We Earth Neurons

September 18, 2001 by Daniel Dennett

Daniel Dennett on knowledge sharing and the fate of the planet, in which he contrasts individuals and their brains with the trillions of neurons that compose them. The planet has grown its own nervous system: us.

Originally published as an academic paper on August 15, 1999. Published on KurzweilAI.net September 18, 2001.

Some years ago a friend of mine in the Peace Corps told me about his efforts on behalf of a tribe of gentle Indians deep in the Brazilian forest. I asked him if he had been required to tell them about the conflict between the USA and the USSR. Not at all, he replied. There would be no point in it. They had not only never heard of either America or the Soviet Union, they had never even heard of Brazil! Who would have guessed that it is still possible to be a human being living in, and subject to the laws of, a nation without the slightest knowledge of that fact? If we find this astonishing, it is because we human beings, unlike all other species on the planet, are knowers. We are the ones–the only ones–who have figured out what we are, and where we are, in this great universe. And we are even beginning to figure out how we got here.

These quite recent discoveries are unnerving, to say the least. What you are–what each of us is–is an assemblage of roughly a trillion cells, of thousands of different sorts. Most of these cells are “daughters” of the egg and sperm cell whose union started you (there are also millions of hitchhikers from thousands of different lineages stowed away in your body), but each cell is a mindless mechanism, a largely autonomous micro-robot, no more conscious than a bacterium, and not a single one of the cells that compose you knows who you are, or cares.

Each trillion-robot team is gathered together in a breathtakingly efficient regime that has no dictator but manages to keep itself organized to repel outsiders, banish the weak, enforce iron rules of discipline–and serve as the headquarters of one conscious self, one mind. These communities of cells are fascistic in the extreme, but your interests and values have almost nothing to do with the limited goals of the cells that compose you–fortunately. Some people are gentle and generous, others are ruthless; some are pornographers and others devote their lives to the service of God, and it has been tempting over the ages to imagine that these striking differences must be due to the special features of some extra thing (a soul) installed somehow in the bodily headquarters, but what we now have figured out is that there is no such extra ingredient; we are each made of mindless robots and nothing else, no non-physical, non-robotic ingredients at all. The differences between people are all due to the way their particular robotic teams are put together, over a lifetime of growth and experience. The difference between speaking French and speaking Chinese is a difference in the organization of the working parts, and so are all the other differences of personality–and knowledge.

Four and a half billion years ago, the earth was formed, and it was utterly without life. And so it stayed for perhaps as long as a billion years. For another billion years, the planet’s oceans teemed with life, but it was all blind and deaf. Simple cells multiplied, engulfing each other, exploiting each other in a thousand ways, but oblivious to the world beyond their membranes. Then much larger, more complex cells evolved–eukaryotes–still clueless and robotic, but with enough internal machinery to begin to specialize. So it continued for more than two billion more years, the time it took for the algorithms of evolution to hit upon good ways of banding these workers together into multi-cellular organisms composed of millions, billions and, (eventually) trillions of cells, each doing its particular mechanical routine, but now yoked into specialized service, as part of an eye or an ear or a lung or a kidney. These organisms (not the individual team members composing them) had become long-distance knowers, able to spy supper trying to appear inconspicuous in the middle distance, able to hear danger threatening from afar. But still, even these whole organisms knew not what they were. Their instincts guaranteed that they tried to mate with the right sorts, and flock with the right sorts, but just as those Brazilians didn’t know they were Brazilians, no buffalo has ever known it’s a buffalo.

In just one species, our species, a new trick evolved: language. It has provided us a broad highway of knowledge-sharing, on every topic. Conversation unites us, in spite of our different languages. We can all know quite a lot about what it is like to be a Vietnamese fisherman or a Bulgarian taxi driver, an eighty-year-old nun or a five-year-old boy blind from birth, a chess master or a prostitute. No matter how different from one another we people are, scattered around the globe, we can explore our differences and communicate about them. No matter how similar to one another buffalos are, standing shoulder to shoulder in a herd, they cannot know much of anything about their similarities, let alone their differences, because they can’t compare notes. They can have similar experiences, side by side, but they really can’t share experiences the way we do.

Even in our species, it has taken thousands of years of communication for us to begin to find the keys to our own identities. It has been only a few hundred years that we’ve known that we are mammals, and only a few decades that we’ve understood in considerable detail how we have evolved, along with all other living things, from those simple beginnings. We are outnumbered on this planet by our distant cousins, the ants, and outweighed by yet more distant relatives we share with the ants, the bacteria, but though we are in the minority, our capacity for long-distance knowledge gives us powers that dwarf the powers of all the rest of the life on the planet. Now, for the first time in its billions of years of history, our planet is protected by far-seeing sentinels, able to anticipate danger from the distant future–a comet on a collision course, or global warming–and devise schemes for doing something about it. The planet has finally grown its own nervous system: us.

We may not be up to the job. We may destroy the planet instead of saving it, largely because we are such free-thinking, creative, unruly explorers and adventurers, so unlike the trillions of slavish workers that compose us. Brains are for anticipating the future, so that timely steps can be taken in better directions, but even the smartest of beasts have very limited time horizons, and little if any ability to imagine alternative worlds. We human beings, in contrast, have discovered the mixed blessing of being able to think even about our own deaths and beyond, and a huge portion of our energy expenditure over the last ten thousand years or so has been devoted to assuaging the concerns provoked by this unsettling new vista. If you burn more calories than you take in, you soon die. If you find some tricks that provide you a surplus of calories, what might you spend them on? You might devote person-centuries of labor to building temples and tombs and sacrificial pyres on which you destroy some of your most precious possessions–and even some of your very own children. Why would you want to do that? These strange and awful expenditures give us clues about some of the hidden costs of our heightened powers of imagination. We did not come by our knowledge painlessly.

Array