Why are some animals so clever?

The unusual behavior of orangutans in a swamp area in Sumatra holds a surprising answer 

by Carl Van Scheik. Published in Scientific American-Israel, issue 24, August-September 2006

We, the humans, write the textbooks, and rightly we can be suspected of being biased, and yet only a few doubt the fact that we are the most intelligent creatures on the planet. Many animals are endowed with special cognitive abilities that give them excellence in their typical habitats, but usually the animals do not solve new problems. Those who do this are called intelligent animals by us, but none of them are as intelligent as we are.

What is it that prioritized the evolution of such extraordinary brain capacity in humans, or rather in our hominid ancestors? One approach to searching for an answer to this question is to examine the factors that might have shaped other creatures that exhibit high intelligence, and see if such forces might also have acted on our ancestors? For example, there are types of birds and non-human mammals that solve problems much better than others: elephants, dolphins, parrots, crows. But there is no doubt that the study of our relatives, the great apes, may enlighten our eyes.

Researchers have offered many explanations for the development of intelligence in primates, the family of animals that includes humans and great apes (along with monkeys, lemurs and lorises). But the orangutan studies my research group has conducted over the past 13 years have unexpectedly produced a new explanation, and we believe it provides a far-reaching answer to the question.

incomplete theories
One attempt to explain the intelligence of primates, an attempt that has greatly influenced researchers, claims that the complexity of social life is the motive for the development of increased cognitive abilities. This Machiavellian hypothesis of intelligence suggests that success in social life depends on cultivating the most profitable relationships and quickly reading the social map - for example, when an animal decides whether to come to the aid of an ally being attacked by another animal. Society's demands therefore encourage intelligence because the most intelligent creature will also be the most successful in making decisions that will protect it, and thus survive to pass its genes on to the next generation. But mechanical properties are not so useful in other families of animals, and not even in all primates, so this approach alone does not answer the question.

One can easily imagine many other factors that would stimulate the evolution of intelligence, such as the need for hard work to obtain food. In this example, someone who can think of how to skillfully reach for hidden food or remember the ever-changing locations of essential food items may gain an advantage over others. The reward of intelligence is the transfer of more genes to the next generation.

My explanation, which does not contradict the other factors, emphasizes social learning. Human intelligence develops over time. Children learn mainly under the guidance of patient adults. Without strong social stimuli, i.e. cultural stimuli, even a potential child prodigy will grow up to be an unsuccessful schlomial adult. We now have evidence that such a process of social learning also applies to great apes. The main point of my argument is that usually the most intelligent animals are the most cultured: they learn from each other creative solutions to environmental and social problems. In short, I argue that culture encourages intelligence.

I came to this suggestion by a detour that passed through the swamps on the west coast of the island of Sumatra in Indonesia, where my colleague and I conducted observations of orangutans. The orangutan is the only great ape in Asia, and its distribution is limited to the islands of Borneo and Sumatra. Orangutans are known to be somewhat solitary. Compared to their more famous relative, the African chimpanzee, these red-headed apes are peaceful and socially reserved creatures and are not hyperactive and sociable like chimpanzees. And yet we found among them the conditions that allow culture to flourish.

Technology in swamps
We were initially drawn to the swamps because they provide shelter for an unusually high number of orangutans. Unlike the dry forests on the island, the humid swamps are a habitat that provides the great apes with abundant food throughout the year and can therefore support a large population. We worked in the area near Suok Balimbing in the Kluet Swamps, an area that may be a paradise for orangutans, but a hell for researchers due to sticky mud, an abundance of stinging insects, oppressive heat and humidity.

One of the first discoveries in this unlikely place amazed us: Suok's orangutans used a variety of tools of their own making. In captivity, the red-haired apes use tools enthusiastically, but the main feature of tools in orangutans observed so far in the wild was their absence. Suak's super monkeys use their tools for two main purposes. First, they look for ants, termites and especially honey (mainly from stingless bees) - more than their fellow orangutans look elsewhere. They often send scrutinizing glances up the tree trunks, looking for air movement coming out of small holes in the tree and entering them. After such a hole is discovered, it is made a focal point for visual examination, and then manually by inserting a finger and probing. Usually the finger is too short, and the orangutan makes a tool for himself using a stick. After he carefully inserts the stick, he gently moves it in and out, takes it out, licks and pushes it in again. Most of this "treatment" is done with the tool held between the teeth. Only the largest tools, used primarily as a hammer to dislodge lumps from termite nests, are hand held.

The second use of tools by the apes in Suak is related to the fruits of the Neesia tree. The tree yields pentagonal glumes up to 25 cm long and up to 10 cm wide. The pickets are full of brown seeds that are the size of bean kernels that contain almost 50% fat, that is, extremely nutritious - a rare and sought-after pleasure in a natural environment free of fast food. The tree protects its seeds with a very hard bark. But, when the seeds ripen, the shell begins to crack and the widening slits reveal neat rows of seeds that have grown handsome, red wrapping shoots (arils) containing about 80% fat. To further deter the seed-eaters, the shell is studded with numerous razor-sharp needles. Suak's orangutans peel short, straight branches, which they hold in their mouths and stick into grooves. They move the tool back and forth in the groove and detach the seeds from their stalks. The seeds then fall straight into the mouth. At the end of the season, the orangutans eat only the red shoots using the same method that allows them to remove them without injury.

The two methods of designing the chopsticks are very common in Suak. In general, extracting honey from tree holes is an occasional activity that takes only a few minutes, but when the fruit of the nissia ripens, the great apes devote most of their waking hours to extracting the seeds or enclosing shoots, and they grow fatter and fatter by the day.

Why is the use of tools a culture?
What explains this rare concentration on tool use in Suak when orangutans elsewhere in the wild do so little? We don't think the animals in Suak are fundamentally smarter: in captivity, most members of this biological species can learn to use tools, an observation that suggests they have a basic brain capacity to do so.

Therefore, we assumed that the answer lies in the environment in which they live. The orangutans studied before us mostly lived in dry forests. In contrast, the swamps are a unique and abundant habitat that it offers. Many more insects nest in tree hollows in swamps than in dryland forests, and Nisia trees only grow in moist places, usually near running water. The environmental explanation sounds tempting, but it doesn't explain why some populations outside Suak completely ignore those rich food sources. He also does not explain why some populations that do feed on seeds, do so without tools (and of course, as a result, they eat much less). The same is true for the tree holes. Occasionally, when the nearby dry forested hills produce an abundance of fruit, Suak's orangutans go there to indulge themselves. When they gather fruit there they use tools to explore the contents of the holes in the trees. The mountainous habitat is very common throughout the orangutans' distribution area, so the question arises: if it is possible to use tools on the slopes above Suak, why not do it elsewhere?

Another hypothesis we considered, a hypothesis that was influenced by the ancient saying that necessity is the father of invention, said that the high population density in Suak creates fierce competition for food. As a result, many will go without food unless they can reach hard-to-reach sources of supply - meaning they must have utensils to eat. The strongest argument against this possibility is that the sweet, high-fat foods that can be reached with the tools are at the top of the orangutans' priority scale, so it was reasonable that they would try to get them elsewhere as well. For example, the red-haired macaques everywhere are willing to risk bee stings many times to get honey. Therefore, the idea of ​​need does not stand the test either.

Another possibility is that this behavior is due to innovative techniques invented by some clever orangutans, and they spread and survived in the population because others learned them by watching these experts. In other words, the use of tools is cultural. Without experimentally introducing changes in the population, the main obstacle in studying culture in the wild is that we can never convincingly demonstrate that a particular animal we observe is actually inventing a new trick. It is possible that he is simply activating an old habit, which he remembers well but rarely uses. We also cannot prove that a certain individual learns a new skill from another group member or that he simply understands on his own what to do. Although we can show in the laboratory that orangutans can observe each other and learn social learning, these studies have no meaning about culture in the wild - neither about its very essence nor about its distribution. Field researchers have therefore had to develop a set of criteria to demonstrate when certain behavior has a cultural basis.

First, there must be geographic variation in the behavior being examined. This shows that it was invented somewhere. It must also be widespread in the place where it was discovered, which shows that it is spreading and persisting in the population. The use of Suak tools easily passes these two tests. The second step is the elimination of simpler explanations that yield the same spatial pattern but without involving social learning. We have already rejected an environmental explanation, according to which individuals exposed to a certain habitat will independently reach the same skill. We also ruled out a genetic explanation because most orangutans in captivity are able to learn to use tools.

The third test, which is the strictest, says that we must find a geographical distribution of the behavior that can be explained by culture and is difficult to explain in any other way. One such crucial pattern could be a situation where the behavior exists in one place but is absent beyond a natural barrier that prevents its spread. The geographical distribution of the nisiya trees provided us with clear clues regarding the use of tools in Suak. Nyssia trees (and orangutans) are found on both sides of the wide Alas River. In the Singkil Swamps, south of Suak and on the same bank of the Alas River, we found vessels thrown on the ground, while in the Batu-Batu Swamps across the river they were conspicuous by their absence in all our many visits there in different years. In Batu-Batu we found that many of the fruits were opened and torn to pieces. The orangutans in the area eat nissia seeds apparently in the same way as their counterparts at a site called Gunung-Palong in faraway Borneo, which is a completely different way from their relatives in Singkil across the river itself.

Batu-Batu is a small wetland area, and it does not include extensive areas of swamp forest of the finest type. Thus, only a few orangutans can exist there. We do not know whether the use of tools was never invented there, or whether it was invented but did not last in the smaller population. But we do know that migrants from across the river never brought the custom there because the river in this area is too wide and orangutans are by no means capable of crossing it. Far up the river, in areas that can be crossed, Nisia trees grow here and there but the orangutans there completely ignore them, perhaps because they are not aware of their rich fruits. A cultural explanation therefore provides the most accurate answer to the existence of intelligent tool users, living in such close and unexpected proximity to animals that rely only on their strength for the same purpose, and also to the existence of complete ignoramuses upriver.

A tolerant neighborhood
Why do we find these one-of-a-kind ways of using tools in Suak and not anywhere else? To delve into this question, we first made a detailed comparison between all the sites where orangutans were studied. We found that even if we omit from the comparison the issue of the use of tools, Suak is a place where there is the largest number of innovations that are common in the population as a whole. Apparently, this finding is not an artifact of our own interest in unusual behaviors, because researchers, eager to discover behavioral innovations acquired through social learning, have studied other sites far more than we have.

We hypothesized that we would find greater variation in the skills learned in populations where individuals have more opportunities to watch their friends in action and populations where there are fewer such opportunities. Indeed, we could verify the fact that on sites where individuals spent more time with each other, a greater variety of learned innovations was found. By the way, a similar relationship is also found among chimpanzees. This relationship was stronger in food-related behaviors. This is plausible because acquiring the skill of obtaining food from someone else requires closer observation than, for example, learning a salient sign for communication. In other words, the animals that have been exposed to few experienced peers show the least amount of cultural variables, just like a country boy compared to his urban friend.

When we carefully examined the difference between the sites we noticed something else. Baby orangutans in all locations spend more than 20,000 hours of daylight in close contact with their verifies and act as enthusiastic campers. But only in Suak did we see that the adults also spend considerable time together when they are looking for food. Unlike any other population of orangutans studied so far, they even fed on the same food item, usually termite-infested branches, and shared the food, the flesh of a loris with heavy movement, for example. The special proximity of this species, and the mutual tolerance, allowed less skilled adults to get close enough to observe the methods of obtaining food, and they did so as enthusiastically as children.

Acquiring the most intellectually challenging inventions, such as the use of tools as seen only in Suak, probably requires prolonged contact with skilled individuals as well as several rounds of observation and practice. A surprising implication that emerges from this requirement is that, although perpetrators learn virtually all of their skills from their peers, a population will be able to preserve certain innovations only if it has tolerant role models who are not mothers. If by chance the mother is not particularly talented, other experts will be around and the young will still be able to learn sophisticated techniques that are probably not learned automatically. That is, the tighter the social network, the more likely the group will retain skills invented in it. Ultimately, tolerant populations support a greater number of such behaviors.

From our work in the field we learned that most learning in nature, apart from simple conditioning, may include a social component, at least among primates. In contrast, most of the laboratory experiments that examined how animals learn were aimed at discovering the individual's capacity for individual learning. Indeed, if the puzzle of the laboratory psychologist is presented to the animal under natural conditions, where many stimuli compete for his attention, he may not understand at all that he has a problem waiting to be solved. In nature, the actions of the skilled members of the community direct the attention of the novice animal.

The cultural roots of reason
Our analysis of orangutans suggests that culture, that is, social learning and specialized skills, not only fosters intelligence, but also encourages the evolution of intelligence in the entire population over time. Different biological species differ greatly in the mechanisms that allow them to learn from others. But formal experiments confirm the impression gained from observing great apes in the wild: they are able to learn by watching what others do. That is, when an orangutan, or for that matter an African great ape, in the wild manages to demonstrate complex behavior from a mental point of view, he acquired this ability through a mixture of observational learning and individual practice, just like children learn skills. And when an orangutan in Suak learns more tricks than his relatives elsewhere, who are fortunate to have had less success than him, he does so because he has had more opportunities for social learning during his lifetime. Social learning may therefore boost an animal's intellectual performance to a higher level.

To appreciate the importance of social input in the development of higher intelligence, let's conduct a thought experiment. Imagine an individual growing up without any social input but given adequate shelter and nutrition. This is a situation similar to the one that prevails when there is no connection between the generations or when the young take care of themselves after they bloom from the nest. Now imagine that one of the females of this species invents a useful skill, for example, a way to crack a nut and extract its nutritious contents. Her way will be successful, and she may have more offspring than other females in the population. But if this skill is not passed on to the next generation it will disappear when the female dies.

Now imagine a situation where the offspring accompany their mother for some period of time before they go their separate ways. Most of the young people will learn the new method from their mother and pass it on - and the accompanying profit - to the next generation. Such a process will usually occur in biological species whose development is slow and where the parent is in a continuous relationship with at least one offspring. But the process will get a strong boost if some individuals form tolerant social groups.

Now we can take another step forward. In species where individuals develop slowly and live in tolerant societies, natural selection will tend to reward a slight improvement in the ability to observe observation more than a similar improvement in the ability to invent. The reason is that in such a society the individual can lean both on the shoulders of his contemporaries and on those of previous generations. We therefore expect a process of positive feedback in which the animals will become more and more innovative and develop better methods of social learning because these two abilities rely on similar thinking mechanisms. In other words, culturalism affects biological species that have a certain capacity for innovation in a way that will develop them towards a higher intelligence. If so, this brings us to the new explanation for cognitive evolution.

This new hypothesis clarifies a phenomenon that would otherwise be puzzling. Many times in the last hundred years people have raised baby great apes as if they were human children. These civilized monkeys acquired a surprising range of skills and easily imitated complex behavior - understanding the meaning of pointing in a certain direction, for example. They even managed to understand some human words, became playful with jokes and drew pictures. Later, formal experiments, such as those conducted by A. Sue Savage-Rambo of Georgia State University on the bonobo monkey Kenzi, revealed remarkable linguistic abilities. Such cases have been repeated consistently, although they have often been dismissed as scientific inaccuracies. They revealed a tremendous and dormant cognitive potential of the great apes. Perhaps we underestimate the complexity of life in the jungle, but I suspect that these civilized apes have become truly over-skilled. During the process that contains the story of human evolution, it is possible to bring a super monkey who was raised as a human to higher cognitive heights than all his friends in nature.

A similar line of thought solves the age-old puzzle of why many primates in captivity willingly use tools, and sometimes even make them, while their counterparts in the wild are not inclined to do so at all. It is often thought that they do not need tools, but observations of orangutans, chimpanzees and capuchin monkeys contradict this claim, as they show that utilizing some skill in the use of tools allows these animals to access the richest food sources in their habitat, or to safely pass through periods thin The riddle is solved when we understand that two individuals of the same biological species can be very different from each other in their intellectual performance depending on the social environment in which they grew up.

Orang-utans bring the phenomenon to a peak. In the world of zoos, they are known as escape artists who skillfully break through cage doors. But despite decades of diligent observation in the wild, the observations have documented only a few technological achievements outside Suak. Individuals captured in the wild usually refuse to get used to the conditions of captivity, and they always maintain their deep and ingrained shyness and suspicion of humans. But super monkeys born in a zoo are happy to see their handlers as valuable role models, pay attention to their actions and objects thrown in the pens and learn how to learn and gain many skills through this.

A test of the intelligence-through-culture theory is the prediction that the most intelligent animals are those who also tend to live in populations where the whole group permanently adopts innovations brought by its members. It is difficult to test this prediction. The senses and the way of life of animals from different families differ so much that it is difficult to find a single touchstone for intelligent performance. For now, all we can do is ask: "Do families that show unequivocal signs of intelligence also show a culture based on innovations, and vice versa?" For example, we do not fully understand the process of self-recognition in the mirror, but it should not be mistaken as a sign of self-awareness and therefore it is also seen as a sign of high intelligence. So far, despite extensive attempts in many animal families, the only groups of mammals that pass this test are great apes and dolphins. These are also the only animals capable of understanding arbitrary signs and among whom we have found the best evidence of imitation, the basis of a culture based on innovation. Flexible use of tools based on innovations, which is another expression of intelligence, is more common among mammals: monkeys, great apes, marine mammals and elephants. All these are families where social learning is also accepted. Although so far only these very crude tests can be conducted, they support the intelligence-through-culture hypothesis.

Another important prediction is that innovativeness and social learning must co-evolve. Indeed, Simon Reeder, now at Utrecht University in the Netherlands, and Kevin N. Leland, now at the University of St. Andrews in Scotland, found that primate species with more evidence of innovation were also those with more evidence of social learning. A more indirect test relies on correlations among different species between the relative size of the brain (after a statistical correction that takes into account body size) and social and developmental variables. The idea is also consistent with well-established correlations between the tendency to live in a group and the size of the brain in different groups of mammals.

Although the new hypothesis is not enough to explain why our ancestors, unique among the great apes, developed such an extreme intellectual capacity, the impressive leap in ability reached by great apes in a rich cultural environment narrows the gap between them and us. Explaining the historical trajectory of change involves many details that need to be painstakingly gathered and woven from rare and confusing fossil evidence and the archaeological record. Many researchers suspect that the decisive change was the invasion of the savannah by the first members of the biological species Homo who could walk and use tools. They had to work as a team, creating tools and formulating strategies to dig and uproot tubers, strip the flesh of carrion and protect it from large mammals. These demands encouraged more and more innovation and increased interdependence, and intelligence snowballed.

Once we became human, cultural history began to work together with our inherent ability to improve performance. Almost 150,000 years after our species was created, sophisticated expressions of human symbolism such as well-crafted objects (artwork, musical instruments, and burial gifts) became widespread [see "The Dawn of Modern Thought", by Kate Wong, Scientific American Israel, October-November 2005]. The explosion of technology in the last 10,000 years shows that cultural input can lead to limitless achievements using Stone Age minds. Indeed culture can create new thinking in old minds.
 Overview / The Orangutan Connection
The author discovered widespread use of tools among the orangutans in the swamps of Sumatra. So far no one has seen orangutans in the wild using tools systematically.
This unexpected finding served the author as a clue to the solution of a long-standing mystery: why are some animals so clever?
He believes that culture is the deciding factor. Primate researchers define the concept of culture as the ability to learn - through observation - skills invented by others. Culture can bring about an ever-increasing sequence of achievements and advance more and more the intelligence of a biological species.

Most orangutans spend their lives without making and using tools. The red-haired macaques at Suak are exceptional, and make a variety of tools. One of the most common tools is a stick (above right) which they make to collect ants, termites and most of all, honey. Without the tool (left), attempts to extract the honey from a hole in the tree, for example by biting it, often fail. The great monkeys in Suak, on the other hand, hold the stick in their mouths, insert it into the hole (arrow in the picture on the right) and gently move it in and out. Then they take it out and lick the honey (extreme photo on the right).

The fruits of the nissia trees (below left) inspired another important tool in the toolbox of the orangutans in Suak. The seeds are highly nutritious, but they are surrounded by razor-sharp needles that deter seed-eating mammals. To avoid painful punctures, Suak's macaques peel short, straight branches, hold them in their mouths, and insert them into the open slot in the ripe fruit (right). The monkey moves the stick back and forth inside the slot and detaches the seeds without being injured. In the middle picture you can see a small fruit with the stick still stuck in it.

About the author
Carl Van Scheik
(van Schaik) is the director of the Anthropological Institute and Museum at the University of Zurich in Switzerland. Dutch by origin, he earned his doctorate at Utrecht University in 1985. After a post-doctorate at Princeton University and another short position in Utrecht, he moved to Duke University where he served as a professor of biological anthropology until he returned to the "Old World" in 2004. His book "Among the Orangutans: Red-Haired Great Apes and the Dawn of Human Civilization" (Harvard University Press) brings in more detail the ideas described in this article.

And more on the subject

A Model for Tool-Use Traditions in Primates: Implications for the Coevolution of Culture and Cognition. CP van Schaik and GR Pradhan in Journal of Human Evolution, Vol. 44, pages 645–664; 2003.
Orangutan Cultures and the Evolution of Material Culture. CP van Schaik, M. Ancrenaz, G. Borgen, B. Galdikas, CD Knott, I. Singleton, A. Suzuki, SS Utami and MY Merrill in Science, Vol. 299, pages 102–105; 2003.
Conformity to Cultural Norms of Tool Use in Chimpanzees. Andrew Whiten, Vicky Horner and Frans de Waal in Nature online; August 2005.

 see also: the forest man