Brief Candle in the Dark

by Richard Dawkins

  My argument was not logically unassailable, but I think it’s still strong. It became, indeed, my answer to the question ‘What do you believe but cannot prove?’ in John Brockman’s annual ‘Edge’ series. It amounted to: ‘Nobody has ever thought of a viable alternative to natural selection.’ I have to admit that, when you put it like that, it is vulnerable to disproof the moment somebody actually comes up with an alternative. But scientists are allowed to have hunches, and the burden of my contribution was the strong hunch that no such disproof will ever – could ever – transpire. I made what I think is an unassailable case in principle, not just in fact, against all known alternatives to natural selection, most notably the Lamarckian theory invoking ‘use and disuse’ and the inheritance of acquired characteristics. Hitherto, biologists had gone along with Ernst Mayr, centenarian founding father of the neo-Darwinian synthesis, who thought that Lamarck’s hypothesis was in principle a good one, slain only by what T. H. Huxley would have called an ugly fact: acquired characteristics are not in fact inherited. An implication of Mayr’s view was that, if there were a planet where acquired characteristics were inherited, evolution on that planet could be Lamarckian and would work just fine. This was what I went out of my way to deny – I think convincingly, and nobody has ever published a refutation.

  It’s a fact that muscles that are much used for a particular purpose grow bigger, and become better for that purpose. Lift weights and your muscles enlarge. Walk around with bare feet and the skin of your soles gets tougher. If you run marathons you become better able to run marathons: your heart, lungs, leg muscles and many other things become better for the purpose. So, on our hypothetical planet with Lamarckian evolution, stronger muscles, leathery feet and trained lungs would be passed on to the next generation. Lamarck thought it was by this principle that improvements evolve. The usual objection is that acquired characteristics are not, as a matter of ugly fact, inherited. My objections were different – principled rather than factual, and threefold.

  First, even if acquired characteristics were inherited, the principle of use and disuse is too crude and unfocused to mediate all but a few examples of adaptive evolution. The lens of an eye is not washed clear by photons streaming through it. Muscular enlargement represents a rather rare example of an improvement that can come about by use and disuse. Only natural selection has chisels fine and sharp enough, and sufficiently accurately aimed, to sculpt the multitude of subtle and often tiny improvements of evolution. The principle of use and disuse is too crude and inept. On the other hand, any genetically mediated improvement, no matter how subtle and no matter how deeply buried inside the cellular chemistry of the organism, is grist to natural selection’s fine-grinding mill.

  Second, only a minority of acquired characteristics are improvements. Yes, muscles grow when you use them, but most parts of the body wear out with repeated use and become smaller, less perfect, often pitted and scarred. It has become almost a cliché that religious circumcision over many generations has signally failed to effect any evolutionary reduction in the foreskin. Lamarckian evolution would have to employ some sort of ‘selection’ mechanism to sort out the few improvements (like leathery feet) from the many disimprovements (wearing out of hip joints etc.) – and that sounds a lot like Darwinian selection!

  Our bodies are not walking inventories of ancestral scars and broken limbs, notwithstanding popular belief. My mother had a beloved dog called Bunch, who had a habit of limping on three of his four legs (luxating patella is a common problem in small dogs). A neighbour had an older dog, Ben, who had lost one hind leg in an accident and limped, perforce, on the only three legs left to him. She tried to persuade my mother that Ben must be Bunch’s father!

  Indulge me in a shameless moment of sentiment. Looking, this week, through a tattered folder of poems that my parents collected for each other over many years, painstakingly copied out by hand, I found the following in my mother’s handwriting, obviously written immediately after the death of Bunch. It is unfinished, as can be seen from the crossings out and corrections, but I think it is beautiful enough to be reproduced here. And if you can’t be sentimental in an autobiography, when can you?

  Dear little ghost of happiness

  Who lopes beside me down the years,

  No dog of flesh and blood will take

  Your place, nor ever stem the tears

  That come unbidden from the heart.

  For you were very part of me –

  And all the fields and all the ways

  Down woodland ride or open hill

  Are empty places now for me.

  You are not there – you are not there

  Dear Bunch. It’s all nonsense to say you can’t miss a dog as much as a person. Or, to put it another way, for purposes of mourning, a dog can become a ‘person’.

  My third objection to any kind of evolution based on the inheritance of acquired characteristics might not necessarily apply universally to all life forms everywhere. It is, however, an objection in the case of any life form whose embryology is ‘epigenetic’ (as Earthly embryology is) rather than ‘preformationistic’. And it remains arguable (for another day) that preformationistic embryology is in principle unworkable. What do those technical terms ‘epigenetic’ and ‘preformationist’ mean? They go way back in the history of embryology. I would now call them ‘origami’ embryology and ‘3-D printer’ embryology respectively. Origami embryology, as I wrote in The Ancestor’s Tale and The Greatest Show on Earth, creates a body by following a recipe or program of instructions to grow tissues and fold them, invaginate them, refold them, turn them inside out. It’s of the nature of origami (epigenetic) embryology that it is irreversible. You can’t take a body and reverse engineer the instructions that made it, any more than you can take an origami bird or boat and reverse engineer the folding sequence that gave rise to it; or take a gourmet dish and reconstruct the words of its recipe.

  Preformationist (or ‘blueprint’) embryology is quite different. It is reversible and it doesn’t exist in the biology of our planet. This is why it is wrong to describe DNA as a ‘blueprint’. Blueprint embryology, if it existed, would be reversible. You can reconstruct the blueprint of a house by measuring its rooms and scaling down. You can’t reconstruct the DNA of an animal, no matter how detailed and meticulous your measurements of its body.

  Preformationist or ‘blueprint’ embryology is well portrayed by a 3-D printer. The 3-D printer is a natural extension of the ordinary paper printer. It builds up the object it is ‘printing’ layer by layer. I first saw one of these astonishing machines as the guest of Elon Musk in his SpaceX rocket factory. This particular 3-D printer was – as an exhibition tour de force – printing chessmen. Unlike a milling machine, which plays the role of a computer-controlled sculptor and subtractively carves objects out of a block of metal, a 3-D printer builds the object up additively, layer upon layer. You can present it with serial scans of an existing 3-D object in layers, and it will then build up the layers again in the new, copied object. Life as we know it develops epigenetically,1 not preformationistically.

  One could (just, perhaps, only just, only perhaps) imagine a preformationistic life form, somewhere in the universe, whose embryology works like a 3-D printer, scanning the parent’s body and then building the child up layer by layer. And such a life form could, in theory, pass on acquired characteristics to the next generation. Whatever scanning mechanisms copied the present body could copy its acquired alterations (presumably including the scars of injury, mutilation, and wear and tear). But everything we know about the DNA/protein-based life of this planet is inimical to the idea of scanning the parental body and rendering the scanned information into the genes for transmission to the next generation. That isn’t, nor could it be, how DNA works. You can’t reconstruct an animal’s genome from its body. And the only way we know to construct a body from its genes is to grow an embryo in a womb or egg. Moreover – to repeat the circumcision point – scanning the body would p
ick up all the injuries as well as the ‘use and disuse’ improvements.

  So, I concluded, Ernst Mayr was wrong to say: ‘Accepting his premises, Lamarck’s theory was as legitimate a theory of adaptation as that of Darwin. Unfortunately, these premises turned out to be invalid.’ No, they didn’t ‘turn out’ to be invalid; they couldn’t do the job even if they were valid, as a matter of principle. And I hope I gave Francis Crick cause to revise these words: ‘No one has given general theoretical objections why such a mechanism must be less efficient than natural selection.’

  At the end of my talk, Stephen Gould stood up and eloquently demonstrated, not for the first time, the way in which massive erudition can sometimes overload the mind to the extent of obscuring the point that matters. He articulately and fluently pointed out that, in the late nineteenth and early twentieth centuries, various alternatives to natural selection were fashionable: mutationism and saltationism, for example. This is historically true but crashingly beside the point. Like Lamarckism (as I also had argued in my Cambridge lecture), neither mutationism nor saltationism nor any other nineteenth-century ‘ism’ is in principle capable of mediating adaptive evolution.

  Take ‘mutationism’ for example. William Bateson (1861–1926) was one of many geneticists (he coined the word) who thought that Mendelian genetics somehow superseded natural selection and that mutation, without selection, was a sufficient explanation of evolution. I gave two quotations from him in The Blind Watchmaker:

  ‘We go to Darwin for his incomparable collection of facts [but] . . . for us he speaks no more with philosophical authority. We read his scheme of Evolution as we would those of Lucretius or Lamarck.’

  And again,

  ‘The transformation of masses of populations by imperceptible steps guided by selection is, as most of us now see, so inapplicable to the fact that we can only marvel both at the want of penetration displayed by the advocates of such a proposition, and at the forensic skill by which it was made to appear acceptable even for a time.’

  What utter nonsense. Gould was certainly right, as a matter of historical fact, that other theories of evolution than those of Darwin and Lamarck were going around in the nineteenth and early twentieth centuries, and Bateson was one of the perpetrators. My point was not to deny the history but to show that those other theories, along with Lamarckism, were in principle wrong. Always had to be wrong. And that should all have been clear from an armchair even before evidence disproved them. Darwinian natural selection is not only supported by evidence. Where adaptive, functionally improving evolution is concerned, natural selection is certainly the only theory we know that is in principle capable of doing the job, and the generalization will – or such is my hunch – stretch to theories we don’t know.

  I didn’t argue for universal Darwinism very well at the Cambridge conference, badly underestimating the time it would take to develop the theme. And in those days I was less skilled at concealing my discomfort when I made a mistake of that kind. This wasn’t the only occasion on which I ran out of time, and I recall the familiar sensation of red overheating and literally sweating with anxiety and panic. During the coffee break after what I perceived as my failure, I sat on, disconsolately motionless, in the emptying lecture hall. A sweet friend who saw my distress came up behind me and silently kissed the top of my head with her hands gently resting on my shoulders. The warmth of feminine tendresse is one of the good reasons for staying alive. When I came to reprise the story of universal Darwinism in the last chapter of The Blind Watchmaker, I told it better.

  Memes

  In the last chapter of (the original edition of) The Selfish Gene I advocated a version of universal Darwinism, in the course of downplaying the gene, which had been the starring hero of the rest of the book. Any self-replicating coded information, I argued, could step into evolution’s play as understudy to DNA. And maybe on some distant planet it has. I should have added – but didn’t make it sufficiently clear until The Extended Phenotype – that the understudy would need an additional qualification: the power to influence the probability of its own replication. Indeed, before I had the title of The Extended Phenotype, I remember that Geoffrey Parker, pioneering evolutionary theorist of Liverpool University, asked me what my next book would be about and I said ‘power’. Geoff got the point immediately, and I can’t think of many other people who would have got it from that single word.

  In 1976, when introducing the idea of universal Darwinism in The Selfish Gene, what other examples of potentially powerful replicators – hypothetical alternatives to DNA – could I turn to? Computer viruses would have done it, but they had only just been invented in some squalid little mind, and even if I’d thought of them I wouldn’t have wanted to advertise the idea. I mentioned the possibility of strange replicators on alien planets and continued:

  But do we have to go to distant worlds to find other kinds of replicator and other, consequent, kinds of evolution? I think that a new kind of replicator has recently emerged on this very planet. It is staring us in the face. It is still in its infancy, still drifting clumsily about in its primeval soup, but already it is achieving evolutionary change at a rate that leaves the old gene panting far behind.

  It is true that cultural evolution is orders of magnitude faster than genetic evolution. But I would have been jumping the gun if I had implied that natural selection of memes should take all credit for cultural evolution. It might, but that would have been a bolder claim than I set out to make. The evolution of language, for example, clearly owes more to drift (memetic drift) than to anything resembling selection. I went on to coin the word itself:

  The new soup is the soup of human culture. We need a name for the new replicator, a noun that conveys the idea of a unit of cultural transmission, or a unit of imitation. ‘Mimeme’ comes from a suitable Greek root, but I want a monosyllable that sounds a bit like ‘gene’. I hope my classicist friends will forgive me if I abbreviate mimeme to meme. If it is any consolation, it could alternatively be thought of as being related to ‘memory’, or to the French word même. It should be pronounced to rhyme with ‘cream’.

  Just as genes are selected for their mutual compatibility so, in principle, might memes be. The large literature on memetics has adopted the word ‘memeplex’ as a contraction of ‘meme complex’. In The Selfish Gene I reiterated the idea of cooperating gene complexes (I used the phrase ‘evolutionarily stable set of genes’) and then tentatively drew the memetic parallel, as follows:

  Mutually suitable1 teeth, claws, guts, and sense organs evolved in carnivore gene pools, while a different stable set of characteristics emerged from herbivore gene pools. Does anything analogous occur in meme pools? Has the god meme, say, become associated with any other particular memes, and does this association assist the survival of each of the participating memes? Perhaps we could regard an organized church, with its architecture, rituals, laws, music, art and written tradition, as a co-adapted stable set of mutually assisting memes.

  And here’s another interesting possibility: if we acknowledge that memes, as well as genes, might be naturally selected, then mutually compatible complexes of memes and genes together might be favoured, each in their respective domains of selection. Thus, if the Genetic Book of the Dead is a description of ancestral environments, why would those ancestral environments of genes not include ancestral memes? Wouldn’t ancestral social practices, ancestral religions, ancestral marriage customs and habits of warfare have constituted an important part of the worlds in which ancestral genes survived? And vice versa.

  In addition to regional differences in climate, exposure to the sun, exposure to cows’ milk etc., there are important differences between populations in culture, religion, traditions, marriage customs and so on, which could have exerted different selective effects on genes. That’s not at all implausible. The populations concerned have been geographically more or less separated for long enough. So the Genetic Book of the Dead might include a description of ancestral cultur
es. Another way to put that is that genes and memes cooperate with each other in mutually compatible cartels. This is what E. O. Wilson meant when he spoke, long ago, of ‘gene–culture coevolution’. Is there a ‘Memetic Book of the Dead’? And does it include descriptions of ancestral genes as well as memes? I leave that as a field for the reader to plough, adding as a seed the suggestion that cultural, linguistic or religious barriers to gene flow and meme flow could play the same role as geographic barriers in fostering evolutionary divergence. Interestingly, such cultural barriers could work even where geographic distances between populations are too small to do so. If the enmities between neighbouring valleys in the New Guinea highlands have isolated their warring populations sufficiently to foster the evolution of a thousand mutually unintelligible languages, what does that do to gene flow between them? If the Genetic Book of the Dead is a description of ancestral worlds including their cultures, why should there not be a Memetic Book of the Dead whose descriptions include ancestral genes? And, mutatis mutandis, why should the Genetic Book of the Dead not include a description of ancestral memes?

  I’ve been a little detached from it, but there has grown up a large literature on memetics, including many books with ‘meme’ in the title. Significant advances in meme theory have been made by, among others, Susan Blackmore (in The Meme Machine), Robert Aunger (in The Electric Meme) and Daniel Dennett (in several books including Consciousness Explained, Darwin’s Dangerous Idea, Breaking the Spell and Intuition Pumps). Both Dennett and Blackmore see memetics as playing a crucial role in human evolution, including the evolution of mind. Sue Blackmore has convened a series of ‘Memelab’ workshops in the eccentrically beautiful Devon house she shares with her husband, the television science presenter Adam Hart-Davis (who, incidentally, was involved, when at Oxford University Press, with the publication of The Selfish Gene). Each one organized as a complete weekend house party, with the participants sleeping in the house and eating meals together, these workshops capture, for me, some of the wonderfully companionable thinking-aloud feeling that I have always found so congenial. If the weather is kind the workshop ends in a windy climb up a Dartmoor tor. On one memorable occasion, Dan Dennett was able to be present and, as he usually does, he raised the game of the rest of us.