The team employed a range of new techniques to preserve this remarkable burial exactly as it had been for more than 5,000 years. Bioarchaeologist Stojanowski analyzed dozens of individuals’ bones and teeth for clues to the two populations. “This individual, for example, had huge leg muscles,” he said of ridges on the thigh bone of a Kiffian male, “which suggests he was eating a lot of protein and had an active, strenuous lifestyle. The Kiffian appear to have been fairly healthy — it would be difficult to grow a body that tall and muscular without sufficient nutrition.” In contrast, the femur ridge of a Tenerian male was barely perceptible. “This man’s life was less rigorous, perhaps taking smaller fish and game with more advanced hunting technologies,” Stojanowski said. Analysis of measurements on Kiffian skulls links them to skulls found across northern Africa, some as old as 16,000 years, Stojanowski said. The Tenerian, however, are not closely linked to these ancient populations. The team is continuing to analyze Gobero bones for more clues to the people’s health and diet. A large-scale return expedition is planned to the site to further explore the two populations that coped with extreme climate change.