The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

2. More important than the sheer size of our lexicon is the fact that only humans have function words that exist exclusively in the context of language. While words like “dog,” “night,” or “naughty” refer to actual things or events, function words have no existence independent of their linguistic function. So even though a sentence such as “If gulmpuk is buga, then gadul will be too” is meaningless, we do understand the conditional nature of the statement because of the conventional usage of “if” and “then.”

3. Humans can use words “off-line,” that is, to refer to things or events that are not currently visible or exist only in the past, the future, or a hypothetical reality: “I saw an apple on the tree yesterday, and decided I will pluck it tomorrow but only if it is ripe.” This type of complexity isn’t found in most spontaneous forms of animal communication. (Apes who are taught sign language can, of course, use signs in the absence of the object being referred to. For example, they can sign “banana” when hungry.)

4. Only humans, as far as we know, can use metaphor and analogy, although here we are in a gray area: the elusive boundary between thought and language. When an alpha male ape makes a genital display to intimidate a rival into submission, is this analogous to the metaphor “F—k you” that humans use to insult one another? I wonder. But even so, this limited kind of metaphor falls far short of puns and poems, or of Tagore’s description of the Taj Mahal as a “tear drop on the cheek of time.” Here again is that mysterious boundary between language and thought.

5. Flexible, recursive syntax is found only in human language. Most linguists single out this feature to argue for a qualitative jump between animal and human communication, possibly because it has more regularities and can be tackled more rigorously than other, more nebulous aspects of language.

These five aspects of language are by and large unique to humans. Of these, the first four are often lumped together as protolanguage, a term invented by the linguist Derek Bickerton. As we’ll see, protolanguage set the stage for the subsequent emergence and culmination of a highly sophisticated system of interacting parts that we call, as a whole system, true language.

TWO TOPICS IN brain research always seem to attract geniuses and crackpots. One is consciousness and the other is the question of how language evolved. So many zany ideas on language origins were being proposed in the nineteenth century that the Linguistic Society of Paris introduced a formal ban on all papers dealing with this topic. The society argued that, given the paucity of evolutionary intermediates or fossil languages, the whole enterprise was doomed to fail. More likely, linguists of the day were so fascinated by the intricacies of rules intrinsic to language itself that they were not curious about how it may have all started. But censorship bans and negative predictions are never a good idea in science.

A number of cognitive neuroscientists, myself included, believe that mainstream linguists have been overemphasizing the structural aspects of language. Pointing to the fact that the mind’s grammatical systems are to a large extent autonomous and modular, most linguists have shunned the question of how these interact with other cognitive processes. They profess interest solely in the rules that are fundamental to the brain’s grammatical circuits, not how the circuits actually work. This narrow focus removes the incentive to investigate how this mechanism interacts with other mental capacities such as semantics (which orthodox linguists don’t even regard as an aspect of language!), or to ask evolutionary questions about how it might have evolved from preexisting brain structures.

The linguists can be forgiven, if not applauded, for their wariness of evolutionary questions. With so many interlocking parts working in such a coordinated manner, it’s hard to figure out, or even imagine, how language could have evolved by the essentially blind process of natural selection. (By “natural selection,” I mean the progressive accumulation of chance variations that enhance the organism’s ability to pass on its genes to the next generation.) It’s not difficult to imagine a single trait, such as a giraffe’s long neck, being a product of this relatively simple adaptive process. Giraffe ancestors that had mutant genes conferring slightly longer necks had better access to tree leaves, causing them to survive longer or breed more, which caused the beneficial genes to increase in number down through the generations. The result was a progressive increase in neck length.