Researchers have discovered remnants of a chimpanzee stone age while working along a riverbank in West Africa. This evidence, found in the middle of a rain forest, indicates that the chimpanzee Stone Age started at least 4,300 years ago. This is the first time researchers have found indications of prehistoric ape behavior.
The researchers found over 200 artifacts in Tai National Park, Ivory Coast. They have said that most of these artifacts were used by prehistoric chimps to crack nuts open. Archaeologist Julio Mercader and his colleagues, who found the artifacts, say that the chimps put the nuts on the flat side of one rock, and then smashed the shells with a second rock.
Of this shell-smashing technique, Mercader says “I’d predict that this type of simple bashing technology goes back to a common ancestor of chimps and humans around 6 million years ago.”
The findings of Mercader and his crew will be presented in an upcoming Proceedings of the National Academy of Sciences.
In 2001 and 2003, the researchers excavated three West African sites. The majority of the artifacts came from the site called Noulo. The archaeologists used radiocarbon measurements of burned wood in the soil to determine the artifacts’ age.
To determine whether or not the artifacts were tools, Mercader and two experts in Stone Age Tools (who will co-author the upcoming article about the artifacts) compared them to stones found at other sites. They used stones from a 5,000 year old human occupation in Canada and tones from the Canadian Rockies which were only altered by geological forces. In almost all cases, the experts could tell that the West African rocks and the ones from the ancient settlement were intentionally modified.
After looking at the full set of specimens from the West African sites the team concluded that most of them represent the hammering of one stone against another. They weighed between 2.2 and 19.8 pounds.
The team saw evidence that people apparently struck flakes off of some of the stones. Mercader thinks that people probably visited the riverbank sites sporadically.
When speaking about the possibility of older chimp artifacts archaeologist Alison S. Brooks of George Washington University in Washington D.C. says “There is no reason why future work should not reveal evidence of even older chimpanzee sites.”
The evidence found by Mercader and his colleagues does provide a “fairly solid case” for prehistoric chimps having used stones to crack nuts, but archaeologist John J. Shea, of State University of New York at Stony Brook believes that the chimps came up with the technique on their own, and not from a common human-chimp ancestor. Either way, these findings could give us clues about the species’ evolution.
“Chimpanzee Stone Age: Finds in Africa Rock Prehistory of Tools” (http://www.sciencenews.org/articles/20070217/fob1.asp)