Chimps are man's closest relative; if other aspects of their biology and anatomy were not enough, DNA analysis came with the most solid proof.

The research of their behavior helps us figure out how human behavior evolved.

Chimpanzees are well-known toolmakers; only chimps and humans have a tool culture: one generation transmits behavioral skills to another by teaching-learning, not through their genes. That's why chimp populations present an extremely varied tool use.

Only one population in Ivory Coast uses stones to crack nuts.

In Gombe National Park (Tanzania) chimps employ sticks to fish termites out of mounds.

For the first time, great apes have been observed making and using tools to hunt mammals, according to a new study.

Chimpanzees are also the only apes that hunt, bare-handed, from baboon offspring to warthog piglets and colobus monkeys.

But a new finding took the researchers by surprise and offered some clues about the evolution of hunting behavior in our species: chimps using tools to hunt in the Senegalese savanna. The scientists recorded on 22 occasions wild chimpanzees designing "spears" from sticks, to kill small primates named lesser bush babies (a kind of lemurs) (photo below).

The chimpanzees broke off a branch at one or two ends and, frequently, sharpened one end with their teeth. The tool was jabbed into tree hollows where bush babies sleep. The "spears", on average, were about 24 inches (60 centimeters) long and 0.4 inch (11 millimeters) around. "Almost without fail, every time they would withdraw the tool, they would sniff it or lick it, and then proceed to stab it in there again," said lead researcher Jill Pruetz, an anthropologist with Iowa State University. "And they did it so forcibly that our assumption is the bush babies would have been injured if there were always bush babies in the hollow," she continued.

In one case, a chimp was seen successfully extracting with the spear a bush baby, which was subsequently tore apart and eaten, but the researchers could not say if the small primate was already dead or not. "But it didn't make any vocalizations, didn't attempt to escape-that sort of thing. So we are hypothesizing they are using the tools to incapacitate the bush babies", said Pruetz.

Primatologist Craig Stanford, of the University of Southern California (USC), not participating in the study, said the 22 observed instances of spearmaking are "stunning good evidence."

But only "one actual kill-and no visual evidence of the spear being used as a spear-weakens it," he said. "There's never really been any evidence or suggestion that chimps would use weapons when they were hunting," he said. "But we've never discovered chimp populations that made the cognitive leap to put those two [skills] together and use weapons to assist in their hunting," Stanford said. "What makes the discovery all the more remarkable is who the hunters are: predominantly mature females and immatures-youngsters between about two and ten years old", said Pruetz.

"We don't think of chimpanzee hunting in terms of the females and immatures. It also suggests that females played a role in the evolution of tool use and hunting among early human ancestral species," she added.

More significant, the Senegalese research site is a savannah similar to the habitat where our early ancestors are thought to have evolved few millions of years ago. "Looking at our closest living relatives in a habitat that is fairly similar to what we see characterizing early hominids six million years ago can help researchers understand early human ancestors' behavior and ecology", she said.

Stanford likens chimpanzees to a window to a past poorly preserved in the archaeological record. "Hunting is something that the chimps do that almost certainly early, early hominids did too. They were just using a material-wood-that does not leave any archaeological trace," said Stanford.

Stanford disagrees with the "spear", regarded as too anthropomorphic, preferring the term "bludgeon."

"They seem to be using it to hit the animal hard, and having a point on the end certainly helps. But I think it's not clear whether the point that they made is in fact even sharp enough to penetrate the animal", said Stanford.

Photo credit: P. Steyn