WOULD A CHIMP MAKE A GOOD DATE - THE BASICS OF HUMAN LIFE - Human: The Science Behind What Makes Us Unique - Michael S. Gazzaniga

Human: The Science Behind What Makes Us Unique - Michael S. Gazzaniga (2008)



A brain is worth little without a tongue.

French proverb

THERE ISN’T A HUMAN BEING ON EARTH WHO DOES NOT LOOK at his or her dog or cat—or old shoe, for that matter—without an irrational reverence and fondness. Nonhuman beings and objects take on humanness almost routinely, and we come to believe in such things as real and enduring. We grant them a kind of agency. “Of course my dog is smart,” one hears. “My cat is psychic.” “Old Nelly never once got stuck in the snow. She knows how to hug the road.” The list is endless.

Our species has had a hard time drawing the line between us and them. In the Middle Ages, we used to have animal courts. If you can believe it, we put animals on trial and held them accountable for their actions. From 824 to 1845, in Europe, animals did not get off scot-free when they violated the laws of man, or perhaps, just disturbed his well-being. Just like common criminals, they too could be arrested and jailed (animal and human criminals would be incarcerated in the same prison), accused of wrongdoing, and have to stand trial. The court would appoint them a lawyer, who would represent them and defend them at a trial. A few lawyers became famous for their animal defenses. The accused animal, if found guilty, would then be punished. The punishment would often be retributive in nature, so that whatever the animal had done would be done to it.

In the case of a particular pig (during those times pigs ran freely through towns, and were rather aggressive) that had attacked the face and pulled the arms off a small child, the punishment was the pig had its face mangled and its forelegs cut off, and then was hanged. Animals were punished because they were harmful. However, sometimes, if the animal was valuable, such as an ox or horse, its sentence would be ameliorated, or perhaps the animal would be given to the church. If the animal had been found guilty of “buggery” (sodomy), both it and the buggerer were put to death. If domestic animals had caused damages and were found guilty, their owners would be fined for not controlling them. There seems to have been some ambivalence as to whether an animal was fully responsible or whether its owner should also be considered responsible. Because animals were peers with humans in judicial proceedings, it was considered uncool to eat the bodies of any animals that were capitally punished (except among the thrifty Flemish, who would enjoy a good steak after a cow was hanged). Animals could also be tortured for confessions. If they didn’t confess—and no one supposed they would—then their sentence could be lessened. You see, it was important to follow the law exactly, for if humans were tortured and didn’t confess, then their sentence could also be changed. Many different types of domestic animals had their day in court: horses for throwing riders or causing carts to tip, dogs for biting, bulls for stampeding and injuring or goring someone, and pigs most commonly of all. These trials were held in civil courts.1

It is easy to see why we humans have struggled with our views of animals. As I mentioned, a feature of the human brain that is both ubiquitous and almost defining is how we reflexively build models in our minds about the intentions, feelings, and goals of others, including animals and objects. We can’t help it. When one visits Rodney Brooks’s artificial intelligence lab at MIT and sees his famous robot, Cog, it takes only a matter of seconds before agency of some kind is conferred on this hunk of steel and wires. Cog turns its head, tracks you around the room with its eyes, and bingo, Cog is a something, a somebody. If it is true for Cog, it is going to be true for Rover.

Veterinarians will tell you the same sort of grieving cycles that occur over humans do so over pets. Those remaining above the ground have a mental model of the deceased, and they must go through a process to put it at peace. I have carried out extensive animal primate research. One quickly identified with each animal, noted its personality, its intelligence, and its cooperativeness. The research frequently required carrying out major neurosurgical procedures, and in some instances, major efforts were necessary for their postoperative care. I found each one taxing and troubling. When the animal survived and flourished after surgery, one’s attachment was close indeed.

I can remember one such animal that I had taken a shine to, now some forty years ago. She needed some vitamins, and yet she hated the taste of the mixture. So I brought out a monkey’s favorite delicacy—the banana. I injected the vitamin mixture into one end of the banana in hopes that she would chomp into it and get her vitamins incidentally to the tasty banana. It worked once. On day two—same plan, same preparation. This time Mozambique took the banana, looked at each end, noticed the end that had the vitamin mixture oozing out of it, broke the banana in two, threw the goopy end on the floor and ate the nonmedicated half! I couldn’t believe my eyes, but I cheered her on.

The problem with this story is I can’t be certain whether what I thought I saw as evidence of great mentation was really more than a chance event, overinterpreted by me and sort of lionized. Would I want to spend a lot of mental time with Mozambique? Indeed would I want to spend a lot of time with a chimp? This is where it starts to get serious and where hard work is needed to really know what it is we have in common with chimps. Of course, there is the flip side of the coin: Is our wanting to tack agency onto everything what makes us human?


Consider the following personal ads:

SFS (single female swinger) seeks strong male companionship. Age is unimportant. I’m a young, svelte, good-looking girl who loves to play. I love rambling in the woods, riding in your pickup truck (make it a late model with leather interior), hunting and camping trips, and hanging out with the locals. I love warm tropical nights you spend running your fingers through my hair. Moonlit dinners will have me eating out of your hand, but don’t try eating out of mine. I’m not one of those girls who always wants to discuss feelings, just rub me the right way and watch me respond. I’ll be at the front door or over at the neighbor’s when you get home from work, wearing only what nature gave me. Kiss me and I’m yours. Bring some friends over too. Call 555-xxxx and ask for Daisy.


SF seeks intelligent male for LTR (long-term relationship). I’m a young, svelte, good-looking girl with a good sense of humor, who loves to play piano, jog, and cook the delicious produce from my garden. I love long walks and talks in the woods, driving in your Porsche, and going to football games. I love to read by the campfire while you are hunting and fishing. I love going to museums, concerts, and art galleries. I love cozy, intimate winter nights spent lying by the fire with just you. Candlelight dinners in gourmet restaurants will have me eating out of your hand. Say the right thing, rub me the right way, don’t forget my birthday, and watch me respond.

Which of the two ads do you relate to? A version of the first ad can be found on snopes.com, an “urban legends” reference page. It was supposedly placed in an Atlanta newspaper, listing a phone number that belonged to the Humane Society, which received 643 calls the first two days it was in print. Daisy was a black lab, not even a chimp. The Humane Society denied ever placing the ad.

How would these dates be different? What miscalculation would you have made if you found yourself facing a chimp at the door after responding to the first ad? Could you date a chimp? Would the two of you have any common ground?


The physical differences and similarities between our closest relatives, the chimps, and us are, of course, quite noticeable. Just exactly what are we talking about when we say “closest relatives”? We often hear that we share 98.6 percent of our total DNA nucleotide sequence with chimpanzees. Yet, this figure is more than a little misleading. This does not mean that we share 98.6 percent of our genes with the chimps. The current estimate is that humans have 30,000 to 31,000 genes. What is generally not emphasized is that these 30,000 genes occupy a little more than 1.5 percent of the whole genome, the rest of the genome being noncoding.2, 3 Thus, the vast majority of the genome sits there—its function largely unknown.

With only 1.5 percent of human DNA coded for genes that are crucial in building a human, are the geneticists telling us 98.6 percent of the 1.5 percent is similar between the chimp and the human? No. Put differently, how can only 1.4 percent of the DNA make such a huge difference? The answer is clear. The relationship between a gene—a DNA sequence—and its ultimate function is not simple. Each gene can express itself in many different ways, and the variation in expression can account for large differences in function.

Here is the abstract from Nature magazine on the report of the sequencing of one chimpanzee chromosome:

Human-chimpanzee comparative genome research is essential for narrowing down genetic changes involved in the acquisition of unique human features, such as highly developed cognitive functions, bipedalism or the use of complex language. Here, we report the high-quality DNA sequence of 33.3 megabases of chimpanzee chromosome 22. By comparing the whole sequence with the human counterpart, chromosome 21, we found that 1.44% of the chromosome consists of single-base substitutions in addition to nearly 68,000 insertions or deletions. These differences are sufficient to generate changes in most of the proteins. Indeed, 83% of the 231 coding sequences, including functionally important genes, show differences at the amino acid sequence level. Furthermore, we demonstrate different expansion of particular subfamilies of retrotranspositions between the lineages, suggesting different impacts of retrotranspositions on human and chimpanzee evolution. The genomic changes after speciation and their biological consequences seem more complex than originally hypothesized.4

The great apes, which include orangutans, gorillas, chimpanzees, bonobos, and humans, all evolved from a common ancestor. The lineage that later evolved to become orangutans branched off about 15 million years ago (mya), and the gorillas 10 mya. It is estimated that somewhere between 5 and 7 mya, we shared a common ancestor with the chimpanzee. That is why that ape is assumed to be our closest living relative. For some reason, and it is often blamed on the climate, which may have caused a change in the food supply, there was a further split in our common line. One branch of the family stayed in the tropical forest, and the other branch stepped out into the open woodland. The branch that stayed in the forest resulted in the chimpanzees and later the bonobos (sometimes known as pygmy chimpanzees, although they are only slightly smaller). Bonobos branched from a common chimp ancestor about 1.5 to 3.0 mya. They occupy the tropical forests south of the Zaire River in central and western Africa, where there are no gorillas to compete for food, whereas the chimps live in the tropical forests north of the Zaire with gorillas. Because the tropical forest has always been home to the chimpanzees, they are called a conservative species. They have not had to adapt to many changes and thus, evolutionarily speaking, have not changed much since branching from our common ancestor.

Not so with the open-woodland branch that left the tropical forest to live on the savanna. They had to adapt to a radically different environment and thus went through many changes. After a few false starts and dead ends, they eventually evolved into Homo sapiens. Humans are the only surviving hominid from the line that split from the common ancestor with the chimps, but there were many that came before us. Lucy, for example, the fossil Australopithecus afarensis found by Donald Johanson in 1974, shocked the anthropological world because she was bipedal but did not have the big brain. Up until that time, it was thought that the big brain led to bipedalism.

In 1992, Tim White, from the University of California at Berkeley, found the oldest known hominid fossils. These were of a bipedal apelike animal that has been called Ardipithecus ramidus and is thought to have lived about 4.4 to 7.0 mya. Recent fossil findings in Ethiopia, again by Tim White, of Australopithecus anamensis, dated to 4.1 mya, suggest that it may have been the descendant of Ardipithecus and the precursor of Lucy. Several different species arose from Australopithecus, including the beginning of our species, Homo. However, our development was not a straight shot from Lucy forward. There were eras when different species of Homo and Australopithecus existed at the same time.


Nonetheless, here we are, and the question once again is, how different are we? Now that we know that the seemingly small 1.5 percent difference in our genome means a lot, we can expect to find some big differences in our species.

First, is bipedalism unique? The Australians are shaking their heads: kangaroos. So although humans are not the only bipedal animals, bipedalism did set in motion a series of physical changes in the hominid line that distinguish us from chimps. We lost our opposable first toe and developed a foot that could carry our upright weight. This has also allowed us to wear Italian designer shoes, a unique behavior known only to humans. Chimpanzees still have an opposable first toe, which acts similarly to a thumb and is good for grasping branches but not for carrying upright weight. As we humans became bipedal, our legs straightened, unlike the bowed legs of a chimp. Our pelvis and hip joints changed their size, shape, and angle of connection. Our spine became curved into an S shape, as opposed to the straight spine of a chimp. The thoracic spinal foramen, the channel that the spinal cord travels through, has enlarged, and the point where the spinal cord enters the skull has moved forward to the middle of our cranium rather than the rear.

Robert Provine, at the University of Maryland, a researcher who studies laughter, postulates that bipedalism actually made speech mechanically possible. In apes walking on all fours, the lungs have to be fully inflated to provide the additional rigidity needed for the thorax to absorb the impact of the ground through the forelimbs while running. Bipedalism broke the link between breathing patterns and stride, and allowed the flexibility for regulating breathing and ultimately speech.5

Other speech-enabling changes occurred: Necks elongated, and the tongue and pharynx dropped lower down into the throat. In chimps and other apes, the nasal passage is directly connected to the lungs. It is completely separate from the food route through the mouth and into the esophagus; this means that the other apes cannot choke on their food, but we can. We have a different system, a unique system, in which air and food share a common pathway in the back of the throat. We have developed a structure called the epiglottis, which closes off the pathway to the lungs when we swallow, and opens when we breathe. It is the anatomy of the pharynx, specifically the larynx, that makes it possible for us to utter the huge variations in sound that we can. We must have gained some survival advantage even though there is an increased risk of death by choking. Was it our increased ability to communicate?

Freeing Up the Forepaws

Once we were walking upright, we had free hands that could carry things, and our thumbs became extraordinary. Actually, our thumbs became unique. Chimps do have opposable thumbs, but they don’t have the range of motion that our thumbs have, and that is key. We can arc our thumbs across to our baby fingers, known as ulnar opposition, but chimps cannot. This means we can pick up objects with the tips of our fingers rather than just the sides. We also have more sensitive fingertips, with thousands of nerves per square inch that send information to the brain. This has given us the ability to perform the finest motor-coordinated tasks not only of all the apes but also of all living creatures.

According to the current fossil evidence, it seems that our hands were up and functioning about two million years ago in Homo habilis, whose fossils were found in the Olduvai Gorge in Tanzania early in 1964, along with the first known hand-wrought tools. This was another shock for anthropologists at the time, because Homo habilis had a brain about half the size of ours. It had been thought that a bigger brain was needed for tool making. In fact, the arcing thumb was what allowed our ancestors to be able to grab objects and pound them together to make the first tools. Remember, tool making is not unique to humans. Chimps, crows, and dolphins have all been observed using sticks, grass, and sponges as tools. However none of them has made a Maserati, which is unique to humans.

The Pelvic Thing: Big Brains, Big Pelvis

The change in the size of the pelvis also had big repercussions. The birth canal became narrower and made birth much more difficult—even as brains, and thus heads, were becoming larger. A wider pelvis would have made bipedalism mechanically impossible. In the embryo, the skulls of primates form in plates that slide over the brain and do not coalesce until after birth. (Remember the soft spot in the baby’s head you were warned not to touch?) This allows the skull to remain pliable enough to fit through the birth canal. Human babies are born very much less developed than other ape babies. In fact, in comparison to other apes, we are born one year prematurely, which is why human babies are so helpless and need to be cared for longer. The plates in our skulls don’t fully join until about age thirty. Our brains are only 23 percent of their adult size at birth and continue to expand until adolescence.

While it appears that certain aspects of our brains may continue to grow throughout our lifetime, it is most likely not due to the addition of new neurons. Instead, it is more likely that the myelin sheaths that surround the neurons continue to grow. Francine Benes, a professor of psychiatry specializing in neuroscience at Harvard Medical School and director of the Harvard Brain Tissue Resource Center, has found that myelination of at least one part of the brain* continues into the sixth decade.6 Myelination of an axon (nerve fiber) increases the propagation of the electrical signals from the cell body to the terminal area of the neuron. She postulates that these axons may play a role in the integration of emotional behaviors with the cognitive process, and that these functions may “grow” and mature throughout adult life. It is also interesting that there is a gender effect. There is increased myelin in females age six to twenty-nine, compared to males the same age.

As it turns out, our physical anatomy is important, and just how much it has affected the development of the brain, and thus our humanness, is unknown. But let’s get back to our date. What we are really concerned about on a date beyond the physical—which in the land of sexual selection is a big deal—is just what makes him or her tick. What do we have in common and what is unbridgeable? Our guy is intelligent and curious. Is he well matched with a chimp?


In the descriptions of our prospective dates there are some major differences. Our chimp date cannot talk, never gained control over fire, doesn’t cook, hasn’t developed a culture of art, music, or literature, is not particularly generous, isn’t monogamous, and doesn’t grow food. However, she is attracted to a strong mate, is status conscious, is omnivorous, and likes to socialize, hunt, eat well, and have close contact with a mate. Let’s look at these similarities and differences.

Do chimps share some of our intelligence? Is there a difference between human and animal intelligence? One could write an entire book on this issue, and many have. The field is nothing but controversial. Definitions of intelligence are commonly given from a human’s point of view. For example, “Intelligence is a general mental capability that involves the ability to think abstractly, comprehend ideas and language, learn, plan, reason and solve problems.”7 But can one species’ intelligence really be compared to another’s? Perhaps a more useful definition of animal intelligence is that of Hubert Markl, former president of the Max Planck Society in Germany, who said it is “the ability to relate different unconnected pieces of information in new ways and to apply the results in an adaptive manner.”8

Daniel Povinelli, director of the Cognitive Evolution Group and the Center for Child Studies at the University of Louisiana, addresses the problem by posing the animal intelligence question this way: “How does thinking differ across species?”9 Or to put it another way: What kind of thinking was needed to allow a species to survive in the environments that it has successfully evolved in? Can you imagine a different way of thinking? It is difficult for us to imagine how to think other than how we do; thus it is difficult to conceive of the mental states of other species. It is hard enough understanding the mental states of our own species. Povinelli is concerned that psychologists have become obsessed with establishing a psychological continuity between humans and other great apes, and so are looking only for similarities. Indeed, he reminds us, “Evolution is real, and it produces diversity.”10 Looking at the diversity of mental states instead of distorting “their true nature by conceiving of their minds as smaller, duller, less talkative versions of our own”9 would perhaps net us better information. John Holmes, a trainer of border collies, stated, “A dog is not ‘almost human’ and I know of no greater insult to the canine race than to describe it as such. The dog can do many things which man cannot do, never could do and never will do.”11 Indeed it is the differences that define a species and make it unique.

This presents a big problem that we face in studying chimpanzees’ mental states and behavior. How do we do it? We can watch them in the wild: long arduous days just to get to where they live, followed by long, arduous, mosquito-infested, humid days trailing after them and observing them. Or we can watch them in a laboratory, where few are equipped to care for chimps, there are few chimps to experiment on, experimental designs are limited, and chimps grow “sophisticated” as they become familiar with the experimental milieu. The scientists who watch them in the wild say that the laboratory is too artificial, that the chimps do not behave normally there, and that they can be influenced by those running the experiments. The laboratory scientists create a hypothesis and predictions, then design an experiment controlling for as many variables as they can, and record and interpret the results. They say that those in the field have no experimental control over the situations in which a behavior is occurring and thus can’t draw an accurate causal inference. Both suffer from the fact that the interpretations are seen through the eyes of humans, who are influenced by their own culture, politics, backgrounds, religion, and theory of mind. Keeping these limitations in mind, we are going to look at evidence and observations from both the lab and the field, and see just how similar and different we are.

Theory of Mind

Humans have an innate ability to understand that other humans have minds with different desires, intentions, beliefs, and mental states, and we have the ability to form theories with some degree of accuracy about what those desires, intentions, beliefs, and mental states are. It was first called Theory of Mind (TOM) by David Premack, whom we have already met in chapter 1, and his colleague Guy Woodruff in 1978. It was an ingenious insight. Another way to put it: It is the ability to observe behavior and then infer the unobservable mental state that is causing it. TOM is fully developed automatically in children by about age four to five, and there are signs that it is partially present before age two.12, 13 It appears to be independent from IQ. Children and adults with autism have deficits in theory of mind and are impaired in their ability to reason about the mental states of others, yet their other cognitive abilities remain intact or increased.14, 15 When looking at the behavior of other animals, our TOM causes us two problems. One is that we may get caught in the trap of seeing a certain animal behavior and with our TOM infer a human mental state in the animal, leading us to an inappropriate anthropomorphic conclusion. Alternatively, we may value our TOM ability to such a degree that it is a gold standard to which everything else is compared, leading us to think that man is completely separate from all other mammals. So do only humans have a theory of mind?

This is one of the major questions in chimpanzee research. Possessing a TOM is an important part of our abilities and has been argued to be uniquely human. To understand that other individuals have beliefs, desires, intentions, and needs affects how we act and react, whether out of sociability or for protection. When Premack and Woodruff coined the term TOM, they asked if chimps had it. There have been thirty years of experiments since that time, and the question has yet to be answered satisfactorily in the laboratory. In 1998, Cecelia M. Heyes from University College London did a review of all the experiments and observations that had been done up until that time on nonhuman primates and put them through a rigorous evaluation. These experiments studied motor imitation (the spontaneous copying of novel acts), self-recognition in a mirror, social relationships, role taking (the ability to adopt the viewpoint of another individual), deception, and perspective taking. (The last concerns the question whether seeing something translates into knowing it, i.e., is there an awareness that others see.) She came to the conclusion that in every case where nonhuman primate behavior had been interpreted as a sign of theory of mind, it could instead have occurred either by chance or as a product of nonmentalistic processes.16 She did not feel that the current procedures had proved or disproved TOM in chimps, although her arguments specifically about mirror self-recognition are not widely held. Now Povinelli and his colleague Jennifer Vonk have since reached the same conclusion.17

But nothing is simple in a field where so much is at stake. Michael Tomasello and his group at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have drawn a different conclusion. “Although chimpanzees almost certainly do not understand other minds in the same way that humans do (e.g. they apparently do not understand beliefs) they do understand some psychological processes (e.g. seeing).”18 They feel that chimpanzees have at least some components of TOM.

If I have a belief about your mental state, and you have one about mine, these are described as orders of intensionality. (Intensionality is used here, spelled with an s, as was the original practice, to refer specifically to the mental states associated with TOM. It is distinguished from intentionality with a t, which is a type of intensionality.) I know (1) that you know (2) that I know (3) that you want me to go to Paris (4) and that I want to. In a conversation about intensionality, fourth order is about as far as most people can grasp, but some can follow up to five or six orders, so I can throw in: and you know (5) I can’t and I know (6) that you know it but keep coming up with reasons to go. Whew. As I said before, to what extent other apes have a theory of mind is still highly contested. It is accepted that they have first-order intensionality. Many researchers, but not all, believe that an individual who practices tactical deception has second-order intensionality. They think that in order to trick another individual, an animal has to believe that another animal believes something. Through the compilation of multiple observational studies, Richard Byrne and Andrew Whiten have shown that instances of tactical deception are extremely rare in prosimians* and New World monkeys, but are common among the socially advanced Old World monkeys and apes—especially chimps.19

Although not all researchers are satisfied by observational studies, many accept that nonhuman primates have second-order intensionality. Scientists at Tomasello’s lab have shown in a series of experiments over the last few years that chimpanzees know what other chimps do and do not see, and can base their behavior accordingly. They will go after food that a more dominant chimp cannot see but will not go after food that the dominant one can see, and some subordinates even engage in strategic maneuvering, such as waiting or hiding, to obtain the food.20 We will learn more about what chimps understand about seeing in chapter 5. Tomasello has also found that they understand some things about the intentions of others, specifically the difference between times when an experimenter is unwilling versus unable to give them food.21 And chimps are more skillful at competitive tasks than those that involve cooperation,22 but when they need to cooperate, they will choose a chimpanzee who was a better collaborator on the task in the past.23

Where the chimps have failed is in a false-belief task that children can do at four to five years old. This test has in the past been used to indicate the full development of theory of mind. However, more recently it has been realized that this is rather overstating the case. As Paul Bloom at Yale University and Tim German, when at the University of Essex, Colchester, United Kingdom, pointed out, there is more to theory of mind than the false-belief task, and there is more to the false-belief task than theory of mind.24

What is this task? It is classically called the Sally and Ann test. Nonverbally, it works like this: Sally hides a reward, such as food, in one of two identical containers while Ann watches, but the subject (the child or chimp) does not. Then the subject watches Ann place a marker on the container that she believes holds the food. The child or the chimp then picks a container to get the food. They both can do this successfully. Then, Sally hides the reward again as Ann watches but the subject does not. Then the subject sees Ann leave the room and while she is gone, watches Sally switch the containers. Ann then comes back into the room and marks the container that she believes the food is in (which of course is the wrong one). Sometime between the age of four and five, children understand that the container that Ann thinks has the food in it has been switched and that Ann doesn’t know it. They understand that Ann has a false belief, and they will pick the correct container with the food, not the one that Ann has marked. However, the chimps and children with autism do not understand that Ann has a false belief, and will pick the container that she has marked.25

In the last couple of years, researchers are beginning to conclude that this test is too hard for kids under three years old. When different versions or a different type of test is done, even eighteen-month-to two-year-old children attend to mental states such as goals, perceptions, and beliefs to explain the behavior of others.26

What does this task actually show us? Why is there such a watershed change between three and five? What is going on in the brains of these kids that enables them to do what a chimp cannot?

Stand back or you’ll get in the fray! Controversy abounds, and two different explanations are being batted around. One is that there is a conceptual change in the children’s understanding of what beliefs really are as they get older: They gain a theoretical understanding of mental states,27 perhaps a domain-general mechanism of theory formation.28 In other words, the theory comes first, and from it concepts are derived. The other is that there is a modular theory of mind mechanism (ToMM) that gradually emerges on a reliable developmental schedule as the children get older.29, 30

In bringing up modules, I am getting ahead of myself a bit, but you are going to be hearing a lot about them soon. For now, think of a module as a hardwired (innate) mechanism that unconsciously directs you to think or act in a certain way, that directs your attention to such states as belief, desire, and pretense and then allows you to learn about these mental states.31, 32 The proposal is that you are born with these concepts. The concepts came first; later, you form theories. The mechanism provides the child with a few choices of belief states, and then a secondary selection process (which is not modular and is able to be influenced by knowledge, circumstance, and experience) infers the underlying mental state that gave rise to the belief state.

For instance, a child would observe and pay attention to a behavior such as a person saying, “Hmmm.” Then up pop the choices: “Well,…it could be she believes that the candy is in the box she marked with the X and it is true, or she believes that but it isn’t true.” But here is the catch: The choice “Well, she believes that and it is true” is the default choice. This choice is always supplied, is usually picked, and in general is correct. What people believe is usually true. But in some instances, others do have false beliefs, and you know it. In such unusual situations, the default should not be selected. In order not to pick this choice, to succeed in the false-belief task, this choice must be inhibited, and there’s the rub. This is what is so difficult for the very young and for our friends the chimps: inhibition. This theory also accounts for why we get better at attributing beliefs to others: Once we have inhibition under our belt, knowledge and experience help out.

Tomasello does not think that chimps have a full theory of mind, but he does hypothesize that chimpanzees “possess a social-cognitive schema enabling them to go a bit below the surface and discern something of the intentional structure of behavior and how perception influences it.”33 Dave Povinelli disputes this conclusion. He does not think that their similarity in behavior reflects a similarity in psychology. He offers his reinterpretation hypothesis, in which he suggests that the majority of the social behaviors that humans and other primates have in common emerged long before the human lineage evolved the psychological means of interpreting those behaviors in terms of second-order intentional states.34

The controversy goes on about consciousness shared with the chimp. What we share is minimal at best, according to Povinelli: “Key aspects of the data point toward the possibility that if chimpanzees do have a theory of mind, it must be radically different from our own.” This leads us back to the question that he poses to begin with: How does thinking differ across species?

Povinelli has a further refinement to that question: “What are their mental states about?” Well, they most certainly are about living in the tropical forest. “It would stand to reason that the mental state of chimpanzees, first and foremost, must be concerned with the things most relevant to their natural ecology—remembering the location of fruit trees, keeping an eye out for predators, and keeping track of the alpha male.” So far, this would be a good date to take camping. He goes on to suggest, “In contrast to humans, chimpanzees rely strictly upon observable features of others to forge their social concepts. If correct, it would mean that chimpanzees do not realize that there is more to others than their movements, facial expressions, and habits of behavior.” In short, Povinelli believes that “for any given ability that humans and chimpanzees share in common, the two species would share a common set of psychological structures, which at the same time, humans would augment by relying upon a system or systems unique to the species.”9 We will talk more about TOM in other animals.

Another aspect of intelligence is being able to plan for the future. Besides doing TOM studies, Nicholas Mulcahy and Josep Call, also at the Max Planck Institute in Leipzig, have looked into whether other great apes can plan. Recently they published a study of five bonobos and five orangutans, finding that they did have the ability to save a suitable tool for future use.35 In their study they first taught the subjects to use a tool to get a food reward from an apparatus in a test room. “Then we placed two suitable and six unsuitable tools in the test room but blocked subjects’ access to the baited apparatus. After five minutes, subjects were ushered outside the test room into the waiting room, and the caretaker removed all objects left in the test room while subjects watched. One hour later subjects were allowed to return to the test room and were given access to the apparatus. Thus to solve the problem, subjects had to select a suitable tool from the test room, bring it to the waiting room, keep it there for one hour, and bring it back into the test room upon their return.” The subjects took a tool with them 70 percent of the time. The researchers repeated the test but with a fourteen-hour delay, and the subjects did well again. Mulcahy and Call concluded that “these findings suggest that the precursor skills for planning for the future evolved in great apes before 14 million years ago, when all extant great ape species shared a common ancestor.” Maybe our chimp date will plan ahead and make a reservation.


So your chimp date may not have much of a theory about you, and as a result, anything you might do with her will be sort of viewed as being without intention. Nonetheless, perhaps she has feelings about her own states of mind that she would like to tell you about. Speech, of course, is the faculty or act of expressing or describing thought, feelings, or perceptions by the articulation of words. But chimps can’t speak. I can remember my friend Stanley Schachter at Columbia always lamenting, “How can Herb Terrace* become famous for showing chimps can’t talk?” In the end, they just don’t have the anatomy to be able to articulate the kinds of sounds that are necessary, so talking per se is out. But that certainly doesn’t mean they can’t communicate.

Communication, quite simply, is the transfer of information by speech, signals, writing, or behavior. In the world of animal communication, it is more specifically defined by any behavior on the part of one animal that has an effect on the current or future behavior of another animal. An example of interspecies communication is when a rattlesnake shakes its rattle: It is a warning that it is going to strike. Of course, language is another type of communication. It is far more complicated in its origins and abilities, and so is its definition. In fact, the definition of language is constantly in a state of revision by linguists, to the consternation of researchers studying human language acquisition in chimps.

Sue Savage-Rumbaugh, a primatologist at Georgia State University who claims apes have a language capacity, vents her frustration: “First the linguists said we had to get our animals to use signs in a symbolic way if we wanted to say they learned language. OK, we did that, and then they said, ‘No, that’s not language, because you don’t have syntax.’ So we proved our apes could produce some combinations of signs, but the linguists said that wasn’t enough syntax, or the right syntax. They’ll never agree that we’ve done enough.”36

Well, language is a system of abstract symbols and the grammar (rules) in which the symbols are manipulated. For instance the words dog, chien, and cane all mean “dog.” The word doesn’t sound like its meaning; it is just a sound that has come to represent “dog” in different languages. It is an abstract symbol. Language does not have to be spoken or written. It can be made with gestures, such as American Sign Language. What is complicated and always changing are opinions about the rules: what they involve and where they came from and what components, if any, of human language are unique.

Syntax is the pattern of formation of sentences or phrases that governs the way the words in a sentence come together. Human language can string phrases together indefinitely to produce an unlimited number of sentences that are all different and have never been said before. If you speak that particular language, you can understand them, because the words are organized in a hierarchical and recursive way, not just randomly. So someone with human language can make a date for a certain time and place and give you directions about how and when to get there. “I’ll meet you at noon in front of the museum that is by the bank” is different from “I’ll meet you at noon in front of the bank that is by the museum.” Which is also different from the nonsense “Bank in meet that you noon is museum by I’ll front the of at.” And why is it nonsense? It is not following the rules of grammar. If language had no syntax, we would just have a bunch of words that you would string together willy-nilly. You could get some rudimentary meaning across perhaps, but you might be unintentionally stood up. Bad for a date.

How did syntax develop? A species either has the ability to learn a language or it does not, and this ability was acquired through an evolutionary process of natural selection. If a species can learn language, then the individual is born with a sense for both symbolic representation and syntax. Of course, there are those who disagree with this theory, in two distinct ways. Some believe that language is not an innate ability but that the ability to learn it is learned. This does not refer to learning a specific language, but rather to the ability to learn any language. In other words, this view holds that an individual does not spontaneously utilize syntax and symbolic representation. Others disagree about the evolution of language. Cognitive linguists, proponents of the “continuity” theory, argue that mental traits are subject to the same forces of natural selection as biological traits. “Discontinuity” theory proponents argue that some elements of behavior and mental traits are qualitatively unique to a given species and share no evolutionary heritage with other living species or archaic species. Noam Chomsky, the distinguished linguist at MIT, proposes that human language is “discontinuous” in this sense.37

Remember that what we are concerned with is looking for what is unique to humans. Our language ability is often put on that list by others besides Chomsky. Can chimps communicate with language? This question is really asking whether nonhuman apes can communicate with a language taught to them by humans. Early efforts to teach language to chimps were first made by David Premack when he was at the University of California at Santa Barbara. I know because the chimp that was being trained sort of had the office next to mine. Sarah was her name, and she was exceptionally bright. Indeed, she might have made tenure if she could ever have gotten the full story straight.

Premack moved on to the University of Pennsylvannia and kept trying. Others jumped into the fray, including Herbert Terrace of Columbia University. In 1979, Terrace published a skeptical account of his efforts to teach American Sign Language to a chimp whimsically named Nim Chimpsky. Nim was able to connect a sign to a meaning and could express simple thoughts, such as “give orange me give eat.” However, Nim could not form new ideas by linking signs in ways he hadn’t been taught; he didn’t grasp syntax. Terrace also reviewed the reports of others’ attempts to teach apes language and concluded the same thing: They aren’t coming up with complex sentences.

This leaves us with Koko the gorilla, who supposedly was taught sign language by Penny Patterson. A problem presents itself when evaluating Koko’s abilities. Patterson, the handler, is the only interpreter of the conversations, and as such, she is not objective. Stephen Anderson, a linguist at Yale, comments that although Patterson says she has kept systematic records, no one else has been able to study them, and that since 1982 all the information about Koko has come through the popular press and Internet chat sessions with Koko, Patterson acting as the interpreter and translator of her signs.36

This ambiguity in interpreting sign language is what led Sue Savage-Rumbaugh to use lexigrams, which are not ambiguous.38 Savage-Rumbaugh has indeed the most tantalizing data and a serendipitous bonobo. She used an artificial symbol system of graphic designs called lexigrams on a computer keyboard.

She began teaching a female bonobo named Matata how to use the keyboard. The experimenters would press a lexigram key and point to the intended object or action. The computer would then say the word and the key would light up. Matata had a baby named Kanzi, who was too young at the time to be separated from his mother, so he sat in on the training sessions with Matata. Matata was not a good pupil, and after two years, she had not learned much. When Kanzi was about two and a half years old, Matata was moved to a different facility, and Kanzi stepped into the spotlight. Although he had had no specific training, just by watching his mother’s sessions he had learned how to use some of the lexigrams on the keyboard in a systematic way!

Savage-Rumbaugh decided to change tactics. Instead of doing the training sessions she had been using with Matata, she would just carry the keyboard around and use it during routine activities. What has Kanzi accomplished? Well, he can match pictures, objects, lexigrams, and spoken words. He freely uses the keyboard to ask for objects he wants and places he wants to go to. He can tell you where he intends to go, and then he goes there. He can generalize a specific reference: He uses the lexigram for bread to mean all breads, including tacos. He can listen to an informational statement and adjust what he is doing using the new information. This is what Sue was referring to when she said, “First the linguists said we had to get our animals to use signs in a symbolic way if we wanted to say they learned language.” And she is right; Kanzi did.

Still, all of this begs the question of syntax. Stephen Anderson points out that both language production (the keyboard) and language recognition (spoken English) need to be evaluated.36 Kanzi uses both keyboard and gesture, and sometimes combines the two to make a sequence. He will use a lexigram first to specify the action, such as “tickle,” and then a pointing gesture to specify the agent—always in that order, even if he has to walk across the room to point to the lexigram first, and then return to indicate the agent. This is an arbitrary rule that Kanzi has developed on his own.* Anderson states that this does not yet satisfy the definition of syntax, in which the type of word (noun, verb, preposition, etc.), its meaning, and its role in the sentence (subject, object, conditional clause, etc.) all contribute to the meaning of the communication, not whether it is typed, gestured, spoken, or written.

Patricia Greenfield, a linguist at UCLA who studies language acquisition in children and has analyzed all of Savage-Rumbaugh’s data, disagrees. She thinks that there is syntactical structure in Kanzi’s multiword combinations. For instance, he can recognize word order: He understands the difference between “Make the doggie bite the snake” and “Make the snake bite the doggie,” and he uses stuffed animals to demonstrate what the two mean. He can respond 70 percent of the time to unfamiliar sentences, such as “Squeeze the hot dog,” given by vocal instruction from a concealed instructor. He is the first nonhuman to demonstrate either of these abilities.

Anderson remains unconvinced. He points out that when the understanding of a sentence depends upon a “grammatical word,” such as a preposition, Kanzi’s performance is poor. He seems to be unable to distinguish between in, on, or next to, and it is unclear if he understands conjunctions, such as and, that, and which. The obvious advantage that Kanzi has as a date is that you wouldn’t be subjected to dangling participles or terminal prepositions, as in “Where are you going to be at?” At his current level, Kanzi has a grasp of words for visual objects and actions. Anderson concludes, “Kanzi can associate lexigrams and some spoken words with parts of complex concepts in his mind, but words that are solely grammatical in content can only be ignored, because he has no grammar in which they might play a role.”36 Although Kanzi is showing remarkable abilities, we must remember that after many years, his abilities are rudimentary.

We learned in the last chapter that there are many similarities in brain structure between humans and the other great apes, especially chimps, but we have bigger brains, more connectivity, and that FOXP2 gene, among other things. We’ve learned that our anatomy has changed a great deal since the divergence from a common ancestor, allowing us to become better at vocalization. Doesn’t it make sense that part of the wiring was already in when we diverged from the common ancestor, and the chimp line made use of it in one way, whereas the multitude of changes that the hominid line underwent produced something else? Sue Savage-Rumbaugh states, “The significance of Kanzi’s possession of certain elements of language is, however, enormous. As the ape brain is just one-third the size of the human brain, we should accept the detection of no more than a few elements of language as evidence of continuity.”*

Are other nonhuman primates communicating with each other? Is there natural language within other species? After all, as Povinelli reminds us, other species have evolved to communicate with each other, not with humans. Well, unfortunately, as Savage-Rumbaugh points out, Kanzi knows more about human language than humans know about bonobo language.39


As I promised, we are now going to look at other types of communication. Language is but one type and clearly a bit shaky. Let’s go to the forest and see what has been observed. Perhaps the best-known studies in intraspecies animal communication have been those done by Robert Seyfarth and Dorothy Cheney in Amboseli National Park in Kenya with vervet monkeys. They have found that vervet monkeys have different alarm calls for different predators: one for snakes, one for leopards, and one for predatory birds.40 The response to a snake call is that the other vervet monkeys will stand up and look down; to the leopard call, they all scamper into the trees; and to the bird call, they go up against the trunks of trees and away from the exposed ends of the branches. It was thought until recently that animal vocalizations were exclusively emotional. However, a vervet does not always make an alarm call: He seldom makes it when he is alone and is more likely to make it when with kin than with non-kin. The calls are not an automatic emotional reaction.

Once again, it was David Premack who observed that it was possible for an affective communication system, even one based entirely on emotion, to become semantic (i.e., conveying information other than the emotion).41 Even though a scream can be an emotional reaction, it can also convey other information. This was a much contested idea for twenty years, but Seyfarth and Cheney, after further investigation with the vervets, agreed with him: “Signalers and recipients, though linked in a communicative event, are nonetheless separate and distinct because the mechanisms that cause a signaler to vocalize do not in any way constrain a listener’s ability to extract information from the call.”42 They explain that if a call is to provide information, it has to be specific: The same call can’t be used for several different reasons. Also the call has to be informative, meaning that it is made whenever a specific situation arises.43 Obviously there is information being given and understood. This could represent a mechanism of how language evolved.

However, Seyfarth and Cheney continue to point out that the most common function of human language is to influence the behavior of others by changing what they know, think, believe, or desire, but most evidence suggests that while animal vocalizations may result in a change, that is not their intention but is inadvertent. Vervet monkeys don’t appear to attribute mental states to others. For example, infant vervets often give the eagle alarm call mistakenly for pigeons. Nearby adults will look up, but they don’t give the alarm call themselves if they don’t see an eagle. However, if the infant is the first to give an alarm call for a genuine predator, adults will sometimes look up and give a second alarm call, but not always. With the random pattern of repeating the infant’s alarm call, the adults do not act as though they know that the infant is ignorant and just learning to spot predators, by validating all correct calls.42

There is similar data about wild chimpanzees, who do not appear to adjust their calls to inform ignorant individuals about their location or about food.44, 45 A mother will hear her lost baby call, but she does not answer back. Meanwhile, in the laboratory, Povinelli has found that a trained chimp cannot teach another chimp to pull a rope for a food reward. In short, nonhuman primates do not seem to make calls or attempt to communicate because they perceive another individual is ignorant or needs information, as a human does. If chimps had a theory of mind, the mother might think: I hear my baby call from a distance. He must not know where I am. I should make a call so he knows where I am. Nevertheless, chimps and other primates may recognize the effect that their calls have on I call in a certain way, and all my buddies run up into the trees. This in no way negates the fact that information is passed; it just may not have been the intention of the caller. So what does this all mean for our date? Well, vocal communication from the chimp’s point of view may just be “It’s all about me,” which when you think about it isn’t all that different from many human dates.

Chimps in the wild have been observed to communicate with a combination of glances, facial expressions, posturing, gesturing, grooming, and vocalization, just as Kanzi uses a combination of lexigrams and gestures. All these modes lead to interesting questions about the origins of language, which have yet to be answered. Has language evolved from hand gestures, a theory championed by Michael Corballis,46 or a combination of hand gestures and facial movements, as postulated by Giacomo Rizzolatti and Michael Arbib?47 Or did it evolve from vocalization alone? Or is the “big bang” theory of human language, postulated by Noam Chomsky, the correct one?

The speech center in humans is located in the left hemisphere. The left hemisphere controls the motor movements of the right side of the body. Chimpanzees exhibit preferential use of the right hand in gestural communication, especially when accompanied by a vocalization,48 and baboons in captivity have been found to gesture primarily with their right hand.49 There are many interesting studies of humans that show how hand gestures and language are connected. One study of twelve congenitally blind speakers found that they gestured as they spoke at the same rate as a group of sighted people, using the same range of gesture forms. The blind people would gesture while they spoke even when speaking to another blind person, which suggests that gestures are tightly coupled to the act of speaking.50 Congenitally deaf people in isolated communities will develop their own fully communicative hand gesture language with syntax.51

Helen J. Neville and her colleagues at the University of Oregon have confirmed through functional magnetic resonance imaging (fMRI) studies that both Broca’s and Wernicke’s areas, the two main language-mediating areas in the left side of the brain that are activated when hearing people speak, are also activated in deaf signers while they watch sentences in ASL. However, when deaf subjects read, they do not activate these regions.52 It has also been observed that anterior lesions in the vicinity of Broca’s area produce deficits in signing itself, but more posterior lesions produce deficits in the comprehension of signing. Neville also found that there was more activity in the right side of the brain in the deaf subjects than in the hearing people. This may be because of the spatial aspect of signing, mostly a right-hemisphere function. A similar thing is going on in the chimp’s brain as it gestures.

Now we’re going to Italy, a land famous for its hand gestures. Giacomo Rizzolatti, Leonardo Fogassi, and Vittorio Gallese, from the beautiful city of Parma, first discovered mirror neurons in the premotor area (area F5) of the brain of monkeys in 1996. These neurons fire when a monkey performs an action in which his hand or mouth interact with an object. They also fire when the monkey merely sees another monkey (or human experimenter) perform the same type of action. Thus they are called mirror neurons. They were later also found in another part of the monkey brain, the inferior parietal lobule.53 It is generally accepted that the F5 region of the monkey brain shares the same ancestry as Broca’s area in the human brain.47 Broca’s area in the human is thought to be the area for speech, and as we have seen above, for signing; the dorsal part of F5 in the monkey is an area for hand movements,54, 55 and the ventral part is an area for mouth and larynx movement.56, 57 Rizzolatti and Michael Arbib, director of the University of Southern California Brain Project, suggest that the mirror system was fundamental for the development of speech, and before speech for other forms of intentional communication,47 such as facial expression and hand gestures. Do humans have these mirror neurons? There is a lot of evidence that we do.58 The cortical areas active during action observation in humans match those active in the monkey. So there seems to be a fundamental mechanism for action recognition that is common to apes and humans.

Here is their proposal about language development: Individuals recognize actions made by others because the pattern of firing neurons made when observing an action is similar to the pattern produced to generate the action. So maybe the speech circuits in humans developed because the precursor structure that later evolved into Broca’s area had a mechanism for recognizing actions in others—and had to have this ability before language could evolve.

Huh? Rizzolatti and his buddies know they are walking on the wild side with this hypothesis, but let’s see where they take us, because this is what neuroscience is all about. You find something interesting on the cellular level and try to connect it all the way to behavior. You propose a hypothesis, and then either it gets shot full of holes or it doesn’t. As in many fields of science, the emotionally weak and the thin-skinned need not apply.

We have already seen that in the vervets there is a gap between recognizing actions and sending messages with communicative intent. How did this intent develop in humans? Normally, when an individual is watching an action or getting ready to perform an action, the premotor areas are on alert. There is a system of inhibition to prevent observers of an action from emitting a motor behavior that mimics it.47 Otherwise we’d be playing follow the leader all the time. However, sometimes if the observed action is particularly interesting, there can be a brief lapse of inhibition and an involuntary response from the observer. This sets up a two-way street. The individual performing the action (the actor) will recognize a response in the observer, and the observer will see that his reaction caused a reaction in the actor. If the observer can control his mirror neuron system, then he can send a voluntary signal and thus begin a rudimentary dialogue of sorts. Voluntary control of the mirror neurons is the necessary foundation for the beginning of language. The ability to notice that one has actually given a signal and the ability to recognize that it caused a reaction did not necessarily arise at the same time. Each ability would have had great adaptive advantage and would have been selected for.

What action are they talking about? Was it facial or gestural? Remember that both F5 and Broca’s area have the neural structures to control both. Speculating on the sequence of events that led to speech, Rizzolatti and Arbib guess that the first gestures used from individual to individual were orofacial. Jane Goodall states that long bouts of eye contact may accompany friendly interactions, and then describes one of many facial expressions: “There is one facial expression which, more than any other has dramatic signal value—the full closed grin. When this expression suddenly appears, it is as though the whole face has been split by a gash of white teeth set in bright pink gums. It is often given silently, in response to an unexpected and frightening stimulus. When an individual turns to his companions with his face transfigured by this horrifying grin, it usually evokes an instant fear response in the beholders.”59

Monkeys, apes, and humans still use orofacial gestures as their main natural way to communicate. The lip smacks and tongue smacks of monkeys persist in humans, where they form syllables in speech production. Did vocalization come next? Rizzolatti and Arbib don’t think so. Remember when we talked about monkey and ape vocalization being a closed system? A manual system could have given more information. In a vocal system of limited anatomy, the only way to enhance an emotional vocalization of “Scream scream scream” telling you to be scared is to do it louder: “Be more scared.” However, a manual gesture system could add information: “Scream scream scream” tells you to be scared and then a gesture to indicate a snake that is big and where it is. This type of behavior has been observed in chimps to a limited extent in the Ivory Coast: When traveling or encountering a neighboring group, the chimps combine a bark with drumming.60

Once this happened, an object or event described with a gesture could be associated with a vocalization that is not a scream but a short ooo or aah. If the same sound was used each time for the same meaning, a rudimentary vocabulary could have been started. In order for this new vocalization to develop into speech, it had to be skillfully controlled by more than just the old emotional vocal centers. The F5-like precursor—which already had mirror neurons, a control of orolaryngeal movements, and a link with the primary motor cortex—could have developed into Broca’s area. Because an effective communication system would provide a survival advantage, eventually the evolutionary pressure to form more complex sounds, and the anatomy that could produce them, would be selected for. Manual gestures would lose their importance (except for Italians) and become an accessory to language, but they would still be able to function if need be, for sign language.

Consider this from Luigi Barzini in his book The Italians:

Often enough, a simple gesture, accompanied by suitable facial expressions, takes the place not of a few words, but of a whole and eloquent speech. This, for instance; imagine two gentlemen sitting at a café table. The first is explaining at great length…. “This continent of ours, Europe, old, decrepit Europe, all divided into different nations, each nation subdivided into provinces, each nation and each province living its own petty life, speaking its incomprehensible dialect, nurturing its ideas, prejudices, defects, hatreds…. Each of us gloating over the memories of the defeats inflicted by us on our neighbours and completely oblivious of the defeats our neighbours inflicted on us. How easy life would become if we were to fuse into one whole, Europa, the Christendom of old, the dream of Charlemagne, of Metternich, of many great men, and why not? The dream of Hitler too.”

The second gentleman is listening patiently, looking intently at the first’s face. At a certain moment, as if overwhelmed by the abundance of his friend’s arguments or the facility of his optimism, he slowly lifts one hand, perpendicularly, in a straight line, from the table, as far as it will go, higher than his head. Meanwhile he utters only one sound, a prolonged “eeeeeh,” like a sigh. His eyes never leave the other man’s face. His expression is placid, slightly tired, vaguely incredulous. The mimicry means: “How quickly you rush to conclusions, my friend, how complicated your reasoning, how unreasonable your hopes, when we all know the world has always been the same and all bright solutions to our problems have in turn produced more and different problems, more serious and unbearable problems than the ones we were accustomed to.” 61


Back to our date. So far we’ve found that she can plan a little, communicate a little, but not with speech or the language skills that we use, probably doesn’t think abstractly, and is mostly going to communicate only about her needs. What about feelings? Emotions?

The research into emotions, until recently, has gone through a period of neglect. The exceptionally talented Joseph LeDoux, a former student of mine who is now at New York University, states that this happened for a couple of reasons. Since the 1950s, it was thought that the limbic system (which involves many brain structures) was responsible for creating emotions, but the more recent emergence of cognitive science has dominated research attention. Although he thinks that the limbic system concept does not adequately explain specific brain circuits of emotions, he does agree that emotions involve relatively primitive circuits that have been conserved throughout mammalian evolution.62

Emotion research had also suffered from the problem of subjectivity, whereas cognitive scientists have been able to show how the brain processes external stimuli (pain, for instance), without having to show how the conscious perceptual experiences come about. Most cognitive processes have been found to occur subconsciously, with only the end product reaching the conscious mind if at all. LeDoux continues, “Contrary to popular belief, conscious feelings are not required to produce emotional responses, which, like cognitive processes, involve unconscious processing mechanisms.” To the extent that many of the systems that function nonconsciously in the human brain function similarly in the brains of other animals, there is considerable overlap among species in the nonconscious aspects of the self.63

One of the best-studied emotions is fear. What happens when you hear the rattle of a rattlesnake or catch a slithering movement in the grass? The sensory inputs go to the thalamus, a type of relay station. Then the impulses are sent to the processing areas in the cortex and relayed to the frontal cortex. There they are integrated with other higher mental processes and into the stream of consciousness; this is when a person becomes consciously aware of the information (there is a rattler!), has to decide to act (a rattlesnake is poisonous, I don’t want it to bite me, I should move back), and put the action into gear (feet don’t fail me now!). All this takes a while. It can take a second or two. But there is a shortcut that obviously is an advantage. It is through the amygdala, which sits under the thalamus and keeps track of everything that is streaming through. If it recognizes a pattern that was associated with danger in the past, it has a direct connection to the brainstem, which then activates the fight-or-flight response and rings the alarm. You jump back before you realize why. This is more apparent when you have jumped back only to realize that it was not a snake. This faster pathway, the old fight-or-flight response, is present in other mammals. To what extent other emotions will be found to inhabit mutual pathways is not yet known, but it is now another hotbed of research.

Not only does it seem that we share at least some of the same unconscious emotions as our chimp date; observational studies in the wild are revealing that we may be more unconsciously apelike than we imagine. Let’s go outside.


Until January 7, 1974, scientists treated the remarkable violence of humanity as something uniquely ours. Then in Gombe National Park, Tanzania, Hillali Matama, the senior field assistant from Jane Goodall’s research center in Gombe, observed for the first time a raiding party of chimps furtively entering the territory of another chimp group and killing a lone male who was quietly eating, and the subsequent systematic killing of the rest of the males in that rival group over the next three years. And the females? Two of the young females transferred into the raiding group, one watched her mother beaten to death by her new group, and four others disappeared. What was more shocking was that these groups had originally all been one community. More observations were recorded from other areas and observers. Toshisada Nishida’s team in Tanzania’s Mahale Mountains National Park (the only twenty-year chimp research program other than Goodall’s) has seen violent charges toward strangers by border patrols and furious clashes between male parties from neighboring communities.

Since these first observations, two entire chimpanzee communities have been exterminated by their own kind. Other observers of nonhuman primates witnessed male gorillas and some monkey species killing infants, and male chimpanzees and orangutans raping females. As more field observations were recorded, we’ve learned that although infanticide is typical behavior in many species within every group of animals—birds, fish, insects, rodents, and primates, practiced by males, females, and infants, depending upon the species—killing adults is not.

Richard Wrangham, professor of biological anthropology at Harvard, believes we can trace the origins of human violence, particularly male violence, to our origins as apes, and more specifically to our common ancestry with the chimp. In his book Demonic Males, he has a convincing argument. 64 He states that the most compelling set of facts that point to this conclusion is involved with the similarities of our two societies. “Very few animals live in patrilineal, male-bonded communities wherein females routinely reduce the risks of inbreeding by moving to neighboring groups to mate. And only two animal species are known to do so with a system of intense, male-initiated territorial aggression, including lethal raiding into neighboring communities in search of vulnerable enemies to attack and kill. Out of four thousand mammals and ten million or more other animal species, this suite of behaviors is known only among chimpanzees and humans.”*

Wrangham reports that observational studies have found chimps to be patriarchal. Males are dominant, inherit territory, raid and kill their neighbors, and gain the spoils (not only increased foraging, but neighboring females), but they also are killed if they lose their territory. Females, however, gain a different advantage. They can remain in their territory and continue to forage by simply changing allegiance to the conquering band. They remain alive to reproduce again, whereas the male is killed. OK, so chimps are patrilineal, but what about humans?

Wrangham reviews the ethnographic records, studies of modern-day primitive peoples, and archaeological finds to show that humans are, and always have been, a patrilineal society, regardless of what some feminist organizations assert. (It is interesting to note that while I type this in my Microsoft Word program, the word patrilineal is underlined by the spell-check feature as having been spelled incorrectly, and the suggested spelling is for the word matrilineal, which is never underlined as having been spelled incorrectly.) It has been argued that this patriarchy is a cultural invention, but a new field of study, branded evolutionary feminism, views patriarchy as a part of human biology.

And lethal raiding? Wrangham postulates that there is the possibility that intergroup aggression has a common origin because it is unusual among other animals. Although human aggression is well known in the modern world, he also sees patterns of violence in current primitive cultures that are similar to the chimps’ violence. One example is the Yanomami, an isolated cultural group of twenty thousand people living in the lowland forests of the Amazon basin, who are famous for intense warfare. They are subsistence farmers having plenty of food, and each community is made up of about ninety members. Men stay in the village of their birth, and the women change communities at marriage. The Yanomami do not fight over resources but most often over women. Thirty percent of Yanomami men die from violence. However, the violent raiders are rewarded. They are honored by their society and have two and a half times the number of wives as other men and three times the number of children. “Lethal raiding among the Yanomamos gives the raiders genetic success.

“The conditions that make Yanomami society similar to that of chimps are their political independence and the fact that they have few material goods and no gold, valuable objects, or stores of food to fight over. In this stark world, some of the more familiar patterns of human warfare disappear. There are no pitched battles, no military alliances, no strategies focused on a prize, and no seizure of stored goods. What remain are the penetrating expeditions in search of a chance to attack, to kill a neighbor, and then to escape.”* Thirty percent of male chimps die from aggression in Gombe National Park, the same percentage found in the Yanomami villages. Mortality rates from aggression in other primitive tribes are similar: in highland New Guinea, Australia, and the !Kung of the Kalahari. As Wrangham observes, hunter-gatherer societies don’t fare any better under the microscope.

A handful of societies have managed to avoid outright war for extended periods. Switzerland is the best modern example. However, to retain their peace, as John McPhee writes in La Place de la Concorde Suisse, “There is scarcely a scene in Switzerland that is not ready to erupt in fire to repel an invasive war.” The Swiss maintain the largest army per capita in the world, enforce compulsory military service, bury live mines at critical bridges and passes, and keep deep caves carved into mountains stocked with enough medical supplies, food, water, and equipment to last the full army and some civilians a year or more. They also are isolated by the Alps.65

So, humans and chimps are patrilineal, and both humans and chimps have a history of lethal raiding. And it is well known that human males are more violent than females. Violent crime statistics from around the world reflect that. So agreeing on our similarities, let’s hear why Wrangham thinks this happened. It boils down to the ecological version of economics; something called cost-of-grouping theory, which basically states that the size of the group depends on its resources. In an environment where food is seasonal or erratic, the party size will vary accordingly: more food, bigger parties; less food, smaller parties. Whether a group has to travel, or how far it has to travel, depends on what they eat. Some species have a food source that is abundant and stable, so their groups end up being stable (such as gorillas, who sit around and eat leaves all day). However, some species have evolved to eat high-quality, difficult-to-find foods that aren’t always available, such as nuts, fruits, roots, and meat. Here we are like the chimps.

Bonobos, on the other hand, are different. They eat what the chimps eat but also the abundant leaves that gorillas eat, without the gorillas to compete with. They don’t have to travel far to find food; they live on Easy Street. The type of food that we and the chimps eat has made males more dominant. Traveling to find food slows down the females, who carry and nurse the infants. The guys and the childless females can go farther and faster and get to the patch of food first, and then hang out together. They can afford to have larger parties. The advantage of moving around to find food with a variable party size gives a species flexibility and the ability to adapt to changing environments, but the disadvantage is that when the group becomes small, it is vulnerable to attack from a temporarily larger group. This is what Wrangham calls a party-gang species: species with coalitionary bonds (the males hanging out together) and variable party size.

What makes it possible for these species to kill, just as it is possible for some species to indulge in infanticide, is once again economic. It is cheap to kill. The cost-to-benefit ratio is good. When you kill an infant, you don’t really risk being injured yourself, so the cost is low. You gain either a food source or increased chance of mating with the female, because when her infant is dead, she will stop lactating and ovulate again. When you are in a gang against a weaker neighbor, once again the risk of injury is low. What do you gain? It weakens the neighbors, which is always good for the future, expands the food supply, and finds you mating once again.

But why are the males so aggressive? Has sexual selection selected for male aggression? Although they do not have large canine teeth, all apes can fight with their fists. Adapted for swinging in trees, the shoulder joint can rotate, and an ape’s long arms and a balled-up fist can pack a punch that keeps opponents at bay. Fists can also grasp weapons. Chimps are known to throw rocks and branches. At puberty, both ape and human males develop increased upper body musculature and broad shoulders as the shoulder cartilage and muscle respond to increasing testosterone levels. But even though there is a physical ability to be aggressive, not all strong animals are.

What is going on in the brain department? We can grasp the idea that animals can’t control their emotions or urges, but aren’t humans able to control their aggression through cool reasoning? Well, it turns out that it isn’t as simple as that. Antonio Damasio, head of the neurology department at the University of Southern California, has studied a group of patients who have all had damage to a particular location of the ventromedial part of the prefrontal cortex.* They all lack initiative, can’t make a decision, and are unemotional. One patient whom he studied closely tested normally in intellectual ability, social sensitivity, and moral sense, and could devise appropriate solutions and foresee consequences to hypothetical problems, but he could never make a decision. Damasio concluded that this patient and other similar ones could not decide because they were unable to connect an emotional value to an option: Pure reason was not enough to make a decision. Reason made the list of options, but emotion made the choice.66 We are going to talk about this in later chapters. What is important to know now is that even though we humans like to think of ourselves as being able to make non-emotional decisions, emotions play a part in all decisions.

Wrangham concludes that if emotion is the ultimate arbitrator of an action, the emotion that underlies aggression for both chimps and man is pride. He states that male chimps in their prime organize their whole lives around their rank. All decisions are guided by it, including when they get up in the morning, with whom they travel, whom they groom, and with whom they share food. All actions have the goal of becoming the alpha male. The difficulty of reaching this position causes aggression. With humans it is much the same. Wrangham quotes Samuel Johnson, who observed in the eighteenth century, “No two people can be half an hour together, but one shall acquire an evident superiority over the other.” Just as today, men flaunt their status with expensive watches, cars, houses, women, and class-conscious societies.

Wrangham hypothesizes that pride “evolved during countless generations in which males who achieved high status were able to turn their social success into extra reproduction.”* It is a legacy of sexual selection. Matt Ridley concludes his chapter about the nature of women in his book The Red Queen, “There has been no genetic change since we were hunter-gatherers, but deep in the mind of the modern man is a simple male hunter-gatherer rule: Strive to acquire power and use it to lure women who will bear heirs; strive to acquire wealth and use it to buy other men’s wives who will bear bastards. It began with a man who shared a piece of prized fish or honey with an attractive neighbor’s wife in exchange for a brief affair and continues with a pop star ushering a model into his Mercedes.”67

So men and chimps are physically prepared for physical aggression and emotionally primed to achieve high status, but so are solitary orangutans, while humans and chimps are social. Pride accounts for social aggression also. Any group—whether it is a team, a religion, a sex, a business, or a country—can have a devoted following, but why? Is it the result of rational deliberation, or is it an innate response of an old ape brain?

Social psychologists have shown that group loyalty and hostility emerge with predictable ease. The process begins with groups’ categorizing into Us and Them. It is called the in-group-out-group bias and is universal and ineradicable: French-speaking Canadians versus English-speaking Canadians, police versus FBI, Broncos fans versus everyone else, Stones fans versus Beatles fans…. This is to be expected in a species with a long history of intergroup aggression. Darwin wrote, “A tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage and sympathy, were always ready to aid one another, and to sacrifice themselves for the common good, would be victorious over most other tribes, and this would be natural selection.”* He wrote this to show how morality could emerge out of natural selection for solidarity. Wrangham also suggests that morality based on intragroup loyalty worked, in evolutionary history, because it made groups more effectively aggressive.


Sometimes looking at the family tree isn’t always pretty, but it can explain many seemingly mysterious behaviors. Many a couple has come to grief because they ignored their prospective partner’s family. In the case of our chimp date, we have a common ancestor; the families have diverged in many respects but still share many characteristics, as Richard Wrangham has pointed out. We have seen how the anatomy of our body has changed significantly and been the basis for changes that have led to many of our unique features. Bipedalism led to free hands and changed breathing patterns. Our arching and opposable thumbs have made it possible for us to develop the finest motor coordination of any species. Our unique larynx has allowed us to make the infinite number of sounds that we use for speech. Our mirror neuron system is far more extensive than has been found in other species, and we will see that it has far more ramifications than just language. Other changes have been going on in our brains, changes that allow us to understand to a far greater extent than our chimp relatives that others have thoughts, beliefs, and desires. Building on these differences, we will move to the next chapter and see where it takes us. I think a day spent with Kanzi would be very interesting, but for the long term, I prefer more culture. Make my date a Homo sapiens.