Scientists Find Ancient Fossil Reef

By MALCOLM RITTER AP Science Writer MAY 04, 2000 - A new study shows ancestral humans began living along a coast as much as 10,000 years earlier than previously known and suggests they may have left Africa along the Red Sea rather than going up the Nile River valley as is traditionally assumed. The conclusions come from what scientists say is the earliest well-dated example of an oyster bar: a fossil reef on Africa's Red Sea coast where humans apparently waded out to collect oysters, clams and crabs some 125,000 years ago. The site, in Eritrea, contains stone tools along with shells but no remains from whoever made the tools. The tools' makers were probably early anatomically modern humans, said Robert Walter of the Center for Scientific Investigation and Higher Education in Ensenada, Mexico. He led the study published in today's issue of the journal Nature. The tools include small stone blades and hand-size, teardrop-shaped stones with sharpened edges. The early humans may have used the tools to remove shellfish from boulders and to crack or pry open shells. Researchers also found fossils of large land mammals such as elephants, rhinos and hippos. The ancient humans may have trapped the animals against the sea and butchered them there, Walter said. A site in South Africa also shows signs that ancient humans lived along a coast and harvested shellfish. The researchers noted evidence that this site is 10,000 years younger than the Eritrea site. But in interviews, other experts put the difference at about 5,000 years. So the Eritrea site is not markedly older, they said. In either case, the two sites show that coastal living spread rapidly in Africa, though it probably didn't begin at the Eritrea site, Walter said. Since that site falls within the dimly understood period when anatomically modern humans arose, the work suggests that coastal sites could reveal new information about the early days of the species, he said. Walter said he suspects the species arose inland and then migrated to the coasts, perhaps driven by climate changes that dried up rivers and lakes. Eventually their coastal settlements may have spread out so much that some settlers left Africa at the northern or southern edge of the Red Sea, using an ancient land bridge, he said. Sally McBrearty, an archaeologist at the University of Connecticut at Storrs, said she isn't convinced that humans were harvesting shellfish at the Eritrea site. Just finding stone tools with shells is not enough for that conclusion, she said. For example, it is not clear whether the humans really left the tools there when the shellfish were alive, she said.