As a result their articulation is greatly impaired, but the problem is more than one of just motor control. In simple repetition tests, affected individuals have trouble reproducing sounds and words in the correct sequence, selecting the right sounds for words, and maintaining an appropriate rhythm. Multisyllabic words like “hippopotamus” can be particularly difficult, and in general, the more unfamiliar a word, the more trouble they will have saying it. Their speech is sometimes unintelligible.
As babies, the affected family members behaved somewhat like deaf children—they were quieter than the average infant. Because the lower part of their face was relatively immobile, they had a limited array of facial expressions, which in general were not as spontaneous as those of the unaffected members of the family.
In the affected family members, structural and functional brain scanning shows changes in the speech and language areas. For example, when you’d expect Broca’s area to be active, the affected KE members show a scattered pattern of activation in regions of the brain that wouldn’t normally be active during language processing.
Vargha-Khadem discovered the family when one of the affected children was seen because of speech and language-related problems. Consequent to this meeting, other members of the family were also assessed, and the profile characteristic of the affected individuals was identified. The disorder, she said, involves a complicated circuit that regulates the movement of the muscles of the lips, tongue, and lower face used in speaking and the hardwiring of the brain structures that are typically used for language. It’s unknown whether the problems begin with the physical challenges that the affected family members have in producing, and to a lesser extent comprehending, speech, or whether the fundamental obstacle lies in the creation and understanding of language in the brain.
Vargha-Khadem asked a group of geneticists at the University of Oxford to see if they could identify the defective gene causing the disorder. The team spent several years closing in on the gene responsible when their search was given a boost by a similar speech and language problem in an unrelated child. That child had problems very much like those of the affected KE family members, and between the two different sets of data the geneticists were able to narrow their focus and find the problem gene, dubbed FOXP2. It was the first, and so far only, time that a single gene was linked to an inherited speech disorder.1
The FOXP2 gene is located on chromosome 7. Because all normal people have two copies of a chromosome, every individual should have two copies of chromosome 7 and two copies of FOXP2. In the KE family affected members have a mutation that leaves them with only one working copy of FOXP2. The result is what geneticists call a dosage effect: If you have two normally functioning copies of FOXP2, brain and language develop normally, as is the case for the unaffected members of the KE family. If you have only one working copy of FOXP2, you are going to have an array of difficulties with language and speech. No living individual with two malfunctioning copies of FOXP2 has ever been found.
FOXP2 is expressed in several organs of the body, including the brain, where its pattern of expression appears to be specific to regions involved with the development of motor control.
Twin and other developmental studies have demonstrated a strong link between genes and disorders of speech and language, but most of these findings have presented a very complicated picture and it is suspected that language impairment is related to many genes. The KE family is the first clear demonstration of a single gene affecting language ability and speech articulation. It is a landmark case and may yet prove to be the twenty-first century’s Phineas Gage in its being a foundational case study for more than a century’s worth of neuroscience.
The announcement of the discovery of FOXP2 inspired a debate about what role the gene would normally play in language function—whether its main function is to process and produce the sounds of language or specific parts of language, like grammar. Initially, it was hailed in the popular media as proof of the existence of a language gene, or even a grammar gene.
Even before the discovery of FOXP2 some researchers argued that the KE family proved the existence of a grammar gene. Why is the idea of a specific language or grammar gene appealing? Why would isolating a gene that controls language and that controls only language be such a coup? First, if such a language gene existed, you could track the development of language very finely over time. The beginning of language in the human race could, theoretically, be exactly pinpointed. Second, if a language gene like this was discovered, it would give great weight to the theory that language appeared with a big bang. Finally, a language gene that was possessed by humans and no other animal would provide compelling evidence for the traditional claim that language is a discrete mental trait unique to our species. Indeed, in 1990 the linguist Derek Bickerton proposed that language evolved because of a single genetic mutation.
One criticism of Chomsky’s view of evolution was that it was almost creationist and that it required some kind of miraculous genetic big bang. The defense to this criticism had always been that Chomsky’s ideas about language didn’t implicate evolution one way or the other, and yet Bickerton made explicit what critics said was implicit all along. Bickerton proposed that in a single female who lived approximately 220,000 years ago, a genetic mutation resulted in changes to the vocal tract and skull, as well as a rewiring of the brain for syntax, thus giving rise to language.
Bickerton’s proposal was vociferously criticized by evolutionary biologists, and he has since modified his position.2 FOXP2-based claims for a grammar gene have likewise petered out. Why? They depend on a view of genes only as atomistic building blocks and the genome as a blueprint for the organism, and neither of these ideas has held up. While few researchers would claim that language and genes are not related, there has been little evidence that language is genetically encoded. Certainly, there is no direct relationship between possession of the FOXP2 gene and fully having language.
This thread in the development of the language gene story runs strongly parallel to all the ideas regarding comparative animal work on gesture and cognition that have so far been discussed.3 The genetic mutation idea echoes all the other suggestions that the extremely complex apparatus that allows you to learn language evolved as a discrete and singular entity—a language organ—that arose without any antecedent.
When Darwin described natural selection a century and a half ago, he was essentially describing a genetic process (the way that genes throw up random mutations and then propagate over time). Today we know that all normal humans have twenty-three pairs of chromosomes, which reside in the nucleus of cells. Chromosomes are made up of DNA, which in turn is made up of four nucleic acid bases, adenine, thymine, guanine, and cytosine. The bases are most commonly designated by their first letters, A, T, G, and C. Stretches of DNA along the chromosome constitute a code for specific proteins, so when molecular machinery reads these segments of DNA, proteins are made in the cell. These segments—these units of code—are called genes. A gene is expressed when the protein it codes for has been produced.
In between the genes, there are stretches of nucleic acid bases that do not code for proteins. These strings of A, T, G, and C, junk DNA, can randomly vary without affecting the organism. The genome of an organism, then, is the entirety of its DNA, junk and genes.
During reproduction, genes are duplicated and carried forward, sometimes having no effect whatsoever. Other times, genes or larger groups of genes get flipped and reinserted in the process of duplication, possibly into the same spot, or they might get moved. This rearrangement occurs at different rates in different species (it is a process we don’t fully understand).
In the last few years our ability to describe what the units of evolution look like and do has culminated in the sequencing of the human, mouse, rat, fruit fly, and chimpanzee genome, among others. We have discovered that our genome is not nearly as large as we thought, and once we got over the shock of this, our understanding of how genes actually work
has grown immeasurably more sophisticated. The sense that a huge gap existed between animals that produced language and animals that did not arose in large part from our narrow view of the abilities of nonlinguistic animals. Now that we are crediting them with greater mental skills, we can see more clearly how the language we have arises from the platform of thinking and communication that we share with them (or, if you want to cut it more finely, from the many platforms we share, each resting on the other, mammalian arising from reptilian, and so on). The common platform arises from common genes.
Since Darwin’s time we have come to understand that not only has all life descended from the same ancestor but many features that arose in more recent ancestors are still shared between us, being built by the same genes. We can see that biologically we are basically African apes who only recently left the motherland. And our most distant human ancestors have been located in time and space. All of us alive today share at least one grandmother who lived 150,000 years ago in East Africa.4 We also share at least one grandfather, an African man who lived 60,000 years ago.5
We see today that differences in complexity between life-forms arise more from the way that genes interact with one another than from their raw number. It’s clear that the notion of a genome as a blueprint—so popular only five years ago—is at best inadequate and at worst completely misleading. Instead of following straightforward predetermined plans, genes operate in a dynamic fashion. Many genes respond to the experience of the organism they are building, and they can be switched off or on by other genes or by the effects of the environment.
If a gene comes on in the right cell at the right stage of development, it has a beneficial effect. The same gene acting at the wrong time or in the wrong place can be devastating. Vision, for example, doesn’t just unfold automatically in certain animals. The animals need to be exposed to light for the right gene to start building the ability to see. Moreover, different genes have dominion over different body parts. HOX genes divide up the body plan of organisms, with each affecting a certain segment. Some genes are noted for their effect on other genes. These manager genes turn numbers of other genes on and off, and in this way changes in a single gene can cause chain reactions of gene expression.
What we have learned about genes has allowed us to understand that we are not so much things merely existing in the world as beings in constant interaction with the world. If you took this idea to an extreme and imagined that you grew up on another planet, the essentially dynamic nature of animal building by genes and environment might mean you’d look very different. Cloned plants that have exactly the same genome can look like very different specimens if planted at different altitudes. In the same way, if you had grown up on a planet with lower gravity or one that was more distant from the sun and had a lower oxygen concentration, you might be incredibly tall, or short, or weedy, or blind…or maybe you’d have a supersized brain. If you took your African ape genome and cultured it on yet another planet, maybe the resulting you would have translucent skin. The point is that although we experience ourselves in some sense as finished or perfected, we are not in any way intended. There is no blueprint for what humans are meant to be. And as this moment is merely one moment in the past and future history of our evolutionary lineage, your life right now is merely an instant in the past and future history of the interaction between your genome and your environment.
At the time the discovery of FOXP2 was announced, Faraneh Vargha-Khadem said that she didn’t believe it was accurate to call it a language or grammar gene. As she explained, “The core deficits of the FOXP2 gene have much more to do with speech and articulation than with the more complex aspects of language.” Certainly it has turned out to be much more complicated than a single-function grammar gene.
FOXP2 is the kind of gene that turns a tree of other genes on and off, so there is no one-to-one correspondence between it and a single trait. As mentioned earlier, it is also expressed in the heart, lungs, and other tissues.6 For that reason calling FOXP2 a language gene is a little like calling gravity a force that makes apples fall from trees. It’s true enough, but it’s hardly the whole story. This fundamental truth about genes, in addition to the way that some genes produce cascading changes in others (as opposed to the purely atomistic “gene + gene + gene = discrete trait” idea), has made it increasingly difficult for skeptics to resist new ideas about language evolution.
One of the most exciting things about the FOXP2 discovery was that it seemed to be more than just a gene that could block normal language development (in the same way that, hypothetically, if your mouth didn’t form, you wouldn’t be able to speak). It looked, rather, as if it had some role in actually building language. In the ensuing years evidence for this has accumulated as other groups have begun to study the effects of the gene in different animals. Although our version of FOXP2 is unique to us, it is highly conserved between species, and in fact predates the dinosaurs. Though there is no direct relationship between possession of the gene and fully having language, FOXP2 does play a role in the communication of a number of different animals.
Scientists say that in humans and songbirds, the gene is 98 percent the same. FoxP2 (nonhuman versions) appears to play a significant role in the learning and expression of song in birds like the zebra finch; its expression increases in certain brain areas at the developmental stage when the birds are learning how to sing. In addition, the expression of FoxP2 in canaries varies seasonally and correlates with a change in song.
The mouse and human versions of the gene are even more alike than the human and songbird versions, and it’s recently been demonstrated that FoxP2 affects the vocalizations of mice.7 Scientists at Mount Sinai Hospital in New York showed that while mice with only one normal FoxP2 had some general developmental delays, more strikingly their patterns of vocalization were affected.8 Typically, if a mouse pup is separated from its mother, it will produce cries that are above the range of human hearing. (It was only a few years ago that we learned mice produce sound in the ultrasonic range. In 2005 scientists at Washington University discovered that male mice sing to females in the ultrasonic range.) The purpose of the pup’s ultrasonic cries is to alert its mother to its whereabouts. Mice with only one working copy of FoxP2 produced far fewer vocalizations when separated from their mothers than normal mice. FoxP2 seems to play a role in both learned and innate vocal production. (The Mount Sinai researchers found that mice with disrupted versions of both of their FoxP2 genes had severe motor difficulties, lacked crucial vocalizations, and died prematurely.)
Even though language ability is not contained in one or two genes and somehow generated out of them, the FOXP2 work is compelling evidence that we need certain genes to have structured communication—and that human communication, of which language constitutes a huge part, depends in some measure on the same genetic foundations that animal communication does.
Gary Marcus, a professor of psychology at New York University and author of The Birth of the Mind, has worked closely with Simon Fisher, one of the geneticists known for FOXP2 research. Marcus explained FOXP2 by way of comparison to another gene, PAX6:
PAX6 is what is called a master control gene—a gene that achieves great influence by guiding the actions of other genes. Strictly speaking, what PAX6 does is the same sort of thing that any other gene does: it gives a template for building a particular protein, and information about when and where that protein should be built. But the protein that PAX6 governs influences the expression of other genes, telling them when and where other genes do their thing. And because it’s atop (or at least close to the top) of a hierarchy, PAX6 can have a huge influence.
One experiment showed that by switching on PAX6 in the right place on a fruit fly’s antenna, the fly can grow a whole extra eye in an entirely new place. FOXP2 may or may not be so high up the food chain, but like PAX6 it clearly does modulate other genes; if it’s not a CEO, it at least seems to be an important middle-level manager. The broader lesson is that all genes
work as parts of hierarchies or cascades. PAX6 isn’t “the eye gene.” It’s a gene that can spawn an eye by influencing thousands of other genes. FOXP2 isn’t “the language gene” but it may have a profound influence by regulating the actions of many other genes.
After the discovery of FOXP2’s language effects, Steven Pinker hailed the possibilities for a new science: cognitive genetics. Vargha-Khadem and her colleagues called it neurogenetics. Whatever this new field ends up being named, the next century will be an exciting time of determining the closeness of the weave of genes, brains, and behavior. The old nature-versus-nurture debate will finally be shucked off and left behind.
In working out the way genes build linguistic brains, one of this new science’s greatest challenges is determining how experience affects the spread of job specialization across the brain. The dynamic interplay between genes and experience as it propels a creature through conception, development, sexual maturity, parenthood, and eventually death is greatly complicated by brain plasticity—which must itself, presumably, be underwritten by genes. Solving the mystery of language and its evolution will involve working out what is innately specified and what alternative routes to processing the same kind of data are enabled by plasticity.
As the field progresses, we will discover more about the reach of FOXP2. In his most recent book, Toward an Evolutionary Biology of Language, Philip Lieberman notes that in addition to vocal learning, “humans possess more cognitive flexibility than other species.” He argues that FOXP2 also underlies this trait, which itself gives rise to creative thinking, language, voluntary motor control in speech, and, perhaps, dancing.
The First Word: The Search for the Origins of Language Page 23