17 August 2008
Ancient cemetery found in the Sahara desert
Dinosaur hunters have stumbled across the largest and oldest Stone Age cemetery in the Sahara desert. Paleontologist Paul Sereno and his team were scouring the rocks between harsh dunefields in northern Niger for dinosaur bones in 2000 when they stumbled across the graveyard, on the shores of a long-gone lake. Excavation seasons in 2005 and 2006 have revealed 200 burials of two vastly different cultures that span five thousand years — the first time such a site has been found at a single site.
Called Gobero, the area is a uniquely preserved record of human habitation and burials from the Kiffian (7700 to 6200 BCE) and the Tenerian (5200 to 2500 BCe) cultures, says a new study led by Sereno of the University of Chicago. The find also offers a new window into how these tribes lived and buried their dead during the extreme Holocene period, when a grassy Sahara dried up in the world's largest desert.
One of the most striking discoveries was what the research team calls the 'Stone Age Embrace': A woman, possibly a mother, and two children laid to rest holding hands, arms outstretched toward each other, on a bed of flowers.
A wobble in Earth's orbit—along with other environmental factors that occurred about 12,000 years ago—brought intense monsoons to the Sahara, greening the desert and attracting a wave of human inhabitants, according to Sereno and colleagues. Scientists already knew that the hunter-gatherer Kiffian occupied the region during a temperate phase. Between 6200 and 5200 BCE, one of the most severe climatic fluxes in that period's history desiccated the land and forced people out, the authors say. Soon afterward a second group arrived, the Tenerian.
But evidence of such population shifts rested largely on tool artifacts, with few human skeletons to analyze—until now.
The team discovered that the older group, the Kiffian, were buried with harpoon points and bone fishhooks, along with 6-foot (1.8-meter) Nile perch skeletons. The presence of the fish bones and tools suggested the lake water was deeper around 7000 BCE, though probably no more than ten feet deep (3 meters), Sereno said. A ridge on a male Kiffian thighbone also told bioarchaeologist Chris Stojanowski of Arizona State University that the people had huge leg muscles, likely from a high-protein diet and strenuous lifestyle.
The Tenerian thighbone, on the other hand, had a smaller ridge, indicating a smaller build. To adapt to an arid climate, Tenerians had a more diverse palate, including clams, fish, and savanna animals, the study says. Their burials often included jewelry or ritual poses. For example, one girl had an upper-arm bracelet carved from a hippo tusk. 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. The most striking find occurred in 2006, when the researchers uncovered what they say is Africa's first triple burial. A petite, 40-year-old Tenerian woman lay on her side, facing two children, an 8-year-old and a 5-year-old. Their entwined arms reached out and their hands clasped in an embrace. These individuals died from undetermined causes 5,300 years ago.
Stefan Krõpelin, of the Institute of Prehistoric Archaeology at the University of Cologne, finds the site impressive. But he points out that it is a single location situated in a unique landscape at the foot of the Aïr Mountains, and shouldn't be linked to broader ancient climatic changes in the Sahara. Krõpelin doubts there will be much support for the theory of a thousand-year break in rainfall throughout the entire Sahara around 6200 to 5200 BCE. But Sereno said that the general climate record, bolstered by lake-core samples and solid animal and pollen evidence, points to this "arid interruption" period that separates the Kiffian and Tenerian.
Sources: National Geographic News, ScienceNews, The New York Times (14 August 2008), Associated Press, Fox News (15 August 2008)