A Fresh Look at Human Exceptionalism
From ancient times, the Western traditions have assumed that a hard line divides humans from other animals, a line that does not exist between other species. By definition, every species is unique. Cows are different from rabbits. But there is no line between cows and rabbits similar to the line that is purported to separate humans from both cows and rabbits. We humans stand alone on our side of the line, while everyone else is lumped together on theirs. Every species may be unique, but we are exceptional. And we believe that our exceptional nature entitles us to use animals however we wish.
Human exceptionalism is a conclusion eternally in search of a rationale. Valid beliefs arise out of evidence and logic. The rationale precedes the belief. But human exceptionalism, like white exceptionalism and male exceptionalism, reverses this process. The belief in human exceptionalism came first, and only later, when it had been challenged, did philosophers begin to seek a rationale that they could use to defend it. Over the centuries one after another such rationale has been proposed—and discredited. But in every case, the majority response has not been to abandon the belief, but to ignore the evidence and double down on it while looking for a new justification. We know we are exceptional, and if we have never been able to support this “knowledge” with evidence and logic, then the evidence and logic must be wrong.
When the conclusion precedes the argument, both are automatically suspect. Putting the caboose—or a whole string of cabooses—before the engine is the salient characteristic of prejudice, which entails evaluating the evidence on the basis of the conclusion instead of coming to a conclusion on the basis of the evidence. Let’s take a quick look at the most influential of the many ways philosophers and theologians have searched over the centuries for an argument that would prove the validity of human exceptionalism.
We humans emerged into history taking our exceptional status for granted. Only recently was human exceptionalism brought into question, during a period of rapid intellectual, spiritual, and ethical progress lasting roughly from 800 BCE until 200 BCE. During this Axial Age, as it was dubbed by German philosopher Karl Jaspers (1883-1969), spiritual pioneers in India, Israel, and Greece proclaimed that all sentient beings are fundamentally alike and morally equal. None is separated out from the pack by some exceptional quality. There is no “line which they cannot pass.” (See Phelps, Longest Struggle, 16-28)
In the West, it was Pythagoras (c 558-c 450 BCE), the early Greek mathematician, geometer, musicologist and religious leader, who first rejected human exceptionalism, arguing that the souls of animals and the souls of humans are immortal and identical. In fact, Pythagoras asserted, the same soul might be incarnated sometimes as a human being and other times as a horse, a pig, or some other animal. Animals are not merely like us, they are us—and we are they. This being the case, sacrificing animals to the gods or eating their flesh is not only cruel, it is murder. Unless Pythagoras’ claim could be refuted, the line could not be preserved and human exceptionalism could not be sustained.
The Myth of Reason
When someone shouts that the emperor is naked, there is only one way to prove that the cry is a false alarm: Parade His Highness, resplendent in the imperial raiment, before the world. And so, Greek philosophers—primarily Aristotle and the Stoics—set about to put on public display the quality that separates humans from the members of all other species.
Aristotle (384-322 BCE) went first, and he asserted that we are exceptional because among all living beings, we alone possess a rational soul—by which he meant that we are able to generalize and to reason abstractly. Animals, he believed, can solve practical problems that confront them directly, such as finding food and escaping from danger, but their mental abilities are limited to the particular and the immediate. Reason, then, is the hard and fast line that separates us from all other species.
In Aristotle’s universe, all beings are arranged in a vertical hierarchy, and those who are lower on the scale exist for the benefit of those who are higher, while those who are higher have few if any obligations to those who languish beneath them. Thus, slaves exist for the benefit of free men, free men exist for the benefit of aristocrats, women exist for the benefit of men—and animals exist for the benefit of human beings. We may use them however we wish. Since this scale mimicked the power structure in classical Greece, Aristotle’s hierarchy is nothing more than a claim that might makes right gussied up in sophisticated-sounding philosophical jargon.
The Stoic philosophers agreed with Aristotle and emphasized a point that he had made in passing, namely that rational beings can share friendship and form a community only with other rational beings. Therefore, humanity is a gated community set apart from the rest of the animal kingdom by our unique ability to reason, and we owe moral consideration only to members of our own community.
There are three fatal flaws in the argument that animals are incapable of rational thought, that because of this we are unable to enter into a communal relationship with them and that, therefore, we are free to exploit them however we see fit. First, we simply do not know whether animals speculate about abstract questions such as the meaning of life. As I will show farther on, cognitive ethologists are now rapidly accumulating evidence that shows beyond doubt that vertebrates are able to employ abstract concepts and to generalize. But in Aristotle’s day, there was little evidence one way or the other. And when a proposition cannot be proven or disproven we must suspend judgment, not assume that the proposition is false. As Carl Sagan reminded us, “Absence of evidence is not evidence of absence.” Aristotle’s assumption that animals lack reason was unsupported and should not have been accepted as fact even in classical Greece.
What was known to Aristotle—and should have given him pause—is that the behavior of nonhuman animals communicates an understanding of the universe very similar to ours. They give every appearance of living in a three-dimensional world of objects and extension, a temporal world in which time flows only forward, and a sensory world which, if not precisely coterminous with ours, overlaps it to a great extent. They manipulate their environments to the limits imposed by their anatomy—build nests, dig burrows, and so on—for many of the same purposes that we do. And they interact with others, including humans, in ways that demonstrate an ability to interpret others’ behavior and respond accordingly.
Despite the self-aggrandizing pretensions of philosophers, reason and intellectualization are not the same thing, and the capacity to engage in multiple levels of subtle and sophisticated intellectualization is not the litmus test for identifying a rational being. A rational being is one who acts intentionally to achieve a previously conceived goal in ways that demonstrate an understanding of causality. The ability to construct elaborate, abstruse theories about the world and our place in it (most of which turn out to be wrong) is merely icing on the cake of reason. Those who have a taste for it may consider it a supreme delicacy, but its nutritional value is zero. In fact, all those empty intellectual calories can do a great deal of harm. Over the centuries, clever sophistries about the alien and inferior nature of animals have called havoc down upon our relatives.
A peasant farmer who can neither read nor write is as much a rational being as a philosopher, even though he may engage in little abstruse intellectualization. Lions hunting are acting rationally and intentionally, as are zebras when they flee the lions, birds when they build nests in which to lay their eggs and raise their young, cats when they rub up against our ankles asking to be fed, and on and on. A capacity and taste for exquisite abstractions are no more signs of inherent superiority than is the ability to plant seeds, navigate by the Earth’s magnetic field, or spin a web. It is no coincidence that Aristotle and the flotilla of professional philosophers who have sailed in his wake deem the skill that sustains their livelihood and their fame to be the highest and noblest quality to which anyone could aspire. Reason, they assure us, makes humanity the pinnacle of creation and philosophers the pinnacle of humanity. This is not philosophy; it is delusional self-promotion.
The second flaw in Aristotle’s claim is that human beings commonly share friendships with other animals, and did so in classical Greece. As the owner of the Western world’s first zoo—populated with exotic birds and animals sent back to him from North Africa, the Middle East and Asia by his friend and former student Alexander the Great—Aristotle should have recognized the capacity of animals to share friendship with human beings. He is famous for his rigorous, systematic observation of living animals and detailed descriptions of their anatomy, physiology and behavior (in captivity). Did he never feel stirrings of friendship for any of them? At the royal compound of Amyntas III of Macedon, where Aristotle spent his childhood, there would have been cows, horses, donkeys, goats and sheep—not to mention dogs and probably cats. Did the philosopher-to-be never play with any of them? Did he never enjoy their company and observe that they enjoyed his? There is more to friendship than playing chess and discussing philosophy. In fact, most friends do neither. Friendship is comfort, it is companionship, it is joy in the presence of another sentient being. Friendship consists more in feeling than in reason. Every social being needs friends of their own kind. But we also form friendships with people of other species. It is a natural, normal, healthy process. Animals who live in proximity to us are functioning members of our community with whom we often establish friendships.
The third flaw in Aristotle’s argument is that there is no reason why a lesser capacity for rational thought should condemn someone to being enslaved and murdered for the appetites and convenience of someone with a greater capacity for rational thought. We would not have allowed Einstein to enslave and slaughter someone who had an IQ of 60. Einstein himself would have been horrified at the idea. Where humans are concerned, we all recognize that it is not reason or intelligence that makes it wrong to enslave and murder someone. It is their aversion to suffering and fear of death. The same principle applies to all sentient beings.
Despite its obvious failings, Aristotle’s assertion that human exceptionalism is rooted in our unique capacity for rational thought became the conventional wisdom of the Greco-Roman world. There were only a few philosophers and writers—most notably the historian and essayist Plutarch (45-120 CE) and Neo-Platonists Plotinus (204-270 CE) and Porphyry (234-305 CE)—who rejected the human exceptionalism of Aristotle in favor of the egalitarianism of Pythagoras. Following the conversion of the Roman Empire to Christianity in the fourth century, competing schools of thought—both religious and secular—were eradicated, and along with them vegetarianism and moral concern for animals. The leading theologians of the Western Church, Saint Augustine (354–430) and Saint Thomas Aquinas (1225–1274), put a Christian spin on the views of Aristotle and the Stoic philosophers by arguing that the nature of God is rationality and the Biblical claim that human beings are made “in the image and likeness of God,” means that we are alone among living creatures in possessing a rational soul. Therefore, they argued, we cannot share friendship with animals and owe them no moral duties.
Augustine’s and Aquinas’ argument fails on its own terms. In plain language, the New Testament identifies God’s defining quality and it is not reason. “God is love, and the one who abides in love abides in God and God abides in him.” (I John 4:16) Greek has three words for “love:” Eros is romantic love; philos is personal love, the love of family and friends; agape (ah-GAH-pay), the word used by the author of I John, is a universal concern for the wellbeing and happiness of others, what we might call “compassion” or “lovingkindness.” It is through love and compassion for others that we reflect the image and likeness of God. Nowhere does the Bible suggest that we reflect the image and likeness of God in our ability to reason.
Moral superiority is not inborn; it is earned by behaving in a morally superior manner. And it does not entitle anyone to exploit or abuse others. Quite the opposite, in fact. As Albus Dumbledore told Harry Potter, “It is not our abilities that determine who we are; it is our choices.” Rights are created by needs. Every being who suffers has a right to have her suffering eased. Every being facing death has a right to have his life spared. Obviously, tragically, not every need can be satisfied, not every right can be honored. If the lamb has a right not to be killed by the lion, the lion has an equal right not to be killed by starvation. These rights cannot be reconciled. This is the moral flaw built into the structure of the cosmos. But that is no excuse not to satisfy the needs, and respect the rights, of as many beings in as many situations as we can. The existence of suffering that we cannot relieve and death that we cannot postpone does not give us the right to inflict unnecessary suffering or death on others. We earn our moral superiority by easing the suffering and sparing the lives of everyone we can, not by adding to it.
Sentience, Contracts, and Autonomy
At the beginning of the Enlightenment, the view that we are exceptional because of our ability to reason—which had been the conventional wisdom for 2000 years—was challenged by Rene Descartes (1596–1650), a French mathematician and early proponent of the scientific method. Aristotle and Aquinas had conceded that animals are sentient. This was a problem for Descartes, who wanted to defend vivisection, which was coming under increasing attack for its wanton cruelty. Descartes solved his problem by arguing that the line between humans and animals should be drawn at sentience rather than reason, and that animals are not sentient. Animals, Descartes claimed, are merely complex machines with no interior lives and no awareness whatsoever. To the objection that animals make pitiful cries when they are injured, he replied that the cries of an animal do not mean that he is suffering any more than the squeaking of a rusty hinge means that the hinge is suffering. To the argument that animal behavior is far too complex to be explained in a purely mechanical way, Descartes replied that if human beings can create machines as complex as Renaissance clocks with their elaborate moving tableaux, surely God could create machines infinitely more complex. Through the 19th and into the 20th century, vivisectors defended their cruelty by relying on Descartes’ claim that animals cannot suffer.
English Enlightenment philosopher and social critic Jeremy Bentham (1748–1832) agreed with Descartes that sentience, not reason, was the quality that entitled beings to moral consideration. But he disagreed sharply with the French apologist for vivisection by arguing that animals are, indeed, sentient and, therefore, entitled to have their interest in not being made to suffer respected.
Up to this point, Bentham seems to be arguing that there is no hard and fast line between humans and animals. And where suffering is concerned, that is precisely what he is doing. But now, Bentham does something peculiar. He argues that animals live in an eternal present; unlike us, they have no concept of the future and no anticipation of future happiness. Therefore, if the deed is done quickly and painlessly, killing an animal does her no harm; and there is no ethical reason why we should not slaughter animals and eat their flesh. In this way Bentham argues that there is, in fact, a hard and fast line between humans and animals, but it applies only to death, not to suffering. We are exceptional in that we have a sense of ourselves as continuing beings with a future to look forward to.
This strange notion that animals have no concept of the future—or at most a very weak concept of the future—has endured down to the present, where it has been espoused by such prominent animal liberation philosophers as Peter Singer, Tom Regan and Mark Rowlands. It is also the philosophical underpinning of the animal welfare philosophy. Killing animals does not harm them, but inflicting suffering does. Therefore, we may kill animals with a clear conscience, but we must inflict as little suffering on them as we can.
Contemplating this, one is forced to wonder if Bentham had ever really paid attention to animals. He was guardian of a cat who liked to sleep on his desk while he was writing. Why did Bentham think that The Reverend John Langhorne jumped up on the desk if not in anticipation of the future pleasure of napping close to his beloved friend? Why do so many dogs go to the window and watch when it is time for their companions to come home from work? And why do squirrels, chipmunks, jays and other animals store up seeds and nuts if not in anticipation of a coming winter when food will be scarce? So much of their behavior reveals a sharp sense of the future that it is hard to see how Bentham could have seriously entertained the idea that animals live in an eternal present.
But there is more to death than the loss of a future. All sentient beings love life and dread death at a raw and primitive level that lies deeper than considerations of lost time. The will to live is so universal and so powerful that Albert Schweitzer thought it more fundamental than even sentience. (See Phelps, “Quest”) The evolutionary advantage of a strong will to live is obvious. Without it, we would not protect our own lives, we would not survive very long, and we would be left in the evolutionary dust by beings who did have an urgent love of life and dread of death. Death harms all sentient beings because it violates this fundamental component of their nature.
Still another approach to the line between humans and animals is found in social contract theory. According to this view—which was first put forward by Thomas Hobbes (1588–1679), John Locke (1632–1704), and Jean-Jacques Rousseau (1712–1778)—human societies are based on a contract entered into by all members of the society. The administrator of the contract is the state, and the terms of the contract are—very roughly—that individuals will not murder, assault, or rob one another, will maintain public order (by not driving on the wrong side of the street, for instance), and will support the society (by paying taxes, participating in civic life, and so on). Human rights derive from participation in the contract. Because I fulfill my obligations, I have certain rights—not to be murdered, assaulted, or robbed, for example. Animals do not even know that the contract exists; they cannot participate in it. And because they cannot fulfill the contract’s obligations, animals are not entitled to its benefits. Therefore, we are free to enslave and slaughter them as we wish. As English philosopher Roger Scruton (b. 1944) puts it, “If animals have rights, then they have duties too.” Since animals are unable to fulfill these duties, according to Scruton they have no rights. (Scruton)
There are severe problems with this view. Most importantly for our purposes, human beings who are unable to fulfill obligations under the contract—small children and the severely disabled, for instance—are nonetheless afforded the protections of society. We respond to their need and ignore their inability to assume duties under the contract. This suggests that the social contract is not the basis for morality, but simply a partial expression of it, a way of assuring that we treat one another in accordance with moral principles that have a more profound origin. And so, the obligation to show compassion and respect to others does not arise from our ability to participate in the social contract, but from some deeper source. This was recognized by Rousseau himself and by the 20th century’s most influential social contract theorist, John Rawls (1921-2002), both of whom acknowledged that the social contract does not encompass all of our moral obligations and that we have ethical duties to animals that lie outside the scope of the contract. (Rousseau, 47; Rawls, 448-449)
The philosopher who best epitomizes the Enlightenment is Immanuel Kant (1724–1804). Kant believed that humans are exceptional because we are autonomous, that is to say, we can make rational decisions and then act on them, while animals cannot. To Kant, this means that human beings are “ends in themselves,” while animals exist to serve humanity. Human beings create their own purposes, while animals exist for our purposes. Kant never defends his claim that animals lack autonomy and exist for the purposes of humanity; he simply treats it as self-evident.
From their behavior, it seems certain that animals who live free are, in fact, autonomous and do create their own purposes, just as we do. As for captive animals, their lack of autonomy is not due to any inherent deficiency, but to the power that we exercise over them. Any slave, whether animal or human, is autonomous only within highly circumscribed boundaries. Human slaves, of course, often do demonstrate some measure of inner autonomy, whether by attempting to escape, by rebelling, by maintaining an inner life that rejects their servitude, or by breaking down emotionally or mentally from the trauma of having their autonomy violently taken from them. As Jason Hribal has documented in Fear of the Animal Planet, many animal slaves also demand autonomy by attacking their overseers or trying to escape. And animals who spend their lives in cages—as in zoos and on fur farms—often adopt repetitive, neurotic behaviors (known as “stereotyped” behaviors) such as pacing endlessly back and forth, sitting and rocking forward and back or from side to side, or gnawing on their own limbs. Stereotyped behavior clearly indicates that the animal has broken down emotionally from the trauma of lost autonomy. Although the interior lives of animals are largely hidden from us by the lack of a common language, their behavior—engaging in play when they have the opportunity, or showing signs of severe depression or even insanity when they are confined in small cages, indicates that autonomy is as essential to the wellbeing of animals as it is to our own wellbeing.
God Put Us in Charge
In 1871, John Wesley, founder of Methodism, entered this long debate when he preached a sermon denying the claim that humans are exceptional because of our ability to reason.
“What then is the barrier between men and brutes? The line which they cannot pass? It was not reason. Set aside that ambiguous term: Exchange it for the plain word, understanding: and who can deny that brutes have this? We may as well deny that they have sight or hearing.” (Wesley, I.5)
It is not reason, Wesley argues, but the unique status we enjoy as a blessing from God that makes us exceptional. God has appointed us God’s viceroys on earth, so that we are, in fact, intermediaries between God and animals. As God has power over us, and as we should honor and obey God, so we have been delegated power over animals and they should honor and obey us. This is the line they cannot pass.
“Man is capable of God; the inferior creatures are not. We have no ground to believe that they are, in any degree, capable of knowing, loving, or obeying God. This is the specific difference between man and brute; the great gulf which they cannot pass over. And as a loving obedience to God was the perfection of man, so a loving obedience to man was the perfection of brutes.” (Wesley, I.5)
Our uniqueness lies in our ability to acknowledge and honor that which we cannot perceive with our senses (God), while animals can only acknowledge and honor that which they can perceive with their senses (human beings).
Like Aristotle before him, Wesley takes the absence of evidence to be evidence of absence. He is making an unsupported assumption. We simply do not know whether animals have spiritual longings and belief systems. And there is no ground for asserting that they do not. I am, of course, taking Wesley on his own terms for the sake of the discussion. It should be obvious to all that his argument is based entirely on a worldview, theism, that can be problematic on epistemological, ontological, and ethical grounds. But that is an issue that lies beyond the scope of this essay. (Full disclosure: I am Buddhist and Unitarian-Universalist.)
Aristotle, the Stoics, Augustine, and Aquinas thought that humanity is exceptional because only humans possess the trait that they valued most in themselves, reason. Wesley believed that humanity is exceptional because only humans possess the trait that he valued most in himself, religious faith. They were all engaging in a form of self-exaltation that reveals a remarkable lack of self-awareness. For the philosophers, the explicit theorem is, “Humans are exceptional among living beings because of their powers of reason.” But the implied corollary is, “I am exceptional among human beings because as a philosopher I have the greatest powers of reason.” For Wesley, substitute “theologian” for “philosopher” and “religious faith” for “reason.”
Although Wesley was probably unaware of this, the view that human exceptionalism resides in our privileged status as God’s designated rulers of all who live on Earth is also taught by Islam. According to the Qur’an, “[God] it is who has made you viceregents on earth.” (Koran, 35:39)
Wesley’s claim raises anthropocentrism to dizzying heights. It implies that we are gods to animals and that domestication is the highest state to which they can aspire. Their fulfillment lies in being our slaves; free living animals, who live according to their own natures and pursue their own ends are living in an inferior state that is not in accordance with God’s will. When we enslave and slaughter animals for our own appetites, we are actually saving them from their own ignorance and giving their lives meaning in accordance with the divine plan. Words like “arrogance,” “hubris,” and “megalomania” fail to capture the breathtaking narcissism of this description of human beings as lesser Gods.
Wesley completes his argument by asserting that it is not cruel for us to enslave and slaughter animals for our benefit because they will receive “recompense” for their suffering in the form of eternal life in heaven.
“Away with vulgar prejudices, and let the plain word of God take place. They “shall be delivered from the bondage of corruption, into glorious liberty,” — even a measure, according as they are capable, — of “the liberty of the children of God. . . . [T]he following blessing shall take place (not only on the children of men; there is no such restriction in the text; but) on every creature according to its capacity: “God shall wipe away all tears from their eyes. And there shall be no more death, neither sorrow, nor crying. Neither shall there be any more pain: For the former things are passed away.”(Wesley, III.2, 3)
Would Wesley have argued that Nero was not being cruel when he burned Christians alive or threw them to the lions? After all, the Christian martyrs would presumably receive “recompense” in Heaven for their suffering on Earth.
Tools and Talk
Wesley’s view is still widely held in Christian circles. But in the secular arena, the 20th century saw attention turn from abstract characteristics such as reason or religious faith to specific accomplishments. First, it was suggested that we are exceptional because of our ability to manufacture and use tools, which was taken as proof that our mental capacities differ from those of animals not merely in degree, but also in kind. But as the century progressed, it was discovered that tool use is by no means limited to human beings.
“Sea otters are tool-users. They use rocks to crack open hard-shelled prey on the surface, either setting a rock on their stomachs while floating on their backs, or holding rocks between their forepaws to pound their prey. Abalone- and urchin-eating otters also use rocks to dislodge these tenacious animals from their underwater footholds.” (Monterey Bay Aquarium)
Ravens have been observed laying the leg bones of deer across the rail of a railway track and then returning to suck out the marrow after a train has run over the bone and cracked it open. (Heinrich, 303)
Dolphins use sponges to help them hunt for food:
“In the 1980s it was discovered that some bottlenose dolphins in Shark Bay, Australia, rip up marine basket sponges from the seafloor and place them on their beaks for protection as they forage for food along rocky substrate. . . . Now Janet Mann and Eric Patterson, biologists at Georgetown University, report that the dolphins do this because it allows them to uncover prey undiscoverable by echolocation.” (Bhanoo)
Elephants do not simply use tools, they modify natural objects to create tools:
“Fly switching with branches is a type of tool use previously shown in captive Asian elephants to be effective in repelling flies and to vary in frequency with the intensity of flies. . . . we presented to 13 captive elephants, maintained under a naturalistic system, branches that were too long or bushy to be effectively used as switches. . . . Eight of these elephants modified the branch on at least one trial to a smaller branch and switched with the altered branch. There were different styles of modification of the branches, the most common of which was holding the main stem with the front foot and pulling off a side branch or distal end with the trunk. We propose that fly switching with branches is a common form of tool use in wild Asian elephants when fly intensity is high.” (Hart et al)
Insofar as we know at present, the champion non-human tool manufacturer is the New Caledonian crow. According to the Behaviourial Ecology Research Group of Oxford University:
“New Caledonian crows use tools frequently, use many different tool types, manufacture their own tools, select tools according to each task, and can create a new design when they need it. . . . New Caledonian crows use tools to forage for invertebrates in dead wood. They use at least four different tool types, including tools cut from the thorny edges of leaves of Pandanus trees. These tools are produced in a series of manufacturing steps and have complex shapes – they are the most sophisticated animal tools yet discovered.” (Behaviourial Ecology)
According to avian ethologists interviewed on the Nova documentary Inside Animal Minds: Bird Geniuses—aired on American public television on April 9, 2014—the tool-making techniques of New Caledonian crows differ from flock to flock, suggesting that they are cultural artifacts rather than pre-programmed behaviors. And not only are these skills passed down from parents to children, but the techniques become more sophisticated over the generations, as each generation builds on the work of previous generations to improve the product—which, of course, is exactly how human technology develops. (Russell)
Of special significance for us, however—for reasons that will become clear in a moment—New Caledonian crows’ tool-making success may be due more to their unique physiology than to unique brains. The Nova documentary points out that New Caledonian crows have unusually long and straight beaks—they are not hooked downward at the tip like the beaks of other corvids—making them especially well-suited to grasping and manipulating twigs and sticks. Compounding this advantage, the eyes of New Caledonian crows are situated more to the front of their heads than the eyes of most corvids, giving them binocular vision and superior depth perception directly in front of them. (Russell)
When tool use and manufacture failed as a basis for human exceptionalism, the focus turned back to language and animals’ supposed inability either to use or create it. Animals’ alleged lack of language had been cited three centuries earlier by Rene Descartes as proof that animals are robots programmed by God. We think in language, argued Descartes, and without language thought is impossible. Since animals have no language, they have no thoughts. Therefore, they must be automatons.
If we cannot think without language, the question arises, How did we invent language in the first place? Creating a language—grasping the very concept of language—would seem to require sophisticated thought. Descartes appears to assume—somewhat fuzzily—that God imbued us with an inherent ability to create and use language. In the 20th century, psycholinguist Noam Chomsky, who admits to being in many respects a modern-day Cartesian, argued that humans are unique in that we possess an inborn “universal grammar” that is hard-wired into our brains. In short, Chomsky simply substituted “evolution” for Descartes’ “God,” and posited, on the basis of no actual evidence, a genetic mutation that occurred in human beings that gave us a capacity for language that no other species possesses. This would constitute a massive discontinuity in the evolutionary sequence that is without parallel or precedent. Evolution proceeds sequentially, by tiny steps over long periods of time. It does not make great leaps across empty space to create wholly new traits that are without precedent in earlier species. Chomsky admits that this is true, but says that in this one case the leap must have occurred because humans are capable of language and other animals are not. Chomsky is simply wrong on his facts. As we shall see in a moment, other animals besides humans create and employ sophisticated languages, and the gene believed to be indispensable for language creation and use, known as “Fox P2,” is found in most vertebrates. A bit farther on, I shall have more to say about “the great leap forward.”
Serious efforts to demonstrate that at least some nonhuman animals are capable of language began with attempts to teach American Sign Language (ASL) to great apes, especially chimpanzees, on the anthropocentric theory that the more closely related an animal was to us the more likely she was to be able to use language. The apes demonstrated that they grasped the concept of language: they understood that words represent objects, actions, relationships, and states of mind; and they acquired a small vocabulary relating to things with which they were familiar. They used language meaningfully to talk with their teachers about their daily lives—their likes, dislikes, desires, and needs. They signed in simple sentences using correct word order, showing that they understood syntax as well as semantics. And they made up their own names for objects for which they had not been taught a name, often by combining words they had learned previously to create a new word.
Progress was severely limited, however, by the fact that adult great apes are powerful animals who sometimes show aggression that to our understanding appears unprovoked. For the safety of their teachers, the apes typically lived in cages, an environment that was not conducive to learning.
Further complicating the matter, the funding organizations and the managers of the institutions in which many of these experiments were conducted seem to have held one of two equally unrealistic expectations about these experiments. Some were so certain that apes could not be taught language that they interpreted all results as failure—nothing more than reading cues from their teachers and regurgitating sentences they had learned by rote. Others seem to have expected that within a year or two the researchers would be holding sophisticated conversations with their students about a wide range of subjects. When this did not materialize, many supporters of the research grew disillusioned and joined opponents in declaring the initiative a failure.
Parrots are among the few nonhuman animals who can form the sounds of human speech, although they use a vocal mechanism that is radically different from ours. They are also inexpensive and easy to care for compared to great apes and socialize readily and reliably with human beings. This inspired a newly minted theoretical chemist with a strong interest in the emerging field of cognitive ethology to purchase a captive-bred African grey parrot with a view to teaching him English. Dr. Irene Pepperberg worked with Alex for the next 30 years using a theoretically promising, but relatively untested, technique developed by Professor Dietmar Todt of the Free University of Berlin called the “model-rival teaching technique.” In the model-rival technique, two teachers work with one student. One teacher plays the role of teacher, while the other pretends to be a student. The pretend “student” models the behavior being taught, in this case by acting out learning the names of objects she is being shown by the teacher and answering questions that she is asked. She also acts as a “rival” to the real student, bringing out his competitive spirit and motivating him to learn more and faster than she does. The model-rival technique is now widely used in teaching autistic human beings, where it has enjoyed considerable success.
Alex acquired a vocabulary of 150 words, which he used appropriately in sentences. He carried on meaningful conversations with the researchers, responding appropriately to questions, making requests of his own, and telling the researchers when he was tired of school and wanted to take a nap. He could count, he understood the meaning of “none” or “not any,” and grasped abstract concepts like color and shape. Asked what color an object was, he could answer correctly. Asked to pick out the square object from among objects of various shapes, he could do so. Dr. Pepperberg, who has described her work with Alex with scientific rigor in The Alex Studies and more informally in Alex and Me, estimates that the adult parrot had the intelligence of a five year old human child. (Economist) And here, I want to insert two caveats.
First, animal intelligence and human intelligence cannot be meaningfully compared. Every species of sentient being has evolved an intelligence suited to its anatomy (its physical capacities), its natural environment (the surroundings in which the species evolved), and its natural lifestyle (the mode of living to which its anatomy and environment predispose it). When we compare the intelligence of an animal to that of a human being, we are not estimating the intelligence of the animal; we are estimating how much the mental capacities of the animal are similar to ours. Intelligence is not a single progression from lesser to greater with us at the top. For every species, intelligence consists of a set of mental skills apposite to the needs, physical capacities and life setting of the members of that species.
There are certainly broad areas of overlap among the modes of intelligence of various species. We all have to navigate the same world. But there are also broad areas of uniqueness in the intelligence of each species. There is doubtless much in the intelligence of a bird or a fish that we cannot even recognize, much less evaluate because we are trapped within our human intelligence. We can say that some human beings are more intelligent than others, but to say that human beings are more intelligent than parrots is meaningless.
When we reduce the intelligence of a species to its areas of overlap with human intelligence, we diminish the animals and inflate ourselves. To say that adult parrots—who organize and manage complex societies, raise and educate children, and survive in the tropical rainforest, all things that a human child cannot do—have the intelligence of a five year old human is destructive nonsense. Substantively, it is meaningless, while functionally, it serves to preserve human prerogatives over parrots and, by extension, over other nonhuman people. In this regard, it is the 21st century equivalent of the 19th century claim that African adults had the intelligence of European children, that they were happy-go-lucky, irresponsible, and incapable of managing their own lives—despite the fact that they had organized their own societies and managed their own lives quite nicely in Africa.
Second, trying to gauge the intelligence (or even the capacity for language) of members of other species by their ability to learn human language is misguided and futile. I would not like to have my linguistic capacities judged by my ability to learn the language of African grey parrots. (It is anthropocentric silliness to think that animals capable of learning a human language would not have created their own languages.) The effort to teach a human language to a nonhuman animal can even be seen as a tacit admission that we lack the mental capacity to learn their languages and hope that they are more capable in this regard than we are.
The correct way to study the language abilities of nonhuman animals has been pioneered by Con Slobodchikoff, professor emeritus of biology at Northern Arizona University in Flagstaff. Dr. Slobodchikoff—who is recognized as one of the world’s leading authorities on prairie dogs—has spent extended periods in the field recording the vocalizations of Gunnison’s prairie dogs in their natural setting and then playing back and analyzing these vocalizations in the laboratory. He is unequivocal about the fact—and the complexity—of prairie dog language.
“We now know that the alarm calls of prairie dogs are part of a sophisticated animal language rather than merely an expression of fear. . . . Two major components [of a genuine language] are semantics and syntax. . . . Prairie dog vocalizations contain both of these basic design elements of a language.”(Slobodchikoff, “Language,” 66)
By careful observation, Dr. Slobodchikoff established that prairie dogs can announce the approach of a predator, indicate whether the predator is in the air or on the ground and the speed at which he is approaching; they can identify predators’ ‟species and even assign individual names to specific predators whom they encounter more than once.” (Slobodchikoff, “Language,” 71)
Dr. Slobodchikoff‟s observation that prairie dog language contains syntax opens the door to a breakthrough in our understanding of language. Any definition of language that does not account for nonhuman languages must be regarded as, at best, provisional and incomplete. To put it more bluntly, Dr. Slobodchikoff’s findings suggest that our current conceptions of what constitutes a genuine language, as promoted by celebrated scholars like Noam Chomsky and Steven Pinker, are distorted by anthropocentric bias.
In addition to predator warnings, Dr. Slobodchikoff describes what he calls the “social chatters” of prairie dogs, conversations among two or more members of the community unrelated to any observable phenomenon like predators or foraging for food. “[T]hese chatters have a definite syntax. They are not given in random order but have a pattern just like words in a human sentence,” (Slobodchikoff, “Language,” 72). It seems apparent that prairie dogs carry on social conversations just as we do.
Perhaps most important of all, Dr. Slobodchikoff discovered that:
“[P]rairie dogs from different colonies differ in how they pronounce ‘human’‟ and ‘dog’. . . . This suggested that the calls might be learned by juvenile animals from their parents, just like human dialects, rather than being determined by some genetically controlled instinct for calling in a precise way,” (Slobodchikoff, “Language,” 69).
In other words, prairie dog language was created by prairie dogs and is transmitted from one generation to the next in the same way that human language was created by human beings and is transmitted from one generation to the next. Like human language, prairie dog language is a cultural artifact.
Dolphins have also been shown to have natural languages that employ syntax. Brenda McCowan of the University of California, Davis has conducted extensive research on the vocalizations of dolphins. According to prominent dolphin specialist Lori Marino of Emory University, Dr. McCowan’s research has established that:
“[T]here is structure in dolphin communication signals. . . . The structure comes from syntax, which is again a very important aspect of true language. And what she has found is that there is structure in dolphin communication signals. What they’re saying is not clear but the fact that they are saying something in a very complex way is pretty clear.” (Animal World)
It seems unlikely that human beings, prairie dogs, and dolphins would just happen to be the only members of the animal kingdom able to create and use language. There is, in fact, no reason to believe that any animal who lives in a community and acts cooperatively with other animals lacks language. Regardless of species, language would seem to be the sine qua non of social organization. As Professor Slobodchikoff puts it, “Where other members of the same species are part of the context of an individual organism, the control, sharing, or withholding of information becomes vitally important, and language is the way that this is achieved.” (Slobodchikoff, Chasing, 37) Among social animals, language should be regarded as the norm, not the exception.
An efficient social organization involving divisions of labor is of tremendous survival and reproductive value, language serves a vital evolutionary function. The kind of cooperative hunting strategies practiced by lions and wolves, for example, depends on the ability of the hunters to communicate with one another, both before and during the hunt. Crows and geese set sentries to watch for predators while they eat, and they rotate the assignment so that everyone gets a chance at the food, a practice my wife and I have observed any number of times. How do they assign the lookouts and schedule the shift changes unless they can discuss both the system and the assignments? The only satisfactory answer is that they use the same mechanism we do: language. Crows and geese, by the way, like many other birds, are very vocal animals, chattering constantly among themselves. Unless they are talking, discussing matters of common interest, perhaps even gossiping—in the manner of Dr. Slobodchikoff’s prairie dogs—it is difficult to construct a credible explanation for this behavior. Constant vocalization to no purpose would be a waste of valuable energy, especially in cold weather or on long flights, and would alert predators to the birds’ presence, both outcomes that would be counterproductive from an evolutionary standpoint. It seems likely, therefore, that this behavior has some countervailing evolutionary value, and that this value lies in communication.
“[P]eople, including linguists, who see language as belonging solely to humans, postulate that a great leap forward was made possible by the human brain. That there suddenly arose an unbridgeable gap between us and the rest of life just doesn’t make sense. After all, every other system in humans has its roots in other species, and can often be traced up the evolutionary line. So why not the Discourse System? If the Discourse System is used to organize, categorize, and integrate information coming in from the environment, and uses that information to produce signals that influence the behavior of others to one’s own advantage, then why wouldn’t this system have evolved in other species?” (Slobodchikoff, Chasing, 42-43)
Dr. Slobodchikoff is alluding to a theory put forward by a number of scholars, most notably Noam Chomsky, psycholinguist Steven Pinker, and cultural geographer Jared Diamond, that at some point in our prehistoric past—Diamond places it 40,000 to 50,000 years ago—humanity experienced a “great leap forward,” when we suddenly began to leave evidence that we were exercising an unprecedented control over our environment and creating a material civilization in the modern sense. This “great leap forward” was, so the theory goes, due to a sudden, dramatic mutation in the human genome which conferred upon us a unique capacity to create and use language. Language, in turn, endowed us with a unique ability to think abstractly, solve complex problems, plan for the future, and conceive both the material and immaterial components of civilization. In short, the “great leap forward” is an elaboration of Noam Chomsky’s theory of a “universal grammar” that is unique to human beings.
A number of paleoanthropologists have objected that the “great leap forward” is an illusion, an expression of Eurocentric bias that overlooks the rich African archeological record from the Middle Stone Age. When this bias is corrected, they argue, the record shows a gradual, but steadily accelerating, advance in our ability to create material civilization by inventing better tools and utilizing more durable materials. (See McBrearty and Brooks) I have already observed that, as Dr. Slobodchikoff points out, evolution is a gradual process in which there are no discontinuities. The evolutionary record reveals no other “great leaps forward,” only small steps. If this leap actually occurred, it is unparalleled. It violates everything we know about natural selection, and clearly Doctor Slobodchikoff and others are right when they argue that it never happened. “The Great Leap Forward” is a fantasy spun by scholars who are so invested in human exceptionalism that they see things in the ancient evidence that are not there. It is simply the most recent example of human exceptionalism searching desperately for a rationale.
Professor Slobodchikoff goes on to point out that, “what has been called the language gene, dubbed FoxP2,” has been discovered “in the fossil remains of Neanderthals,” dating back 300,000 years, 250,000 years before the supposed “great leap forward.” And he notes that it has also been identified in many other species of animals, including nearly all vertebrates. (Slobodchikoff, Chasing, 43)
It is now well documented in the scientific literature that the reasons relied upon to defend human exceptionalism are all spurious. It is so well documented, in fact, that a writer in The New York Times can make the following assertions without feeling the need to attribute them to any specific source:
“[A]dvanced neurological and genetic research . . . has shown that animals like chimpanzees, orcas and elephants possess self-awareness, self-determination and a sense of both the past and future. They have their own distinct languages, complex social interactions and tool use. They grieve and empathize and pass knowledge from one generation to the next. The very same attributes, in other words, that we once believed distinguished us from other animals.” (Siebert)
And Yet, There Is a Line
Despite all of this, we have to admit that a line between humans and other animals does exist. There is a way in which we are undeniably exceptional. We have a level of control over our surroundings—over the material world—that no other species can approach. We can plant, tend, and harvest fruits, grains, and vegetables, build cities with sophisticated infrastructures, construct complex machinery, create new chemicals and medicines, and manipulate the material world to our own advantage in myriad ways that no other animal can. In short, we have a unique capacity for creating technology, from the spear to the hydrogen bomb, from the mud hut to the skyscraper, from the wheel to the space shuttle, from the stylus and clay tablet to the computer.
As we have seen, it is commonly believed that our superior brains account for our unique ability to build sophisticated tools and to use these tools to create the material components of civilization; all other animals are too stupid. But as we have also seen, there is no evidence for this claim. And there is another, more natural explanation for which we have a superabundance of evidence right before our eyes. Our brains could not have created our technology if it were not for our unique hands. We are the only species that is fully bipedal—leaving our front legs free to evolve into arms that end in flexible hands with an opposable thumb and fingers capable (thanks to our unique wrist design) of both a strong grip and fine motor discrimination.
Without our hands we could never have built and employed the tools and weapons that created and sustain our power and our material civilization. We do not know whether our minds are exceptional or not. But we do know that our hands are exceptional. If horses, dogs, dolphins, or even chimpanzees had human brains, they would still not be able to create and use tools and weapons that would empower them the way our implements have empowered us. Their hooves, paws, flippers, hands simply would not allow it. With their own brains, animals succeed in creating the material aspects of civilization: nests, burrows, storehouses, etc., to the extent that their anatomies permit. Thus, we have no grounds for assuming the inferiority of their minds.
Paws, hooves, wings, and fins are visible to us. We can see their limitations, and we can recognize that they render their owners incapable of building sophisticated tools and weapons, and, therefore, incapable of creating the material components of human civilization. There is no need to look for a further explanation. There is no reason to overlook the hand and go straight to the brain for an explanation of our power and our material skills.
For the most part, we do not know what the mental capacities of other animals may or may not be. But to assume that they lack the more complex intellectual capacities simply because we have not thus far observed them is the height of arrogance and provincialism. We assumed that all other animals lacked the mental capacity for language until pioneering ethologists like Roger Fouts, Francine Patterson, and Sue Savage-Rumbaugh (great apes), Irene Pepperberg (parrots), Con Slobodchikoff (prairie dogs), and Brenda McCowan (dolphins) proved otherwise. Once again, the absence of evidence is not evidence of absence. When we think we are describing the absence of intelligence in animals, we are describing our own ignorance instead. When I was in elementary school, 65 years ago, I was taught that ours was the only solar system in the galaxy. Now, with better instruments, we have discovered that solar systems are the norm, not the exception. Sixty-five years from now, we may well have discovered that the ability to reason and generalize, to ponder abstract questions and engage in sophisticated thought processes, to appreciate beauty, and create (oral) literature is the norm among complex social animals, not the exception.
If nonhuman animals can create and culturally transmit language (as Doctor Slobodchikoff”s and Doctor McCowan’s research indicates), it seems natural that they should create and maintain other non-material components of culture, as well. Seasonal migrations along traditional migration routes—in animals as unlike as African elephants, gray whales, and Canada geese—would seem to be examples of cultural practices. With the proliferation along the flyways of suburban golf courses, cemeteries, and parks with small artificial lakes, fewer and fewer Canada geese are making the annual migration to Central America and the Caribbean. Some fly part of the way and winter in the southern United States, while an increasing number on the Atlantic flyway now live year around in the Middle Atlantic region. This suggests that rather than being an instinctual, inborn behavior, seasonal migrations are a cultural practice, not unlike the cultural practice of human “snowbirds” spending the winter in Florida.
Culture—rules, customs, shared beliefs, a common history—is what binds any society together, and it is hard to see how a community of any species could sustain itself without a culture. And, in fact, we find evidence of nonhuman culture not only in the languages of the Gunnison’s prairie dogs of northern Arizona and the seasonal migrations of elephants, whales, and Canada geese, but also in the well-known social hierarchies of canids and chickens, and a thousand other behaviors across the animal kingdom. But our ability to access the cultures of other animals ends with behavior that we are able to observe and open-minded enough to understand. Do elephants recite, in bardic fashion, histories of their communities? Do gray whales pass on tales of the heroes of long-ago migrations? Is there a gray whale Leif Eriksson? Or a Canada goose Zheng He? Do dolphins have religions? Do horses pray? Do sea bass have a philosophy of life? The existence of organized societies and complex languages implies that the answer to many questions of this sort may be, “Yes.” But more than that we cannot say with certainty—at least for now.
What we do know is that when we keep social animals in captivity, we destroy their cultures. How can a baby dog born in a breeding facility learn the language and traditions of dogs? How can a baby elephant born in a zoo learn the ways of elephants? Or captive-born dolphins? Horses, cows, sheep, chickens? They are all social animals. When they live in freedom, it seems certain that they all have languages and cultures suited to their physiology, their inner natures, and their environment. But in captivity, they are denied their birthright.
Human exceptionalism is nothing more than human power. Human power resides in technology. And technology is the creation of the unique human hand. Viewed this way, human exceptionalism is not all that impressive. And it certainly does not endow us with moral superiority or the right to enslave and slaughter our neighbors who find themselves at our mercy because we have hands and they do not. Our pride should not be in our power, but in how we employ it. Power entails responsibility. And throughout history, we have exercised our power with criminal irresponsibility. We have used the power given us by our strong, flexible fingers and opposable thumb to enslave and slaughter billions, trillions of innocent animals.
Here we must ask the question, Do we hold human civilization in such high esteem because it is genuinely superior or because it is ours? In The Hitchhiker’s Guide to the Galaxy, Douglas Adams posed that question this way:
“For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much—the wheel, New York, wars and so on—whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man—for precisely the same reasons.” (Adams, 127)
Viewed functionally, the civilizations of other animals serve the same purposes for them that our civilizations serve for us. Ours are superior only from our parochial point of view. Viewed substantively, our civilizations cannot be compared to those of other animals: first, because we cannot know the complete content of other animals’ cultures; and second, because we are trapped within our own culture and cannot achieve a perspective—a distance, if you will—from which we could make an objective comparison. The cultures of every species are as important to the members of that species as our cultures are to us, and for that reason, they must be accorded equal value. Our civilizations give us no grounds to consider ourselves superior to other species except in regards to power. And power confers no inherent worth upon those who possess it. To suggest otherwise is to argue, as defenders of human exceptionalism have argued since classical Greece, that might makes right.
Our values and our morality are not universally valid across species lines. This is not, as is commonly believed, because other species do not have values or standards of morality; clearly they do. No society can exist without such standards. But their different physiologies and different life settings often require members of other species to have different values and different moral schemes than we have. We value (or should value) nonviolence. But being dependent on a diet of fish, dolphins cannot value nonviolence, at least not toward fish. Nonviolence toward fish would be violence toward themselves; it would be suicide. We cannot appraise the moral codes of other animals by comparing them to our own. Our standards cannot be theirs any more than their standards can be ours.
Freedom Without Power
Because it is grounded in physiology, the power imbalance between humans and other species is permanent—at least until another species evolves with greater physical capacities than ours. With other social justice movements, the success of the movement has empowered the beneficiaries so that the power gap between the oppressors and the oppressed is either eliminated or sharply reduced. In fact, empowering the beneficiaries has always been one of the primary objectives of social justice movements. By contrast, the challenge facing the animal liberation movement is to end the exploitation and oppression of animals in the face of our inability to empower them. We can (and should) empower humans to protect animals— to cite just one example, by having courts appoint human guardians to look after their interests—but that is a far cry from empowering the victims themselves.
Because animals cannot be empowered, maintaining animals’ rights in perpetuity may prove to be an even greater challenge than winning them initially. Obviously, this is not yet a live issue, since animals’ rights are far from won. But it is worth thinking about. Freed slaves and their descendants suffered terribly for a century following the end of Reconstruction, and are still suffering today, because adequate provisions were not made for their educational, economic, political, and social integration into the mainstream of American society. Human slaves were liberated without being empowered, and the results were tragic. Granting animals legal status as persons, while a necessary step, will not automatically secure their rights any more than the Fifteenth Amendment to the Constitution automatically secured for Southern blacks the right to vote. Our society’s dismal record regarding African slaves and their descendants should serve as a reminder that we ought to begin thinking now about how we will maintain the rights of animals once those rights have been achieved.
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 Aristotle’s father was the royal physician; as an adult, Aristotle returned to the Macedonian court to serve as tutor to Amyntas’ grandson, the future Alexander the Great.
 There were heretical sects, such as the Cathars, that practiced vegetarianism, for reasons that are not clear; but they were persecuted and driven underground or eradicated by the Church.
 To be fair to Aquinas, he did call for animals to be treated with kindness, but on the grounds that cruelty to animals would lead to cruelty to human beings. He also conceded that humans could love animals, provided they loved them as expressions of God’s generosity, and not for their own sakes.
 Some scholars trace social contract philosophy to Socrates’ argument that because he had accepted the benefits of Athenian citizenship, he had an obligation to accept Athens’ decision to put him to death. I think these scholars are correct, but as a formal, systematic theory, the social contract began with the Enlightenment and Hobbes, Locke, and Rousseau.
 Although Augustine and Aquinas would likely have denied this, it is clear from their writings that they took the most pride in their ability to philosophize, to reason. When asked why he stayed in Italy and wrote books instead of travelling to the Muslim world as a missionary where he could actually save souls, Aquinas replied that everyone has an obligation to use their highest skill level, and writing books on theology was a higher skill level than preaching to the unsaved.
 In later life, Wesley was an on-and-off vegetarian, but for reasons of health rather than concern for animals. He suffered from a digestive disorder.
 Tthe quotations are from Romans 8:19-21 and Revelation 21:4.
 Note that tool making and tool use imply a strong sense of the future.
 The structure of American Sign Language differs in several important respects from the structure of English, although the vocabulary is largely the same in that most signs represent one or more English words. For example, ASL does not use articles or conjugate verbs (although there are signs to indicate past and future when this is not clear from the context). Thus the transcription, “Koko want apple,” might look like bad English, but is grammatically correct ASL. The absence of an “s” at the end of “want” and an “an” in front of “apple” does not mean that Koko failed to grasp the subtleties of English grammar. It means that she was speaking ASL, which was the language she had been taught to speak.
 There are a number of excellent books describing these experiments, their successes, setbacks, and the difficulties of working with captive adult great apes. Among the best are, in no particular order, Apes, Men, and Language by Eugene Linden, Next of Kin by Roger Fouts, Apes, Language, and the Human Mind by Sue Savage-Rumbaugh et al, Kanzi: The Ape at the Brink of the Human Mind by Sue Savage-Rumbaugh, The Education of Koko by Francine Patterson and Eugene Linden, and Nim Chimpsky: The Ape Who Would Be Human by Elizabeth Hess.