The Art of Genes How Organisms Make Themselves

upside-down, turning it the right way round again. If mutations altered the orienting response, such that after the flower became inverted by 180ºthe gravity receptors did not become silent but continued to be active, further twisting might occur until the flower went through another 180º, turning it back to the upright position. This might be achieved by mutations in genes for the receptors, changing the way they respond to gravity, or perhaps by mutations in the genes involved in the chain of events following stimulation of the receptors. Whatever the mechanism, it had to involve mutations in genes, tinkering with the DNA, to bring about the variation. Direct tinkering with the flower alone could not have been the cause.

Tinkering revisited

To clarify matters, we need to take a closer look at the tinkering process. Think of a tinkerer playing about with various oddments. As objects happen to get juxtaposed, say an old spring and a piece of wood with a hook in it, the tinkerer thinks of some sort of simple contraption, like a rudimentary weighing machine. Further tinkering with the contraption, combining it with other oddments by trial and error, leads the tinkerer to produce a different device, say a simple musical instrument that makes a sound when the spring is hit. The tinkerer continues in this way, changing bits and pieces, assessing them and moving on to combine more oddments, modifying the contraption in some way each time. Of course, the tinkerer need not always be adding new bits; perhaps as the contraption gets more elaborate some old bits are eventually taken off or simply rearranged. The outcome of the tinkering is a series of contraptions, each with a slightly different structure and function. The final contraption may be a rather complicated device that bears little resemblance to the original simple weighing machine.

To see how this relates to evolutionary change, it will help to distinguish between two types of activity during the tinkering process. One is the physical activity of juxtaposing and rearranging objects, putting new combinations together. The other is assessing how well they work, deciding whether or not they make sense as part of a contraption. You need both activities to tinker successfully. If you combine bits and pieces without any sort of assessment you end up with a hotchpotch of objects put together in any old fashion. If you can assess things but are unable to combine any bits and pieces, there will be no way of moving from one contraption to the next. Clearly the two activities are intimately dependent on each other: the tinkerer's assessment depends on what happens to have been put together, and each assessment in turn sets the scene for the next combination of objects.

Now when it comes to the evolution of organisms, these two types of activity, alterations and assessment, occur in a different way. Almost all of the alterations have to occur at the level of DNA. You can rearrange the parts of an organism any way you want, but these alterations will be of little significance for evolution unless they are passed on from one generation to the next. As I have just described, this effectively means that the alterations have to occur in DNA: they have to be mutations in genes. They could involve substituting one base for another in the DNA sequence, say an A for a G, or the duplication of a gene, or some other change in the DNA. Whatever the details, the alterations during tinkering— the changes in the bits and pieces— occur at the level of genes. DNA provides the storehouse of raw material for tinkering.

The second aspect of tinkering, the assessment of the alterations, occurs for the most part at the level of the organism, or more strictly speaking at the level of populations of organisms. The

significance of any change in DNA only becomes apparent as the organism develops and reproduces. If a mutation results in an organism that is less able to survive and reproduce relative to other members of the population, it will tend to be selected against. If the mutation confers some advantage to survival and reproduction, it is likely to be selected for in the population. The continual assessment of organisms, through natural selection, is an essential part of evolutionary tinkering. Without some sort of assessment, evolution would not give rise to organisms with adaptive features.

We can now begin to see how the tinkering metaphor can be misleading. In human tinkering the parts that are physically played with are also the components of the final contraption. Each of the bits and pieces that have been tinkered with to make a Heath Robinson device are visible as the working parts of the machine. In biological evolution, the parts of an organism are not the raw material for tinkering. The parts cannot be directly rearranged; instead, some feature in the genes has to be altered which then influences the way parts form. Evolution is a more indirect form of tinkering. Perhaps this is one of the main reasons that Darwin was attracted to the idea that acquired characters are inherited. It is after all so much easier to think about tinkering if the alterations and the assessment are all carried out at the same level. Tinkering with an orchid by simply rearranging some of its component parts seems a lot easier to conceive than first having to fiddle about with something else that affects the parts.

The indirect nature of evolutionary tinkering helps to explain an otherwise curious observation: as we have acquired a deeper knowledge about genes, so hitherto unsuspected degrees of tinkering have been revealed. The reason is that as long as you look purely at the anatomy of organisms, the arrangement of their various parts, you can appreciate tinkering only indirectly. You are looking at only part of the story, the visible manifestation of tinkering rather than the underlying raw material. This means that two structures may seem to be entirely distinct when in fact they have evolved from tinkering with similar genes. The organisation of vertebrates and insects from head to tail looks entirely different from the point of view of anatomy, yet they depend on a remarkably similar pattern of hidden colours, coded for by related genes. It is just that these colours are interpreted and become manifest in very different ways. Similarly, the sexual chemistry of yeast bears no obvious relationship to the parts of a flower, yet they are both based on tinkering with a common palette of basic colours (Chapter 17). As the relationship between genes and development has become clearer, so our conception of how organisms compare with each other has had to change. This is because we can begin to see both sides of the tinkering process, the genes together with their significance and meaning for the organism. In my view, we are still at a very early stage of chipping away at the iceberg of tinkering, revealing a few pieces here and there that lie beneath the surface. One of the great challenges for the future will be to get a sense of what the iceberg as a whole looks like, the true manner in which the various ways organisms develop are related to their genes.

Development and fabrication

With this view of evolution and tinkering in mind, I now want to return to the basis of fabrication and development. Recall that we compared evolution to the way a tinkerer comes up with a contraption, whereas development corresponded to the consistent manufacture of the contraption once it was devised. Now to get from tinkering to manufacture, we have to devise a

set of instructions for making the same contraption again and again. The instructions might be a series of pictures showing how to build the contraption, or they could be written down as a series of commands, like 'attach spring to a piece of wood' or 'join spring to a hook', etc.

Now the key point is that whatever the nature of the instructions, they are always devised after the event has been carried out or conceived. A tinkerer can write down 'attach spring to a piece of wood' only after he has already come up with the idea of taking a piece of wood and attaching a spring to it. He may have had the idea while fiddling around with some bits of wood and a spring, or he may have simply had the idea first and then looked around for the pieces. Either way, the instruction comes after the event, not before. Try to imagine, for example, that it was the other way round: that the instruction came first. This would mean that the tinkerer was actually following the instruction 'attach spring to a piece of wood' before he came up with the idea. But then who is giving this instruction? Is there a little instructor inside the tinkerer's head telling him what to do or think? And if so, who is instructing the tiny instructor? We end up with an infinite regress.

To plan something, you need to have in advance a conception of what it is you are trying to achieve. The product has in some sense already to be there before you devise the detailed plan. Without foresight, planning is impossible. That is why, once you have a Heath Robinson contraption before you, it is possible to devise a set of instructions for how to make it again and again; you already know what is being aimed at.

Compare this with the parallel process of going from evolution to development. If the evolution of DNA corresponded to devising a set of instructions, the changes in DNA would have to somehow anticipate their outcome. Information about the final state of the organism would need to come before any change in the hereditary material. This is exactly the way Darwin saw things: variation in the organism came first, and was then transmitted to the offspring. In this view it might be legitimate to talk of development as fabrication because the instructions arise after the event. But as we have seen, this is simply not the way that development has evolved: alterations in the DNA precede their manifestation in the organism. It is not the case that parts of the organism arose first and were then planned for by DNA. Any modification to the parts is a later manifestation of tinkering with genes: mutating, rearranging or duplicating bits of DNA.

As soon as we look more closely at how development has evolved, we see that the analogy between development and fabrication starts to come apart at the seams. Rather than arising in comparable ways, they are based on opposite principles: instructions for fabrication are devised after the event, whereas changes in DNA precede developmental modifications. Of course, it might still be argued that by their very nature, such comparisons between biological and human processes are bound to be imperfect. Perhaps the dual analogy is the best of a bad job. In my view, there is a better way of looking at the problem; one that is more coherent and more firmly grounded.

The art of development

The dual analogy assumes that there are two primary processes: human creativity and evolution. What are these processes themselves based upon? In the case of evolution, it was Darwin's great achievement to show how this was grounded in the process of natural selection. Over many millions of years, the action of natural selection could account for the features of organisms today.

But when we turn to the human parallel, creativity, things are less clear. We tend to think of creativity as coming from nowhere— it just happens spontaneously. This is after all what it feels like when we are inspired with a new idea or create something for the first time; it seems to come from out of the blue. If we were to interpret this literally, we would be driven to believe in some form of vitalism; that there really is something out there providing the source of our creativity. Of course, there is a more scientific alternative: although we are not aware of the source of creativity as we experience it, it is nevertheless grounded in the way our brain works. Now because our brain is itself something that has evolved, this means that creativity is grounded in evolution. Darwin pointed this out in The Descent of Man, where he argued that human mental powers had evolved gradually:

If no organic being excepting man had possessed any mental power, or if his powers had been of a wholly different nature from those of the lower animals, then we should never have been able to convince ourselves that our high faculties had been gradually developed. But it can be shewn that there is no fundamental difference of this kind.

We have ended up with a curious double standard. On the one hand, creativity can be seen as parallel to evolution (dual analogy); on the other, creativity appears to be an outcome of evolution. I believe that the reason we have been caught in this double bind stems from our failure to understand the nature of development, because it is this that provides the key link between evolution and creativity. So long as we think of development as akin to fabrication, we will tend to think of creativity as something that comes earlier, as analogous to evolution. But as we have learned more about the internal mechanisms of development, we have seen that it is quite unlike fabrication: there is no clear separation between plan and execution. Rather, it involves a continual process of interpretation and elaboration, in which genes, organism and environment interact. Once this is appreciated, our brain processes no longer seem divorced from development; rather, they can be seen as an extension of it (Chapter 12). In other words, creativity becomes grounded in development, just as development is grounded in evolution.

We can summarise the relationship between the various processes as follows. At an early stage of evolution, life consisted solely of unicellular organisms. Eventually, some of these organisms adopted a multicellular lifestyle, bringing the possibility of elaborating structures in a new way: through the process of development. Hidden colours, scents and sensitivities, already present in unicellular organisms, were now put to a new use— the elaboration of spatial patterns as a single cell developed into a multicellular individual. In some evolutionary lineages, the developmental process led to the production of individuals with complex nervous systems. The most elaborate of these to have evolved so far is the human brain, with its remarkable creative potential. Human creativity in turn ushered in new possibilities as each generation could learn and build upon the creative discoveries of the previous one. Through this, a novel form of making was arrived at— the process of fabrication according to a plan. This enabled humans to churn out many copies of their creations in a systematic and reproducible way.

The order of events was therefore: evolution-development-creativity-fabrication. I should emphasise that this is not a sequence of separate processes; rather, each process is woven into the fabric of what went before. I have tried to illustrate this diagrammatically in Fig. 18.6, where each process is shown as a circle embedded within and permeated by its predecessors.

Fig. 18.6 Four processes shown as circles embedded within each other.The shading illustrates how each process is permeated by its predecessors.

According to this viewpoint, there is only one process that underlies all others: evolution. In contrast, the dual analogy invokes two primary processes: one of which, creativity, seems to be a free-floating entity. The analogy between fabrication and development is therefore based on a notion of creativity as a mystical force that comes from nowhere. In contrast, the view of development and creativity that I have tried to present here is more firmly grounded.

I do not pretend that the view I have given can lead to a completely self-contained account of creativity. This is because our theories of evolution and development are themselves products of creative minds: scientific understanding is based on a creative process in which we continually come up with hypotheses and test them against observations. Our very conception of evolution therefore depends on the way our mind works and interacts with the world around us. In this sense, creativity precedes our notion of evolution. This does not mean, however, that we cannot investigate the source of our creativity. As highly creative organisms, we have the privilege of being able to question the world in which we find ourselves, including the origin of our own abilities; always accepting that the answers we obtain will be coloured by our creative outlook. The theory of evolution is the best explanation we have come up with for our biological origins. In my view, our recent understanding of development takes us a step further by providing a bridge between evolution and creativity. Rather than thinking of human creativity as a black box that exists in isolation, we can begin to see it as a process that shares features with a more general form of making— development— from which it has itself arisen.

We can also see more dearly how fabrication fits in. As creative organisms, humans have come up with a special way of making things consistently. They create a plan that is then executed. By separating plan from execution, they ensure that anyone can comprehend and follow the instructions and will end up with the same product. But although this is a convenient way for humans to arrange things, it is not the way that evolution works. Evolution is a much more interactive process which does not plan ahead, as is so aptly captured by the tinkering metaphor. This may seem rather complicated to us because we like to order things in terms of plans, but

evolution does not care about making itself easy for us to comprehend. The same applies not just to evolution but also to the processes that have arisen from it: development and creativity. The interactions of evolution pervade development and the way our own brain works. It is only in the case of fabrication that human comprehension is essential: otherwise no one could carry it out. That is why we need to separate plan from execution so clearly in this case. But we make a fundamental error when we try to impose the same sort of logic on biological processes such as development. To my mind, trying to see development in this way is reminiscent of another type of Heath Robinson contraption, the Magnetic Apparatus for Putting Square Pegs into Round Holes (Fig. 18.7).

Fig. 18.7 Magnetic Apparatus for Putting Square Pegs into Round Holes (c. 1943), Heath Robinson. Private collection.

In the light of all these considerations, why is it that comparisons between development and creative processes have been so firmly resisted in the past? I believe the answer has to do with our previous ignorance about the mechanisms of development. As long as there was no clear grasp of how development worked, comparisons with human creativity were at best unrevealing; at worst, they raised the spectre of vitalism. Predictable fabrication seemed like a much safer option. But as I have tried to show in this book, the more we have learned about development, the more we have come to see it as a highly interactive process in which there is no clear separation between plan and execution, between software and hardware, or between the maker and the made. Genes do not provide an instruction manual that is interpreted by a separate entity; they are part and parcel of the process of interpretation and elaboration. Genes both generate master proteins (hidden colours) and interpret them through their regulatory regions; they both produce signalling (scents) or

receptor (sensitivity) proteins and respond to their effects; they both influence and respond to the way cells divide, grow, move or die. In all these cases, there is a process of continual interaction and elaboration that can eventually lead to a very complex structure.

This is very similar to what happens when humans create something. We do not know the outcome in advance when we are being creative, but this does not mean that creativity comes out of the blue; it is grounded in the biological and cultural heritage of each individual. How else can we explain the fact that artists have a recognisable style? We usually have no difficulty in distinguishing Leonardo's works from those of others. What Leonardo produced was highly constrained; he could no more have produc ed a Picasso than a frogs egg could develop into a prince. Yet this does not detract from the fact the Leonardo was being fully creative when painting a picture. If we try to standardise the conditions enough, as with the example of Leonardo the amnesiac (Chapter 10), we can even imagine someone continually churning out the same sort of picture whilst at the same time being genuinely creative. Although the outcome may be reproducible, it is not arrived at by the execution of a plan.

In my view, our recent understanding of development provides the clearest example of how such a process can work, how a complex viable outcome can result without its having been manufactured according to a plan. Not only does this liberate us from misconceptions about development, but I believe that it also helps us to see creativity in a clearer light. We no longer need regard creativity as a spontaneous process that comes from nowhere. Nor do we need to go to the other extreme of seeing it as the execution of a separable plan or program in the brain. Rather, like the developmental process from which it has arisen, we can view creativity as a highly interactive process that continually interprets and builds on what went before in a historically informed manner. By coming to a better understanding of development, we have therefore arrived at a new framework for looking at ourselves.

Sources of quotations

Chapter 1

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p. 13 Collingwood, R. G. (1938). The Principles of Art, p. 21. Oxford University Press, Oxford.

Chapter 2

p. 16 MacCurdy, E. (1954). The Notebooks of Leonardo da Vinci, Vol. 2, p. 269. Reprint Society, London.

p.20 Hughes, A. (1959). A History of Cytology, p. 38. Abelard-Schuman.

p. 29 Watson, J. D. and Crick, F. H. (1953). A structure for deoxyribose nucleic acid. Nature 171,

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p. 37 Haeckel, E. (1874; trans. 1906 by J. McCabe). The Evolution of Man (5th edn), p. 11. Watts & Co., London.

Chapter 3

p.43 Stern, C. (1968). Developmental Genetics of Pattern. In Genetic Mosaics and other Essays, p. 140. Harvard University Press, Cambridge, Mass.

p.47 Richter, I. A. (1977). Selections from the Notebooks of Leonardo da Vinci, p. 182. Oxford University Press.

Chapter 4

p. 56 Goethe, J. W. (1817; trans. 1952 by B. Meuller). Natural Sciences in General; Morphology in Particular, Vol. 1, No. 1. In Goethe's Botanical Writings, p. 161. University of Hawaii Press, Honolulu.

p. 57 Goethe, J. W. (1786-1788; trans. 1970 by W. H. Auden and E. Mayer). Italian Journey, p. 366. Penguin, London.

p. 59 Rousseau, J. J. (1782; trans. 1807 by T. Martyn). Letters on the Elements of Botany, pp. 27-8. John White, London.

p. 60 Goethe, J. W. (1817; trans. 1952 by B. Mueller). Natural Sciences in General; Morphology in Particular (Vol. 1, No. 1). In Goethe's Botanical Writings, pp. 178-9. University of Hawaii Press, Honolulu.

p. 70 Goethe, J. W. (1790; trans. 1946 by A. Arber). Goethe's Botany: The Metamorphosis of Plants. Chronica Botanica (Waltham, Mass.), Vol. 10, p. 92.

p. 71 Bateson, W. M. (1894). Materials for the Study of Variation, p. 146. Macmillan, London. pp. 73, 74 From interview with E. Lewis.

Chapter 7

p.106 Kafka, E (1933; repr. 1992). Metamorphosis, p. 9. Mandarin, London.

p. 109 Doyle, A. G. (1891; repr. 1987). A Study in Scarlet, p. 15. Chancellor Press, London.

p. 110 Coleman, W. (1964). Georges Cuvier Zoologist, p. 68. Harvard University Press,

Cambridge, Mass.

p. 115 Appel, T. A. (1987). The Cuvier-Geoffroy Debate, p. 109. Oxford University Press, New York.

p. 116 Darwin, C. (1859; repr. 1968). On the Origin of Species, p. 233. Penguin, Harmondsworth, Middlesex.

p. 116 Darwin, C. (1859; repr. 1968). On the Origin of Species, p. 416. Penguin, Harmondsworth, Middlesex.

p.117 Darwin, G. (1859; repr. 1968). On the Origin of Species, p. 233. Penguin, Harmondsworth, Middlesex.

p. 119 Lawrence, P. A. (1992). The Making of a Fly, p. 218. Blackwell Scientific, Oxford. p. 120 From interview with R. Krumlauf.

Chapter 8

p.133 Coates, T. (1989) Creating a Self-Portrait, p. 56. Mitchell Beazley, London.

p. 133 Needham, J. (1934). A History of Embryology, p. 174. Cambridge University Press, Cambridge.

Chapter 9

p.146 From interview with G. NüssleinVolhard.

p. 155 Morgan, T. H. (1897). Regeneration in Allolobophora foetida. Roux Archiv für Entwickelungsmechanic der Organismen 5, p. 582.

Chapter 10

p. 174 MacCurdy, E. (1954). The Notebooks of Leonardo da Vinci, Vol. 2, p. 226. Reprint Society, London.

Chapter 11

p. 188 Needham, J. (1939). Biochemical aspects of organizer phenomena. Growth Suppl., p. 52.

Chapter 12

p. 207 Richter, L. (1909). Lebenserinnerungen eines deutchen Malers. Quoted in Gombrich, E. H. (1977). Art and Illusion, p. 55. Phaidon, Oxford.

p. 208 Hughes, P. and Brecht, G. (1975). Vicious Circles and Infinity, legend to Fig. 7. Penguin, London.

p. 221 Réamur, R. A. F. de (1712). Sur les diverses reproductions qui se font dans les Ecrevisse, les Omars, les Crabes, etc. et entr'autres sur celles de leurs lambes et de leurs Ecailles. Mere. Acad. Roy. Sci. Quoted in Skinner, D. M. and Cook, J. S. (1991). New limbs for old: some highlights in the history of regeneration in Crustacea. In A History of Regeneration Research (ed. C. E. Dinsmore) p. 31. Cambridge University Press, Cambridge.

p. 226 Popper, Karl R. (1963). Conjectures and Refutations, p. 192. Routledge and Kegan Paul, London.

Chapter 13

p. 230 MacCurdy, E. (1954). The Notebooks of Leonardo da Vinci, Vol. 1, p. 104. Reprint

Society, London.

p. 243 Gustafsson, Å. (1979). Linnaeus' Peloria: The History of a Monster. Theoretical and Applied Genetics 54, p. 242.

Chapter 15

p. 287 Goethe, J. W. (1790; trans. 1946 by A. Arber). Goethe's Botany: The Metamorphosis of Plants. Chronica Botanica (Waltham, Mass.), Vol. 10, p. 107.

p. 289 Bower, E O. (1911). Plant-Life on Land Considered in some of its Biological Aspects, p. 67. Cambridge University Press, London.

p. 302 Wittgenstein, L. (1958). Philosophical Investigations, p. 35. Blackwell, Oxford.

Chapter 16

p. 306 Conway, W. M. (trans. and ed.) (1958). The Writings of Albrecht Dürer, p. 241. Peter Owen, London.

p. 308 Thompson, D'A. (1942). On Growth and Form, p. 1085. Cambridge University Press, Cambridge.

p. 309 Woodger, J. H. (1945). On biological transformations. In Essays on Growth and Form: Presented to D'Arcy Wentworth Thompson (eds W. E. Le Gros Clark and E B. Medawar), p. 115. Clarendon Press, Oxford.

P. 309 Medawar, P. B. (1945). Size, shape and age. In Essays on Growth and Form: Presented to D'Arcy Wentworth Thompson (eds W. E. Le Gros Clark and E B. Medawar), p. 168. Clarendon Press, Oxford.

p. 310 Medawar, E B. (1945). Size, shape and age. In Essays on Growth and Form: Presented to D'Arcy Wentworth Thompson (eds W. E. Le Gros Clark and E B. Medawar), p. 185. Clarendon Press, Oxford.

p. 311 Thompson, D'A. (1942). On Growth and Form, p. 1049. Cambridge University Press, Cambridge.

p. 320 Levi-Montalcini, R. (1988). In Praise of Imperfection, p. 96. Basic Books, New York.

Chapter 17

pp. 325 Gombrich, E. H. (1950). The Story of Art, pp. 392-3. Phaidon, London.

Chapter 18

p.344 Lévi-Strauss, C. (1966; trans. 1996). The Savage Mind, p. 18. Oxford University Press. p. 345 Jacob, F. (1982). The Possible and the Actual, p. 34. Pantheon, New York.

p.347 Darwin, C. (1862). On the Various Contrivances by Which British Orchids are Fertilised by Insects, p. 283. John Murray, London.

p.349 Darwin, C. (1862). On the Various Contrivances by Which British Orchids are Fertilised by Insects, p. 284. John Murray, London.

p. 351 Darwin, C. (1868; repr. 1905). The Variation of Animals and Plants Under Domestication, Vol. 2, p. 473. John Murray, London.

p.351 Darwin, C. (1868; repr. 1905). The Variation of Animals and Plants Under Domestication, Vol. 1, p. 558. John Murray, London.

p. 358 Darwin, C. ( 1871; repr. 1901). The Descent of Man, p. 99. John Murray, London.