Washington, August 15 : The excavation of over 200 burials in an ancient cemetery in Uganda, has shed new light on the period when the Sahara desert was lush green.
According to a report in National Geographic News, 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.
The scientists eventually uncovered 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 B.C.) and the Tenerian (5200 to 2500 B.C.) cultures, according to a new study led by Sereno of the University of Chicago.
The "watershed" 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.
Sereno and colleagues have also made several dinosaur discoveries in the region, including the bizarre cow-like dino Nigersaurus and the bus-size SuperCroc.
According to Sereno and colleagues, 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.
Between 6200 and 5200 B.C., one of the most severe climatic fluxes in that period's history dried out the land and forced people out, according to the researchers.
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. Radiocarbon dating of the bones has provided an "outstanding record" of the ancient Saharans," said Sereno. "We have the Green Sahara written in those sand dunes, and the people who lived in it," he added.
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 B.C., though probably no more than ten feet deep (three meters), according to Sereno. The bones of catfish and tilapia in Tenerian burials suggest the lake was shallower later in the Holocene.