jueves, 31 de agosto de 2006

Chimpanzees Can Transmit Cultural Behavior To Multiple 'Generations'

Transferring knowledge through a chain of generations is a behavior not exclusive to humans, according to new findings by researchers at the Yerkes National Primate Research Center of Emory University and the University of St. Andrews, Scotland. For the first time, researchers have shown chimpanzees exhibit generational learning behavior similar to that in humans. Unlike previous findings that indicated chimpanzees simply conform to the social norms of the group, this study shows behavior and traditions can be passed along a chain of individual chimpanzees. These findings, based upon behavioral data gathered at the Yerkes Field Station in Lawrenceville, Ga., will publish online in the August 28 early edition of the Proceedings of the National Academy of Sciences.

Rescued chimpanzee (Pan troglodytes) near Djoum, South Province, Cameroon. (Photo by Brian Smithson / Courtesy of Wikimedia Commons)

Using a research design that simulated transmission over multiple generations, researchers Victoria Horner, PhD, of the University of St. Andrews and the Yerkes Research Center, along with Yerkes researcher Frans B.M. de Waal, PhD, and St. Andrews researcher Andrew Whiten, PhD, were able to more closely examine how chimpanzees learn from each other and the potential longevity of their culture. In doing so, they confirmed that a particular behavior can be transmitted accurately along a chain of up to six chimpanzees, representing six simulated generations equaling approximately 90 years of culture in the wild. A comparative benchmark study with three-year-old human children, conducted by St. Andrews researcher Emma Flynn, PhD, revealed similar results, providing further evidence chimpanzees, like humans, are creatures of culture.

In the study, researchers began by introducing a foraging technique to two chimpanzees, one each from two separate social groups, to train them to open a special testing box one of two ways -- either by sliding or lifting the door -- to reveal fruit inside. Chimpanzees in a third social group, used as the control group, were allowed to explore the testing box but were given no instruction or training to open the testing box. Once each individual animal from the first two social groups proved successful, another animal from the same social group was allowed to observe the process before interacting with the testing box. Once the second animal succeeded, another chimpanzee would enter and observe the technique, and so on down the chain. In the two social groups trained to slide or lift the door, the technique used by the original animal was passed to up to six chimpanzees. The chimpanzees in the control group were able to discover both methods through individual exploration, suggesting the exclusive use of a single technique in the non-control groups was due to behavioral transmission from a previous animal.

"The chimpanzees in this study continued using only the technique they observed rather than an alternative method," said Horner. "This finding is particularly remarkable considering the chimpanzees in the control group were able to discover both methods through individual exploration. Clearly, observing one exclusive technique from a previous chimpanzee was sufficient for transmission of behavior along multiple cultural generations."

This research may contribute to a better understanding of how chimpanzees learn complex behaviors in the wild. "By conducting controlled cultural experiments with captive chimpanzees, we are able to learn more about wild population-specific behavioral differences, thought to represent a form of cultural variation," said Horner. "These findings also show great similarity between human and chimpanzee behavior, suggesting cultural learning may be rooted deep within the evolutionary process."

Further studies by researchers at the Yerkes-based Living Links Center, established in 1997 to facilitate primate studies that shed light on human behavioral evolution, may expand on these findings by examining the cognitive mechanisms involved in cultural learning and the generational transmission of behavior and traditions.

For more than seven decades, the Yerkes National Primate Research Center of Emory University has been dedicated to advancing scientific understanding of primate biology, behavior, veterinary care and conservation, and to improving human health and well-being. Today, the center, as one of only eight National Institutes of Health-funded national primate research centers, provides specialized scientific resources, expertise and training opportunities. Recognized as a multidisciplinary research institute, the Yerkes Research Center is making landmark discoveries in the fields of microbiology and immunology, neuroscience, psychobiology and sensory-motor systems. Research programs are seeking ways to: develop vaccines for AIDS and malaria; treat cocaine addiction; interpret brain activity through imaging; increase understanding of progressive illnesses such as Parkinson's and Alzheimer's; unlock the secrets of memory; determine behavioral effects of hormone replacement therapy; address vision disorders; and advance knowledge about the evolutionary links between biology and behavior.

Fuente: http://www.sciencedaily.com/releases/2006/08/060830075548.htm

Fecha: 30/08/2006

miércoles, 30 de agosto de 2006

Tool Use Observed in 2nd Group of Chimps

ts practice in Cameroon -- 1,000 miles from the first sighting -- suggests it arose independently. By Tony Perry
Times Staff Writer

August 26, 2006

The noise came from the trees: crack, crack, crack.

As the researchers and their village guides crept closer, they saw something that was not supposed to be happening in the Ebo forest in the central African nation of Cameroon: chimpanzees using rocks as hammers to break open tough-shelled nuts.

Previous research had found that kind of tool use only in chimps 1,000 miles away, across the wide N'Zo-Sassandra River in Ivory Coast. Researchers thought the behavior was either a genetic trait or maybe a learned skill passed from one generation to another.

The discovery of tool use among chimps in Cameroon, separated from their cousins in Ivory Coast by the "information barrier" of the river, suggests that the skill was invented independently in each place, according to a study published Tuesday in the journal Current Biology.

Lead author Bethan J. Morgan, a postdoctoral researcher from the San Diego Zoo, and senior research assistant Ekwoge E. Abwe reported seeing three adult chimps breaking coula nuts with quartz stones. When the animals spotted the researchers, a female chimp and a chimp of undetermined gender fled, but a male stayed behind, continuing to break nuts for three minutes.

The ground beneath the coula tree was littered with broken nutshells and quartz stones.

Morgan said the discovery pointed out how little might be known about the chimp subspecies Pan troglodytes vellerosus even as it is in danger of extinction by "bushmeat" poachers.

She said she hoped the find would spark new interest in preservation among environmentalists and African nations. Although the chimp is on a protected list in Cameroon and neighboring Nigeria, poaching is rampant.

Interaction between researchers and hunters has not been pleasant. One group, Morgan said, threatened to burn down the researchers' camp.

"Luckily, other field assistants were wonderful and stayed in the forest and protected the campsite," she said from Cameroon in a telephone interview. "None of these forests are safe."
Fuente: Los Angeles Times, http://www.latimes.com/news/science/la-sci-chimps26aug26,0,1384382.story?coll=la-story-footer

miércoles, 23 de agosto de 2006

Use of stone hammers sheds light on geographic patterns of chimpanzee tool use


In a finding that challenges a long-held belief regarding the cultural spread of tool use among chimpanzees, researchers report that chimpanzees in the Ebo forest, Cameroon, use stone hammers to crack open hard-shelled nuts to access the nutrient-rich seeds. The findings are significant because this nut-cracking behavior was previously known only in a distant chimpanzee population in extreme western Africa and was thought to be restricted by geographical boundaries that prevented cultural spread of the technique from animal to animal. The findings, which involve the most endangered and least-understood subspecies of chimpanzee, are reported by Dr. Bethan Morgan and Ekwoge Abwe of the Zoological Society of San Diego's Conservation and Research for Endangered Species (CRES) and appear in the August 22nd issue of the journal Current Biology, published by Cell Press.

Prior to this discovery, it was thought that chimpanzee nut-cracking behavior was confined to the region west of the N'Zo-Sassandra River in Cote d'Ivoire. Because there are no relevant ecological or genetic differences between populations on either side of this "information barrier," explain the researchers of the new study, the implication had been that nut-cracking is a behavioral tradition constrained in its spread by a physical barrier: It was absent to the east of the river because it had not been invented there. The new finding that chimpanzees crack open nuts more than 1700 km east of the supposed barrier challenges this long-accepted model. According to the authors of the study, the discontinuous distribution of the nut-cracking behavior may indicate that the original "culture zone" was larger, and nut-cracking behavior has become extinct between the N'Zo-Sassandra and Ebo. Alternatively, it may indicate that nut-cracking has been invented on more than one occasion in widely separated populations.

This is one of the first reports of tool use for Pan troglodytes vellerosus, the most endangered and understudied chimpanzee subspecies. It highlights the necessity to preserve the rich array of cultures found across chimpanzee populations and communities, which represent our best model for understanding the evolution of hominid cultural diversity. As such, the new finding promises to both benefit research and inform the conservation of our closest living relative.


The researchers include Bethan J. Morgan of Conservation and Research for Endangered Species (CRES), Zoological Society of San Diego in Escondido, CA and WCS/CRES in Yaoundé, Cameroon; Ekwoge E. Abwe of WCS/CRES in Yaoundé, Cameroon.

They are grateful to the Government of Cameroon for research authorisation, to WWF and WCS in Cameroon for technical support, to the Zoological Society of San Diego, United States Fish and Wildlife Service's Great Ape Conservation Fund, Margot Marsh Biodiversity Foundation and the Of field Family Foundation for continued financial support.

Morgan et al.: "Chimpanzees use stone hammers in Cameroon." Publishing in Current Biology Vol 16 No 16 R632-3, August 22, 2006, www.current-biology.com

Related Dispatch by Richard W. Wrangham: "Chimpanzees: The Culture-Zone Concept Becomes Untidy."

Report Reignites Feud Over ‘Little People of Flores



After the 18,000-year-old bones of diminutive people were found on the Indonesian island of Flores, the discoverers announced two years ago that these were remains of a previously unknown species of the ancestral human family. They gave it the name Homo floresiensis.

Doubts were raised almost immediately. But only now have opposing scientists from Indonesia, Australia and the United States weighed in with a comprehensive analysis based on their own first-hand examination of the bones and a single mostly complete skull.

The evidence, they reported yesterday, strongly supports their doubts. The discoverers, however, hastened to defend their initial new-species interpretation.

The critics concluded in an article in the current issue of The Proceedings of the National Academy of Sciences that the “little people of Flores,” as they are often called, were not a newfound extinct species.

They were, instead, modern Homo sapiens who resemble pygmies now living in the region and, as suggested in particular by the skull, appear to have been afflicted with the developmental disorder microcephaly, which causes the head and brain to be much smaller than average.

The international team of paleontologists, anatomists and other researchers who conducted the study was headed by Teuku Jacob of Gadjah Mada University, who is one of Indonesia’s senior paleontologists.

In the report, Dr. Jacob and his colleagues cited 140 features of the skull that they said placed it “within modern human ranges of variation.” They also noted features of two jaws and some teeth that “either show no substantial deviation from modern Homo sapiens or share features (receding chins and rotated premolars) with Rampasasa pygmies now living near Liang Bua Cave,” where the discovery was made.

“We have eliminated the idea of a new species,” Robert B. Eckhardt, a professor of developmental genetics at Penn State who was a team member, said in a telephone interview. “After a time, this will be admitted.”

That time has not yet come.

Peter Brown, a paleontologist at the University of New England in Armidale, Australia, who was a leader of the team that discovered the “little people” bones, took sharp issue with the new report.

In an e-mail message, Dr. Brown said, “The authors provide absolutely no evidence that the unique combination of features found in Homo floresiensis are found in any modern humans.”

The features he referred to include body size, body proportions, brain size, receding chin, shape of premolar teeth and their roots, and the shape and projection of the brow ridge. But the critics asserted that many of the features in the specimen with the cranium, said to be diagnostic of a new species, are present in the Rampasasa pygmies.

Dr. Brown said the critics’ claim of “the asymmetry of the skull being the result of abnormal growth is fiction.” The skeleton was buried deep in sediment, he said, and this brought on “some slight distortion.”

In response, Dr. Eckhardt said, “Our paper accounts neatly for everything we see in the asymmetry” of the face and other parts of the skeletons.

Dr. Brown said an independent study led by Debbie Argue, an anthropologist at the Australian National University in Canberra, discounted microcephaly as an explanation. He said the report, accepted for publication in The Journal of Human Evolution, “completely supports my arguments for a new species.”

Dr. Argue’s group, which included Colin Groves, also of the Australian National University and an authority on primate taxonomy, wrote that its comparisons of the Flores specimen with modern and early humans, pygmies and microcephalic humans showed it was unlikely that the skull belonged to a microcephalic human or to any known species.

The bones at the center of the controversy were excavated from a limestone cave on Flores, an island 370 miles east of Bali, by Australian and Indonesian archaeologists.

The most complete specimen was estimated to be 18,000 years old, and other remains of as many as seven other individuals ranged from 95,000 to 13,000 years old.

The Floresian adults stood just three and a half feet high and had brains of 380 cubic centimeters, about the size of the apelike human ancestors known as australopithecines, which lived more than three million years ago.

The find was announced in October 2004 in the journal Nature by a group headed by Michael J. Morwood, also of the University of New England. Dr. Brown was the lead author of a companion report that assigned the little people to a new human species.

In the time since, the dispute over the interpretation has often veered in nonscientific directions, sometimes trampling on national pride.

Indonesian paleontologists complained that the Australian scientists took most of the credit for the discovery and put their own stamp on the interpretations. They were also upset by what they said was the limited access they had to the specimens for their own analysis.

The discoverers countered that the Indonesian researchers had mishandled the bones. They also disparaged the quality of the critics’ research, noting that several of their rebuttals were rejected for publication in prominent journals.

On one aspect of the debate, Dr. Brown said, the discovery team has backed down. He had proposed that Homo erectus, an immediate predecessor to Homo sapiens, reached Flores 840,000 years ago and, in isolation, evolved into Homo floresiensis.

“I have moved away from the isolation and dwarfing argument,” Dr. Brown has said. “Seems most likely that they arrived small brained and small bodied.”

In their new report, the critics emphasized the facial asymmetry of the single skull specimen, known as LB1. A team member, David W. Frayer of the University of Kansas, composed split photographs of LB1’s face, combining two left or two right sides as composite faces. The dissimilarities between the original face and the two left or right composites were striking, he said.

Although most faces are not perfectly symmetrical, the scientists said, some of the differences in the two sides of the LB1 face exceeded “clinical norms” and “provided evidence for rejecting any contention that the LB1 cranium is developmentally normal.”

Maciej Henneberg, an anatomist at the University of Adelaide, Australia, and an author of the new report, said that many characteristics of the face point to a growth disorder, but that it would require much more research “to diagnose the specific syndrome present.”

Of 184 syndromes that include microcephaly, 57 cause short stature, and some also include facial asymmetry and dental anomalies. The critics said one of the next steps would be for scientists specializing in developmental disorders to join the hunt for the particular syndrome that afflicted at least one, and perhaps more of the extinct little people.

As for the species question, some scientists said it might take DNA tests to place the Floresians securely within the modern human family or somewhere on a slightly separate branch as a separate species.

Publicado en NEW YORK TIMES: http://www.nytimes.com/2006/08/22/science/22tiny.html?pagewanted=1&_r=2