After noting that rationality has arisen only in man and that attempts to discover animal analogues to human rationality have largely failed, Barr states:
[Why Only Us] is a breathtaking intellectual synthesis. Using an array of sophisticated arguments based on discoveries in linguistics, neuroscience, genetics, computer science, evolutionary theory, and studies of animal communication, [the authors] develop a set of hypotheses about the nature and origins of human language, which will (if they hold up) have far-reaching implications. As the title of their book implies, Berwick and Chomsky argue that only human beings have language. It is not that there are other animals possessing it in germ or to a slight degree; no other animals, they insist, possess it at all. The language capacity arose very suddenly, they say, likely in a single member of the species Homo sapiens, as a consequence of a very few fortuitous and unlikely genetic mutations.It is indeed breath-taking that Berwick and Chomsky have concluded that language, the sine qua non of rational beings, appeared first in a single human. We'll return to this thought in a moment, but first Barr elaborates on the distinctions Berwick and Chomsky draw between human language and animal communication:
Animal communication can be quite intricate. For example, some species of “vocal-learning” songbirds, notably Bengalese finches and European starlings, compose songs that are long and complex. But in every case, animal communication has been found to be based on rules of linear order. Attempts to teach Bengalese finches songs with hierarchical syntax have failed. The same is true of attempts to teach sign language to apes. Though the famous chimp Nim Chimpsky was able to learn 125 signs of American Sign Language, careful study of the data has shown that his “language” was purely associative and never got beyond memorized two-word combinations with no hierarchical structure.Having argued that language is unique to the human species Barr returns to the difficulties inherent in thinking that it evolved gradually over eons of time. The genetic mutations necessary to produce the changes which gave rise to language must have been so sudden and so extensive that Berwick and Chomsky acknowledge they must have occurred in just a single individual. Barr quotes from Why Only Us:
Such a change takes place in an individual—and perhaps, if fortunate, in all of [his or her] siblings too, passed on from one or (less likely) both parents. Individuals so endowed would have advantages, and the capacity might proliferate through a small breeding group over generations.In other words, a sudden, extensive discontinuity occurs in a single generation of a species. A unique being was produced with a genetic capacity radically exceeding that of his/her parents. Even so, what good is being able to speak in language unless there are lexical precursors ready at hand to be exploited by this novel ability? Here's Barr:
This brings us to a deep puzzle, which Berwick and Chomsky are brave enough to point out. The Merge procedure [a technique for forming language] requires something “to work on,” namely the “word-like atomic elements,” which they also call “conceptual atoms of thought,” “lexical items,” “atoms of computation,” “symbols of human language and thought,” and simply “human concepts.” Where did these originate? They write,So, let's absorb this. Human rationality and the capacity for language that makes rational thought possible first arose in a single individual which found the constituent elements of language already laying about, as it were. This is far more astounding, I think, than Barr's measured prose would suggest. Indeed, it sounds very much like modern secular linguistic anthropologists are advancing a theory which is, in some significant respects, very similar to the Genesis account of the origin of the human race.The atomic elements pose deep mysteries. The minimal meaning-bearing elements of human languages—word-like, but not words—are radically different from anything known in animal communication systems. Their origin is entirely obscure, posing a very serious problem for the evolution of human cognitive capacities, language in particular.
Barr concludes with this:
Is there an ontological discontinuity between humans and other animals? Berwick and Chomsky arrive, on purely empirical grounds, at the conclusion that there is. All animals communicate, but only humans are rational; and for Berwick and Chomsky, human language is primarily an instrument of rationality. They present powerful arguments that this astonishing instrument arose just once and quite suddenly in evolutionary history—indeed, most likely in just one member of Homo sapiens, or at most a few. At the biological level, this involved a sudden upgrade of our mental machinery, and Berwick and Chomsky’s theories of this are both more plausible than competing theories and more consistent with data from a variety of disciplines. But they recognize that more than machinery is involved. The basic contents and meanings, the deep-lying elements of human thought—“word-like but not words”—were somehow there, mysteriously, in the beginning.Mysterious indeed, and fascinating.