April 2, 2011 | 7
SACRAMENTO—It is one of the most poignant scenes ever captured in the human fossil record—a woman and two children buried together some 5,300 years ago on a bed of flowers, holding hands. They lived by the shores of a shallow freshwater lake in what is now Niger, at a time when the Sahara was green. A team led by famed dinosaur hunter Paul Sereno of the University of Chicago discovered this burial and hundreds of others at a site called Gobero in the Ténéré Desert, which is part of the Sahara. On April 1, Sereno told attendees here at the annual meeting of the Society for American Archaeology what his team has discovered about Gobero since he unveiled the finds in 2008.
Further excavation at the site, which spans the time from around 10,000 to 5,000 years ago, is on hold until Niger stabilizes politically, but the team has been busy working on materials recovered previously. One area of focus is pollen analysis, because the site preserves a rich pollen record. Sereno and his colleagues concluded that the individuals in the triple burial had been placed atop flowers based on pollen found in the grave. More recently, pollen recovered from a burial of a 10-year-old girl wearing an exquisite bracelet fashioned from a hippo tusk revealed that holly was placed under her feet and head. This holly has not turned up anywhere else at the site.
The team has also been analyzing the hardened plaque on the teeth of the Gobero individuals to piece together what they ate. And studies of pea-size structures called otoliths from fish remains, which preserve annual and seasonal growth rings, reveal when people caught the fish—data that are aiding in the reconstruction of how the Gobero diet changed throughout the year.
Analyses of a skeleton of an adult female, meanwhile, have shown that she was shot in the leg with a stone projectile. Whether the incident was accidental or intentional remains unclear, but Sereno is hoping to figure out exactly what kind of projectile was used. Artifacts found at the site include large projectile points and tiny microliths, as well as a number of different kinds of harpoons—none of which scientists expected to see in a population of this age in this part of the world.
The picture emerging from these and other findings suggests that the ancient Gobero people settled mostly in one place (as opposed to being nomadic), by the shores of this ancient lake. They used a wider variety of tools than previously thought and sustained themselves without growing food. Instead they lived as hunter-gatherers. Meanwhile, at a site just a couple hundred miles north of Gobero called Adrar Bous, people were subsisting as cattle herders. “These were contemporary populations living very differently,” Sereno observes.
Many of these finds might not have come to light if not for the combination of traditional and unorthodox excavation techniques Sereno employed. When his team happened upon the spectacular Stone Age cemetery while hunting for dinosaurs, the archaeologists he contacted about it were not happy. Sereno wanted to incorporate excavation methods he employs when digging up dinosaurs and other fossilized animals, removing blocks of sediment containing the fragile skeletons, covering them with protective plaster jackets and sending them to his lab in Chicago for preparation. He envisioned doing a special kind of preparation that exposes the bones on either side of the slab while preserving the original positions of the bones. "They thought I would destroy the site," he told Scientific American. The usual archaeological approach would be to photograph the skeletons in situ and then remove them bone by bone from their resting spots. Sereno felt it was important to save not just the bones, but also the elaborate poses of the skeletons, the placement of the artifacts, and other precious evidence. “I wanted to preserve it for [Niger]” and minimize the loss of information, he says. Eventually, the original fossils will be returned to Niger and put on public display, and Sereno will keep a cast of the remains.