Chimp "Stone Age" Finds Are Earliest Nonhuman Ape Tools, Study Says
Humans might not be as pioneering as we're cracked up to be.
That's one possible explanation for new evidence that West African chimpanzees learned to use stone tools on their own to crack nuts at least 4,300 years ago.
The research pushes back chimpanzee tool use thousands of years. It casts into doubt the long-standing theory that direct human ancestors were the only animals to independently develop tools—and that chimps learned to use stone tools by watching humans.
(Follow a time line of human evolution.)
Instead both humans and chimps could have inherited the ability to crack nuts with rocks from a common ancestor, Julio Mercader of the University of Calgary in Canada and co-authors report in today's issue of the Proceedings of the National Academy of Sciences.
Or chimps may have developed the behavior on their own. In either case, it's no longer likely that chimps learned to use stones as tools only by imitating humans.
At 4,300 years old, the chimps' tools correspond to the late Stone Age of human history—before the advent of agriculture in West Africa.
"Until recently people used to say that among modern-day chimpanzees the behavior came from imitation of farmers," Mercader said. "That assumption is no longer valid. What we present predates the presence of farming."
Ancient Nutcrackers
Mercader and colleagues found subtly altered rocks in Côte d'Ivoire (Ivory Coast) in Africa at a research site that houses the only known prehistoric chimpanzee settlement.
(Related news: "Chimp Nut-Cracking Site Offers Clues to Early Tool Use" [May 23, 2002].)
The excavated stones resemble those used by ancient humans and modern chimpanzees to smash nuts—showing evidence of flakes, chips, and worn edges.
Archaeologist Julio Mercader at the University of Calgary has discovered hammer-like tools dating back 4300 years.  The tools are thought to have been used by non-human primates to crack nuts.

The large size of the stones are of too great a weight to have been favoured as tools by humans.  Further, humans are not believed to have been in that area at that time for the primates to have learned from them by observation.

Mercader suggests that this implies the primates learned to use the tools either independently of humans or else by a common ancestor (of common descent). 

Further evidence supporting the hypothesis that the hammers were not used by humans includes that the nut residue on the tools are of nuts which were not regularly a part of a human diet.

Mercader elaborates in a prepared statement: “Some of the nuts require a compression force of more than a thousand kilograms to crack. And the idea is to crack the shell but not smash it — it’s not a simple technique.”  Editorial correction: force is a vector while mass is a scalar. By context, the force is approximately 10KN (10 KiloNewtons).

Social and Political implications follow from the findings also.  Anthropologist Agustín Fuentes (at Indiana’s University of Notre Dame) said, “It puts the nail in the coffin on those who say chimp tool use is atypical.”

This parallel of human evolution may also lead to further debate on the legal rights of primates.