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

But how can multiple traits, each of which would be useless without the other, evolve in tandem? Many complex, interwoven systems in biology have been held up by would-be debunkers of evolutionary theory to argue for so-called intelligent design—the idea that the complexities of life could only occur through divine intervention or the hand of God. For example, how could the vertebrate eye evolve via natural selection? A lens and a retina are mutually necessary, so each would be useless without the other. Yet by definition the mechanism of natural selection has no foresight, so it couldn’t have created the one in preparation for the other.

Fortunately, as Richard Dawkins has pointed out, there are numerous creatures in nature with eyes at all stages of complexity. It turns out there is a logical evolutionary sequence that leads from the simplest possible light-sensing mechanism—a patch of light-sensitive cells on the outer skin—to the exquisite optical organ we enjoy today.

Language is similarly complex, but in this case we have no idea what the intermediate steps might have been. As the French linguists pointed out, there are no fossil languages or half-human creatures around for us to study. But this hasn’t stopped people from speculating on how the transition might have come about. Broadly speaking, there have been four main ideas. Some of the confusion between these ideas results from failing to define “language” clearly in the narrow sense of syntax versus the broader sense that includes semantics. I will use the term in the broader sense.

THE FIRST IDEA was advanced by Darwin’s contemporary Alfred Russel Wallace, who independently discovered the principle of natural selection (though he rarely gets the credit he deserves, probably because he was Welsh rather than English). Wallace argued that while natural selection was fine for turning fins into feet or scales into hair, language was too sophisticated to have emerged in this way. His solution to the problem was simple: Language was put into our brains by God. This idea may or may not be right but as scientists we can’t test it, so let’s move on.

Second, there’s the idea put forward by the founding father of modern linguistic science, Noam Chomsky. Like Wallace, he too was struck by the sophistication and complexity of language. Again, he couldn’t conceive of natural selection being the correct explanation for how language evolved.

Chomsky’s theory of language origins is based on the principle of emergence. The word simply means the whole is greater—sometimes vastly so—than the mere sum of the parts. A good example would be the production of salt—an edible white crystal—by combining the pungent, greenish, poisonous gas chlorine with the shiny, light metal sodium. Neither of these elements has anything saltlike about it, yet they combine into salt. Now if such a complex, wholly unpredictable new property can emerge from a simple interaction between two elementary substances, then who can predict what novel unforeseen properties might emerge when you pack 100 billion nerve cells into the tiny space of the human cranial cavity? Maybe language is one such property.

Chomsky’s idea isn’t quite as silly as some of my colleagues think. But even if it’s right, there’s not much one can say or do about it given the current state of brain science. There’s simply no way of testing it. And although Chomsky doesn’t speak of God, his idea comes perilously close to Wallace’s. I don’t know for sure that he is wrong, but I don’t like the idea for the simple reason that one can’t get very far in science by saying (in effect) something miraculous happened. I’m interested in finding a more convincing explanation that’s based on the known principles of organic evolution and brain function.

The third theory, proposed by one of the most distinguished exponents of evolutionary theory in this country, the late Stephen Jay Gould, argues that contrary to what most linguists claim, language is not a specialized mechanism based on brain modules and that it did not evolve specifically for its most obvious present purpose, communication. On the contrary, it represents the specific implementation of a more general mechanism that evolved earlier for other reasons, namely thinking. In Gould’s theory, language is rooted in a system that gave our ancestors a more sophisticated way to mentally represent the world and, as we shall see in the Chapter 9, a way to represent themselves within that representation. Only later did this system get repurposed or extended into a means of communication. In this view, then, thinking was an exaptation—a mechanism that originally evolved for one function and then provided the opportunity for something very different (in this case language) to evolve.