Chimpanzee culture 'confirmed'

Primate experts say they have proven that chimpanzees, like humans, show social conformity.

By training captive chimps to use tools in different ways, they have shown experimentally that primates develop cultural traditions through imitation.

This has long been suspected from observations in the wild, but has not been shown directly.

It suggests that culture has ancient origins, scientists write in Nature.

The study was carried out by a team at the University of St Andrews in the UK and the National Primate Research Center of Emory University in Atlanta, US.

They presented two different groups of chimps with a problem relevant to their wild cousins: how to retrieve an item of food stuck behind a blockage in a system of tubes.

One chimpanzee from each group was secretly taught a novel way to solve the problem. Ericka was taught how to use a stick to lift the blockage up so that the food fell out.

Another female chimp, Georgia, was shown how to poke at the blockage so that the ball of food rolled out of the back of the pipes.

Each chimp was then reunited with its group, and the scientists watched how they behaved.

They found that the chimps gathered around Ericka or Georgia and soon copied their behaviour. By the end of two months, the two different groups were still using their own way of getting at the food and two distinct cultural traditions had been established.

"This is the first time that any scientist has experimentally created two different traditions in any primate," Professor Andrew Whiten of the University of St Andrews told the BBC News website.

"Moreover, it is the first time anyone has ever done this with tool use in any animal."

Ancient origins

The research adds weight to decades of field studies on wild primates suggesting that they have rich cultural traditions unmatched in species other than our own.

Chimpanzees in West Africa, for example, use stones and pieces of wood to crack open nuts for food; but this has never been observed in chimps living in East Africa.

It suggests that the common ancestor of chimps and humans, living some four to six million years ago, probably also had a desire to conform - the hallmark of human culture.

"If both species have elements of culture, it is highly likely the ancient ancestor had too," said co-author Dr Victoria Horner, "so culture probably has a deep-rooted ancient origin."

The research is published in the online edition of the journal Nature.

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Published: 2005/08/22 10:12:11 GMT

Ancient chimps 'used stone tools'

Chimpanzees in West Africa used stone tools to crack nuts 4,300 years ago.

The discovery represents the oldest evidence of tool use by our closest evolutionary relative.

The skill could have been inherited from a common ancestor of chimps and humans, the authors say, or learnt from humans by imitation.

Alternatively, humans and chimps may have developed tool use independently, the Proceedings of the National Academy of Sciences journal reports.

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.

Nut crunch

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.

"Chimpanzee material culture has a long prehistory whose deep roots are only beginning to be uncovered," write the researchers in Proceedings.

The tools were found to be 4,300 years old, which, in human terms, corresponds to the later Stone Age, before the advent of agriculture in the area.

The age of the tools was determined by subjecting charcoal from the same ground layers to the technique of radiocarbon dating.

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Published: 2007/02/13 11:12:29 GMT

Chimpanzees 'hunt using spears'

Chimpanzees in Senegal have been observed making and using wooden spears to hunt other primates, according to a study in the journal Current Biology.

Researchers documented 22 cases of chimps fashioning tools to jab at smaller primates sheltering in cavities of hollow branches or tree trunks.

The report's authors, Jill Pruetz and Paco Bertolani, said the finding could have implications for human evolution.

Chimps had not been previously observed hunting other animals with tools.

Pruetz and Bertolani made the discovery at their research site in Fongoli, Senegal, between March 2005 and July 2006.

"There were hints that this behavior might occur, but it was one time at a different site," said Jill Pruetz, assistant professor of anthropology at Iowa State University, US.

"While in Senegal for the spring semester, I saw about 13 different hunting bouts. So it really is habitual."

Jabbing weapon

Chimpanzees were observed jabbing the spears into hollow trunks or branches, over and over again. After the chimp removed the tool, it would frequently smell or lick it.

In the vast majority of cases, the chimps used the tools in the manner of a spear, not as probes. The researchers say they were using enough force to injure an animal that may have been hiding inside.

However, they did not photograph the behaviour, or capture it on film.

In one case, Pruetz and Bertolani, , from the Leverhulme Centre for Human Evolutionary Studies in Cambridge, UK, witnessed a chimpanzee extract a bushbaby with a spear.

In most cases, the Fongoli chimpanzees carried out four or more steps to manufacture spears for hunting.

In all but one of the cases, chimps broke off a living branch to make their tool. They would then trim the side branches and leaves.

In a number of cases, chimps also trimmed the ends of the branch and stripped it of bark. Some chimps also sharpened the tip of the tool with their teeth.

Female lead

Adult males have long been regarded as the hunters in chimp groups.

But the authors of the paper in Current Biology said females, particularly adolescent females, and young chimps in general were seen exhibiting this behaviour more frequently than adult males.

"It's classic in primates that when there is a new innovation, particularly in terms of tool use, the younger generations pick it up very quickly. The last ones to pick up are adults, mainly the males", said Dr Pruetz, who led the National Geographic-funded project.

This is because young chimps pick the skill up from their mothers, with whom they spend a lot of their time.

"It's a niche that males seem to ignore," Dr Pruetz told BBC News.

Many areas where chimpanzees live are also home to red colobus monkey, which the chimps hunt. However, the Senegal site is lacking in this species, so chimps may have needed to adopt a new hunting strategy to catch a different prey - bushbaby.

The authors conclude that their findings support a theory that females may have played a similarly important role in the evolution of tool technology among early humans.

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Published: 2007/02/22 17:13:50 GMT