Arquivo da tag: Primatologia

Human Brain Limit of ‘150 Friends’ Doesn’t Check Out, New Study Claims (Science Alert)

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Peter Dockrill – 5 MAY 2021

It’s called Dunbar’s number: an influential and oft-repeated theory suggesting the average person can only maintain about 150 stable social relationships with other people.

Proposed by British anthropologist and evolutionary psychologist Robin Dunbar in the early 1990s, Dunbar’s number, extrapolated from research into primate brain sizes and their social groups, has since become a ubiquitous part of the discourse on human social networks.

But just how legitimate is the science behind Dunbar’s number anyway? According to a new analysis by researchers from Stockholm University in Sweden, Dunbar’s famous figure doesn’t add up.

“The theoretical foundation of Dunbar’s number is shaky,” says zoologist and cultural evolution researcher Patrik Lindenfors.

“Other primates’ brains do not handle information exactly as human brains do, and primate sociality is primarily explained by other factors than the brain, such as what they eat and who their predators are.”

Dunbar’s number was originally predicated on the idea that the volume of the neocortex in primate brains functions as a constraint on the size of the social groups they circulate amongst.

“It is suggested that the number of neocortical neurons limits the organism’s information-processing capacity and that this then limits the number of relationships that an individual can monitor simultaneously,” Dunbar explained in his foundational 1992 study.

“When a group’s size exceeds this limit, it becomes unstable and begins to fragment. This then places an upper limit on the size of groups which any given species can maintain as cohesive social units through time.”

Dunbar began extrapolating the theory to human networks in 1993, and in the decades since has authored and co-authored copious related research output examining the behavioral and cognitive mechanisms underpinning sociality in both humans and other primates.

But as to the original question of whether neocortex size serves as a valid constraint on group size beyond non-human primates, Lindenfors and his team aren’t so sure.

While a number of studies have offered support for Dunbar’s ideas, the new study debunks the claim that neocortex size in primates is equally pertinent to human socialization parameters.

“It is not possible to make an estimate for humans with any precision using available methods and data,” says evolutionary biologist Andreas Wartel.

In their study, the researchers used modern statistical methods including Bayesian and generalized least-squares (GLS) analyses to take another look at the relationship between group size and brain/neocortex sizes in primate brains, with the advantage of updated datasets on primate brains.

The results suggested that stable human group sizes might ultimately be much smaller than 150 individuals – with one analysis suggesting up to 42 individuals could be the average limit, with another estimate ranging between a group of 70 to 107.

Ultimately, however, enormous amounts of imprecision in the statistics suggest that any method like this – trying to compute an average number of stable relationships for any human individual based off brain volume considerations – is unreliable at best.

“Specifying any one number is futile,” the researchers write in their study. “A cognitive limit on human group size cannot be derived in this manner.”

Despite the mainstream attention Dunbar’s number enjoys, the researchers say the majority of primate social evolution research focuses on socio-ecological factors, including foraging and predation, infanticide, and sexual selection – not so much calculations dependent on brain or neocortex volume.

Further, the researchers argue that Dunbar’s number ignores other significant differences in brain physiology between human and non-human primate brains – including that humans develop cultural mechanisms and social structures that can counter socially limiting cognitive factors that might otherwise apply to non-human primates.

“Ecological research on primate sociality, the uniqueness of human thinking, and empirical observations all indicate that there is no hard cognitive limit on human sociality,” the team explains.

“It is our hope, though perhaps futile, that this study will put an end to the use of ‘Dunbar’s number’ within science and in popular media.”

The findings are reported in Biology Letters.

Orangutans Plan Their Future Route and Communicate It to Others (Science Daily)

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Sep. 11, 2013 — Male orangutans plan their travel route up to one day in advance and communicate it to other members of their species. In order to attract females and repel male rivals, they call in the direction in which they are going to travel. Anthropologists at the University of Zurich have found that not only captive, but also wild-living orangutans make use of their planning ability.

Male orangutans face the direction they plan to travel and emit ‘long calls’ in that direction. (Credit: UZH)

For a long time it was thought that only humans had the ability to anticipate future actions, whereas animals are caught in the here and now. But in recent years, clever experiments with great apes in zoos have shown that they do remember past events and can plan for their future needs. Anthropologists at the University of Zurich have now investigated whether wild apes also have this skill, following them for several years through the dense tropical swamplands of Sumatra.

Orangutans communicate their plans

Orangutans generally journey through the forest alone, but they also maintain social relationships. Adult males sometimes emit loud ‘long calls’ to attract females and repel rivals. Their cheek pads act as a funnel for amplifying the sound in the same way as a megaphone. Females that only hear a faint call come closer in order not to lose contact. Non-dominant males on the other hand hurry in the opposite direction if they hear the call coming loud and clear in their direction.

“To optimize the effect of these calls, it thus would make sense for the male to call in the direction of his future whereabouts, if he already knew about them,” explains Carel van Schaik. “We then actually observed that the males traveled for several hours in approximately the same direction as they had called.”

In extreme cases, long calls made around nesting time in the evening predicted the travel direction better than random until the evening of the next day.Carel van Schaik and his team conclude that orangutans plan their route up to a day ahead. In addition, the males often announced changes in travel direction with a new, better-fitting long call. The researchers also found that in the morning, the other orangutans reacted correctly to the long call of the previous evening, even if no new long call was emitted.

“Our study makes it clear that wild orangutans do not simply live in the here and now, but can imagine a future and even announce their plans. In this sense, then, they have become a bit more like us,” concludes Carel van Schaik.

Journal Reference:

  1. Carel P. van Schaik, Laura Damerius, Karin Isler. Wild Orangutan Males Plan and Communicate Their Travel Direction One Day in Advance. PLoS ONE, 2013; 8 (9): e74896 DOI: 10.1371/journal.pone.0074896

Chimpanzees Successfully Play the Ultimatum Game: Apes’ Sense of Fairness Confirmed (Science Daily)

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Jan. 14, 2013 — Researchers at the Yerkes National Primate Research Center, Emory University, are the first to show chimpanzees possess a sense of fairness that has previously been attributed as uniquely human. Working with colleagues from Georgia State University, the researchers played the Ultimatum Game with the chimpanzees to determine how sensitive the animals are to the reward distribution between two individuals if both need to agree on the outcome.

Researchers have shown that chimpanzees possess a sense of fairness that has previously been attributed as uniquely human. (Credit: © Sunshine Pics / Fotolia)

The researchers say the findings, available in an early online edition of the Proceedings of the National Academy of Sciences (PNAS) available this week, suggest a long evolutionary history of the human aversion to inequity as well as a shared preference for fair outcomes by the common ancestor of humans and apes.

According to first author Darby Proctor, PhD, “We used the Ultimatum Game because it is the gold standard to determine the human sense of fairness. In the game, one individual needs to propose a reward division to another individual and then have that individual accept the proposition before both can obtain the rewards. Humans typically offer generous portions, such as 50 percent of the reward, to their partners, and that’s exactly what we recorded in our study with chimpanzees.”

Co-author Frans de Waal, PhD, adds, “Until our study, the behavioral economics community assumed the Ultimatum Game could not be played with animals or that animals would choose only the most selfish option while playing. We’ve concluded that chimpanzees not only get very close to the human sense of fairness, but the animals may actually have exactly the same preferences as our own species.” For purposes of direct comparison, the study was also conducted separately with human children.

In the study, researchers tested six adult chimpanzees (Pan troglodytes) and 20 human children (ages 2 — 7 years) on a modified Ultimatum Game. One individual chose between two differently colored tokens that, with his or her partner’s cooperation, could be exchanged for rewards (small food rewards for chimpanzees and stickers for children). One token offered equal rewards to both players, whereas the other token favored the individual making the choice at the expense of his or her partner. The chooser then needed to hand the token to the partner, who needed to exchange it with the experimenter for food. This way, both individuals needed to be in agreement.

Both the chimpanzees and the children responded like adult humans typically do. If the partner’s cooperation was required, the chimpanzees and children split the rewards equally. However, with a passive partner, who had no chance to reject the offer, chimpanzees and children chose the selfish option.

Chimpanzees, who are highly cooperative in the wild, likely need to be sensitive to reward distributions in order to reap the benefits of cooperation. Thus, this study opens the door for further explorations into the mechanisms behind this human-like behavior.

For eight decades, the Yerkes National Primate Research Center, Emory University, has been dedicated to conducting essential basic science and translational research to advance scientific understanding and to improve the health and well-being of humans and nonhuman primates. Today, the center, as one of only eight National Institutes of Health-funded national primate research centers, provides leadership, training and resources to foster scientific creativity, collaboration and discoveries. Yerkes-based research is grounded in scientific integrity, expert knowledge, respect for colleagues, an open exchange of ideas and compassionate quality animal care.

Within the fields of microbiology and immunology, neurologic diseases, neuropharmacology, behavioral, cognitive and developmental neuroscience, and psychiatric disorders, the center’s research programs are seeking ways to: develop vaccines for infectious and noninfectious diseases; treat drug addiction; interpret brain activity through imaging; increase understanding of progressive illnesses such as Alzheimer’s and Parkinson’s diseases; unlock the secrets of memory; determine how the interaction between genetics and society shape who we are; and advance knowledge about the evolutionary links between biology and behavior.

Journal Reference:

  1. Darby Proctor, Rebecca A. Williamson, Frans B. M. de Waal, and Sarah F. Brosnan. Chimpanzees play the ultimatum game. PNAS, January 14, 2013 DOI:10.1073/pnas.1220806110

Bonobos Will Share With Strangers Before Acquaintances (Science Direct)

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Jan. 2, 2013 — You’re standing in line somewhere and you decide to open a pack of gum. Do you share a piece with the coworker standing to one side of you, or with the stranger on the other?

This is an infant bonobo feeding on papaya. (Credit: Jingzhi Tan)

Most humans would choose the person they know first, if they shared at all.

But bonobos, those notoriously frisky, ardently social great apes of the Congo, prefer to share with a stranger before sharing with an animal they know. In fact, a bonobo will invite a stranger to share a snack while leaving an acquaintance watching helplessly from behind a barrier.

“It seems kind of crazy to us, but bonobos prefer to share with strangers,” said Brian Hare, a professor of evolutionary anthropology at Duke University. “They’re trying to extend their social network.” And they apparently value that more than maintaining the friendships they already have.

To measure this willingness to share, Hare and graduate student Jingzhi Tan ran a series of experiments with bonobos living in the Lola ya Bonobo sanctuary in Kinshasa, Democratic Republic of Congo. The experiments involved piles of food and enclosures that the test subjects were able to unlock and open. Tan and Hare describe their work in a paper in the Jan. 2, 2013 edition of PLOS ONE.

In the first series of experiments, a pile of food was placed in a central enclosure flanked by two enclosures, each of them holding another animal. The test subject had the knowledge and ability to open a door to either of the other chambers, or both. On one side was a bonobo they knew from their group (not necessarily a friend or family member) and in the other was a bonobo they had never really met, but had only seen at a distance.

Upon entering the chamber with the food, the test subjects could easily just sit down and consume it all themselves, or they could let in one or both of the other animals to share.

Nine of the 14 animals who went through this test released the stranger first. Two preferred their groupmates. Three showed no particular preference in repeated trials. The third animal was often let in on the treat as well, but more often it was the stranger, not the test subject, who opened the door for them.

Tan said that by letting the third animal into the enclosure, the stranger voluntarily outnumbered himself or herself with two bonobos who knew each other, which a chimpanzee would never do. In 51 trials of the experiment, there was never any aggression shown, although there was quite a bit of typical bonobo genital rubbing between the strangers.

To isolate how much motivation the animals receive from social interaction, the researchers ran a second set of experiments in which the subject animal wouldn’t receive any social contact with another animal. In the first of these experiments, the subjects couldn’t get any food for themselves regardless of whether they chose to open the door to allow the other animal to get some food. Nine out of ten animals shared with the stranger at least once.

In the final experiment without social contact, the subject animal was given access to the food in such a way that opening the door to share with the other animal would cost them some food. But they still wouldn’t have any social contact as a reward. In this instance, the animals chose not to share. “If they’re not going to see a social benefit, they won’t share,” Hare said.

This second test is similar to something called the dictator game in which humans are given the chance to share cash with a stranger, Hare said. Most people will share anonymously, but they share even more when they aren’t anonymous. Bonobos won’t share at all in the anonymous condition if it costs them food.

“They care about others,” Hare said, but only in a sort of selfish way. “They’ll share when it’s a low-cost/low-benefit kind of situation. But when it’s a no-benefit situation, they won’t share. That’s different from a human playing the dictator game. You really have to care about others to give anonymously.”

The findings, which Hare calls “one of the crazier things we’ve found” in more than a decade of bonobo research, form yet another distinction between bonobos and chimpanzees, our two closest relatives. “Chimps can’t do these tests, they’d be all over each other.”

The work was funded by the National Science Foundation and the European Research Council.

Journal Reference:

  1. Tan J, Hare B. Bonobos Share with Strangers. PLOS ONE, 2013; 8 (1): e51922 DOI:10.1371/journal.pone.0051922

UCSB anthropologist studies reciprocity among chimpanzees and bonobos (UC Santa Barbara)

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20-Nov-2012
By Andrea Estrada

Primate behavior may reveal clues to evolution of favor exchange in humans

Adrian Jaeggi, a postdoctoral researcher in anthropology at UC Santa Barbara, and a junior research fellow at the campus’s SAGE Center for the Study of the Mind, is studying this question of reciprocity, using chimpanzees and bonobos as his test subjects. His findings appear in the current online issue of the journal Evolution & Human Behavior.(Santa Barbara, Calif.) –– When your neighbor asks to borrow a cup of sugar and you readily comply, is your positive response a function of the give and take that characterize your longstanding relationship? Or does it represent payment –– or prepayment –– for the cup of sugar you borrowed last week, or may need to borrow a month from now?

“The article focuses on the question of whether individuals do favors because they expect them to be reciprocated at some other time, and, more specifically, whether such exchanges have to happen immediately, or can take place over longer time spans,” Jaeggi explained. “We studied the question in chimpanzees and bonobos –– our two closest living relatives –– and looked at the exchanges of grooming and food sharing, which are two common types of favors among these apes.”

Two female chimpanzees take food from a male (center).

According to Jaeggi, while results of his research provide some evidence for immediate exchanges, they more strongly support the notion that favors are exchanged over long periods of time. Calculated exchanges, in which individuals keep a detailed score of past interactions, are much less common than the more loosely balanced exchanges that take place in stable relationships.

“In the chimp group we studied, we knew there was a lot of this long-term exchange,” said Jaeggi. “We didn’t find any evidence for a short-term effect.” Chimpanzees live in stable social groups, he continued, and have a relatively long life span. They recognize others in the group, form long-term relationships, and associate with individuals who have helped them in the past.

“In the wild, for example, chimps hunt for smaller monkeys, and they commonly share the meat. It’s similar to what hunters and gatherers do,” Jaeggi said. “Our experiment is meant to mimic the situation in which you have a large monopolized food item.” Using grooming as the favor, the researchers studied whether or not a chimp that had just been groomed was more likely to share food with the pal who had groomed him. “That would provide evidence for keeping track of who has done a favor,” Jaeggi said. However, grooming releases endorphins, he added, and that general sense of wellbeing on the part of the food owner might lead to more indiscriminate food sharing.

One female bonobo rests her hand on another’s shoulder.

Bonobos, on the other hand, presented a different result. While chimpanzees have a formalized dominance hierarchy, food is available to most individuals, no matter what their group status. That is not the case with bonobos. Bonobos don’t establish formal hierarchies, so they don’t know on an individual basis where they fit within the group. Also, they don’t form coalitions as much as chimpanzees do. “The food sharing situation sort of freaked them out,” said Jaeggi. “All of a sudden there’s all this food that’s owned by one individual, and they don’t really know what to do about it. They want to get it, but they don’t dare, because they don’t know what the consequence will be.””We found that sharing was predicted by who the chimps’ long-term friends and partners were,” he said. “Grooming just before didn’t play a role. Food owners didn’t share specifically with their groomers. Nor did the groomers act in return. They didn’t pay for the food, and they didn’t reward the food owner’s generosity afterward.”

Jaeggi added that bonobos did a lot more grooming, most likely because they sought the calming effects of the endorphins. “And there we did see an effect of grooming on sharing,” he said. “Chimps would go and take food pretty confidently, but Bonobos were more reticent. They’d reach out and then groom. It seemed to be that they’d groom to release tension, and then there would be these short-term reciprocal exchanges.”

But even those exchanges seem to be more a byproduct of the need to reduce tension, he noted, rather than short-term contingencies used to establish reciprocity.

So, what do these findings tell us about ourselves? Jaeggi suggests we should take seriously this evidence of long-term reciprocity in animals. “It’s really not qualitatively different from what people do,” he said. “They establish these lasting relationships, and within them, services are exchanged without the participants keeping close track of who’s doing what for whom.”

However, humans also have the capacity for more contingent reciprocity, which raises questions about its purpose, and how it developed. “Maybe that’s something that’s more culturally learned,” said Jaeggi.

What do chimps and humans have in common? Gut bacteria (MSNBC)

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It’s nearly identical, and suggests patterns evolved before the two split and went own ways

Chimpanzees at Gombe Stream National Park in Tanzania have a lot in common with humans. And they both like to eat, apparently. Photo: Ian Gilby

By Stephanie Pappas

updated 11/13/2012 3:30:35 PM ET

 

Humans share about 99 percent of our genomes with chimpanzees. Now, research finds we share something else: gut bacteria.

The bacterial colonies that populate the chimpanzee intestinal tract are mirror images of those found in the human gut, researchers report Tuesday in the journal Nature Communications. The findings suggest gut bacteria patterns evolved before chimps and humans split and went their evolutionarily separate ways.

Human gut bacteria are crucial to health, with infants relying on healthy microbe populations to influence the developing immune system. Problems with microbe populations may also contribute to obesity and inflammatory bowel diseases.

Three intestinal ecosystems

In 2011, researchers learned that everyone’s gut bacteria fall into one of three different types, almost analogous to blood types. In each type, certain bacteria dominate. These types weren’t linked to any personal characteristics such as geographic area, age or gender. Researchers dubbed these distinct bacterial ecosystems “enterotypes.” (“Entero” means gut or intestine.)

“No one really knows why these three enterotypes exist,” said study researcher Andrew Moeller, a doctoral student at Yale University.

Along with his adviser Howard Ochman and their colleagues, Moeller wants to understand how these enterotypes arose. They could be distinctly human, he told LiveScience, which would suggest they arose relatively recently, perhaps in response to the development of agriculture. Or they could be ancient, shared among our closest primate relatives.

The researchers analyzed gut bacteria samples from 35 chimpanzees from Gombe Stream National Park in Tanzania. The chimpanzees were all in the subspecies Pan troglodytes schweinfurthii, the eastern chimpanzee, which arose about the same time as Homo sapiens.

Shared bacteria

The researchers found that, just like humans, chimps’ guts harbor one of three distinct types of bacterial colonies. Even more intriguingly, these enterotypes matched humans’ precisely. In type 1, for example, both humans and chimps show a predominance of Bacteroides,Faecalibacterium and Parabacteroides.

There were some differences. For example, in humans and chimps, enterotype 2 is marked by an overabundance of bacteria called Lachnospiraceae. In humans, the bacteria Prevotellae is also prevalent in type 2. In chimps, Prevotellae appears in significant numbers in all three enterotypes, perhaps because it is associated with a high-carbohydrate diet.

Other differences could help explain certain human health issues. By comparing human and chimpanzee gut bacteria, the researchers found many of the bacteria present only in humans are linked to diseases such as inflammatory bowel diseases, conditions that cause pain, diarrhea and vomiting.

Seven of the chimps in the study were tested repeatedly over eight years, and their gut microbes were found to change from type to type over that time period. No one has ever tested humans for changes over a period longer than two weeks, Moeller said, but the results suggest our enterotypes may shift over time, too.

Our shared history

The similarities between chimp and human colonies suggest enterotypes predate our species, which in turn suggests that none of the three ecosystems are better than the others, Moeller said.

“Before we found this in chimpanzees, there was a possibility that enterotypes were a product of modernization, which could mean they have some negative effects on health,” he said. “I don’t think there’s any reason to think one enterotype is going to have an effect on health that’s going to be better” than the others.

Moeller and his colleagues are now examining gorilla fecal samples to find out where they stand as slightly more distant primate relatives to humans.

“The next step is to try to find out the processes and mechanisms responsible for producing these three community states,” Moeller said, “which is kind of a lofty goal, but I think more sampling will actually reveal why these communities exist.”

Reciprocity an Important Component of Prosocial Behavior: Scorekeeping of Past Favors Isn’t, However, a Factor (Science Daily)

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ScienceDaily (Sep. 3, 2012) — While exchanging favors with others, humans tend to think in terms of tit-for-tat, an assumption easily extended to other animals. As a result, reciprocity is often viewed as a cognitive feat requiring memory, perhaps even calculation. But what if the process is simpler, not only in other animals but in humans as well?

Researchers at the Yerkes National Primate Research Center, Emory University, have determined monkeys may gain the advantages of reciprocal exchange of favors without necessarily keeping precise track of past favors. Malini Suchak, a graduate student at Emory University, and Frans de Waal, PhD, director of the Living Links Center at Yerkes and C.H. Candler Professor of Psychology at Emory, led the study. Their findings will appear in an Early Online Edition of theProceedings of the National Academy of Sciences this week.

“Prosocial is defined as a motivation to assist others regardless of benefits for self, explained Suchak. “We used a prosocial choice test to study whether direct reciprocity could promote generosity among brown capuchin monkeys. We found one monkey willing to do another favors if the first monkey was the only one to choose, and we found the monkeys became even more prosocial if they could alternate and help each other. We did not find any evidence that the monkeys paid close attention to each other’s past choices, so they were prosocial regardless of what their partner had just done,” she continued.

Suchak and de Waal suggest the synchronization of the same actions in alternation creates a more positive attitude the same way humans who row a boat together or work toward a shared goal develop a more positive attitude about each other.

Another interesting finding according to the researchers is the capuchin monkeys were prosocial whether they were paired with a familiar partner from their own group {in-group} or a partner from a different social group {out-group}.

According to de Waal, “This research has several implications for better understanding human behavior. First, we observed an increase in prosocial behavior as a result of reciprocity, but the monkeys did not develop a contingency between their own and their partners’ behaviors. Like humans, the capuchins may have understood the benefits of reciprocity and used this understanding to maximize their own benefits. Second, that the capuchins responded similarly to in-group and out-group partners has implications for the commonly held view that humans are unique in their ability to cooperate with strangers,” de Waal explained.

According to the researchers, capuchin monkeys (Cebus apella) are ideal subjects for this type of study given the numerous observations of cooperative and prosocial behavior in the field, their sensitivity to other monkeys’ efforts in coordination experiments, and their robust, spontaneous prosocial behavior in the prosocial choice test compared with, for example, chimpanzees, which seem more sensitive to methodological variables.

In this study, the researchers tested 12 brown capuchin monkeys in pairs on a prosocial choice task. The monkeys had the choice between a selfish token that benefited only them and a prosocial token that benefited themselves and a partner. By comparing each monkey’s behavior with a familiar partner from the monkey’s own group and a partner from a different social group, the researchers examined the influence of each monkey’s relationship outside the experimental context on prosocial behavior. There was no difference between in-group and out-group pairs in any of the test conditions. To test the role of reciprocity, the researchers allowed the monkeys to take turns making choices and found this greatly increased prosocial behavior, but the researchers did not observe any tit-for-tat behavior. The researchers also tested whether the monkeys could overcome their aversion for inequity by creating a situation in which both individuals could provide each other with superior rewards, making reciprocity an even more attractive strategy. The monkeys did, but again without keeping track of each other’s choices. Finally, through a series of control conditions, the researchers established the monkeys were responding to their partners’ behaviors, rather than the rewards delivered by their partners, and that the monkeys understood the values of the tokens and were flexibly responding to changing conditions throughout the test sessions.

This research opens several avenues for future research, including further examining the emergence of reciprocity among humans without the cognition required for tit-for-tat and the tendency to cooperate with out-group partners.

Journal Reference:

  1. Malini Suchak and Frans B. M. de Waal. Monkeys benefit from reciprocity without the cognitive burden.Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1213173109

Chimpanzees Create ‘Social Traditions’: Unique Handclasp Grooming Behavior Reveals Local Difference (Science Daily)

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ScienceDaily (Aug. 28, 2012) — Researchers have revealed that chimpanzees are not only capable of learning from one another, but also use this social information to form and maintain local traditions.

Wrist-to-wrist grooming handclasp. (Credit: Mark Bodamer)

A research collaboration between the Gonzaga University and the Max Planck Institute shows that the way in which chimpanzees groom each other depends on the community to which they belong. Specifically, it is the unique handclasp grooming behaviour that reveals this local difference.

The specific behaviour that the researchers focused on was the ‘grooming handclasp’, a behaviour where two chimpanzees clasp onto each other’s arms, raise those arms up in the air, and groom each other with their free arm. This behaviour has only been observed in some chimpanzee populations. The question remained whether chimpanzees are instinctively inclined to engage in grooming handclasp behaviour, or whether they learn this behaviour from each other and pass it on to subsequent generations.

Edwin van Leeuwen and Katherine Cronin of the Comparative Cognitive Anthropology research group of the Max Planck Institute for Psycholinguistics led by Daniel Haun conducted their observations between 2007 and 2012 at the Chimfunshi Wildlife Orphanage Trust in Zambia. At Chimfunshi, a mix of wild- and captive-born chimpanzees live in woodlands in some of the largest enclosures in the world. The Max Planck team collaborated with students from Gonzaga University led by Mark Bodamer, a team of local chimpanzee caretakers, and Roger Mundry of the Max Planck Institute for Evolutionary Anthropology in order to collect and comprehend the detailed chimpanzee data.

Previous research suggested that the grooming handclasp might be a cultural phenomenon, just like humans across cultures engage in different ways of greeting each other. However, these suggestions were primarily based on observations that some chimpanzee communities handclasp and others don’t — not whether there are differences between communities that engage in handclasping. Moreover, the early observations could have been explained by differences in genetic and/or ecological factors between the chimpanzee communities, which precluded the interpretation that the chimpanzees were exhibiting ‘cultural’ differences.

The present research shows that even between chimpanzee communities that engage in the grooming handclasp, subtle yet stable differences exist in the styles that they prefer: one chimpanzee group highly preferred the style where they would grasp each other’s hands during the grooming, while another group engaged much more in a style where they would fold their wrists around each other’s wrists.

“We don’t know what mechanisms account for these differences,” van Leeuwen says. “But our study at least reveals that these chimpanzee communities formed and maintained their own local grooming traditions over the last 5 years. Our observations may also indicate that chimpanzees can overcome their innate predispositions, potentially allowing them to manipulate their environment based on social constructs rather than on mere instincts.”

Apart from the different style preferences of the chimpanzee communities, the research team also observed that the grooming handclasp behaviour was a long-lasting part of the chimpanzees’ behavioural repertoire: the behaviour was even transmitted to the next generation of potential handclaspers.

“By following the chimpanzees over time, we were able to show that 20 young chimpanzees gradually developed the handclasp behaviour over the course of the five-year study. The first handclasps by young individuals were mostly in partnership with their mothers. These observations support the conclusion that these chimpanzees socially learn their local tradition, and that this might be evidence of social culture,” Bodamer explains.

“Continued monitoring of these groups of chimpanzees will shed light on the question of how these group-traditions are maintained over time and potentially even why the chimpanzees like to raise their arms up in the air during social grooming in the first place,” van Leeuwen adds.

Journal Reference:

  1. Edwin J. C. van Leeuwen, Katherine A. Cronin, Daniel B. M. Haun, Roger Mundry and Mark D. Bodamer. Neighbouring chimpanzee communities show different preferences in social grooming behaviour. Proceedings of the Royal Society B, August 29, 2012

Ape ‘genius’ smarter than the average chimp (Discovery News)

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Geniuses exist among non-humans, but no one attribute constitutes intelligence.

By Jennifer Viegas – Mon Aug 27, 2012 06:01 AM ET

Chimp

Natasha, who appears in this photo, outperformed other chimps on tests given by researchers to measure intelligence. Max Planck Institute for Evolutionary Anthropology/Esther Herrmann

Certain apes appear to be much smarter than others, with at least one chimpanzee now called “exceptional” when compared to other chimps.

The standout chimp, an adult female in her 20s named Natasha, scored off the charts in a battery of tests. The findings, published in the latest Philosophical Transactions of the Royal Society B, suggest that geniuses exist among non-humans, but that no one attribute constitutes intelligence.

Instead, a perfect storm of abilities seems to come together to create the Einsteins of the animal kingdom. Natasha’s keepers at the Ngamba Island chimpanzee sanctuary in Uganda knew she was special even before the latest study.

“The caretakers named Natasha as the smartest chimpanzee, precisely the same chimpanzee that our tests had revealed to be exceptional,” study authors Esther Herrmann and Josep Call of the Max Planck Institute for Evolutionary Anthropology wrote.

“All three of the most experienced caretakers included Natasha in their lists (of the most intelligent chimps),” they added.

Natasha has made headlines over the months for her attention-grabbing antics. For instance, she repeatedly escaped her former enclosure, surrounded by an electric fence. She did this by tossing branches at the fence until she didn’t see a spark, letting her know that the power was off.

She also learned how to tease humans, beckoning them to throw food her way, only to spray the unsuspecting person with water.

Herrmann and Call decided to study this chimp, along with numerous others, to see if there really are chimp prodigies among non-human great apes. To do this, the researchers created a multi-part mental challenge consisting of eight tasks.

chimp"WATCH VIDEO: See how chimp family groups cope with the death of a close relative. (Caution: Images may be disturbing to some viewers.)

For the first task, the chimps had to find hidden food, testing their spatial knowledge. For the second, the chimps wielded a tool — avoiding a trap — to again obtain a food reward. The remaining tasks demonstrated understanding of things like color, size and shape.

“We identified some individuals who consistently scored well across (the) multiple tasks,” wrote the authors, who again made note of Natasha, who aced nearly every task.

The researchers could not identify “a general intelligence factor.” They instead indicate that ape intelligence might be a bundling of skills related to learning, tool usage, understanding of quantities, and an ability to reach conclusions based on evidence and reasoning.

As the saying goes, necessity may be the mother of invention and, at least in some cases, one reason behind chimp cleverness.

Call, for example, told Discovery News about chimps that make tools for extracting termites out of mounds. The process requires several steps.

“They uproot the stem or use their teeth to clip the stem at the base and then remove the large leaf from the distal end by clipping it with their teeth before transporting the stem to the termite nest, where they complete tool manufacture by modifying the end into a ‘paint brush’ tip by pulling the stem through their teeth, splitting the probe lengthwise by pulling off strands of fiber, or separating the fibers by biting them,” he said.

As for why only some chimps go through such an elaborate process, “a lot depends on the ecological constraints and needs,” he said.

In terms of other animals, Herrmann and Call mention the dogs Rico and Chaser, who knew the meaning of hundreds of words.

“Interestingly,” the scientists point out, “all of these dogs (considered to be very smart) are border collies. And many of their owners reported that they did not train the dogs to play the fetching game; it was the dogs who trained them!”

The jury is still out on what exactly constitutes such cleverness. The researchers propose that more studies be conducted, with “tasks that capture cognitive, motivational and temperament dimensions.”

That’s because, in part, a willingness to learn and a positive attitude seem to make as big of a difference in dogs, chimps and other animals as they do in humans.

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Bonobo genius makes stone tools like early humans did (New Scientist)

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13:09 21 August 2012 by Hannah Krakauer

Kanzi the bonobo continues to impress. Not content with learning sign language or making up “words” for things like banana or juice, he now seems capable of making stone tools on a par with the efforts of early humans.

Even a human could manage this <i>(Image: Elizabeth Rubert-Pugh (Great Ape Trust of Iowa/Bonobo Hope Sanctuary))</i>

Even a human could manage this (Image: Elizabeth Rubert-Pugh (Great Ape Trust of Iowa/Bonobo Hope Sanctuary))

Eviatar Nevo of the University of Haifa in Israel and his colleagues sealed food inside a log to mimic marrow locked inside long bones, and watched Kanzi, a 30-year-old male bonobo chimp, try to extract it. While a companion bonobo attempted the problem a handful of times, and succeeded only by smashing the log on the ground, Kanzi took a longer and arguably more sophisticated approach.

Both had been taught to knap flint flakes in the 1990s, holding a stone core in one hand and using another as a hammer. Kanzi used the tools he created to come at the log in a variety of ways: inserting sticks into seams in the log, throwing projectiles at it, and employing stone flints as choppers, drills, and scrapers. In the end, he got food out of 24 logs, while his companion managed just two.

Perhaps most remarkable about the tools Kanzi created is their resemblance to early hominid tools. Both bonobos made and used tools to obtain food – either by extracting it from logs or by digging it out of the ground. But only Kanzi’s met the criteria for both tool groups made by early Homo: wedges and choppers, and scrapers and drills.

Do Kanzi’s skills translate to all bonobos? It’s hard to say. The abilities of animals like Alex the parrot, who could purportedly count to six, and Betty the crow, who crafted a hook out of wire, sometimes prompt claims about the intelligence of an entire species. But since these animals are raised in unusual environments where they frequently interact with humans, their cases may be too singular to extrapolate their talents to their brethren.

The findings will fuel the ongoing debate over whether stone tools mark the beginning of modern human culture, or predate our Homo genus. They appear to suggest the latter – though critics will point out that Kanzi and his companion were taught how to make the tools. Whether the behaviour could arise in nature is unclear.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1212855109