The Language Instinct: How the Mind Creates Language

by Steven Pinker

  Language could have arisen, and probably did arise, in a similar way: by a revamping of primate brain circuits that originally had no role in vocal communication, and by the addition of some new ones. The neuroanatomists A1 Galaburda and Terrence Deacon have discovered areas in monkey brains that correspond in location, input-output cabling, and cellular composition to the human language areas. For example, there are homologues to Wernicke’s and Broca’s areas and a band of fibers connecting the two, just as in humans. The regions are not involved in producing the monkeys’ calls, nor are they involved in producing their gestures. The monkey seems to use the regions corresponding to Wernicke’s area and its neighbors to recognize sound sequences and to discriminate the calls of other monkeys from its own calls. The Broca’s homologues are involved in control over the muscles of the face, mouth, tongue, and larynx, and various subregions of these homologues receive inputs from the parts of the brain dedicated to hearing, the sense of touch in the mouth, tongue, and larynx, and areas in which streams of information from all the senses converge. No one knows exactly why this arrangement is found in monkeys and, presumably, their common ancestor with humans, but the arrangement would have given evolution some parts it could tinker with to produce the human language circuitry, perhaps exploiting the confluence of vocal, auditory, and other signals there.

  Brand-new circuits in this general territory could have arisen, too. Neuroscientists charting the cortex with electrodes have occasionally found mutant monkeys who have one extra visual map in their brains compared to standard monkeys (visual maps are the postage-stamp-sized brain areas that are a bit like internal graphics buffers, registering the contours and motions of the visible world in a distorted picture). A sequence of genetic changes that duplicate a brain map or circuit, reroute its inputs and outputs, and frob, twiddle, and tweak its internal connections could manufacture a genuinely new brain module.

  Brains can be rewired only if the genes that control their wiring have changed. This brings up another bad argument about why chimp signing must be like human language. The argument is based on the finding that chimpanzees and humans share 98% to 99% of their DNA, a factoid that has become as widely circulated as the supposed four hundred Eskimo words for snow (the comic strip Zippy recently quoted the figure as “99.9%”). The implication is that we must be 99% similar to chimpanzees.

  But geneticists are appalled at such reasoning and take pains to stifle it in the same breath that they report their results. The recipe for the embryological soufflé is so baroque that small genetic changes can have enormous effects on the final product. And a 1% difference is not even so small. In terms of the information content in the DNA it is 10 megabytes, big enough for the Universal Grammar with lots of room left over for the rest of the instructions on how to turn a chimp into a human. Indeed, a 1% difference in total DNA does not even mean that only 1% of human and chimpanzee genes are different. It could, in theory, mean that 100% of human and chimpanzee genes are different, each by 1%. DNA is a discrete combinatorial code, so a 1% difference in the DNA for a gene can be as significant as a 100% difference, just as changing one bit in every byte, or one letter in every word, can result in a new text that is 100% different, not 10% or 20% different. The reason, for DNA, is that even a single amino-acid substitution can change the shape of a protein enough to alter its function completely; this is what happens in many fatal genetic diseases. Data on genetic similarity are useful in figuring out how to connect up a family tree (for example, whether gorillas branched off from a common ancestor of humans and chimps or humans branched off from a common ancestor of chimps and gorillas) and perhaps even to date the divergences using a “molecular clock.” But they say nothing about how similar the organisms’ brains and bodies are.

  The ancestral brain could have been rewired only if the new circuits had some effect on perception and behavior. The first steps toward human language are a mystery. This did not stop philosophers in the nineteenth century from offering fanciful speculations, such as that speech arose as imitations of animal sounds or as oral gestures that resembled the objects they represented, and linguists subsequently gave these speculations pejorative names like the bow-wow theory and the ding-dong theory. Sign language has frequently been suggested as an intermediate, but that was before scientists discovered that sign language was every bit as complex as speech. Also, signing seems to depend on Broca’s and Wernicke’s areas, which are in close proximity to vocal and auditory areas on the cortex, respectively. To the extent that brain areas for abstract computation are placed near the centers that process their inputs and outputs, this would suggest that speech is more basic. If I were forced to think about intermediate steps, I might ponder the vervet monkey alarm calls studied by Cheney and Seyfarth, one of which warns of eagles, one of snakes, and one of leopards. Perhaps a set of quasi-referential calls like these came under the voluntary control of the cerebral cortex, and came to be produced in combination for complicated events; the ability to analyze combinations of calls was then applied to the parts of each call. But I admit that this idea has no more evidence in its favor than the ding-dong theory (or than Lily Tomlin’s suggestion that the first human sentence was “What a hairy back!”).

  Also unknown is when, in the lineage beginning at the chimp-human common ancestor, proto-language first evolved, or the rate at which it developed into the modern language instinct. In the tradition of the drunk looking for his keys under the lamppost because that is where the light is best, many archaeologists have tried to infer our extinct ancestors’ language abilities from their tangible remnants such as stone tools and dwellings. Complex artifacts are thought to reflect a complex mind which could benefit from complex language. Regional variation in tools is thought to suggest cultural transmission, which depends in turn on generation-to-generation communication, perhaps via language. However, I suspect that any investigation that depends on what an ancient group left behind will seriously underestimate the antiquity of language. There are many modern hunter-gatherer peoples with sophisticated language and technology, but their baskets, clothing, baby slings, boomerangs, tents, traps, bows and arrows, and poisoned spears are not made of stone and would not into nothing quickly after their departure, obscuring their linguistic competence from future archaeologists.

  Thus the first traces of language could have appeared as early as Australopithecus afarensis (first discovered as the famous “Lucy” fossil), at 4 million years old our most ancient fossilized ancestor. Or perhaps even earlier; there are few fossils from the time between the human-chimp split 5 to 7 million years ago and A. afarensis. Evidence for a lifestyle into which language could plausibly be woven gets better with later species. Homo habilis, which lived about 2.5 to 2 million years ago, left behind caches of stone tools that may have been home bases or local butchering stations; in either case they suggest some degree of cooperation and acquired technology. Habilis was also considerate enough to have left us some of their skulls, which bear faint imprints of the wrinkle patterns of their brains. Broca’s area is large and prominent enough to be visible, as are the supramarginal and angular gyri (the language areas shown in the brain diagram in Chapter 10), and these areas are larger in the left hemisphere. We do not, however, know whether habilines used them for language; remember that even monkeys have a small homologue to Broca’s area. Homo erectus, which spread from Africa across much of the old world from 1.5 million to 500,000 years ago (all the way to China and Indonesia), controlled fire and almost everywhere used the same symmetrical, well-crafted stone hand-axes. It is easy to imagine some form of language contributing to such successes, though again we cannot be sure.

  Modern Homo sapiens, which is thought to have appeared about 200,000 years ago and to have spread out of Africa 100,000 years ago, had skulls like ours and much more elegant and complex tools, showing considerable regional variation. It is hard to believe that they lacked language, given that biologically they were us, and all biologically modern humans have
language. This elementary fact, by the way, demolishes the date most commonly given in magazine articles and textbooks for the origin of language: 30,000 years ago, the age of the gorgeous cave art and decorated artifacts of Cro-Magnon humans in the Upper Paleolithic. The major branches of humanity diverged well before then, and all their descendants have identical language abilities; therefore the language instinct was probably in place well before the cultural fads of the Upper Paleolithic emerged in Europe. Indeed, the logic used by archaeologists (who are largely unaware of psycholinguistics) to pin language to that date is faulty. It depends on there being a single “symbolic” capacity underlying art, religion, decorated tools, and language, which we now know is false (just think of linguistic idiot savants like Denyse and Crystal from Chapter 2, or, for that matter, any normal three-year-old).

  One other ingenious bit of evidence has been applied to language origins. Newborn babies, like other mammals, have a larynx that can rise up and engage the rear opening of the nasal cavity, allowing air to pass from nose to lungs avoiding the mouth and throat. Babies become human at three months when their larynx descends to a position low in their throats. This gives the tongue the space to move both up and down and back and forth, changing the shape of two resonant cavities and defining a large number of possible vowels. But it comes at a price. In The Origin of Species Darwin noted “the strange fact that every particle of food and drink which we swallow has to pass over the orifice of the trachea, with some risk of falling into the lungs.” Until the recent invention of the Heimlich maneuver, choking on food was the sixth leading cause of accidental death in the United States, claiming six thousand victims a year. The positioning of the larynx deep in the throat, and the tongue far enough low and back to articulate a range of vowels, also compromised breathing and chewing. Presumably the communicative benefits outweighed the physiological costs.

  Lieberman and his colleagues have tried to reconstruct the vocal tracts of extinct hominids by deducing where the larynx and its associated muscles could have fit into the space at the base of their fossilized skulls. They argue that all species prior to modern Homo sapiens, including Neanderthals, had a standard mammalian airway with its reduced space of possible vowels. Lieberman suggests that until modern Homo sapiens, language must have been quite rudimentary. But Neanderthals have their loyal defenders and Lieberman’s claim remains controversial. In any case, e lengeege weth e smell nember ef vewels cen remeen quete expresseve, so we cannot conclude that a hominid with a restricted vowel space had little language.

  So far I have talked about when and how the language instinct might have evolved, but not why. In a chapter of The Origin of Species, Darwin painstakingly argued that his theory of natural selection could account for the evolution of instincts as well as bodies. If language is like other instincts, presumably it evolved by natural selection, the only successful scientific explanation of complex biological traits.

  Chomsky, one might think, would have everything to gain by grounding his controversial theory about a language origin in the firm foundation of evolutionary theory, and in some of his writings he has hinted at a connection. But more often he is skeptical:

  It is perfectly safe to attribute this development [of innate mental structure] to “natural selection,” so long as we realize that there is no substance to this assertion, that it amounts to nothing more than a belief that there is some naturalistic explanation for these phenomena…. In studying the evolution of mind, we cannot guess to what extent there are physically possible alternatives to, say, transformational generative grammar, for an organism meeting certain other physical conditions characteristic of humans. Conceivably, there are none—or very few—in which case talk about evolution of the language capacity is beside the point.

  Can the problem [the evolution of language] be addressed today? In fact, little is known about these matters. Evolutionary theory is informative about many things, but it has little to say, as of now, about questions of this nature. The answers may well lie not so much in the theory of natural selection as in molecular biology, in the study of what kinds of physical systems can develop under the conditions of life on earth and why, ultimately because of physical principles. It surely cannot be assumed that every trait is specifically selected. In the case of such systems as language…it is not easy even to imagine a course of selection that might have given rise to them.

  What could he possibly mean? Could there be a language organ that evolved by a process different from the one we have always been told is responsible for the other organs? Many psychologists, impatient with arguments that cannot be fit into a slogan, pounce on such statements and ridicule Chomsky as a crypto-creationist. They are wrong, though I think Chomsky is wrong too.

  To understand the issues, we first must understand the logic of Darwin’s theory of natural selection. Evolution and natural selection are not the same thing. Evolution, the fact that species change over time because of what Darwin called “descent with modification,” was already widely accepted in Darwin’s time but was attributed to many now-discredited processes such as Lamarck’s inheritance of acquired characteristics and some internal urge or drive to develop in a direction of increasing complexity culminating in humans. What Darwin and Alfred Wallace discovered and emphasized was a particular cause of evolution, natural selection. Natural selection applies to any set of entities with the properties of multiplication, variation, and heredity. Multiplication means that the entities copy themselves, that the copies are also capable of copying themselves, and so on. Variation means that the copying is not perfect; errors crop up from time to time, and these errors may give an entity traits that enable it to copy itself at higher or lower rates relative to other entities. Heredity means that a variant trait produced by a copying error reappears in subsequent copies, so the trait is perpetuated in the lineage. Natural selection is the mathematically necessary outcome that any traits that foster superior replication will tend to spread through the population over many generations. As a result, the entities will come to have traits that appear to have been designed for effective replication, including traits that are means to this end, like the ability to gather energy and materials from the environment and to safeguard them from competitors. These replicating entities are what we recognize as “organisms,” and the replication-enhancing traits they accumulated by this process are called “adaptations.”

  At this point many people feel proud of themselves for spotting what they think is a fatal flaw. “Aha! The theory is circular! All it says is that traits that lead to effective replication lead to effective replication. Natural selection is ‘the survival of the fittest’ and the definition of ‘the fittest’ is ‘those who survive.’” Not!! The power of the theory of natural selection is that it connects two independent and very different ideas. The first idea is the appearance of design. By “appearance of design” I mean something that an engineer could look at and surmise that its parts are shaped and arranged so as to carry out some function. Give an optical engineer an eyeball from an unknown species, and the engineer could immediately tell that it is designed for forming an image of the surroundings: it is built like a camera, with a transparent lens, contractable diaphragm, and so on. Moreover, an image-forming device is not just any old piece of bric-a-brac but a tool that is useful for finding food and mates, escaping from enemies, and so on. Natural selection explains how this design came to be, using a second idea: the actuarial statistics of reproduction in the organism’s ancestors. Take a good look at the two ideas:

  A part of an organism appears to have been engineered to enhance its reproduction.

  That organism’s ancestors reproduced more effectively than their competitors.

  Note that (1) and (2) are logically independent. They are about different things: engineering design, and birth and death rates. They are about different organisms: the one you’re interested in, and its ancestors. You can say that an organism has good vision and that good vision should help it r
eproduce (1), without knowing how well that organism, or any organism, in fact reproduces (2). Since “design” merely implies an enhanced probability of reproduction, a particular organism with well-designed vision may, in fact, not reproduce at all. Maybe it will be struck by lightning. Conversely, it may have a myopic sibling that in fact reproduces better, if, for instance, the same lightning bolt killed a predator who had the sibling in its sights. The theory of natural selection says that (2), the ancestors’ birth and death rates, is the explanation for (1), the organism’s engineering design—so it is not circular in the least.

  This means that Chomsky was too flip when he dismissed natural selection as having no substance, as nothing more than a belief that there is some naturalistic explanation for a trait. In fact, it is not so easy to show that a trait is a product of selection. The trait has to be hereditary. It has to enhance the probability of reproduction of the organism, relative to organisms without the trait, in an environment like the one its ancestors lived in. There has to have been a sufficiently long lineage of similar organisms in the past. And because natural selection has no foresight, each intermediate stage in the evolution of an organ must have conferred some reproductive advantage on its possessor. Darwin noted that his theory made strong predictions and could easily be falsified. All it would take is the discovery of a trait that showed signs of design but that appeared somewhere other than at the end of a linage of replicators that could have used it to help in their replication. One example would be the existence of a trait designed only for the beauty of nature, such as a beautiful but cumbersome peacock tail evolving in moles, whose potential mates are too blind to be attracted to it. Another would be a complex organ that can exist in no useful intermediate form, such as a part-wing that could not have been useful for anything until it was one hundred percent of its current size and shape. A third would be an organism that was not produced by an entity that can replicate, such as some insect that spontaneously grew out of rocks, like a crystal. A fourth would be a trait designed to benefit an organism other than the one that caused the trait to appear, such as horses evolving saddles. In the comic strip Li’l Abner, the cartoonist Al Capp featured selfless organisms called shmoos that laid chocolate cakes instead of eggs and that cheerfully barbecued themselves so that people could enjoy their delicious boneless meat. The discovery of a real-life shmoo would instantly refute Darwin.