WASHINGTON, Feb. 13 (Xinhua) -- Researchers have
found evidence that West African chimpanzees used stone tools to crack nuts
4,300years ago, pushing chimpanzee tool use back thousands of years and
indicating Chimpanzees also have their own Stone Age, according to a research
published Tuesday on the journal Proceedings of the National Academy of
Sciences.
The international team, led by Julio Mercader,
Department of Archaeology, University of Calgary, Canada, suggests that
chimpanzees developed this behavior on their own or inherited the trait from a
common ancestor with humans.
Chimpanzees were first observed using stone tools in
the 19th century. Julio Mercader and colleagues found stone tools at the Noulo
site in Ivory Coast, the only known prehistoric chimpanzee settlement. The
excavated stones showed the hallmarks of use as tools for smashing nuts when
compared with ancient human or modern chimpanzee stone tools.
Also, several types of starch grains were found on
the stones, which the researchers say is residue derived from cracking local
nuts.
The tools were found to be 4,300 years old, which, in
human terms, corresponds to the later Stone Age and was before the advent of
agriculture.
The researchers say these findings add further
support to the current body of evidence showing that chimpanzees transmit
cultural information. This type of tool use could have originated with an
ancestor common with humans, instead of arising independently among hominins and
chimpanzees or through imitation of humans.
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