Chimps share human learning trait

Un-apelike: Georgia researcher finds that animals pass knowledge from one generation to the next, as people do.

By Bill Hendrick
The Atlanta Journal-Constitution
Published on: 09/26/06

Unlike many of their human cousins, chimps aren't chumps.

Scientists have learned that chimpanzees don't just ape the behavior of their fellows, but actually learn from watching it. And then they pass down what they've learned as a cultural trait from generation to generation.

As far as scientists know, this ability is unique to chimps and humans —- though chimps' Homo sapiens cousins often learn by trial and painful error.

"Culture depends on learning from others," said Victoria Horner, formerly a primate behaviorist at the University of St. Andrews in Scotland who's now at the Yerkes National Primate Research Center in the piney wilds of Gwinnett County.

She published her findings in the Aug. 28 issue of the Proceedings of the National Academy of Science with co-authors Frans de Waal, Yerkes' longtime top ape expert, and St. Andrews scholar Andrew Whiten.

Great apes, which include humans, chimps, gorillas, orangutans and bonobos, are so prone to copying each other's behavior than the name "ape" has become synonymous with miming. But Horner said this study was groundbreaking because it showed that a chain of six chimps went beyond simple mimicking and "faithfully and accurately transmitted behaviors" to each other exactly, down a line of individuals.

It "shows behaviors can spread within a group and down a chain of animals without human intervention, so the chimps effectively learn from each other," she said. "The behavior does not degrade when passed along a chain. Researchers knew chimps could copy human behavior, but this research shows how they learn and copy from each other."

What this means, Horner said, is that chimps possess one of the critical skills necessary to create and maintain cultural differences between groups, and that their behaviors become traditions.

Horner and her colleagues set up experiments at the primate center in which they trained a chimp to open a small brown box containing fruit in one of two ways —- either by lifting the lid or by sliding a small door.

After the first chimp learned to lift the lid of the box open to get to the fruit, they let another one watch the "teacher" demonstrate the technique several times. After the teacher was removed, the new chimp was brought in. And it went straight to the box, lifted the lid and got the fruit out the same way its teacher had. This went on through six teacher-student generations.

The same experiment was replicated after another "teacher" retrieved the fruit by sliding open the door. Then another chimp was brought in, who learned to get the fruit just like that teacher had. This went on until it was clear that each chimp consistently carried on behavior learned from the one it had a chance to watch. A control group showed researchers that through trial and error they could discover a way into the box, even without a teacher.

It became obvious that the chimps were transferring knowledge through a chain of simulated generations, Horner said, showing for the first time that chimps exhibit generational learning behaviors just like humans do.

"The chimpanzees in this study continued using only the technique they observed, rather than an alternative method," Horner said. "This finding is particularly remarkable considering the chimpanzees in the control group were able to discover both methods through individual exploration."

Such research is important, de Waal said, because chimps are humans' closest cousins, and by learning more about how they learn, it helps us to understand ourselves.

"Everything in human culture was passed down through the generations," de Waal said. "Now we've shown in the chimps that the learning mechanisms needed to have culture are there."

"This tells us that they're darn near as smart as humans. We share 98.4 percent of our genes. It is important to know what makes us special and not so special," de Waal said. "We are looking at them for clues about how we got to be what we are and why we do what we do."

Find this article at:
http://www.ajc.com/news/content/metro/stories/2006/09/26/meshchimps0926a.html

Hallado en Etiopía el fósil de una niña con rasgos simiescos de hace 3,3 millones de años

EUROPA PRESS
MADRID

20-09-2006

Un equipo de investigadores dirigidos por el Instituto Max Plank de Antropología Evolutiva en Leipzig (Alemania) ha descubierto en Etiopía el fósil de una niña de hace 3,3 millones de años de la especie Astrolopithecus afarensis y que tiene rasgos simiescos. Las conclusiones de su estudio se publican esta semana en la revista Nature.

Los investigadores han descubierto los restos fósiles de una niña de esta primitiva especie humana, a la que pertenece el fósil de Lucy. El esqueleto representa el descubrimiento de los primeros restos infantiles en este periodo de la evolución humana, lo que lo convierte en el niño más antiguo descubierto hasta el momento.

Caminaba erguido

El fósil, que posee 3,3 millones de años de antigüedad, y fue descubierto en una excavación en Dikika (Etiopía), pertenece probablemente a una niña que tenía no más de tres años cuando murió. Las características del esqueleto apoyan la teoría de que el Astrolopithecus afarensis caminó erguido, pero los brazos similares a los del gorila sugieren que podría haber tenido la capacidad de balancearse a través de los árboles.

El descubrimiento fue realizado en una región, denominada Formación Hadar, que posee importantes antecedentes de hallazgos fósiles.

Fuente: www.elperiodico.com

Más información: http://www9.nationalgeographic.com/ngm/dikikababy/

http://www.nature.com/nature/focus/hominiddevelopment/index.html

Big chimp refuge offers life with no cages

The Associated Press

ORT PIERCE - Chimps in tutus - it's enough to start Carol Noon on a tirade.

"It's degrading," she says. "It's hard to engender respect for a species when they're sitting there in a tutu."

Noon is gruff, her words are clipped and it's clear she's not fond of human interaction. She refuses to pose for a picture with a baby chimp, saying it's wrong to take one from it's mother for a prop.

But put her around the chimps, her 93 children, and her whole demeanor softens. Her life's work reflects that.

She's managed to do what no one else has done for the endangered species, building what she says will be the largest chimpanzee refuge in the world. When it's complete in 2008, 291 chimps will roam virtually free on 12 islands, dotted with jungle gyms, hammocks, tire swings - and no cages.

They've had enough of cages in their lives, says Noon, who sued the Air Force in 2000 to get custody of 21 chimps. Though she was successful, most of the damage had already been done.

The chimps were poked, injected with diseases and operated on for experiments after the Air Force sold them to The Coulston Foundation, a now-closed biomedical research facility in Alamogordo, N.M.

Noon calls it "the dungeon."
Spitting her words, she says Coulston's lab had the worst history of abuse in the country. It was the only one charged by the U.S. Department of Agriculture for violating the federal Animal Welfare Act four times.

"These chimps have had so many experiments done on them," she says with a sigh.

She says one of the chimps, Dana, donated a kidney to a baboon. Others were fitted in space suits and strapped into centrifuges to see how long it took them to black out. All were isolated - torture for such social beings - and left in cold, tiny cages, too small for them to stand up.

Noon bought the facility when it bankrupted in 2002 and got custody of an additional 266 chimps. Almost immediately, she gutted the place, widening the cages, replacing the bars with mesh to bring in sunlight and giving the chimps blankets, toys and fresh food.

"When I gave out blankets for the first time in New Mexico, a lot of people were afraid of them," she says.

Eventually, Noon started what has become the great American chimp migration as she transports 10 at a time in a custom-built 38-foot trailer, where each animal has its own air-conditioned window seat.

Forming families
She didn't start out wanting to dedicate her life to primates. She watched some in a zoo and was fascinated by their behavior. It sort of snowballed from there.

An anthropologist who got her Ph.D. from the University of Florida, Noon specializes in resocialization and carefully chooses which chimps will go together to form "families" on the islands. But it was her training in 1989 at the Chimfunshi Wildlife Orphanage in Zambia - where the animals were kept in 14-acre enclosures - that Noon says changed everything.

She wanted to bring the same idea back to the U.S.

"It took someone like Carole Noon to rescue the chimpanzees at Coulston," said Jane Goodall, the famed primatologist. "I was absolutely thrilled to see them on the island at the Florida sanctuary. The individual stories of their rehabilitation are truly moving."

On a recent afternoon, Noon tools around the 200-acre compound in a golf cart, a walkie-talkie clipped to her dirty pants and her dog Esther riding in the front seat.

"That's the old lady running for the first time in 40 years," she says proudly, pointing to Lisa, a shiny, black 45-year-old who spent 43 years in labs after she was captured from Africa as a baby.

All around the facility, construction workers are pounding away, hurrying to finish another feeding room or jungle gym. Four of the 12 islands remain unoccupied.

When she bought the land in 1999, her construction company dug the 17-foot deep moats, built the feeding houses and erected the jungle gyms. Almost two years later, the first batch of chimps moved in.

An estimated 200,000 chimps still live in Africa, a rapid decrease from a few million just 50 years ago. The U.S. is home to 2,400 captive chimps, a few hundred of them live in zoos and work in Hollywood. About 1,700 are used in biomedical testing.

Most of the chimps on the island are in their 40s and maybe have another decade left to live. Because Noon doesn't believe in captive breeding, the males have had vasectomies. The animals weigh about 200 pounds and are three times stronger than humans.

Progress, hard work
Since arriving on the islands, the chimps' progress is both subtle and extraordinary.

Tami and Henrietta refused to gain weight, despite the number of high-calorie nutrition drinks they were fed in New Mexico. Here, they developed a bit of a belly. Ebony, who was almost hairless from the waist down, suddenly has hair. Shy, insecure Alice transformed on the ride over, banging on her window to draw the attention of passersby.

Yes, Noon knows them all by name. And they clearly recognize her voice, about 11 congregate at the food house, clamoring for her attention.

"That's Marissa, you can tell by the attitude. That's Ted on the right and Spudnut" she says.

"They're so complicated. If they fight, they pick sides and they make up. They play, they fight, they steal food and share food, they're exactly like a family."

Sarah refuses to share her plastic toy mirror, hiding it in her belly when she isn't gazing at it. Roxy carries around her two stuffed animals - a chimp and a monkey - on her hip and lately has been teaching them to climb.

It takes a staff of 69 to run the two facilities. On Wednesday, about six are busy in the spacious kitchen cutting apples, lettuce, carrots, oranges and of course bananas into large plastic bins. The chimps also eat granola bars, smoothies and juice boxes, but their favorite meal is dinner, when they feast on organic meal replacement bars donated by a local company.

The chimps eat about $160,000 worth of food a year and drink nearly 20,000 gallons of water a day, Noon says.

It takes a small fortune to run the two facilities - though she will close the one in New Mexico once the chimps are all in Florida. Save the Chimps receives no government money, relying solely on donations to fund the $2.5 million a year operation. For $120 a year donors can click on www.savethechimps.org and adopt an animal.

But it's the least we can do for them, says Noon. She recalls the first day she brought the chimps to the islands, how she watched their thick bodies embrace each other, romp on the jungle gyms together and feel grass under their feet for the first time.

"I said to the staff, 'Do you think we'll ever get tired of this?' Four years later, I feel the same way I felt that first day."

Article published Sep 5, 2006
Sep 4, 2006

Fuente: www.gainesville.com

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

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

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

By JOHN NOBLE WILFORD

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