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

We need to bear in mind that the exaptation itself must have evolved by conventional natural selection. Failure to appreciate this has resulted in much confusion and bitter feuds. The principle of exaptation is not an alternative to natural selection, as Gould’s critics believe, but actually complements and expands its scope and range of applicability. For instance, feathers originally evolved from reptilian scales as an adaptation to provide insulation (just like hair in mammals), but then were exapted for flight. Reptiles evolved a three-bone multihinged lower jaw to permit swallowing large prey, but two of these three bones became an exaptation for improved hearing. The convenient location of these bones made possible the evolution of two little sound-amplifying bones inside your middle ear. No engineer would have dreamed of such an inelegant solution, which goes to illustrate the opportunistic nature of evolution. (As Francis Crick once said, “God is a hacker, not an engineer.”) I will expand on these ideas about jawbones transforming into ear bones at the end of this chapter.

Another example of a more general-purpose adaptation is the evolution of flexible fingers. Our arboreal ancestors originally evolved them for climbing trees, but hominins adapted them for fine manipulation and tool use. Today, thanks to the power of culture, fingers are a general-purpose mechanism that can be used for rocking a cradle, wielding a scepter, pointing, or even counting for math. But no one—not even a naïve adaptationist or evolutionary psychologist—would argue that fingers evolved because they were selected for pointing and counting.

Similarly, Gould argues, thinking may have evolved first, given its obvious usefulness in dealing with the world, which then set the stage for language. I agree with Gould’s general idea that language didn’t originally evolve specifically for communication. But I don’t like the idea that thinking evolved first and language (by which I mean all of language—not just in the Chomskian sense of emergence) was simply a byproduct. One reason I don’t like it is that it merely postpones the problem rather than solving it. Since we know even less about thinking and how it might have evolved than we do about language, saying language evolved from thought doesn’t tell us very much. As I have said many times before, you can’t get very far in science by trying to explain one mystery with another mystery.

The fourth idea—diametrically opposed to Gould’s—was proposed by the distinguished Harvard University linguist Steven Pinker, who declares language to be an instinct, as ingrained in human nature as coughing, sneezing, or yawning. By this he doesn’t mean it’s as simple as these other instincts, but that it is a highly specialized brain mechanism, an adaptation that is unique to humans and that evolved through conventional mechanisms of natural selection expressly for communication. So Pinker agrees with his former teacher Chomsky in asserting (correctly, I believe) that language is a highly specialized organ, but disagrees with Gould’s views on the important role played by exaptation. I think there is merit to Pinker’s view, but I also think his idea is far too general to be useful. It is not actually wrong, but it is incomplete. It seems a bit like saying that the digestion of food must be based on the first law of thermodynamics—which is true for sure, but it’s also true for every other system on earth. The idea doesn’t tell you much about the detailed mechanisms of digestion. In considering the evolution of any complex biological system (whether the ear or the language “organ”), we would like to know not merely that it was done by natural selection, but exactly how it got started and then evolved to its present level of sophistication. This isn’t as important for a more straightforward problem like the giraffe’s neck (although even there, one wants to know how genes selectively lengthen neck vertebrae). But it is an important part of the story when you are dealing with more complex adaptations.

So there you have it, four different theories of language. Of these we can discard the first two—not because we know for sure that they are wrong, but because they can’t be tested. But of the remaining two, who’s right—Gould or Pinker? I’d like to suggest that neither of them is, although there’s a grain of truth in each (so if you are a Gould/Pinker fan, you could say they were both right but didn’t take their arguments far enough).