An international team of archaeologists has discovered stone tools used by chimpanzees thousands of years ago to help feed themselves. The same stone tools are used by chimps today, raising the possibility that humans and apes derived from a common ancestor. VOA's Jessica Berman reports.

Stone tools excavated in Taï National Park, Ivory Coast

Chimps that live in the Tai rain forest in Ivory Coast use stone hammers weighing up to 20 kilos to break hard nuts and other specialized stone tools to extract the four or five tiny kernels inside the nuts. It is a behavior that has not changed in thousands of years.

Hedwige Bosch, of with Wild Chimpanzee Foundation in Leipzig, Germany, has studied the chimps' nutcracking behavior.

"People hear this pounding and it's like carpenters if you don't know what it is," she said.

Boesch's husband, Cristophe, and a team led by University of Calgary archaeologist Julio Mercader discovered the 4,300-year-old, irregularly shaped stone hammers. They are virtually identical to ones used by modern-day chimps in the Tai forest.

The experts say the discovery suggests the possibility of a "chimpanzee stone age," the authors write in the Proceedings of the National Academy of Sciences.

Study co-author Huw Barton, of the University of Leicester in Britain, finds the possibility of discovery of a stone-age relic intriguing.

"This is the first time that someone has really looked and tried to find an archaeology of chimps and now we've got a date of 4,300," said Barton. "It's a bit more of an open question now as to how long chimps have been using stone tools, and something that we would normally claim for our own, you know, these are the things that make us human."

Experts say it is not clear whether apes and humans learned nutcracking from a common ancestor or whether they invented it separately. Either way, they say, it provides tantalizing evidence for studies of human evolution.