A study of chimpanzees' use of hammers to open nuts in western Africa may provide fresh clues to how tools developed among human ancestors.

A paper published in the May 24 issue of the journal Science documents the first archaeological examination of a non-human primate workplace and establishes new links between the use of tools by chimpanzees and similar developments among human ancestors (hominids). The research was supported in part by the National Science Foundation (NSF). The research site is in the Tai Forest, about 375 miles west of the capital of the Ivory Coast, Abidjan.

A team from George Washington University (GWU) and the Max Planck Institute for Evolutionary Anthropology of Leipzig, Germany (which provided the primary funding for the work) studied a site where chimpanzees had carried in stone hammers from nearby areas to open nuts on tree roots, which they used as anvils. The researchers last fall, recovered 479 stone pieces, chips of granite, laterite, feldspar and quartz broken from the hammers.

"Some of the stone by-products of the chimpanzee nut cracking are similar to what we see among the technologically simplest Oldowan [hominid] sites in East Africa," said rainforest archaeologist Julio Mercader of GWU, the lead author of the journal article, titled "Excavation of a Chimpanzee Stone Tool Site in the African Rainforest."

Other scholars have documented similarities between the hammers used by chimpanzees to open nuts and those used by hominids, but no researchers have used the techniques of human archaeology on non-human primate sites, Mercader said.

The researchers have proved "archaeology to be a feasible method of uncovering past chimpanzee sites and activity areas in rainforest environments. This introduces the possibility of tracing the development of at least one aspect of ape culture through time," said Mercader, a visiting assistant professor at GWU.

Melissa Panger, a GWU post-doctoral research fellow who receives support through NSF's Integrative Graduate education and Research Traineeship (IGERT) program, said the discovery could help archaeologists establish new dates for tool development. She and Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology co-authored the paper with Mercader.

"We know that flaked stone tools were used 2.5 million years ago, but stone tools may have been used by hominids as much as 5 million years ago," Panger said. "If we look for assemblages of stone pieces like those we have found left behind by the chimpanzees, we can infer that those assemblages may relate to tool use, even if we don't have the tools themselves."

Mark Weiss, NSF program director for physical anthropology said, "Understanding the activities of our early ancestors involves a lot of detective work. Mercader, Panger and Boesch's work is an ingenious approach to trying to tease out more information from the archaeological record-trying to flesh out the context of the earliest flake assemblages."

-NSF-