Posted on 05/24/2002 8:01:45 AM PDT by dead
Researchers have discovered a band of chimpanzees in West Africa which use crude stone hammers to crack open nuts, a sophisticated use of tools the monkeys have been teaching to each new generation for more than a century.
Using carefully selected stones weighing up to 15kg, the chimps pound the tough shell of the panda nut to extract a high-energy kernel that is an important part of the animal's diet, researchers report Friday in the journal Science.
"It is a very skillful behavior that takes up to seven years for them to learn," said Melissa Panger, a George Washington University researcher and co-author of the study. "It looks easy, but if you sit down and try it is a very difficult task."
The panda nuts fall to the ground inside an outer husk. Inside the husk is a golfball-sized nut covered by a shell that can require up to a tonne of pressure to break open. Yet, if the animals pound too hard, the nut shatters and is inedible, Panger said.
"What is remarkable is that they are controlling the force precisely," she added.
Inside the shell are three nutritious kernels. During nut-smashing season, some chimps spend two or three hours a day opening as many as 100 panda nuts. The nuts can provide up to 3,000 calories a day, researchers said.
The chimps establish nut-cracking stations, usually centered on a battered root of a hardwood tree that they use as an anvil.
Panger said the chimps leave the hammer stones beside the anvils and some of the tools have apparently been used for generations. Some animals have been seen carrying pounding stones from one anvil to another, just as a repairman might carry tools from place to place, she said.
Nut cracking demonstrates a degree of sophisticated learning because it required the animals to select hammer stones at a distant rock outcropping and then carry them to the anvil. Panger said selection of the stones requires some thought by the chimps: The crude hammers have to be flat on one side, heavy enough to smash the nuts and have a place to grasp.
"They have to use it without crushing their fingers," said Panger. "Some of these hammers have been used so many times that they have deep pits, suggesting that they have been used for many generations, over and over again."
Mothers teach their children to bang on nuts, and some young chimps have been seen hitting nuts with smaller stones, imitating their parent.
The researchers said the nut-smashing technique is known to only some bands of West African chimpanzees. It has not been seen among chimps in central Africa, although the apes there have nuts and stones available to them.
This suggests that nut smashing is a cultural, learned behavior that has not spread widely among the apes.
"There has to be knowledge of the size and hardness of the rock," said Julio Mercader, another George Washington University researcher and the first author of the study. "And that knowledge is transmitted from chimp to chimp and from generation to generation."
In their research, Mercader and Panger used archaeological methods to dig around an anvil site. They found stone chips that had apparently broken off stone hammers in past generations. Age dating of deposits at one site showed that the apes had used it as nut-cracking station for at least 110 years, Panger said.
She said it is likely that early hominids, the direct ancestors of modern humans, also had nut-cracking sites in Africa and that sharp chips flaking from the stone hammers may have helped humans learn tool making.
"If they were hammering and unintentionally make some of these sharp-edged flakes, then the leap to making a cutting tool is not as great," she said.
Robson Bonnichsen, a stone tool expert at Oregon State University in Corvallis, said humans first began shaping stone tools about 2.5 million years ago and that chips from that work have a distinctive shape, which researchers would not confuse with the pieces of stone randomly broken from stone hammers by chimps.
Bonnichsen said the research by Panger, Mercader and their co-author, Christophe Boesch of Max Planck Institute in Germany, gives important new insights into tool use by primates.
"This is really interesting," he said. "I applaud their work."
AP
We'll know they've become civilized when some of the chimps steal all of the hammer stones and then lend them out to the other chimps in exchange for some of the nuts.
His theory is that we owe our large brains to the adaptation for hunting by throwing rocks at the prey. Lotsa neurons were needed for precise timing of the release, paving the way for language and thought.
Dubya is right on top of this development as part of his globalist "free" trade agenda.
Rock star Bono and US Treasury Secretary O'Neill plug aid for Africa
A true barter system.
Fine, just as long as they don't adapt some half baked, crazed religion that focuses on world domination and heavenly virginal chimpanzees to die for. We don't need that...oh wait a minute, we've already got that problem...never mind.
I ain't got no theory. Hunting is a factor, but my guess is that large brains are a great benefit in warfare. When they get themselves organized, and start using weapons against each other, that's when the selection for better brains will kick into high gear.
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