Now finally I would like to turn to language, how did language evolve? This has always been a very controversial topic and the question is look, here we have this amazing ability called language with all the nesting of clauses, this hierarchical structure of language, this recursive embedding of clauses, our enormous lexicon and it's an extraordinarily sophisticated mechanism. How could it possibly have evolved through the blind workings of chance through natural selection? How did we evolve from the grunts and howls and groans of our ape-like ancestors to all the sophistication of a Shakespeare or a George Bush? Now there have been several theories about this. Alfred Russell Wallace said the mechanism is so complicated it couldn't have evolved through natural selection. It was done by god, divine intervention. Maybe he's right but we can't test it so let's throw it away. Next theory was by Chomsky. Chomsky said actually something quite similar although he doesn't use the word god. He said this mechanism is so sophisticated and elaborate it couldn't have emerged through natural selection, through the blind workings of chance but god knows what happens if you pack one hundred billion nerve cells in such a tiny space, you may get new laws of physics emerging. Aha, that's how you explain language so he almost says it's a miracle although he doesn't use the word miracle. Now even if that's true we can't test it so let's throw it away. So then what actually happened? How did language evolve? I suggest the clue, the vital clue comes from the booba/kiki example, from synesthesia and I'd like to replace this idea with what I call the synesthetic boot-strapping theory of language origins, and I'll get to that in a minute.

So the next idea is Pinker's idea and his idea is look there's no big mystery here. You're seeing the final result of evolution, of language but you don't know what the intermediate steps are so it always looks mysterious but of course it evolved through natural selection even though we don't know what the steps were. Now I think he's right but he doesn't go far enough because as a biologist, we want the devils and the details. We want to know what those intermediate steps are, not merely that it could have happened through natural selection. Of course it happened through natural selection. There is nothing else so let's take the lexicon, words. How did we evolve such a wonderful huge repertoire of words, thousands of words? Did our ancestral hominoids sit near the fireplace and say, let's look at that. OK, everybody call it an axe, say everybody axe. Of course not! I mean you do that in kindergarten but that's not what they did. If they didn't do that, what did they do? Well what I'm arguing is that the booba/kiki example provides the clue. It shows there is a pre-existing translation between the visual appearance of the object represented in the fusiform gyrus and the auditory representation in the auditory cortex. In other words there's already a synesthetic cross-modal abstraction going on, a pre-existing translation if you like between the visual appearance and the auditory representation. Now admittedly this is a very small bias, but that's all you need in evolution to get it started and then you can start embellishing it.

But that's only part of the story, part one. Part two, I'm going to argue, there's also a pre-existing built-in cross-activation. Just as there is between visual and auditory, the booba/kiki effect, there's also between visual in the fusiform and the motor brocas area in the front of the brain that controls the sequence of activations of muscles of vocalisation, phonation and articulation - lips, tongue and mouth. How do I know that? Well let's take an example. Let's take the example of something tiny, say teeny weeny, un peu, diminutive - look at what my lips are doing. The amazing thing is they're actually physically mimicking the visual appearance of the object - versus enormous, large. We're actually physically mimicking the visual appearance of the object so what I'm arguing is that also again a pre-existing bias to map certain visual shapes onto certain sounds in the motor maps in the brocas area.

Lastly, the third factor - I think there's also a pre-existing cross-activation between the hand area and the mouth area because they are right next to each other in the Penfield motor map in the brain and let me give you an example, and I got scooped. Charles Darwin first described this. What he showed was when people cut with a pair of scissors you clench and unclench your jaws unconsciously as if to echo or mimic the movements of the fingers. He didn't explain why but I'd like to give it a name. I call it synkinesia - and that's because the hand and mouth areas are right next to each other and maybe there is some spill-over of signals. Now so what? Well, imagine your ancestral hominids evolving a system of gestures for communication, and this would have been important because vocalisation, you can't engage them in your hunting. Now the right hemisphere produces guttural emotional utterances along with the anterior singular. Now your mouth and tongue are already, there's a pre-existing translation of the visual symbols into mouth lip and tongue movements. Combine that with guttural utterances coming from the right hemisphere and anterior cingulate, what do you get? You get the first words, you get proto-words.

So now you've got three things in place - hand to mouth, mouth in brocas area to visual appearance in the fusiform and auditory cortex, and auditory to visual, the booba/kiki effect. Each of these is a small effect but acting together there's a synergistic boot-strapping effect going on and an avalanche effect, culminating in the emergence of language. Finally you say well what about the hierarchical structure of syntax? How do you explain that? Well I think like when you say he knows that I know that he knows that I know that I had an affair with his wife. How do you do this hierarchic embedding in language? Well partly I think that comes from semantics, from the region of the TPO where I said you'd engage in abstraction and I already explained how abstraction might have evolved, so partly abstraction feeds into syntactic structure, but partly from tool use. Early hominids were very good at tool use and especially what I call the sub-assembly technique in tool use where you take a piece of flint, make it into a head - step one. Then you haft it onto a handle - step two, and then the whole thing becomes one entity which is then used to hit you the subject, you hit the object. You do something to the object and this bears a certain operational analogy with the embedding of noun clauses. So what I'm arguing is what evolved for tool use in the hand area is now exapted and assimilated in the brocas area to be used in syntactic hierarchic embedding. So now look, each of these has a small bias but acting in conjunction they culminate in language. It's very different from Steve Pinker's idea which is that language is a specific adaptation which evolved step by step for the sole purpose of communication. What I'm arguing here is no, it's the fortuitous synergistic combination of a number of mechanisms which evolved for other purposes initially and then became assimilated into the mechanism that we call language. This often happens in evolution but it's a style of thinking that has yet to permeate neurology and psychology and it's very odd that neurologists don't usually think of evolution given that nothing in biology makes any sense except in the light of evolution as Dobzhansky once said.

So let me summarise what we've done. We begin with a disorder that's been known for a century but treated as a curiosity. And then we showed that the phenomenon is real, what the underlying brain mechanisms might be, and lastly spelt out what the broader implications of this curious phenomenon might be. So what have we done here with synesthesia? Let's take a look. One day we might be able to clone the gene or genes, because if you find a large enough family you might be able to do this. Then we can go on to the brain anatomy and say look, it's expressed in the fusiform gyrus and you get lower synesthesia. You go to angular gyrus you get higher synesthesia. If it's expressed all over you get artsy types! Then from the brain anatomy you go to detailed perceptual psychophysics. Either the pop-out effect, you know the 2s against the 5s which you can measure, and then finally all the way to understanding abstract thought and how it might have emerged, metaphor, Shakespeare, even the evolution of language - all of this in this one little quirk that people used to call synesthesia. So I agree wholeheartedly with what Huxley said in the last century just across the road here at the University Museum, contrary to Benjamin Disraeli's views and the views of Bishop Wilberforce. We are not angels, we are merely sophisticated apes. Yet we feel like angels trapped inside the bodies of beasts, craving transcendence and all the time trying to spread our wings and fly off, and it's really a very odd predicament to be in, if you think about it.