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The Ditchley Foundation Annual Lecture XVII

11 July 1980
On the Usefulness of Biology
Delivered by:
Lewis Thomas, MD
President, Memorial Sloan-Kettering Cancer Center, New York

Male songbirds are able to sing because they possess, in the left side of their brains, a solid cluster of nerve cells for mediating and regulating this function. Females, songless, do not have such centres; we must assume that they have other specialized receptor cells for listening to the song, but we don’t know where these are. It is an interesting observation, frequently cited these days in the vast literature of neurobiology as a piece of evidence for lateralization of brain function in animals other than ourselves, perhaps analogous to the localization of speech centres in the left hemisphere of right-handed humans.

The calls of songbirds have been analyzed by acoustic physiologists for their information content; an immense literature has evolved just in the last decade or so, reducing birdsong to its essential, species-specific content of signals.

A female firefly attracts, from distant trees in the dead of night, males of her own species for the purpose of mating. She does this by emitting sets of flashes in code—repetitions of two tightly coupled flares, for example. Not long ago it was reported in Nature that the females of one species regularly switched signals after successful mating, attracting thus a flurry of males of another species which they then ate.

Bees are able to navigate with accuracy the route between the hive and sugar sources because of lenses for sensing polarized light from the sun. Pigeons find their way home on cloudy days by the use of tiny magnets just beneath their skulls. Certain strains of marine bacteria are also equipped with magnetite, enabling them to orient themselves in deep waters containing nutrient.

The Skylab satellite lost its predicted altitude and fell to earth because of sunspots; the planet’s atmosphere expanded just enough to lightly brush against the vehicle, trapping it with friction.

News items like these turn up in almost every week’s cascade of scientific journals, and there is no doubt that we are caught up in something like a revolution in science, with the speed of entry of new bits of information increasing each year. It is not only known that DNA is the essential stuff of reproduction; this material can be handled in the laboratory as easily as tape, spliced, edited, inserted into other strips of DNA and so forth. Bacteria can be induced to make insulin; fused cells can be invented to produce absolutely pure antibodies. Science moves, it seems, from strength to strength.
You’d think that fifty years of such progress would have provided all of us with so rich a library of reductionist detail that we might now begin to settle back with satisfaction at having at hand so many final answers. The trouble is that what come in looking like answers turn out, on close inspection, to be new puzzles.

I claim that puzzlement is an identifying characteristic of the human species, genetically governed, universal, and a central determinant of human behaviour. I can go this far with socio-biology, but then, influenced by this same trait, my mind falls away in confusion. Uncertainty, the sure sense that the ground is shifting at every step, is one of the marks of humanity. We keep changing our minds together, in a biological process rather similar, in its outlines, to evolution itself.

The great body of science, built like a vast hill over the past 300 years, is a mobile, unsteady structure, made up of solid-enough single bits of information but with all the bits always moving about, fitting together in different ways, adding new bits to themselves with flourishes of adornment as though always consulting a mirror, giving the whole arrangement something like the unpredictability and unreliability of living flesh. Human knowledge doesn’t stay put, it evolves by what we call trial and error, or as is more usually the sequence, error and trial.

Other animals differ from us in this respect. Each of them has at least one thing to be very good at, even superlatively skilled, surefooted. Any beetle can live a flawless, impeccable life, infallible in the business of procreating beetles. Not us: we are not necessarily good at anything in particular except language, and using this we tend to get things wrong. It is built into our genes to veer off from the point; somehow or other we have been selected in evolution for the gift of ambiguity.

This is how we fell into the way of science. The endeavour is not, as is sometimes thought, a way of building a solid indestructible body of immutable truth, fact laid precisely upon fact in the manner of twigs in an anthill. Science is not like this at all; it keeps changing, shifting, revising, discovering that it was wrong and then heaving itself explosively apart to redesign everything. It is a living thing, a celebration of human fallibility. At its very best, it is rather like an embryo.

Ordinarily, scientists do not talk this way about their trade, because there is always in the air the feeling that this time we have it right, this time we are about to come into possession of a finished science, knowing almost everything about everything. Biology has been moving so fast, in just the last few years, that there is some risk of making it seem nearly complete, at the very stage in its development when it is, in real life,just getting ready to take off. It is nothing like finished, it is only just at the beginning.

We are in trouble whenever persuaded that we know everything. Today, an intellectually fashionable view of man’s place in nature is that there is really no problem: the plain answer is that it makes no sense, no sense at all. The universe is meaningless for human beings; we bumbled our way into the place by a series of random and senseless biological accidents. The sky is not blue; this is an optical illusion: the sky is black. You can walk on the moon if you feel like it, but there is nothing to do there except look at the earth, and when you’ve seen one earth, you’ve seen them all. The animals and plants of the planet are at hostile odds with one another, each bent on elbowing any nearby neighbour off the earth. Genes, tapes of polymer, are the ultimate adversaries and, by random, the only real survivors.

This grasp of things is sometimes presented as though based on science, with the implication that we already know most of the important knowable matters and this is the way it all turns out. It is the wisdom of the 20th century, contemplating as its only epiphany the news that the world is an absurd apparatus.

In the circumstance, we would surely have no obligations except to our individual selves, and of course to the genes coding out those selves.

I believe something considerably less than this. I take it as an article of faith that we humans are a profoundly immature species, only now beginning the process of learning how to learn. Our most spectacular biological attribute, which identifies us as our particular sort of animal, is of course, language and the deep nature of this gift is a mystery. We are aware of our consciousness, but we cannot even make good guesses as to how this awareness arises in our brains, or even, for that matter, that it does arise there for sure. We do not understand how a solitary cell, fused from two, can differentiate into an embryo and then into the systems of tissues and organs that become us, nor do we know how a tadpole accomplishes his emergence, nor even a flea. We can make up instant myths, transiently satisfying but always subject to abandonment, about the origin of life on the planet. We do not understand why we make music, or dance, or paint or write poems. We are bewildered, especially in this century, by the pervasive latency of love.

Our place in the life of the world is still unfathomable because we have so much to learn, but it is surely not absurd. We matter. For a time, anyway, it looks as though we will be responsible for the thinking of the system which seems to mean, at this stage, the responsibility not to do damage to the rest of life if we can help it. There is no hope of thinking our way through the quandary except by learning more, and part of the learning (not all of it, mind you, but a good part) can only be achieved by science, more and better science, not for our longevity or comfort or affluence but for comprehension, without which our long survival is unlikely.

The culmination of a liberal arts education ought to include, among other matters, the news that we do not understand a flea, much less the making of a thought. We can get there one day if we keep at it, but we are nowhere near and there are mountains and centuries of work still to be done.
The physicists are more candid than the biologists in acknowledging the profundity of their ignorance. They have had to live more unsettling lives, having survived one astonishment after another, running into queerness after queerness in their explorations of the very small and very large affairs of nature. They know better than to conclude that they can conclude. You can see this in the offhand diffidence of their technical jargon, terms designed to stay away from anything like meaning: strange particles, particles with flavour and colour, the choice of Joyce for quarks; best of all, that most extraordinarily ordinary, banal phrase for the starting up of the whole universe: The Big Bang. It is an evidence of maturity in physics that such fiat, sparsely evocative, unallusive words as Big Bang came into the language to describe so great an occasion. But just think of the more accurate alternative: it couldn’t have been a Bang, of course—without an atmosphere it must have been absolutely silent; the proper term would be The Great Light, but today’s physicists, most of them anyway, puzzled by the inconclusiveness of their knowledge, know better than to talk that way.

One major question needing to be examined is the general attitude of nature. A century ago there was a consensus about this: nature was ‘red in tooth and claw’, evolution was a record of open warfare among competing species, the fittest were the strongest aggressors and so forth. Now it begins to look different. The tiniest and most fragile of organisms dominate the life of the earth: the chloroplasts inside the cells of plants, which turn solar energy into food and supply the oxygen for breathing, appear to be the descendants of ancient blue-green algae, living now as permanent lodgers within the cells of ‘higher’ forms; the mitochondria of all nucleated cells, which serve as engines for all the functions of life, are the progeny of bacteria which took to living as cells-inside-cells long ago. The urge to form partnerships, to link up in collaborative arrangements, is perhaps the oldest, strongest and most fundamental force in nature. There are no solitary, free- living creatures; every form of life is dependent on other forms. The great successes in evolution, the mutants who have, so to speak, made it, have done so by fitting in with, and sustaining, the rest of life.

The hardest of all the problems confronting our species is the linkage between each of our individual, unique, person-specific selves and all the rest of us. We are perhaps no different from the bees in our general arrangement of interdependence, but an individual bee has a lot less brain to think with, and therefore, I would assume, a lot less to think about. We have enormous brains, the best brains on earth so we say, and along with these marvellous organs comes the gift of worry. The main worry, I’d guess, is how to be single, sentient beings, fully aware of being aware and, at the same time, the working parts of a social species.

An optimistic view of this dilemma, which I take for my comfort, is that we have come only part of the way along, and there is an embarrassing asymmetry in our evolutionary progress to date. We are already highly skilled at being individuals, and we are reasonably skilled although still prone to error, at living in families. Each of us has a circle of friends, and each member of that circle has another circle of friends, and so it goes, and you’d think this would end up in a solid geometry of friendship all around the earth, but something always goes wrong, at one border or another. In small groups, we tend to like each other, or at least we are glad to put up with each other.
But get us together in large clusters, especially dense clusters in bad times, and we can become the most primitive, self-destructive, failure-doomed of creatures. Not always, of course. There is another side to our grouped selves, immensely heartening: you see it best in concert halls, every one listening intently, all together, listening together. We are, for sure, a mixed breed, but when we are collectively engaged in listening to music we are at our very best, the most highly social animals on earth. This is a genuine mystery, and not one to be solved soon by science. What goes on in the human mind in response to music is anyone’s guess.

My own guess, unsupported by anything resembling data, is that music is the sound made by thinking. It is not about thinking about anything in particular; it is the way words arrange themselves into ideas, and ideas into meaning. It is about grammar. I do not believe there is ever such a thing as a single thought. Each time you try to do this—just think about the word music, for instance—you discover that distant tympani of thought are heard at the same time, and still more strings of thought a few moments later, and then descants of ideas, popping into the mind as we say. Some of the lines of thought run together, in parallel, but other separate notions, subthoughts, weave in and out, interrupting and embellishing, changing the whole meaning into something different, then swinging away into other orbits, setting up resonances in other regions of the mind. Very old, deeply seated thoughts are sounded in a recurring series like a continuo, holding up all the higher bits of idea in a coherent structure.

You cannot think about music and about nothing else at the same time; your mind is set alive and conducts itself as though it contained its own orchestra. The Art of Fugue is the sound made by a profound mind, meditating, thinking of two things at once, then four, then sixteen, and the ideas multiply in a geometric series until they are expanding at the speed of light and the whole sound becomes a wave of pure white thought, and then in the Last Great Fugue, Bach signs his name.

It may be that the neurobiologists will be able, some day, to tell us how this works. The cortex of the brain is made up of what are called ‘modules’, clusters of nerve cells arranged in columns, all interconnected with each other and with the other clusters in an immense network. When one of the cells in a column is sounded there is activity in the others, and then the firing off of cells in other columns set at great distances in other regions of the brain.

Perhaps music is a way of finding out how the brain works. We usually put it the other way round, when we think about it at all, and say that if we could know more about the mind we might then begin to understand music. I prefer the first approach. Start with the notion that music describes the process of thinking, and work your way back. It will take a long time, generations of the brightest people in town, vast sums in government grants, new buildings on the outskirts of Washington to house a National Institute of Bach, and I would rather pay taxes for this than anything, even oil, even solar energy.

We like to think of ourselves as unique individuals, each marvellously different from every other, and we set great store on the human self as the centre of the universe; we have constructed whole societies and their religions on the idea that the individual person is the unique culmination of nature’s progress and the most special thing around. And, at the same time, we have imagined that there is a sameness, or an absence of individuality, an interchangeability among all the members of other species. The minnows in a school are, for all practical purposes, all versions of the same minnow. Mice are simply mice.

It is, as it turns out, not so. All creatures are unique selves. Minnows can tell each other apart as though they wore name-tags; catfish can do the same. The only genuine duplicates are the odd set of identical twins and those strains of interminably inbred mice that end up with interchangeable parts. Even the individual motile bacteria cloned from a single colony have been discovered to differ from each other in significant ways: they swim in different ways, tumble at different intervals, and the differences are characteristic and consistent for each single organism observed. There is nothing unique about being unique.

Moreover, the markers governing selfness are specific and invariant, allowing for no errors. If you are going to have a closed ecosystem containing an endless variety of organisms as the ultimate destiny for planetary life—as I believe has become demonstrably the case—you would have to begin by setting up the necessary linkages and inter-dependencies on which any such system of life would have to depend. It is a particularly urgent problem if you have to keep adapting to new varieties of creatures all the time, as was foreordained by the built-in mutability, the error-proneness, of the DNA molecule. In order to get the thing going, and then to keep it going in the face of constant changes in the configurations of living things, you would have to have something like symbiosis as a fundamental and universal process.

But partnerships have to have a certain steadiness and predictability to survive for any length of time. You cannot have linkages between creatures that have nothing at all to offer to each other, and partners have to be equipped with accurate information about the identity of each other. There would, in short, be required an information system capable of emitting signals indicating usefulness. You can see this sort of system still conspicuously at work in the life of the sea. There are here no unattached, isolated animals. Creatures live on each other, next to each other, inside the same carapaces and, most commonly of all, inside each other. The emergence of mitochondria and chloroplasts as organelles is only one example, perhaps one of the earliest and most spectacular, of this tendency in nature. According to recent investigations, the cilia at the surface of modem eukaryotic cells like the cells in our own bronchial tubes, are the descendants of spirochaetes which originally became attached as symbionts. You can still observe the beginnings of this kind of partnership in the protozoans which live inside the digestive tract of certain termites. These single-celled animals are famous for the speed and accuracy with which they are propelled through the termite’s digestive contents, in search of bits of wood. Propulsion is provided by the rhythmic, synchronized beating of what look like cilia under low magnification but turn out to be perfectly formed spirochaetes under electron microscopy.

Indeed, the Australian termite is really all you need for a paradigm of symbiosis. The termite lives as a useful partner with forests, converting dead wood to reusable forms of organic matter. The protozoan, myxotricha paradoxa, propelled by its symbiotic spirochaetes, engulfs the fragments of wood chewed to proper size by the termite. Inside the protozoan, the wood is digested by enzymes provided by bacteria which live as permanent symbionts within and on the surface of the protozoan’s flesh. The termite is not just an animal, it is a committee, rather like a government — but this puts a high value on government.

For minisystems like this to work, there have to be infallible recognition mechanisms. The spirochaetes must find information at the protozoan’s surfaces, to know where and how to attach; the bacteria have to incorporate themselves and be recognized by the host as organelles; the protozoan has to find the termite, and here the recognition mechanisms are crucial: only one species of myxotricha can live in only one species of termite.

Sometimes symbiosis produces biological freaks, which seem to make no sense at all, but possess at the same time, a puzzling kind of beauty.

The mimosa girdler is an excellent example. This is the brainiest insect I know of, thinking hard all the way. I recently received a gift of this beetle, packed in cotton from a young pathologist friend who recently moved from Manhattan to Houston and bought a house in the country with a capacious backyard containing, among various growths, several mimosa trees. He discovered his prize when he noticed some small, neat mounds of wood cylinders, precisely cut into quarter-inch lengths, about a millimetre in diameter, on the floor of the deck which extends behind his house under the shade of one of the mimosa trees. Clinically trained for quick observation and action, he looked above for the source of such craft and found his first girdler. Later, in astonishment tinged with dismay, he found he had lots of them, but only on his mimosas, not on any of the other trees around.

So, the first thing to say about the mimosa girdler is that this tree has evolved an attractant of some sort, guiding this particular beetle through a confusion of other tree smells to the base of a mimosa, up the trunk and out onto a branch where the work is performed, perhaps in a gradient of irresistible fragrance all the way. It is important to note here that the mimosa thrives, more than most trees of its size, on pruning. Untouched, it has a limited life span; it will grow pretty well for 25 years or so and then dies off, but with constant trimming the mimosa can go on and on, bursting with flowers year after year. From the tree’s point of view, this seems to be the function of the mimosa girdler.

The insect is about an inch long, a quiet-looking animal in a clerical grey carapace with a subdued stripe of lighter grey across the middle. The beetle has in mind three crucial pieces of behaviour. First, of course, is finding the right tree and climbing it. Second is the laying of eggs. This is done by cutting a narrow slit, longitudinally placed out at the periphery of the limb, the eggs, four or five of them, are deposited in the slit, which then heals over so neatly that it cannot be seen.

Then, the last step. The eggs cannot hatch in live wood, nor can the larvae survive. This is the point of the girdle, which the beetle makes, beaver style, by hunching itself around, chiselling out the wood in tiny cylinders with a sharp protuberance of its mandible. Mind you, the beetle obtains, so far as is known, no profit from this action. The wood is not eaten; it drops to the ground. It is an immense expenditure of energy, consuming several hours of hard work by the beetle, equivalent to ten years of labour for us. But it is essential for the success or egg-laying. Once girdled, the branch dies, and falls in the next brisk wind. Then the larvae can hatch, at home in an abundance of food, and the cycle can start again.

This, as I say, takes thinking and planning, and I am more curious about what goes on in the mind of that beetle than about the meditation of whales or the small talk of dolphins. Also, I’d like a better understanding of how these three separate, seemingly independent but tightly interlocked pieces of behaviour got selected in the evolution of this beetle. I know the doctrine, and I believe it of course: these are aspects of adaptive, heritable behaviour which probably started out as quite different ‘preadaptive’ ceremonies, intended for other purposes. Pure chance, and successive modifications of the DNA in certain individual beetles, over an interminable period of time, led, by a sort of biological accident, to today’s successful girdler, and today’s pruned mimosa trees.

But there is a primitive part of my mind, probably a network in my limbic system, which keeps insisting that I’ve got it wrong. I hear a voice that says, you’ve got it wrong. That’s a smart bug, smarter than you’ll ever be, and it knows exactly what it is doing every step of the way, and why. Trouble is, you don’t know how to talk to a beetle, or even listen.

The greatest single achievement of nature to date was surely the intention of the molecule of DNA. We have had it from the very beginning, built into the first cell to emerge, membranes and all, somewhere in the soupy water of the cooling planet three thousand million years ago. All of today’s DNA, strung through all the cells of the earth, is simply an extension and elaboration of that first molecule. In a fundamental sense we cannot claim to have made progress, since the method used for growth and replication is essentially unchanged.

It is a lucky thing for us that nature has exhibited such a restraint and good taste in evolution. Given brains of the size and complexity of ours, capable of manufacturing an infinity of sentences in strings long enough to stretch from here to the sun and back again, we are given at the same time a sense of limitation, preventing us from settling all our affairs once and for all by words alone. In a lesser world, we might have been condemned long ago to string out one huge set of sentences, wrapping ourselves in a cocoon of changeless words, immutable, in which to live forever like the termites who can never revolutionize the inner structure of their hills. We in contrast, can make up new thoughts whenever we feel like it. Nature has been kind to us, leaving us leeway, never piling it on too much. Having been given brains with a certain power but limited by a certain fallibility, we are better equipped for finding our way through the future.

Biology needs a better word than error for the driving force in evolution. Or maybe error will do after all, when you remember that it came from an old Indo-European root meaning to wander about, looking for something.

I cannot abide the notion of purposelessness and blind chance in nature, and yet I do not know what to put in its place for the quietening of my mind. It is absurd to say that a place like this place is absurd, when it contains in front of our eyes so many billions of different forms of life, each one in its way absolutely perfect, all linked together to form what would surely seem to an outsider a huge, spherical organism.

Some people believe that we are in trouble because of science, and that we should stop doing science and go back to living in nature, with nature, contemplating nature. It is too late for us to do this, too late by several hundred years, and there are now too many of us here: four billion already, with the likelihood of doubling that population and doubling it again within the lifetime of some of the people alive today.

What I would like to know most about the developing earth is: does it already have a mind? Or will it some day gain a mind and are we part of that? Are we a tissue for the earth’s awareness?

I like this thought, even though I cannot take it anywhere, and I must say it embarrasses me. I have that nagging hunch that it is a presumption, a piece of ultimate hubris. A single insect may have only two thoughts, maybe three, but there are a lot of insects. The million blind and almost mindless termites in a hill make up, in their collective life, an intelligence, a kind of brain, now capable of building endless vaulted chambers and turning perfect arches, thinking all the way. I would like to know what whales are thinking about, or dolphins, but if I were hoping to find out how intercommunication really works on this planet, I would study termites.

I am willing to predict, uncertainly, provisionally, that there is one central, universal aspect of human behaviour, genetically set by our very nature, biologically governed, driving each of us along. Depending on how one looks at it, it can be defined as the urge to be useful. This urge drives society along, sets our behaviour as individuals and in groups, invents all our myths, writes our poetry, composes our music.

This is why it is so hard being a juvenile species, still milling around in groups, trying to construct a civilization that will last. Being useful is easy for an ant; you just wait for the right chemical signal, at the right stage of the construction of the hill, and then you go looking for a twig of exactly the right size for that stage and carry it back, up the flank of the hill, and put it in place, and then you go and do that again. An ant can dine out on his usefulness, all his life, and never get it wrong.

It is a different problem for us, carrying such risks of doing it wrong, getting the wrong twig, losing the hill, not even recognizing, yet, the outline of the hill. We are beset by strings of DNA, immense arrays of genes, instructing each of us to be helpful, impelling us to try our whole lives to be useful, but never telling us how. The instructions are not coded out in anything like an operator’s manual; we have to make guesses all the time. The difficulty is increased when groups of us are set to work together; I have seen, and sat on, numberless feckless committees, not one of which intended anything other than great merit. Larger collections of us, cities for instance, hardly ever get anything right. And, of course, there is the modern nation, probably the most stupefying example of biological error since the age of the great reptiles, wrong at every turn, but always felicitating itself loudly on its great value. It is a biological problem, as much so as a coral reef or a rain forest, but such things as happen to human nations, error piled on error, could never happen in a school of fish. It is, when you think about it, a humiliation, but then humble and human are cognate words; both derived from an old root word meaning, simply, earth. We are smarter than the fish but their instructions come along in their eggs; ours we are obliged to figure out, and we are, in this respect, slow learners.

If you are going to make up a story about the earth, based on today’s scientific information, it is useful to have a third person to tell the tale. For this role, I summon that sagacious and ubiquitous gentleman known as the Extraterrestrial Visitor. Zipping through our part of the galaxy, his attention is caught by our small, suburban solar system, and he comes in among the planets, carrying along a number of instruments in a vehicle whose details I need not bother imagining.

He spots the earth and sees the difference immediately, moving in for a closer look. No matter where he came from, or what he has seen before, I take it for granted that his first reaction is an indrawn breath at its sheer beauty. I have no doubt that there are colonies of life elsewhere in the universe, and perhaps he has seen them all, but I choose to doubt that there can be many celestial bodies at the very springtime of their development, marked so extravagantly by exuberance, youth and perfection of detail, as this one.

Let me change the story here, to insert more time. He sees the earth now, but he is one of the older Extraterrestrial Visitors, and has been making periodic detours in our direction since the birth of the structure, the laying down of bone four billion years ago, and taking time-lapse photographs close up, every few hundred thousand years. Running the whole film through, this year, say, what sort of impression would he have of us?

I think he would conclude that his lens had caught the gestation, still in progress, of a stupendous embryo, clinging to a warm round stone by what we call earth, or soil, turning slowly in the sun. He would have seen this creature starting from a single cell, fertilized by lightening or ultraviolet light or cosmic rays or what-have-you. For two billion-odd years he would observe the formation of a sort of blastula, a huge cluster of cells multiplying first in the sea and later on land, all pretty much the same kind of primitive, non-nucleated cell. Then the film would show a green tinge here and there, and then, with the appearance of oxygen, and thanks to the sun, an explosive emergence of new forms of life would be seen everywhere, new cells with nuclei, new collections of cells gathering to form tissues, coral reefs, and, finally, roses, dolphins and then at last ourselves, off and running, making metaphors and music, the newest and youngest working parts of the planet.

I would like to think that we are on our way to becoming an embryonic central nervous system for the whole system; I even like the notion that our cities, still primitive, archaic, fragile structures, could turn into the precursors of ganglia, to be ultimately linked in a network around the planet. But I do worry, from time to time, about that other possibility:
that we are a transient tissue, replaceable, biologically representing a try at something needing better means of perfection, and therefore on our way down under the hill, interesting fossils for contemplation by some other kind of creature. In my more depressed moments I find this a plausible form of heartsink. But at better times, remembering how skilled our species is with language and metaphor almost from birth, how good we are at recognizing and recording our mistakes, and how spectacularly we excel all other creatures on this planet because of the presence in our midst, from time to time, of people like Johann Sebastian Bach and Mark Twain displaying for all the world what we can do as a species with our brains when we put our minds to it, and remembering that Nature is by nature parsimonious, tending to hang on to useful things when they really do work, I have hopes for our survival into maturity. I say: just get us through the next 20 years, maybe 25, and then we will have thousands of years ahead. Perhaps, after all, we do have a long way to go. If this is so we have a lot to learn, and I do like that thought.

It is, after all, the oldest of human ideas, and still by all odds the best one.