Think Darwin

There is now, I think, a consensus that the brain is the final frontier. We have plumbed the depths of the oceans and we have floated awestruck through space; we have conquered diseases that terrorised our forebears and we have built machines of incredible power and technical sophistication. But one prize has eluded us - understanding the very thing that has made all these possible: the brain.

We are now in the midst of the decade of the brain, so it is perhaps inevitable that a plethora of books about brains is tumbling out of the publishers' lists. William Calvin, who describes himself as a theoretical neurophysiologist, has written a number of popular science books about the brain, in addition to academic books such as the one reviewed below. In this slim volume for the general reader, he tries to capture something of the sense of excitement that is driving neuroscience in its bid to understand how brains produce those two central facts of human life, consciousness and language.

Calvin takes particular issue with physicists like Roger Penrose who have mused so extensively on the nature of consciousness. Their focus on the simple reductionist explanations that characterise the physical sciences often causes them to overlook the real biological issue - the fact that in many cases the properties of biological systems are, precisely, systemic. Their attempts to explain consciousness, he says, are tantamount to trying to explain a grid-locked traffic system by pointing to the failed spark plugs of the car at the centre of the catastrophe. But, as he rightly points out, the log-jam that tails back through the surrounding streets has nothing to do with the rusty set of spark plugs in the offending vehicle; it has to do with the organisational characteristics of the traffic system as a whole - the layout of the road system, the flow rates of traffic and the fact that, once in the system, drivers do not think of escaping into side-roads until it is too late. Physicists, he says, commonly commit the janitor's dream fallacy of trying to leap from the basement to the penthouse in one go.

We must beware, he warns us, of hazards having to do with the end points of explanation: the New Age everything-is-related-to-everything and the reductionist explanations at an inappropriate level of organisation (offered by the consciousness physicists and ecclesiastical neuroscientists) are seductive traps for the unwary. The most complex object in the universe deserves a more serious attempt at explanation than the trite nonsense these approaches have to offer. This is fighting talk.

Calvin's views are firmly in the Darwinian mould. His aim is to try to show us how the cerebral cortex (the bit that gives us our thinking) might function as a Darwin machine, thereby creating a constantly shifting focus of consciousness. As a problem-solving device, the brain (or at least its crucial outer layers) filters and manages the incoming information and builds models of how things seem to be. Different models are in constant competition with each other, battling it out for supremacy in a war of the survival of the fittest (where fittest here means those best able to compete in the internal universe of memes or ideas). It is this, he suggests, that accounts for the constantly shifting focus of consciousness and the way subconscious thoughts occasionally pop into our conscious mind. The point is, of course, well taken: once we have freed our minds of the stultifying influence of the "Darwinism equals genetic determinism" so beloved of the muddled debates that bedevil public discussions of the evolutionary approach, it is easy to see that learning itself is simply a Darwinian process, and a particularly efficient one at that.

Calvin suggests that this cerebral Darwin machine works as effectively as it does in our case because of grammar. He argues that the formation of grammatical sentences allows us to compress information about the world into a form that is so much more efficient to analyse that it catapults us into a new domain of reasoning about the world.

This is no doubt true, but Calvin skates over two substantive issues at this juncture. One is why we needed to evolve language at all. The other has to do less with the way language organises our thoughts (helpful though this may be) than with the fact that language allows us to exchange information about the world and to coordinate our activities within groups. It is surely this latter fact that has been more important than any other, because without it we would individually each be forced to reinvent the wheel. Language allows us, in Einstein's celebrated phrase, to stand upon the shoulders of the intellectual giants of the past. I do not need to be an Aristotle or an Einstein to use a word processor: I can leave it to those who really do understand how these things work (because they in turn learned most of the story from their predecessors), yet I still benefit from their intellectual efforts.

Much of the book is, inevitably, taken up with an explanation of how neural systems work to produce the emergent properties of consciousness and thought. The integration of whole banks of neurons also provides us with the dampening effects that are necessary in the control of fine movement. This Calvin sees as an important precursor for the evolution of speech. Aimed throwing, he suggests, provided both the neural basis on which the fine motor control needed in speech production and the process of mental rehearsal that is so crucial in our daily lives. I am less convinced by his claim that nonhuman primates lack the ability to rehearse mentally what they are about to do, but he is surely right to insist that mental rehearsal is a crucial feature of human behaviour.

The last chapter turns to artificial intelligence and the uses to which we might put this. Work-alike robots, as Calvin calls them, have the potential to provide us with enormous benefits, even though they bring with them their own dangers. There will, he says, be three hard parts to implementing such a programme. One is to ensure that the robots fit into the ecology of our planet: we cannot have organisms that compete too closely with us and the other species that share our world. The second will be instilling moral values into them. The first-generation robots will surely be as amoral as our pets and children, and we will need to build in safeguards that ensure that they remain as subservient to our interests as our pets are. The last hard part will be persuading other humans not to panic at the mere thought of space-age robots in their midst. So effectively have the Hollywood film-makers preyed on our fears that this may prove to be much the hardest task.

This, then, is an entertaining book that skitters across a wide range of sciences. That produces its own costs, of course, not least the sometimes jerky shifts of topic and the occasionally irritating asides into personal experience. I found Calvin's musings as he watched the bald eagles on his way to see Alaska's Hubbard Glacier an unnecessary intrusion into a story that is quite exciting enough on its own. The extra space might have been put to more profitable use.

Robin Dunbar is professor of evolutionary psychology, University of Liverpool.