Imperfections in the
execution
of the instructions result in imperfect junks (phenotypes) but they are not passed on to future generations: they are non-memetic.
Richard-Dawkins-The-Devil-s-Chaplain
This is still controversial.
It will be settled, one way or the other, along with countless other such disputes, by 2050.
It will be settled because the Hippo Genome Project, the Pig Genome Project, and the Whale (if our Japanese friends haven't eaten them all by then) Genome Project will have been completed.
Actually, it will not be necessary to sequence entire genomes to dissolve taxonomic uncertainty forever.
A spin-off benefit, which will perhaps have its greatest impact in the United States, is that full knowledge of the tree of life will make it even harder to doubt the fact of evolution. Fossils will become by comparison irrelevant to the argument, as hundreds of separate genes, in as many surviving species as we can bear to sequence, are found to corroborate each other's accounts of the one true tree of life.
It has been said often enough to become a platitude but I had better say it again: to know the genome of an animal is not the same as to understand that animal. Following Sydney Brenner (the single individual regarding whom, more than any other, I have heard people wonder at the absence so far of a Nobel Prize*), I shall think in terms of three steps, of increasing difficulty, in 'computing' an animal from its
*Stop press: Sydney Brenner's Nobel Prize was announced while this book was in proof. 112
? genome. Step 1 was hard but has now been completely solved. It is to compute the amino acid sequence of a protein from the nucleotide sequence of a gene. Step 2 is to compute the three-dimensional folding pattern of a protein from its one-dimensional sequence of amino acids. Physicists believe that in principle this can be done, but it is hard, and it may often be quicker to make the protein and see what happens. Step 3 is to compute the developing embryo from its genes and their interaction with their environment - which mostly consists of other genes. This is the hardest step, but the science of embryology (especially of the workings of Hox and similar genes) is advancing at such a rate that by 2050 it will probably be solved. In other words, I conjecture that an embryologist of 2050 will feed the genome of an unknown animal into a computer, and the computer will simulate an embryology that will culminate in a full rendering of the adult animal. This will not be a particularly useful accomplishment in itself, since a real embryo will always be a cheaper computer than an electronic one. But it will be a way of signifying the completeness of our understanding. And parti- cular implementations of the technology will be useful. For instance, detectives finding a bloodstain may be able to issue a computer image of the face of a suspect - or rather, since genes don't mature with age, a series of faces from babyhood to dotage!
I also think that by 2050 my dream of the Genetic Book of the Dead will become a reality. Darwinian reasoning shows that the genes of a species must constitute a kind of description of the ancestral environments through which those genes have survived. The gene pool of a species is the clay which is shaped by natural selection. As I put it in Unweaving the Rainbow:
Like sandbluffs carved into fantastic shapes by the desert winds, like rocks shaped by ocean waves, camel DNA has been sculpted by survival in ancient deserts, and even more ancient seas, to yield modern camels. Camel DNA speaks - if only we could read the language - of the changing worlds of camel ancestors. If only we could read the language, the DNA of tuna and starfish would have 'sea' written into the text. The DNA of moles and earthworms would spell 'underground'.
I believe that by 2050 we shall be able to read the language. We shall feed the genome of an unknown animal into a computer which will reconstruct not only the form of the animal but the detailed world in which its ancestors (who were naturally selected to produce it) lived, including their predators or prey, parasites or hosts, nesting sites, and even hopes and fears.
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What about more direct reconstructions of ancestors, Jurassic Park style? DNA in amber is, unfortunately, unlikely to be preserved intact, and no sons or even grandsons of Moore's Law are going to bring it back. But there probably are ways, many of them as yet scarcely dreamed of, by which we can use the copious data banks of surviving DNA that we shall have even before 2050. The Chimpanzee Genome Project is already under way and, thanks to Son of Moore's Law, should be completed in a fraction of the time taken by the human genome.
In a throwaway remark at the end of his own piece of millennial
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crystal-gazing, Sydney Brenner made the following startling sugges-
tion. When the chimpanzee genome is fully known, it should become possible, by a sophisticated and biologically intelligent comparison with the human genome (the two differ in only a tiny percentage of their DNA letters), to reconstruct the genome of the ancestor we share. This animal, the so-called 'missing link', lived between 5 million and
8 million years ago, in Africa. Once Brenner's leap is accepted, it is tempting to extend the reasoning all over the place, and I am not one to resist such temptation. The Missing Link Genome Project (MLGP) completed, the next step might be to line up the MLG with the human genome for a base-by-base comparison. Splitting the difference between the two (in the same kind of embryologically informed way as before) should yield a generalized approximation to Australopithecus, the genus of which Lucy has become the iconic representative. By the time the LGP (Lucy Genome Project) has been completed, embryology should have advanced to the point where the reconstructed genome could be inserted into a human egg and implanted in a woman, and a new Lucy born into the light of today. This will doubtless raise ethical worries.
Though concerned for the happiness of the individual australopithecine reconstructed (this is at least a coherent ethical issue, unlike fatuous worries about 'playing God'), I can see positive ethical benefits, as well
as scientific ones, emerging from the experiment. At present we get away with our flagrant speciesism because the evolutionary intermediates between us and chimpanzees are all extinct. In my contribution to The Great Ape Project I pointed out that the accidental contingency of such extinction should be enough to destroy absolutist valuings of human
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life above all other life. 'Pro life', for example, in debates on abortion
or stem cell research, always means pro human life, for no sensibly articulated reason. The existence of a living, breathing Lucy in our midst would change, forever, our complacent, human-centred view of morals and politics. Should Lucy pass for human? The absurdity of the question should be self-evident, as in those South African courts which
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? tried to decide whether particular individuals should 'pass for white'. The reconstruction of a Lucy would be ethically vindicated by bringing such absurdity out into the open.
While the ethicists, moralists and theologians (I fear there still will be theologians in 2050) are busy agonizing over Project Lucy, biologists could, with relative impunity, be cutting their teeth on something even more ambitious: Project Dinosaur. And they might do it by, among other things, helping birds to cut teeth as they haven't done for 60 million years.
Modern birds are descended from dinosaurs (or at least from ancestors we would now happily call dinosaurs if only they had gone extinct as decent dinosaurs should). A sophisticated 'evo-devo' (evolution and development) interpretation of modern bird genomes and the genomes of other surviving archosaurian reptiles such as crocodiles might enable us, by 2050, to reconstruct the genome of a generalized dinosaur. It is encouraging already that a chicken beak can be experimentally induced to grow tooth buds (and snakes induced to grow legs), indicating that ancient genetic skills still linger. If the Dinosaur Genome Project is successful, we could perhaps implant the genome in an ostrich egg to hatch a living, breathing, terrible lizard. Jurassic Park notwithstanding, my only anxiety is that I am unlikely to live long enough to see it. Or to extend my short arm to a new Lucy's long one and shake her tearfully by the hand.
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I have long been academically attracted, and humanly repelled, by the idea that self-replicating information leaps infectiously from mind to mind like (what we now know as) computer viruses. Whether or not we use the name 'meme' for these mind viruses, the theory needs to be taken seriously. If rejected, it must be rejected for good reasons. One of those who have taken it very seriously is Susan Blackmore, in her admirable book, The Meme Machine. The first essay in this section, Chinese Junk and Chinese Whispers (3. 1), is a shortened version of my Foreword to her book. I used the opportunity to think afresh about memes, and I concluded by rebutting the suggestion that I have gone cold on memes since introducing them in 1976. As with other Forewords to books, those parts which were con- cerned specifically with the book itself have been cut, not because I no longer stand by them (I do), but because they are too particular for a collection such as this.
From 1976 onwards, I always thought religions provided the prime
examples of memes and meme complexes (or 'memeplexes'). In Viruses
of the Mind (3. 2) I developed this theme of religions as mind parasites, and
also the analogy with computer viruses. It first appeared in an edited book
of responses to the thinking of Daniel Dennett, a philosopher of science
whom scientists like because he bothers to read science. My choice of
topic acknowledged Dennett's fertile development of the meme concept in
73 Consciousness Explained and Darwin's Dangerous Idea.
To describe religions as mind viruses is sometimes interpreted as con- temptuous or even hostile. It is both. I am often asked why I am so hostile to 'organized religion'. My first response is that I am not exactly friendly towards disorganized religion either. As a lover of truth, I am suspicious of strongly held beliefs that are unsupported by evidence: fairies, unicorns, werewolves, any of the infinite set of conceivable and unfalsifiable beliefs epitomized by Bertrand Russell's hypothetical china teapot orbiting the Sun (see 'The Great Convergence', pp. 149-50). The reason organized
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religion merits outright hostility is that, unlike belief in Russell's teapot, religion is powerful, influential, tax-exempt and systematically passed on to children too young to defend themselves. * Children are not compelled to spend their formative years memorizing loony books about teapots. Government-subsidized schools don't exclude children whose parents prefer the wrong shape of teapot. Teapot-believers don't stone teapot- unbelievers, teapot-apostates, teapot-heretics and teapot-blasphemers to death. Mothers don't warn their sons off marrying teapot-shiksas whose parents believe in three teapots rather than one. People who put the milk in first don't kneecap those who put the tea in first.
The rest of this section is all about religion, not specifically the viral analogy, although that is always in my mind when I consider religion. f The Great Convergence (3. 3) discusses, and rejects, a fashionable claim that science and religion, having drifted apart, are now coming together again. Dolly and the Cloth Heads (3. 4) criticizes the tendency for decent, liberal societies, and especially our public media, to grant religious spokesmen a privileged platform, and an exaggerated respect which goes beyond that due them as individuals. It is a general complaint, but the particular stimulus for this article was Dolly the charismatic sheep. Of course theologians are as entitled as anybody else to hold opinions on such matters. What I objected to was only the automatic, unquestioned assumption that opinions should be given an inside track to our attention simply because they come from religion.
The attack on automatic respect continues in the next essay, Time to Stand Up (3. 5). I wrote it in the immediate aftermath of the religious atrocity committed in New York on 11 September 2001, and it has a more savage tone than I customarily adopt. Were I to rewrite it now, I should probably tone it down, but that was an extraordinary time when people spoke with extraordinary passion, and I admit that I was no exception.
*See page 128 and also Nicholas Humphrey's brilliant Amnesty Lecture, 'What shall we tell the children? ', originally published in W. Williams (ed. ), The Values of Science: The Oxford Amnesty Lectures 1997 (Boulder, Westview Press, 1999) and now reprinted in Humphrey's collection of essays, The Mind Made Flesh (Oxford, Oxford University Press, 2002).
tWhich is not to imply that the viral theory, on its own, suffices to explain the phenomenon
of religion. Two thoughtful books that have taken a biological, or psychological, approach to the question are Robert Hinde, Why Gods Persist (London, Routledge, 1999) and Pascal Boyer, Religion Explained (London, Heinemann, 2001).
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? It 3? I
Chinese Junk and Chinese Whispers74 From the Foreword to The Meme Machine by Susan Blackmore
As an undergraduate I was chatting to a friend in the college lunch queue. He regarded me with increasingly quizzical amusement, then asked: 'Have you just been with Peter Brunet? ' I had indeed, though I couldn't guess how he knew. Peter Brunet was our much loved tutor, and I had come hot foot from a tutorial hour with him. T thought so,' my friend laughed. 'You are talking just like him; your voice sounds exactly like his. ' I had, if only briefly, 'inherited' intonations and manners of speech from an admired, and now greatly missed, teacher.
Years later, when I became a tutor myself, I taught a young woman who affected an unusual habit. When asked a question which required deep thought, she would screw her eyes tight shut, jerk her head down to her chest and then freeze for up to half a minute before looking up, opening her eyes, and answering the question with fluency and intelligence. I was amused by this, and did an imitation of it to divert my colleagues after dinner. Among them was a distinguished Oxford philosopher. As soon as he saw my imitation, he immediately said: 'That's Wittgenstein! Is her surname by any chance? ' Taken aback, I said that it was. T thought so,' said my colleague. 'Both her parents are devoted followers of Wittgenstein. ' The gesture had passed from the great philosopher, via one or both of her parents, to my pupil. I suppose that, although my further imitation was done in jest, I must count myself a fourth generation transmitter of the gesture. And who knows where Wittgenstein got it?
Imitation is how a child learns its particular language rather than some other language. It is why people speak more like their own parents than like other people's parents. It is why regional accents, and on a longer timescale separate languages, exist. It is why religions persist along family lines rather than being chosen afresh in every generation. There is at least a superficial analogy to the longitudinal transmission of genes down generations, and to the horizontal transmission of genes in
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viruses. Without prejudging the issue of whether the analogy is a fruitful one, if we want even to talk about it we had better have a name for the entity that might play the role of gene in the transmission of words, ideas, faiths, mannerisms and fashions. Since 1976, when the word was coined, increasing numbers of people have adopted the name 'meme' for the postulated gene analogue.
The compilers of the Oxford English Dictionaries operate a sensible criterion for deciding whether a new word shall be canonized by inclusion. The aspirant word must be commonly used without needing to be denned and without its coining being attributed. To ask the metamemetic question, how widespread is 'meme', a far from ideal, but nevertheless convenient method of sampling the meme pool, is provided by the World Wide Web. I did a quick search of the web on the day of writing this, which happened to be 29 August 1998. 'Meme' is mentioned about half a million times, but that's a ridiculously high figure, obviously confounded by various acronyms and the French meme. The adjectival form 'memetic' is genuinely exclusive, and it clocked up 5042 mentions. To put this number into perspective, I compared a few other recently coined words or fashionable expressions. Spin doctor (or spin-doctor) gets 1412 mentions, dumbing down 3905, docudrama (or docu-drama) 2848, sociobiology 6679, catastrophe theory 1472, edge of chaos 2673, wannabee 2650, zippergate 1752, studmuffin 776, post-structural (or poststructural) 577, extended phenotype 515, exaptation 307. Of the 5042 mentions of memetic, more than 90 per cent make no mention of the origin of the word, which suggests that it does indeed meet the OED's criterion. And the Oxford Dictionary now does contain the following definition: meme: 'a self-replicating element of culture, passed on by imitation. '
Further searching of the internet reveals a newsgroup talking-shop, 'alt. memetics', which has received about 12,000 postings during the past year. There are on-line articles on, among many other things, 'The New Meme', 'Meme, Counter-meme', 'Memetics: a Systems Metabiology', 'Memes, and Grinning Idiot Press', 'Memes, Metamemes and Polities', 'Cryonics, religions and memes', 'Selfish Memes and the evolution of cooperation', and 'Running down the Meme'. There are separate web pages on 'Memetics', 'Memes', 'The C Memetic Nexus', 'Meme theorists on the web', 'Meme of the week', 'Meme Central', 'Arkuat's Meme Workshop', 'Some pointers and a short introduction to memetics', 'Memetics Index' and 'Meme Gardening Page'. There is even a new religion (tongue in cheek, I think), called the 'Church of Virus', complete with its own list of Sins and Virtues, and its own patron saint (Saint
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? Charles Darwin, canonized as 'perhaps the most influential memetic engineer of the modern era') and I was alarmed to discover a passing reference to 'Saint Dawkins'.
Memes travel longitudinally down generations, but they travel hori- zontally too, like viruses in an epidemic. Indeed, it is largely horizontal epidemiology that we are studying when we measure the spread of a word like memetic, docudrama or studmuffin over the internet. Crazes among schoolchildren provide particularly tidy examples. When I was about nine, my father taught me to fold a square of paper to make an origami Chinese junk. It was a remarkable feat of artificial embryology, passing through a distinctive series of intermediate stages: catamaran with two hulls, cupboard with doors, picture in a frame, and finally the junk itself, fully seaworthy or at least bathworthy, complete with deep hold, and two flat decks each surmounted by a large, square-rigged sail. The point of the story is that I went back to school and infected my friends with the skill, and it then spread around the school with the speed of the measles and pretty much the same epidemiological time- course. I don't know whether the epidemic subsequently jumped to other schools (a boarding school is a somewhat isolated backwater of the meme pool). But I do know that my father himself originally picked up the Chinese Junk meme during an almost identical epidemic at the same school 25 years earlier. The earlier virus was launched by the school matron. Long after the old matron's departure, I had reintroduced her meme to a new cohort of small boys.
Before leaving the Chinese junk, let me use it to make one more point. A favourite objection to the meme/gene analogy is that memes, if they exist at all, are transmitted with too low fidelity to perform a gene-like role in any realistically Darwinian selection process. The difference between high fidelity genes and low fidelity memes is assumed to follow from the fact that genes, but not memes, are digital. I am sure that the details of Wittgenstein's mannerism were far from faithfully reproduced when I imitated my pupil's imitation of her parents' imitation of Wittgenstein. The form and timing of the tic undoubtedly mutated over the generations, as in the childhood game of Chinese Whispers (Americans call it Telephone).
Suppose we assemble a line of children. A picture of, say, a Chinese junk is shown to the first child, who is asked to draw it. The drawing, but not the original picture, is then shown to the second child, who is asked to make her own drawing of it. The second child's drawing is shown to the third child, who draws it again, and so the series proceeds until the twentieth child, whose drawing is revealed to everyone and
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compared with the first. Without even doing the experiment, we know what the result will be. The twentieth drawing will be so unlike the first as to be unrecognizable. Presumably, if we lay the drawings out in order, we shall notice some resemblance between each one and its immediate predecessor and successor, but the mutation rate will be so high as to destroy all semblance after a few generations. A trend will be visible as we walk from one end of the series of drawings to the other, and the direction of the trend will be degeneration. Evolutionary geneticists have long understood that natural selection cannot work unless the mutation rate is low. Indeed, the initial problem of overcoming the fidelity barrier has been described as the Catch-22 of the Origin of Life. Darwinism depends upon high fidelity gene replication. How then can the meme, with its apparently dismal lack of fidelity, serve as quasi-gene in any quasi-Darwinian process?
It isn't always as dismal as you think, and high fidelity is not necessarily synonymous with digital. Suppose we set up our Chinese Whispers game again, but this time with a crucial difference. Instead of asking the first child to copy a drawing of a junk, we teach her, by demonstration, to make an origami model of a junk. When she has mastered the skill and made her own junk, the first child is asked to turn round to the second child and teach him how to make one. So the skill passes down the line to the twentieth child. What will be the result of this experiment? What will the twentieth child produce, and what shall we observe if we lay the 20 efforts out in order along the ground? I haven't done it, but I will make the following confident prediction, assuming that we run the experiment many times on different groups of 20 children. In several of the experiments, a child somewhere along the line will forget some crucial step in the skill taught him by the previous child, and the line of phenotypes will suffer an abrupt macro- mutation which will presumably then be copied to the end of the line, or until another discrete mistake is made. The end result of such mutated lines will not bear any resemblance to a Chinese junk at all. But in a good number of experiments the skill will correctly pass all along the line, and the twentieth junk will be no worse and no better, on average, than the first junk. If we then lay the 20 junks out in order, some will be more perfect than others, but imperfections will not be copied on down the line. If the fifth child is hamfisted and makes a clumsily asymmetrical or floppy junk, his quantitative errors will be corrected if the sixth child happens to be more dexterous. The 20 junks will not exhibit a progressive deterioration in the way that the 20 drawings of our first experiment undoubtedly would.
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? Why? What is the crucial difference between the two kinds of experi- ment? It is this. Inheritance in the drawing experiment is Lamarckian (Susan Blackmore calls it 'copying the product'). In the origami experiment it is Weismannian (Blackmore's 'copying the instructions'). In the drawing experiment, the phenotype in every generation is also the genotype - it is what is passed on to the next generation. In the origami experiment, what passes to the next generation is not the paper phenotype but a set of instructions for making it.
Imperfections in the execution of the instructions result in imperfect junks (phenotypes) but they are not passed on to future generations: they are non-memetic. Here are the first five instructions in the Weismannian meme-line of instructions for making a Chinese junk:
1. Take a square sheet of paper and fold all four corners exactly into the middle.
2. Take the reduced square so formed, and fold one side into the middle.
3. Fold the opposite side into the middle, symmetrically.
4. In the same way, take the rectangle so formed, and fold its two ends
into the middle.
5. Take the small square so formed, and fold it backwards, exactly
along the straight line where your last two folds met.
. . . And so on, through 20 or 30 instructions of this kind. These instruc- tions, though I would not wish to call them digital, are potentially of very high fidelity, just as if they were digital. This is because they all make reference to idealized tasks like 'fold the four corners exactly into the middle'. If the paper is not exactly square, or if a child folds ineptly so that, say, the first corner overshoots the middle and the fourth corner undershoots it, the junk that results will be inelegant. But the next child in the line will not copy the error, for she will assume that her instructor intended to fold all four corners into the exact centre of a perfect square. The instructions are self-normalizing. The code is error- correcting.
The instructions are more effectively passed on if verbally reinforced, but they can be transmitted by demonstration alone. A Japanese child could teach an English one, though neither has a word of the other's language. In the same way, a Japanese master carpenter could convey his skills to an equally monoglot English apprentice. The apprentice would not copy obvious mistakes. If the master hit his thumb with a hammer, the apprentice would correctly guess, even without
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understanding the Japanese for '** **** **! ', that he meant to hit the nail. He would not make a Lamarckian copy of the precise details of every hammer blow, but copy instead the inferred instruction: drive the nail in with as many blows of your hammer as it takes your arm to achieve the same idealized end result as the master has achieved with his - a nail-head flush with the wood.
I believe that these considerations greatly reduce, and probably remove altogether, the objection that memes are copied with insufficient fidelity to be compared with genes. For me, the quasi-genetic inheritance of language, and of religious and traditional customs, teaches the same lesson. Another objection is that we don't know what memes are made of or where they reside. Memes have not yet found their Watson and Crick; they even lack their Mendel. Whereas genes are to be found in precise locations on chromosomes, memes presumably exist in brains, and we have even less chance of seeing one than of seeing a gene (though the neurobiologist Juan Delius has pictured his conjecture of
75
whatamememightlooklike ). Aswithgenes,wetrackmemesthrough
populations by their phenotypes. The 'phenotype' of the Chinese junk meme is made of paper. With the exception of 'extended phenotypes' such as beaver dams and caddis larva houses, the phenotypes of genes are normally parts of living bodies. Meme phenotypes seldom are.
But it can happen. To return to my school again, a Martian geneticist, visiting the school during the morning cold bath ritual, would have unhesitatingly diagnosed an 'obvious' genetic polymorphism. About 50 per cent of the boys were circumcised and 50 per cent were not. The boys, incidentally, were highly conscious of the polymorphism and we classified ourselves into Roundheads versus Cavaliers (I have recently read of another school in which the boys even organized themselves into two football teams along the same lines). It is, of course, not a genetic but a memetic polymorphism. But the Martian's mistake is completely understandable; the morphological discontinuity is of exactly the kind that one normally expects to find produced by genes.
In England at the time, infant circumcision was a medical whim, and the roundhead/cavalier polymorphism at my school probably owed less to longitudinal transmission than to differing fashions in the various hospitals where we happened to have been born - horizontal memetic transmission yet again. But through most of history circumcision has been longitudinally transmitted as a badge of religion (ofparents' religion I hasten to point out, for the unfortunate child is normally too young to know his own religious mind). Where circumcision is religiously or traditionally based (the barbaric custom of female 'circumcision'
? always is), the transmission will follow a longitudinal pattern of heredity, very similar to the pattern for true genetic transmission, and often persisting for many generations. Our Martian geneticist would have to work quite hard to discover that no genes are involved in the genesis of the roundhead phenotype.
The Martian geneticist's eyes would also pop out on stalks (assuming they weren't on stalks to begin with) at the contemplation of certain styles of clothing and hairdressing, and their inheritance patterns. The black skullcapped phenotype shows a marked tendency towards longi- tudinal transmission from father to son (or it may be from maternal grandfather to grandson), and there is clear linkage to the rarer pigtail- plaited sideburn phenotype. Behavioural phenotypes such as genuflecting in front of crosses, and facing east to kneel five times per day, are inherited longitudinally too, and are in strong linkage disequilibrium with the previously mentioned phenotypes, as is the red-dot-on- forehead phenotype, and the saffron robes/shaven head linkage group.
Genes are accurately copied and transmitted from body to body, but some are transmitted at greater frequency than others - by definition they are more successful. This is natural selection, and it is the explana- tion for most of what is interesting and remarkable about life. But is there a similar meme-based natural selection? Perhaps we can use the internet again to investigate natural selection among memes? As it happens, around the time the word meme was coined (actually a little
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later), a rival synonym, 'culturgen', was proposed. Today, culturgen is
mentioned 20 times on the World Wide Web, compared with meme's 5042. Moreover, of those 20, 17 also mention the source of the word, falling foul of the Oxford Dictionary's criterion. Perhaps it is not too fanciful to imagine a Darwinian struggle between the two memes (or culturgens), and it is not totally silly to ask why one of them was so much more successful. Perhaps it is because meme is a monosyllable similar to gene, which therefore lends itself to quasi-genetic sub- coinings: meme pool (352), memotype (58), memeticist (163), memeoid (or memoid) (28), retromeme (14), population memetics (41), meme complex (494), memetic engineering (302) and metameme (71) are all listed in a 'Memetic Lexicon' on the World Wide Web (the numbers in brackets count the mentions of each word on the World Wide Web on my sampling day). Culturgen-based equivalents would be less snappy. Or the success of meme against culturgen may have been initially just a non-Darwinian matter of chance - memetic drift (85) - followed by a self-reinforcing positive feedback effect ('unto every one that hath shall be given, and he shall have abundance: but from him
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that hath not shall be taken away even that which he hath' (Matthew 25:29).
I have mentioned two favourite objections to the meme idea: memes have insufficient copying fidelity, and nobody really knows what a meme physically is. A third is the vexed question of how large a unit deserves the name meme. Is the whole Roman Catholic Church one meme, or should we use the word for one constituent unit, such as the idea of incense or the transubstantiation? Or for something in between? The answer is to be found in the concept of the meme-complex or 'memeplex'.
Memes, like genes, are selected against the background of other memes in the meme pool. The result is that gangs of mutually compatible memes - coadapted meme complexes or memeplexes - are found cohabiting in individual brains. This is not because selection has chosen them as a group, but because each separate member of the group tends to be favoured when its environment happens to be dominated by the others. An exactly similar point can be made about genetic selection. Every gene in a gene pool constitutes part of the environmental background against which the other genes are naturally selected, so it's no wonder natural selection favours genes that 'cooperate' in building those highly integrated and unified machines called organisms. By analogy with coadapted gene complexes, memes, selected against the background of each other, 'cooperate' in mutually supportive memeplexes - supportive within the memeplex but hostile to rival memeplexes. Religions may be the most convincing examples of memeplexes, but they are by no means the only ones.
I am occasionally accused of having backtracked on memes; of having lost heart, pulled in my horns, had second thoughts. The truth is that my first thoughts were more modest than some memeticists might have wished. For me, the original mission of the meme was negative. The word was introduced at the end of a book which other- wise must have seemed entirely devoted to extolling the selfish gene as the be-all and end-all of evolution, the fundamental unit of selection, the entity in the hierarchy of life which all adaptations could be said to benefit. There was a risk that my readers would misunderstand the message as being necessarily about genes in the sense of DNA molecules. On the contrary, DNA was incidental. The real unit of natural selection was any kind of replicator, any unit of which copies are made, with occasional errors, and with some influence or power over their own probability of replication. The genetic natural selection identified by neo-Darwinism as the driving force of evolution on this planet was only
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? a special case of a more general process that I came to dub 'Universal Darwinism'. Perhaps we'd have to go to other planets in order to discover any other examples. But maybe we didn't have to go that far. Could it be that a new kind of Darwinian replicator was even now staring us in the face? This was where the meme came in.
I would have been content, then, if the meme had done its work of simply persuading my readers that the gene was only a special case: that its role in the play of Universal Darwinism could be filled by any entity in the universe answering to the definition of Replicator. The original didactic purpose of the meme was the negative one of cutting the selfish gene down to size. I became a little alarmed at the number of my readers who took the meme more positively as a theory of human culture in its own right - either to criticize it (unfairly, given my original modest intention) or to carry it far beyond the limits of what I then thought justified. This was why I may have seemed to backtrack.
But I was always open to the possibility that the meme might one day be developed into a proper hypothesis of the human mind, and I did not know how ambitious such a thesis might turn out to be. I am delighted that others are now undertaking it. *
CHINESE JUNK AND CHINESE WHISPERS
*In addition to Susan Blackmore's The Meme Machine, other books that make heavy use of the meme idea are R. Brodie, Virus of the Mind: the New Science of the Meme (Seattle, Integral Press, 1996) (not to be confused with my essay (see over page), which was published three years earlier); A. Lynch, Thought Contagion: How Belief Spreads Through Society (New York, Basic Books, 1998); J. M. Balkin, Cultural Software (New Haven, Yale University Press, 1998); H. Bloom, The Lucifer Principle (Sydney, Allen & Unwin, 1995); Robert Aunger, The Electric Meme (New York, Simon & Schuster, 2002); Kevin Laland and Gillian Brown, Sense and Nonsense (Oxford, Oxford University Press, 2002); and Stephen Shennan, Genes, Memes and Human History (London, Thames and Hudson, 2002). A turning point in the fortunes of the meme was its adoption and development by Daniel Dennett as a cornerstone of his theory of the evolution of the mind, especially in his two books Consciousness Explained (Boston, Little Brown, 1991) and Darwin's Dangerous Idea (New York, Simon & Schuster, 1995).
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The haven all memes depend on reaching is the human mind, but a human mind is itself an artifact created when memes restructure a human brain in order to make it a better habitat for memes. The avenues for entry and departure are modified to suit local conditions, and strengthened by various artificial devices that enhance fidelity and prolixity of replication: native Chinese minds differ dramatically from native French minds, and literate minds differ from illiterate minds. What memes provide in return to the organisms in which they reside is an incalculable store of advantages - with some Trojan horses thrown in for good measure . . .
78 Daniel Dennett
Duplication-Fodder
A beautiful child close to me, six and the apple of her father's eye, believes that Thomas the Tank Engine really exists. She believes in Father Christmas, and when she grows up her ambition is to be a tooth fairy. She and her schoolfriends believe the solemn word of respected adults that tooth fairies and Father Christmas really exist. This little girl is of an age to believe whatever you tell her. If you tell her about witches changing princes into frogs, she will believe you. If you tell her that bad children roast forever in hell, she will have nightmares. I have just discovered that without her father's consent this sweet, trusting, gullible six-year-old is being sent, for weekly instruction, to a Roman Catholic nun. What chance has she?
A human child is shaped by evolution to soak up the culture of her people. Most obviously, she learns the essentials of their language in a matter of months. A large dictionary of words to speak, an encyclopaedia of information to speak about, complicated syntactic and semantic rules to order the speaking, all are transferred from older brains into hers well before she reaches half her adult size. When you are
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? preprogrammed to absorb useful information at a high rate, it is hard to shut out pernicious or damaging information at the same time. With so many mindbytes to be downloaded, so many mental codons to be duplicated, it is no wonder that child brains are gullible, open to almost any suggestion, vulnerable to subversion, easy prey to Moonies, Scientologists and nuns. Like immune-deficient patients, children are wide open to mental infections that adults might brush off without effort.
DNA, too, includes parasitic code. Cellular machinery is extremely good at copying DNA. Where DNA is concerned, it seems to have an eagerness to copy, like a child's eagerness to imitate the language of its parents. Concomitantly, DNA seems eager to be copied. The cell nucleus is a paradise for DNA, humming with sophisticated, fast and accurate duplicating machinery.
Cellular machinery is so friendly towards DNA-duplication that it is small wonder cells play host to DNA parasites - viruses, viroids, plasmids and a riff-raff of other genetic fellow travellers. Parasitic DNA even gets itself spliced seamlessly into the chromosomes themselves. 'Jumping genes' and stretches of 'Selfish DNA' cut or copy themselves out of chromosomes and paste themselves in elsewhere. Deadly oncogenes are almost impossible to distinguish from the legitimate genes between which they are spliced. In evolutionary time, there is probably a continual traffic from 'straight' genes to 'outlaw', and back again. DNA is just DNA. The only thing that distinguishes viral DNA from host DNA is its expected method of passing into future generations. 'Legitimate' host DNA is just DNA that aspires to pass into the next generation via the orthodox route of sperm or egg. 'Outlaw' or parasitic DNA is just DNA that looks to a quicker, less cooperative route to the future, via a sneezed droplet or a smear of blood, rather than via a sperm or egg.
For data on a floppy disk, a computer is a humming paradise just as cell nuclei hum with eagerness to duplicate DNA. Computers and their associated disk and tape readers are designed with high fidelity in mind. As with DNA molecules, magnetized bytes don't literally 'want' to be faithfully copied. Nevertheless, you can write a computer program that takes steps to duplicate itself. Not just duplicate itself within one computer but spread itself to other computers. Computers are so good at copying bytes, and so good at faithfully obeying the instructions contained in those bytes, that they are sitting ducks to self-replicating programs: wide open to subversion by software parasites. Any cynic familiar with the theory of selfish genes and memes would have known
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that modern personal computers, with their promiscuous traffic of floppy disks and email links, were just asking for trouble. The only surprising thing about the current epidemic of computer viruses is that it has been so long in coming.
Computer Viruses: a Model for an Informational Epidemiology
Computer viruses are pieces of code that graft themselves into existing, legitimate programs and subvert the normal actions of those programs. They may travel on exchanged floppy disks, or over networks. They are technically distinguished from 'worms' which are whole programs in their own right, usually travelling over networks. Rather different are 'Trojan horses', a third category of destructive programs, which are not in themselves self-replicating but rely on humans to replicate them because of their pornographic or otherwise appealing content. Both viruses and worms are programs that actually say, in computer language, 'Duplicate Me'. Both may do other things that make their presence felt and perhaps satisfy the hole-in-corner vanity of their authors. These side effects may be 'humorous' (like the virus that makes the Macintosh's built-in loudspeaker enunciate the words 'Don't panic', with predictably opposite effect); malicious (like the viruses that erase the hard disk after a sniggering screen-announcement of the impending disaster); political (the Spanish Telecom and Beijing viruses protest about telephone costs and massacred students respectively); or simply inadvertent (the programmer is incompetent to handle the low-level system calls required to write an effective virus or worm). The famous Internet Worm, which paralysed much of the computing power of the United States on 2 November 1988, was not intended (very) maliciously but got out of control and, within 24 hours, had clogged around 6000 computer memories with exponentially multiplying copies of itself.
Memes now spread around the world at the speed of light, and replicate at rates that make even fruit flies and yeast cells look glacial in comparison. They leap promiscuously from vehicle to vehicle, and from medium to medium, and are proving to be virtually unquarantinable. [Dennett again]
Computer viruses aren't limited to electronic media such as disks and data lines. On its way from one computer to another, a virus may pass through printing ink, light rays in a human lens, optic nerve impulses and finger muscle contractions. A computer fanciers' magazine that printed the text of a virus program for the interest of its readers has been widely condemned. Indeed, such is the appeal of the virus idea to
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? a certain kind of puerile mentality (the masculine gender is used advisedly), that publication of any kind of 'How to' information on designing virus programs is rightly seen as an irresponsible act.
I am not going to publish any virus code. But there are certain tricks of effective virus design that are sufficiently well known, even obvious, that it will do no harm to,mention them, as I need to do in order to develop my theme. They all stem from the virus's need to evade detection while it is spreading.
A virus that clones itself too prolifically within one computer will soon be detected because the symptoms of clogging will become too obvious to ignore. For this reason many virus programs check, before infecting a system, to make sure that they are not already on that system. Incidentally, this opens the way for a defence against viruses that is analogous to immunization. In the days before a specific anti- virus program was available, I myself responded to an early infection of my own hard disk by means of a crude 'vaccination'. Instead of deleting the virus that I had detected, I simply disabled its coded instructions, leaving the 'shell' of the virus with its characteristic external 'signature' intact. In theory, subsequent members of the same virus species that arrived in my system should have recognized the signature of their own kind and refrained from trying to double-infect. I don't know whether this immunization really worked, but in those days it probably was worthwhile 'gutting' a virus and leaving a shell like this, rather than simply removing it lock, stock and barrel. Nowadays it is better to hand the problem over to one of the professionally written anti-virus programs.
A virus that is too virulent will be rapidly detected and scotched. A virus that instantly and catastrophically sabotages every computer in which it finds itself will not find itself in many computers. It may have a most amusing effect on one computer - erase an entire doctoral thesis or something equally side-splitting - but it won't spread as an epidemic. Some viruses, therefore, are designed to have an effect that is small enough to be difficult to detect, but which may nevertheless be extremely damaging. There is one type which, instead of erasing disk sectors wholesale, attacks only spreadsheets, making a few random changes in the (usually financial) quantities entered in the rows and columns. Other viruses evade detection by being triggered probabilistically, for example erasing only one in 16 of the hard disks infected. Yet other viruses employ the time-bomb principle. Most modern computers are 'aware' of the date, and viruses have been triggered to manifest them- selves all around the world, on a particular date such as Friday 13th or
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April Fool's Day. From the parasitic point of view, it doesn't matter how catastrophic the eventual attack is, provided the virus has had plenty of opportunity to spread first (a disturbing analogy to the Medawar/ Williams theory of ageing; we are the victims of lethal and sub-lethal genes that mature only after we have had plenty of time to reproduce). In defence, some large companies go so far as to set aside one 'miner's canary' among theirfleetof computers, and advance its internal calendar a week so that any time-bomb viruses will reveal themselves prematurely before the big day.
Again predictably, the epidemic of computer viruses has triggered an arms race. Antiviral software is doing a roaring trade. These antidote programs - 'Interferon', 'Vaccine', 'Gatekeeper' and others - employ a diverse armoury of tricks. Some are written with specific, known and named, viruses in mind. Others intercept any attempt to meddle with sensitive system areas of memory and warn the user.
The virus principle could in theory be used for non-malicious, even
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beneficial purposes. Harold Thimbleby coins the phrase 'Liveware' for
his already-implemented use of the infection principle for keeping multiple copies of databases up to date. Every time a disk containing the database is plugged into a computer, it looks to see whether there is already another copy present on the local hard disk. If there is, each copy is updated in the light of the other. So, with a bit of luck, it doesn't matter which member of a circle of colleagues enters, say, a new biblio- graphic citation on his personal disk. His newly entered information will readily infect the disks of his colleagues (because the colleagues promiscuously insert their disks into one another's computers) and will spread like an epidemic around the circle. Thimbleby's liveware is not entirely virus-like: it could not spread to just anybody's computer and do damage. It spreads data only to already-existing copies of its own database; and you will not be infected by liveware unless you positively opt for infection.
Incidentally, Thimbleby, who is much concerned with the virus menace, points out that you can gain some protection by using computer systems that other people don't use. The usual justification for purchasing today's numerically dominant personal computer is simply and solely that it is numerically dominant. Almost every knowledgeable person agrees that, in terms of quality and especially user-friendliness, the rival, minority system is superior. Nevertheless, ubiquity is held to be a good in itself, sufficient to outweigh sheer quality. Buy the same (albeit inferior) computer as your colleagues, the argument goes, and you'll be able to benefit from shared software, and from a generally
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A spin-off benefit, which will perhaps have its greatest impact in the United States, is that full knowledge of the tree of life will make it even harder to doubt the fact of evolution. Fossils will become by comparison irrelevant to the argument, as hundreds of separate genes, in as many surviving species as we can bear to sequence, are found to corroborate each other's accounts of the one true tree of life.
It has been said often enough to become a platitude but I had better say it again: to know the genome of an animal is not the same as to understand that animal. Following Sydney Brenner (the single individual regarding whom, more than any other, I have heard people wonder at the absence so far of a Nobel Prize*), I shall think in terms of three steps, of increasing difficulty, in 'computing' an animal from its
*Stop press: Sydney Brenner's Nobel Prize was announced while this book was in proof. 112
? genome. Step 1 was hard but has now been completely solved. It is to compute the amino acid sequence of a protein from the nucleotide sequence of a gene. Step 2 is to compute the three-dimensional folding pattern of a protein from its one-dimensional sequence of amino acids. Physicists believe that in principle this can be done, but it is hard, and it may often be quicker to make the protein and see what happens. Step 3 is to compute the developing embryo from its genes and their interaction with their environment - which mostly consists of other genes. This is the hardest step, but the science of embryology (especially of the workings of Hox and similar genes) is advancing at such a rate that by 2050 it will probably be solved. In other words, I conjecture that an embryologist of 2050 will feed the genome of an unknown animal into a computer, and the computer will simulate an embryology that will culminate in a full rendering of the adult animal. This will not be a particularly useful accomplishment in itself, since a real embryo will always be a cheaper computer than an electronic one. But it will be a way of signifying the completeness of our understanding. And parti- cular implementations of the technology will be useful. For instance, detectives finding a bloodstain may be able to issue a computer image of the face of a suspect - or rather, since genes don't mature with age, a series of faces from babyhood to dotage!
I also think that by 2050 my dream of the Genetic Book of the Dead will become a reality. Darwinian reasoning shows that the genes of a species must constitute a kind of description of the ancestral environments through which those genes have survived. The gene pool of a species is the clay which is shaped by natural selection. As I put it in Unweaving the Rainbow:
Like sandbluffs carved into fantastic shapes by the desert winds, like rocks shaped by ocean waves, camel DNA has been sculpted by survival in ancient deserts, and even more ancient seas, to yield modern camels. Camel DNA speaks - if only we could read the language - of the changing worlds of camel ancestors. If only we could read the language, the DNA of tuna and starfish would have 'sea' written into the text. The DNA of moles and earthworms would spell 'underground'.
I believe that by 2050 we shall be able to read the language. We shall feed the genome of an unknown animal into a computer which will reconstruct not only the form of the animal but the detailed world in which its ancestors (who were naturally selected to produce it) lived, including their predators or prey, parasites or hosts, nesting sites, and even hopes and fears.
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What about more direct reconstructions of ancestors, Jurassic Park style? DNA in amber is, unfortunately, unlikely to be preserved intact, and no sons or even grandsons of Moore's Law are going to bring it back. But there probably are ways, many of them as yet scarcely dreamed of, by which we can use the copious data banks of surviving DNA that we shall have even before 2050. The Chimpanzee Genome Project is already under way and, thanks to Son of Moore's Law, should be completed in a fraction of the time taken by the human genome.
In a throwaway remark at the end of his own piece of millennial
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crystal-gazing, Sydney Brenner made the following startling sugges-
tion. When the chimpanzee genome is fully known, it should become possible, by a sophisticated and biologically intelligent comparison with the human genome (the two differ in only a tiny percentage of their DNA letters), to reconstruct the genome of the ancestor we share. This animal, the so-called 'missing link', lived between 5 million and
8 million years ago, in Africa. Once Brenner's leap is accepted, it is tempting to extend the reasoning all over the place, and I am not one to resist such temptation. The Missing Link Genome Project (MLGP) completed, the next step might be to line up the MLG with the human genome for a base-by-base comparison. Splitting the difference between the two (in the same kind of embryologically informed way as before) should yield a generalized approximation to Australopithecus, the genus of which Lucy has become the iconic representative. By the time the LGP (Lucy Genome Project) has been completed, embryology should have advanced to the point where the reconstructed genome could be inserted into a human egg and implanted in a woman, and a new Lucy born into the light of today. This will doubtless raise ethical worries.
Though concerned for the happiness of the individual australopithecine reconstructed (this is at least a coherent ethical issue, unlike fatuous worries about 'playing God'), I can see positive ethical benefits, as well
as scientific ones, emerging from the experiment. At present we get away with our flagrant speciesism because the evolutionary intermediates between us and chimpanzees are all extinct. In my contribution to The Great Ape Project I pointed out that the accidental contingency of such extinction should be enough to destroy absolutist valuings of human
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life above all other life. 'Pro life', for example, in debates on abortion
or stem cell research, always means pro human life, for no sensibly articulated reason. The existence of a living, breathing Lucy in our midst would change, forever, our complacent, human-centred view of morals and politics. Should Lucy pass for human? The absurdity of the question should be self-evident, as in those South African courts which
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? tried to decide whether particular individuals should 'pass for white'. The reconstruction of a Lucy would be ethically vindicated by bringing such absurdity out into the open.
While the ethicists, moralists and theologians (I fear there still will be theologians in 2050) are busy agonizing over Project Lucy, biologists could, with relative impunity, be cutting their teeth on something even more ambitious: Project Dinosaur. And they might do it by, among other things, helping birds to cut teeth as they haven't done for 60 million years.
Modern birds are descended from dinosaurs (or at least from ancestors we would now happily call dinosaurs if only they had gone extinct as decent dinosaurs should). A sophisticated 'evo-devo' (evolution and development) interpretation of modern bird genomes and the genomes of other surviving archosaurian reptiles such as crocodiles might enable us, by 2050, to reconstruct the genome of a generalized dinosaur. It is encouraging already that a chicken beak can be experimentally induced to grow tooth buds (and snakes induced to grow legs), indicating that ancient genetic skills still linger. If the Dinosaur Genome Project is successful, we could perhaps implant the genome in an ostrich egg to hatch a living, breathing, terrible lizard. Jurassic Park notwithstanding, my only anxiety is that I am unlikely to live long enough to see it. Or to extend my short arm to a new Lucy's long one and shake her tearfully by the hand.
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I have long been academically attracted, and humanly repelled, by the idea that self-replicating information leaps infectiously from mind to mind like (what we now know as) computer viruses. Whether or not we use the name 'meme' for these mind viruses, the theory needs to be taken seriously. If rejected, it must be rejected for good reasons. One of those who have taken it very seriously is Susan Blackmore, in her admirable book, The Meme Machine. The first essay in this section, Chinese Junk and Chinese Whispers (3. 1), is a shortened version of my Foreword to her book. I used the opportunity to think afresh about memes, and I concluded by rebutting the suggestion that I have gone cold on memes since introducing them in 1976. As with other Forewords to books, those parts which were con- cerned specifically with the book itself have been cut, not because I no longer stand by them (I do), but because they are too particular for a collection such as this.
From 1976 onwards, I always thought religions provided the prime
examples of memes and meme complexes (or 'memeplexes'). In Viruses
of the Mind (3. 2) I developed this theme of religions as mind parasites, and
also the analogy with computer viruses. It first appeared in an edited book
of responses to the thinking of Daniel Dennett, a philosopher of science
whom scientists like because he bothers to read science. My choice of
topic acknowledged Dennett's fertile development of the meme concept in
73 Consciousness Explained and Darwin's Dangerous Idea.
To describe religions as mind viruses is sometimes interpreted as con- temptuous or even hostile. It is both. I am often asked why I am so hostile to 'organized religion'. My first response is that I am not exactly friendly towards disorganized religion either. As a lover of truth, I am suspicious of strongly held beliefs that are unsupported by evidence: fairies, unicorns, werewolves, any of the infinite set of conceivable and unfalsifiable beliefs epitomized by Bertrand Russell's hypothetical china teapot orbiting the Sun (see 'The Great Convergence', pp. 149-50). The reason organized
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religion merits outright hostility is that, unlike belief in Russell's teapot, religion is powerful, influential, tax-exempt and systematically passed on to children too young to defend themselves. * Children are not compelled to spend their formative years memorizing loony books about teapots. Government-subsidized schools don't exclude children whose parents prefer the wrong shape of teapot. Teapot-believers don't stone teapot- unbelievers, teapot-apostates, teapot-heretics and teapot-blasphemers to death. Mothers don't warn their sons off marrying teapot-shiksas whose parents believe in three teapots rather than one. People who put the milk in first don't kneecap those who put the tea in first.
The rest of this section is all about religion, not specifically the viral analogy, although that is always in my mind when I consider religion. f The Great Convergence (3. 3) discusses, and rejects, a fashionable claim that science and religion, having drifted apart, are now coming together again. Dolly and the Cloth Heads (3. 4) criticizes the tendency for decent, liberal societies, and especially our public media, to grant religious spokesmen a privileged platform, and an exaggerated respect which goes beyond that due them as individuals. It is a general complaint, but the particular stimulus for this article was Dolly the charismatic sheep. Of course theologians are as entitled as anybody else to hold opinions on such matters. What I objected to was only the automatic, unquestioned assumption that opinions should be given an inside track to our attention simply because they come from religion.
The attack on automatic respect continues in the next essay, Time to Stand Up (3. 5). I wrote it in the immediate aftermath of the religious atrocity committed in New York on 11 September 2001, and it has a more savage tone than I customarily adopt. Were I to rewrite it now, I should probably tone it down, but that was an extraordinary time when people spoke with extraordinary passion, and I admit that I was no exception.
*See page 128 and also Nicholas Humphrey's brilliant Amnesty Lecture, 'What shall we tell the children? ', originally published in W. Williams (ed. ), The Values of Science: The Oxford Amnesty Lectures 1997 (Boulder, Westview Press, 1999) and now reprinted in Humphrey's collection of essays, The Mind Made Flesh (Oxford, Oxford University Press, 2002).
tWhich is not to imply that the viral theory, on its own, suffices to explain the phenomenon
of religion. Two thoughtful books that have taken a biological, or psychological, approach to the question are Robert Hinde, Why Gods Persist (London, Routledge, 1999) and Pascal Boyer, Religion Explained (London, Heinemann, 2001).
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Chinese Junk and Chinese Whispers74 From the Foreword to The Meme Machine by Susan Blackmore
As an undergraduate I was chatting to a friend in the college lunch queue. He regarded me with increasingly quizzical amusement, then asked: 'Have you just been with Peter Brunet? ' I had indeed, though I couldn't guess how he knew. Peter Brunet was our much loved tutor, and I had come hot foot from a tutorial hour with him. T thought so,' my friend laughed. 'You are talking just like him; your voice sounds exactly like his. ' I had, if only briefly, 'inherited' intonations and manners of speech from an admired, and now greatly missed, teacher.
Years later, when I became a tutor myself, I taught a young woman who affected an unusual habit. When asked a question which required deep thought, she would screw her eyes tight shut, jerk her head down to her chest and then freeze for up to half a minute before looking up, opening her eyes, and answering the question with fluency and intelligence. I was amused by this, and did an imitation of it to divert my colleagues after dinner. Among them was a distinguished Oxford philosopher. As soon as he saw my imitation, he immediately said: 'That's Wittgenstein! Is her surname by any chance? ' Taken aback, I said that it was. T thought so,' said my colleague. 'Both her parents are devoted followers of Wittgenstein. ' The gesture had passed from the great philosopher, via one or both of her parents, to my pupil. I suppose that, although my further imitation was done in jest, I must count myself a fourth generation transmitter of the gesture. And who knows where Wittgenstein got it?
Imitation is how a child learns its particular language rather than some other language. It is why people speak more like their own parents than like other people's parents. It is why regional accents, and on a longer timescale separate languages, exist. It is why religions persist along family lines rather than being chosen afresh in every generation. There is at least a superficial analogy to the longitudinal transmission of genes down generations, and to the horizontal transmission of genes in
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viruses. Without prejudging the issue of whether the analogy is a fruitful one, if we want even to talk about it we had better have a name for the entity that might play the role of gene in the transmission of words, ideas, faiths, mannerisms and fashions. Since 1976, when the word was coined, increasing numbers of people have adopted the name 'meme' for the postulated gene analogue.
The compilers of the Oxford English Dictionaries operate a sensible criterion for deciding whether a new word shall be canonized by inclusion. The aspirant word must be commonly used without needing to be denned and without its coining being attributed. To ask the metamemetic question, how widespread is 'meme', a far from ideal, but nevertheless convenient method of sampling the meme pool, is provided by the World Wide Web. I did a quick search of the web on the day of writing this, which happened to be 29 August 1998. 'Meme' is mentioned about half a million times, but that's a ridiculously high figure, obviously confounded by various acronyms and the French meme. The adjectival form 'memetic' is genuinely exclusive, and it clocked up 5042 mentions. To put this number into perspective, I compared a few other recently coined words or fashionable expressions. Spin doctor (or spin-doctor) gets 1412 mentions, dumbing down 3905, docudrama (or docu-drama) 2848, sociobiology 6679, catastrophe theory 1472, edge of chaos 2673, wannabee 2650, zippergate 1752, studmuffin 776, post-structural (or poststructural) 577, extended phenotype 515, exaptation 307. Of the 5042 mentions of memetic, more than 90 per cent make no mention of the origin of the word, which suggests that it does indeed meet the OED's criterion. And the Oxford Dictionary now does contain the following definition: meme: 'a self-replicating element of culture, passed on by imitation. '
Further searching of the internet reveals a newsgroup talking-shop, 'alt. memetics', which has received about 12,000 postings during the past year. There are on-line articles on, among many other things, 'The New Meme', 'Meme, Counter-meme', 'Memetics: a Systems Metabiology', 'Memes, and Grinning Idiot Press', 'Memes, Metamemes and Polities', 'Cryonics, religions and memes', 'Selfish Memes and the evolution of cooperation', and 'Running down the Meme'. There are separate web pages on 'Memetics', 'Memes', 'The C Memetic Nexus', 'Meme theorists on the web', 'Meme of the week', 'Meme Central', 'Arkuat's Meme Workshop', 'Some pointers and a short introduction to memetics', 'Memetics Index' and 'Meme Gardening Page'. There is even a new religion (tongue in cheek, I think), called the 'Church of Virus', complete with its own list of Sins and Virtues, and its own patron saint (Saint
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? Charles Darwin, canonized as 'perhaps the most influential memetic engineer of the modern era') and I was alarmed to discover a passing reference to 'Saint Dawkins'.
Memes travel longitudinally down generations, but they travel hori- zontally too, like viruses in an epidemic. Indeed, it is largely horizontal epidemiology that we are studying when we measure the spread of a word like memetic, docudrama or studmuffin over the internet. Crazes among schoolchildren provide particularly tidy examples. When I was about nine, my father taught me to fold a square of paper to make an origami Chinese junk. It was a remarkable feat of artificial embryology, passing through a distinctive series of intermediate stages: catamaran with two hulls, cupboard with doors, picture in a frame, and finally the junk itself, fully seaworthy or at least bathworthy, complete with deep hold, and two flat decks each surmounted by a large, square-rigged sail. The point of the story is that I went back to school and infected my friends with the skill, and it then spread around the school with the speed of the measles and pretty much the same epidemiological time- course. I don't know whether the epidemic subsequently jumped to other schools (a boarding school is a somewhat isolated backwater of the meme pool). But I do know that my father himself originally picked up the Chinese Junk meme during an almost identical epidemic at the same school 25 years earlier. The earlier virus was launched by the school matron. Long after the old matron's departure, I had reintroduced her meme to a new cohort of small boys.
Before leaving the Chinese junk, let me use it to make one more point. A favourite objection to the meme/gene analogy is that memes, if they exist at all, are transmitted with too low fidelity to perform a gene-like role in any realistically Darwinian selection process. The difference between high fidelity genes and low fidelity memes is assumed to follow from the fact that genes, but not memes, are digital. I am sure that the details of Wittgenstein's mannerism were far from faithfully reproduced when I imitated my pupil's imitation of her parents' imitation of Wittgenstein. The form and timing of the tic undoubtedly mutated over the generations, as in the childhood game of Chinese Whispers (Americans call it Telephone).
Suppose we assemble a line of children. A picture of, say, a Chinese junk is shown to the first child, who is asked to draw it. The drawing, but not the original picture, is then shown to the second child, who is asked to make her own drawing of it. The second child's drawing is shown to the third child, who draws it again, and so the series proceeds until the twentieth child, whose drawing is revealed to everyone and
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compared with the first. Without even doing the experiment, we know what the result will be. The twentieth drawing will be so unlike the first as to be unrecognizable. Presumably, if we lay the drawings out in order, we shall notice some resemblance between each one and its immediate predecessor and successor, but the mutation rate will be so high as to destroy all semblance after a few generations. A trend will be visible as we walk from one end of the series of drawings to the other, and the direction of the trend will be degeneration. Evolutionary geneticists have long understood that natural selection cannot work unless the mutation rate is low. Indeed, the initial problem of overcoming the fidelity barrier has been described as the Catch-22 of the Origin of Life. Darwinism depends upon high fidelity gene replication. How then can the meme, with its apparently dismal lack of fidelity, serve as quasi-gene in any quasi-Darwinian process?
It isn't always as dismal as you think, and high fidelity is not necessarily synonymous with digital. Suppose we set up our Chinese Whispers game again, but this time with a crucial difference. Instead of asking the first child to copy a drawing of a junk, we teach her, by demonstration, to make an origami model of a junk. When she has mastered the skill and made her own junk, the first child is asked to turn round to the second child and teach him how to make one. So the skill passes down the line to the twentieth child. What will be the result of this experiment? What will the twentieth child produce, and what shall we observe if we lay the 20 efforts out in order along the ground? I haven't done it, but I will make the following confident prediction, assuming that we run the experiment many times on different groups of 20 children. In several of the experiments, a child somewhere along the line will forget some crucial step in the skill taught him by the previous child, and the line of phenotypes will suffer an abrupt macro- mutation which will presumably then be copied to the end of the line, or until another discrete mistake is made. The end result of such mutated lines will not bear any resemblance to a Chinese junk at all. But in a good number of experiments the skill will correctly pass all along the line, and the twentieth junk will be no worse and no better, on average, than the first junk. If we then lay the 20 junks out in order, some will be more perfect than others, but imperfections will not be copied on down the line. If the fifth child is hamfisted and makes a clumsily asymmetrical or floppy junk, his quantitative errors will be corrected if the sixth child happens to be more dexterous. The 20 junks will not exhibit a progressive deterioration in the way that the 20 drawings of our first experiment undoubtedly would.
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? Why? What is the crucial difference between the two kinds of experi- ment? It is this. Inheritance in the drawing experiment is Lamarckian (Susan Blackmore calls it 'copying the product'). In the origami experiment it is Weismannian (Blackmore's 'copying the instructions'). In the drawing experiment, the phenotype in every generation is also the genotype - it is what is passed on to the next generation. In the origami experiment, what passes to the next generation is not the paper phenotype but a set of instructions for making it.
Imperfections in the execution of the instructions result in imperfect junks (phenotypes) but they are not passed on to future generations: they are non-memetic. Here are the first five instructions in the Weismannian meme-line of instructions for making a Chinese junk:
1. Take a square sheet of paper and fold all four corners exactly into the middle.
2. Take the reduced square so formed, and fold one side into the middle.
3. Fold the opposite side into the middle, symmetrically.
4. In the same way, take the rectangle so formed, and fold its two ends
into the middle.
5. Take the small square so formed, and fold it backwards, exactly
along the straight line where your last two folds met.
. . . And so on, through 20 or 30 instructions of this kind. These instruc- tions, though I would not wish to call them digital, are potentially of very high fidelity, just as if they were digital. This is because they all make reference to idealized tasks like 'fold the four corners exactly into the middle'. If the paper is not exactly square, or if a child folds ineptly so that, say, the first corner overshoots the middle and the fourth corner undershoots it, the junk that results will be inelegant. But the next child in the line will not copy the error, for she will assume that her instructor intended to fold all four corners into the exact centre of a perfect square. The instructions are self-normalizing. The code is error- correcting.
The instructions are more effectively passed on if verbally reinforced, but they can be transmitted by demonstration alone. A Japanese child could teach an English one, though neither has a word of the other's language. In the same way, a Japanese master carpenter could convey his skills to an equally monoglot English apprentice. The apprentice would not copy obvious mistakes. If the master hit his thumb with a hammer, the apprentice would correctly guess, even without
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understanding the Japanese for '** **** **! ', that he meant to hit the nail. He would not make a Lamarckian copy of the precise details of every hammer blow, but copy instead the inferred instruction: drive the nail in with as many blows of your hammer as it takes your arm to achieve the same idealized end result as the master has achieved with his - a nail-head flush with the wood.
I believe that these considerations greatly reduce, and probably remove altogether, the objection that memes are copied with insufficient fidelity to be compared with genes. For me, the quasi-genetic inheritance of language, and of religious and traditional customs, teaches the same lesson. Another objection is that we don't know what memes are made of or where they reside. Memes have not yet found their Watson and Crick; they even lack their Mendel. Whereas genes are to be found in precise locations on chromosomes, memes presumably exist in brains, and we have even less chance of seeing one than of seeing a gene (though the neurobiologist Juan Delius has pictured his conjecture of
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whatamememightlooklike ). Aswithgenes,wetrackmemesthrough
populations by their phenotypes. The 'phenotype' of the Chinese junk meme is made of paper. With the exception of 'extended phenotypes' such as beaver dams and caddis larva houses, the phenotypes of genes are normally parts of living bodies. Meme phenotypes seldom are.
But it can happen. To return to my school again, a Martian geneticist, visiting the school during the morning cold bath ritual, would have unhesitatingly diagnosed an 'obvious' genetic polymorphism. About 50 per cent of the boys were circumcised and 50 per cent were not. The boys, incidentally, were highly conscious of the polymorphism and we classified ourselves into Roundheads versus Cavaliers (I have recently read of another school in which the boys even organized themselves into two football teams along the same lines). It is, of course, not a genetic but a memetic polymorphism. But the Martian's mistake is completely understandable; the morphological discontinuity is of exactly the kind that one normally expects to find produced by genes.
In England at the time, infant circumcision was a medical whim, and the roundhead/cavalier polymorphism at my school probably owed less to longitudinal transmission than to differing fashions in the various hospitals where we happened to have been born - horizontal memetic transmission yet again. But through most of history circumcision has been longitudinally transmitted as a badge of religion (ofparents' religion I hasten to point out, for the unfortunate child is normally too young to know his own religious mind). Where circumcision is religiously or traditionally based (the barbaric custom of female 'circumcision'
? always is), the transmission will follow a longitudinal pattern of heredity, very similar to the pattern for true genetic transmission, and often persisting for many generations. Our Martian geneticist would have to work quite hard to discover that no genes are involved in the genesis of the roundhead phenotype.
The Martian geneticist's eyes would also pop out on stalks (assuming they weren't on stalks to begin with) at the contemplation of certain styles of clothing and hairdressing, and their inheritance patterns. The black skullcapped phenotype shows a marked tendency towards longi- tudinal transmission from father to son (or it may be from maternal grandfather to grandson), and there is clear linkage to the rarer pigtail- plaited sideburn phenotype. Behavioural phenotypes such as genuflecting in front of crosses, and facing east to kneel five times per day, are inherited longitudinally too, and are in strong linkage disequilibrium with the previously mentioned phenotypes, as is the red-dot-on- forehead phenotype, and the saffron robes/shaven head linkage group.
Genes are accurately copied and transmitted from body to body, but some are transmitted at greater frequency than others - by definition they are more successful. This is natural selection, and it is the explana- tion for most of what is interesting and remarkable about life. But is there a similar meme-based natural selection? Perhaps we can use the internet again to investigate natural selection among memes? As it happens, around the time the word meme was coined (actually a little
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later), a rival synonym, 'culturgen', was proposed. Today, culturgen is
mentioned 20 times on the World Wide Web, compared with meme's 5042. Moreover, of those 20, 17 also mention the source of the word, falling foul of the Oxford Dictionary's criterion. Perhaps it is not too fanciful to imagine a Darwinian struggle between the two memes (or culturgens), and it is not totally silly to ask why one of them was so much more successful. Perhaps it is because meme is a monosyllable similar to gene, which therefore lends itself to quasi-genetic sub- coinings: meme pool (352), memotype (58), memeticist (163), memeoid (or memoid) (28), retromeme (14), population memetics (41), meme complex (494), memetic engineering (302) and metameme (71) are all listed in a 'Memetic Lexicon' on the World Wide Web (the numbers in brackets count the mentions of each word on the World Wide Web on my sampling day). Culturgen-based equivalents would be less snappy. Or the success of meme against culturgen may have been initially just a non-Darwinian matter of chance - memetic drift (85) - followed by a self-reinforcing positive feedback effect ('unto every one that hath shall be given, and he shall have abundance: but from him
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that hath not shall be taken away even that which he hath' (Matthew 25:29).
I have mentioned two favourite objections to the meme idea: memes have insufficient copying fidelity, and nobody really knows what a meme physically is. A third is the vexed question of how large a unit deserves the name meme. Is the whole Roman Catholic Church one meme, or should we use the word for one constituent unit, such as the idea of incense or the transubstantiation? Or for something in between? The answer is to be found in the concept of the meme-complex or 'memeplex'.
Memes, like genes, are selected against the background of other memes in the meme pool. The result is that gangs of mutually compatible memes - coadapted meme complexes or memeplexes - are found cohabiting in individual brains. This is not because selection has chosen them as a group, but because each separate member of the group tends to be favoured when its environment happens to be dominated by the others. An exactly similar point can be made about genetic selection. Every gene in a gene pool constitutes part of the environmental background against which the other genes are naturally selected, so it's no wonder natural selection favours genes that 'cooperate' in building those highly integrated and unified machines called organisms. By analogy with coadapted gene complexes, memes, selected against the background of each other, 'cooperate' in mutually supportive memeplexes - supportive within the memeplex but hostile to rival memeplexes. Religions may be the most convincing examples of memeplexes, but they are by no means the only ones.
I am occasionally accused of having backtracked on memes; of having lost heart, pulled in my horns, had second thoughts. The truth is that my first thoughts were more modest than some memeticists might have wished. For me, the original mission of the meme was negative. The word was introduced at the end of a book which other- wise must have seemed entirely devoted to extolling the selfish gene as the be-all and end-all of evolution, the fundamental unit of selection, the entity in the hierarchy of life which all adaptations could be said to benefit. There was a risk that my readers would misunderstand the message as being necessarily about genes in the sense of DNA molecules. On the contrary, DNA was incidental. The real unit of natural selection was any kind of replicator, any unit of which copies are made, with occasional errors, and with some influence or power over their own probability of replication. The genetic natural selection identified by neo-Darwinism as the driving force of evolution on this planet was only
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? a special case of a more general process that I came to dub 'Universal Darwinism'. Perhaps we'd have to go to other planets in order to discover any other examples. But maybe we didn't have to go that far. Could it be that a new kind of Darwinian replicator was even now staring us in the face? This was where the meme came in.
I would have been content, then, if the meme had done its work of simply persuading my readers that the gene was only a special case: that its role in the play of Universal Darwinism could be filled by any entity in the universe answering to the definition of Replicator. The original didactic purpose of the meme was the negative one of cutting the selfish gene down to size. I became a little alarmed at the number of my readers who took the meme more positively as a theory of human culture in its own right - either to criticize it (unfairly, given my original modest intention) or to carry it far beyond the limits of what I then thought justified. This was why I may have seemed to backtrack.
But I was always open to the possibility that the meme might one day be developed into a proper hypothesis of the human mind, and I did not know how ambitious such a thesis might turn out to be. I am delighted that others are now undertaking it. *
CHINESE JUNK AND CHINESE WHISPERS
*In addition to Susan Blackmore's The Meme Machine, other books that make heavy use of the meme idea are R. Brodie, Virus of the Mind: the New Science of the Meme (Seattle, Integral Press, 1996) (not to be confused with my essay (see over page), which was published three years earlier); A. Lynch, Thought Contagion: How Belief Spreads Through Society (New York, Basic Books, 1998); J. M. Balkin, Cultural Software (New Haven, Yale University Press, 1998); H. Bloom, The Lucifer Principle (Sydney, Allen & Unwin, 1995); Robert Aunger, The Electric Meme (New York, Simon & Schuster, 2002); Kevin Laland and Gillian Brown, Sense and Nonsense (Oxford, Oxford University Press, 2002); and Stephen Shennan, Genes, Memes and Human History (London, Thames and Hudson, 2002). A turning point in the fortunes of the meme was its adoption and development by Daniel Dennett as a cornerstone of his theory of the evolution of the mind, especially in his two books Consciousness Explained (Boston, Little Brown, 1991) and Darwin's Dangerous Idea (New York, Simon & Schuster, 1995).
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The haven all memes depend on reaching is the human mind, but a human mind is itself an artifact created when memes restructure a human brain in order to make it a better habitat for memes. The avenues for entry and departure are modified to suit local conditions, and strengthened by various artificial devices that enhance fidelity and prolixity of replication: native Chinese minds differ dramatically from native French minds, and literate minds differ from illiterate minds. What memes provide in return to the organisms in which they reside is an incalculable store of advantages - with some Trojan horses thrown in for good measure . . .
78 Daniel Dennett
Duplication-Fodder
A beautiful child close to me, six and the apple of her father's eye, believes that Thomas the Tank Engine really exists. She believes in Father Christmas, and when she grows up her ambition is to be a tooth fairy. She and her schoolfriends believe the solemn word of respected adults that tooth fairies and Father Christmas really exist. This little girl is of an age to believe whatever you tell her. If you tell her about witches changing princes into frogs, she will believe you. If you tell her that bad children roast forever in hell, she will have nightmares. I have just discovered that without her father's consent this sweet, trusting, gullible six-year-old is being sent, for weekly instruction, to a Roman Catholic nun. What chance has she?
A human child is shaped by evolution to soak up the culture of her people. Most obviously, she learns the essentials of their language in a matter of months. A large dictionary of words to speak, an encyclopaedia of information to speak about, complicated syntactic and semantic rules to order the speaking, all are transferred from older brains into hers well before she reaches half her adult size. When you are
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? preprogrammed to absorb useful information at a high rate, it is hard to shut out pernicious or damaging information at the same time. With so many mindbytes to be downloaded, so many mental codons to be duplicated, it is no wonder that child brains are gullible, open to almost any suggestion, vulnerable to subversion, easy prey to Moonies, Scientologists and nuns. Like immune-deficient patients, children are wide open to mental infections that adults might brush off without effort.
DNA, too, includes parasitic code. Cellular machinery is extremely good at copying DNA. Where DNA is concerned, it seems to have an eagerness to copy, like a child's eagerness to imitate the language of its parents. Concomitantly, DNA seems eager to be copied. The cell nucleus is a paradise for DNA, humming with sophisticated, fast and accurate duplicating machinery.
Cellular machinery is so friendly towards DNA-duplication that it is small wonder cells play host to DNA parasites - viruses, viroids, plasmids and a riff-raff of other genetic fellow travellers. Parasitic DNA even gets itself spliced seamlessly into the chromosomes themselves. 'Jumping genes' and stretches of 'Selfish DNA' cut or copy themselves out of chromosomes and paste themselves in elsewhere. Deadly oncogenes are almost impossible to distinguish from the legitimate genes between which they are spliced. In evolutionary time, there is probably a continual traffic from 'straight' genes to 'outlaw', and back again. DNA is just DNA. The only thing that distinguishes viral DNA from host DNA is its expected method of passing into future generations. 'Legitimate' host DNA is just DNA that aspires to pass into the next generation via the orthodox route of sperm or egg. 'Outlaw' or parasitic DNA is just DNA that looks to a quicker, less cooperative route to the future, via a sneezed droplet or a smear of blood, rather than via a sperm or egg.
For data on a floppy disk, a computer is a humming paradise just as cell nuclei hum with eagerness to duplicate DNA. Computers and their associated disk and tape readers are designed with high fidelity in mind. As with DNA molecules, magnetized bytes don't literally 'want' to be faithfully copied. Nevertheless, you can write a computer program that takes steps to duplicate itself. Not just duplicate itself within one computer but spread itself to other computers. Computers are so good at copying bytes, and so good at faithfully obeying the instructions contained in those bytes, that they are sitting ducks to self-replicating programs: wide open to subversion by software parasites. Any cynic familiar with the theory of selfish genes and memes would have known
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that modern personal computers, with their promiscuous traffic of floppy disks and email links, were just asking for trouble. The only surprising thing about the current epidemic of computer viruses is that it has been so long in coming.
Computer Viruses: a Model for an Informational Epidemiology
Computer viruses are pieces of code that graft themselves into existing, legitimate programs and subvert the normal actions of those programs. They may travel on exchanged floppy disks, or over networks. They are technically distinguished from 'worms' which are whole programs in their own right, usually travelling over networks. Rather different are 'Trojan horses', a third category of destructive programs, which are not in themselves self-replicating but rely on humans to replicate them because of their pornographic or otherwise appealing content. Both viruses and worms are programs that actually say, in computer language, 'Duplicate Me'. Both may do other things that make their presence felt and perhaps satisfy the hole-in-corner vanity of their authors. These side effects may be 'humorous' (like the virus that makes the Macintosh's built-in loudspeaker enunciate the words 'Don't panic', with predictably opposite effect); malicious (like the viruses that erase the hard disk after a sniggering screen-announcement of the impending disaster); political (the Spanish Telecom and Beijing viruses protest about telephone costs and massacred students respectively); or simply inadvertent (the programmer is incompetent to handle the low-level system calls required to write an effective virus or worm). The famous Internet Worm, which paralysed much of the computing power of the United States on 2 November 1988, was not intended (very) maliciously but got out of control and, within 24 hours, had clogged around 6000 computer memories with exponentially multiplying copies of itself.
Memes now spread around the world at the speed of light, and replicate at rates that make even fruit flies and yeast cells look glacial in comparison. They leap promiscuously from vehicle to vehicle, and from medium to medium, and are proving to be virtually unquarantinable. [Dennett again]
Computer viruses aren't limited to electronic media such as disks and data lines. On its way from one computer to another, a virus may pass through printing ink, light rays in a human lens, optic nerve impulses and finger muscle contractions. A computer fanciers' magazine that printed the text of a virus program for the interest of its readers has been widely condemned. Indeed, such is the appeal of the virus idea to
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? a certain kind of puerile mentality (the masculine gender is used advisedly), that publication of any kind of 'How to' information on designing virus programs is rightly seen as an irresponsible act.
I am not going to publish any virus code. But there are certain tricks of effective virus design that are sufficiently well known, even obvious, that it will do no harm to,mention them, as I need to do in order to develop my theme. They all stem from the virus's need to evade detection while it is spreading.
A virus that clones itself too prolifically within one computer will soon be detected because the symptoms of clogging will become too obvious to ignore. For this reason many virus programs check, before infecting a system, to make sure that they are not already on that system. Incidentally, this opens the way for a defence against viruses that is analogous to immunization. In the days before a specific anti- virus program was available, I myself responded to an early infection of my own hard disk by means of a crude 'vaccination'. Instead of deleting the virus that I had detected, I simply disabled its coded instructions, leaving the 'shell' of the virus with its characteristic external 'signature' intact. In theory, subsequent members of the same virus species that arrived in my system should have recognized the signature of their own kind and refrained from trying to double-infect. I don't know whether this immunization really worked, but in those days it probably was worthwhile 'gutting' a virus and leaving a shell like this, rather than simply removing it lock, stock and barrel. Nowadays it is better to hand the problem over to one of the professionally written anti-virus programs.
A virus that is too virulent will be rapidly detected and scotched. A virus that instantly and catastrophically sabotages every computer in which it finds itself will not find itself in many computers. It may have a most amusing effect on one computer - erase an entire doctoral thesis or something equally side-splitting - but it won't spread as an epidemic. Some viruses, therefore, are designed to have an effect that is small enough to be difficult to detect, but which may nevertheless be extremely damaging. There is one type which, instead of erasing disk sectors wholesale, attacks only spreadsheets, making a few random changes in the (usually financial) quantities entered in the rows and columns. Other viruses evade detection by being triggered probabilistically, for example erasing only one in 16 of the hard disks infected. Yet other viruses employ the time-bomb principle. Most modern computers are 'aware' of the date, and viruses have been triggered to manifest them- selves all around the world, on a particular date such as Friday 13th or
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April Fool's Day. From the parasitic point of view, it doesn't matter how catastrophic the eventual attack is, provided the virus has had plenty of opportunity to spread first (a disturbing analogy to the Medawar/ Williams theory of ageing; we are the victims of lethal and sub-lethal genes that mature only after we have had plenty of time to reproduce). In defence, some large companies go so far as to set aside one 'miner's canary' among theirfleetof computers, and advance its internal calendar a week so that any time-bomb viruses will reveal themselves prematurely before the big day.
Again predictably, the epidemic of computer viruses has triggered an arms race. Antiviral software is doing a roaring trade. These antidote programs - 'Interferon', 'Vaccine', 'Gatekeeper' and others - employ a diverse armoury of tricks. Some are written with specific, known and named, viruses in mind. Others intercept any attempt to meddle with sensitive system areas of memory and warn the user.
The virus principle could in theory be used for non-malicious, even
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beneficial purposes. Harold Thimbleby coins the phrase 'Liveware' for
his already-implemented use of the infection principle for keeping multiple copies of databases up to date. Every time a disk containing the database is plugged into a computer, it looks to see whether there is already another copy present on the local hard disk. If there is, each copy is updated in the light of the other. So, with a bit of luck, it doesn't matter which member of a circle of colleagues enters, say, a new biblio- graphic citation on his personal disk. His newly entered information will readily infect the disks of his colleagues (because the colleagues promiscuously insert their disks into one another's computers) and will spread like an epidemic around the circle. Thimbleby's liveware is not entirely virus-like: it could not spread to just anybody's computer and do damage. It spreads data only to already-existing copies of its own database; and you will not be infected by liveware unless you positively opt for infection.
Incidentally, Thimbleby, who is much concerned with the virus menace, points out that you can gain some protection by using computer systems that other people don't use. The usual justification for purchasing today's numerically dominant personal computer is simply and solely that it is numerically dominant. Almost every knowledgeable person agrees that, in terms of quality and especially user-friendliness, the rival, minority system is superior. Nevertheless, ubiquity is held to be a good in itself, sufficient to outweigh sheer quality. Buy the same (albeit inferior) computer as your colleagues, the argument goes, and you'll be able to benefit from shared software, and from a generally
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