... the vast number of existing animal species (about one million) and the small number of major classes (about fifty) and of major phyla or divisions (about ten), could be compared with the vast number of works of literature and the small number of basic themes or plots. All works of literature are variations on a limited number of leitmotifs, derived from man's archetypal experiences and conflicts, but adapted each time to a new environment -- the costumes, conventions and language of the period. Not even Shakespeare could invent an original plot. Goethe quoted with approval the Italian dramatist Carlo Gozzi*, according to whom there are only thirty-six tragic situations. Goethe himself thought that there were probably even less; but their exact number is a well-kept secret among writers of fiction. A work of literature is constructed out of thematic holons. [7] * Author of Turandot and many other successful works.
But there is still plenty of scope left for the writer to make what he can out of Gozzi's meagre list of thirty-six themes. And there is plenty of scope for evolutionary strategies to make the best of the limited possibilities inherent in the physico-chemical structure of living matter as it exists on earth -- and presumably on other planets where conditions are similar to those on earth. We shall return to this speculative subject later on.
4
It may be objected that to talk of the 'strategy of evolution' means falling into the trap of anthropomorphism -- attributing human motivations to nature. In fact the approach suggested here should rather be called 'biomorphic', because it is based on the purposeful aspects inherent in the phenomena of life, as opposed to the 'robotomorphic' approach of reductionism. Science ought not to be afraid of applying the terms 'purpose' and 'strategy' to evolution; they do not imply that there is a divine Strategist at work. Yet it is precisely this unjustified fear that has muddied the controversy and landed the orthodox theorists in a morass of contradictions. To quote once more a representative spokesman, Professor G. G. Simpson, evolution' . . . turns out to be basically materialistic, with no sign of purpose . . . and with any possible Purposer pushed back to the incomprehensible position of First Cause . . . Man is the result of a purposeless and materialistic process that did not have him in mind. He was not planned.' [8]
Here the logical fallacy, based on a spurious alternative, is explicitly revealed: evolution is either purposeless or there must be a divine Purposer at work. One wonders how it comes to pass that naturalists, once they specialize in genetics, become so blind to nature that they fail to see purposiveness as a fundamental characteristic of life which does not require the postulate of a Purposer because it is inherent in the concept of life itself; or -- to quote Sinnott -- because purpose is 'the directive activity shown by individual organisms that distinguishes living things from inanimate objects'. [9] The term 'purposiveness', applied to a living organism, means goal-directed instead of random activity; flexible strategies to attain a goal instead of rigid, mechanized responses; adapting to the environment, but on the organism's own terms, often in rather fanciful ways like the orchid or the butterfly; and adapting the environment to its own needs. Or, as the Nobel laureate H. J. Muller wrote: 'Purpose is not imported into nature, and need not be puzzled over as a strange or divine something else that gets inside and makes life go . . . it is simply implicit in the fact of biological organization." [10]
Thus it has now become more or less respectable to talk of purpose or directiveness in ontogeny, that is, the individual's development during its life -- history; but it is still considered heretical to apply the same terms to phylogeny, that is, the history of evolution. Ontogeny is purposive, phylogeny blind; ontogeny is guided by memory and learning, phylogeny is unaffected by either of them. Yet we have seen that the more thoughtful among the neo-Darwinians feel increasingly unhappy about this artificially created chasm, and have started to build bridges across it -- such as Monod's 'teleonomy', or the concept of genetic micro-hierarchies which filter and coordinate hereditary changes. Simpson himself, in spite of his dogmatism, was led to realize that phylogeny is an abstraction unless regarded as a sequence of ontogenies, and that 'the course of evolution is through changes of ontogenies'. But if ontogenies are purposeful, it is difficult to see why their summation should be purposeless -- unless we subscribe to the Weismann-Crick dogma of the 'unalterable germ-track' (which would be the only example found in nature of a biological process devoid of feedback).
Thus the hoary conundrum about the Purposer behind the purpose can be laid to rest. The Purposer is each and every individual organism from the inception of life, which struggled and strove to make the best of its limited possibilities; and the sum total of these ontogenies reflects the active striving of living matter towards the optimal realization of the planet's evolutionary potential.
5
The emphasis in the last paragraph was on 'active striving'. When orthodox evolutionists talk of 'adaptations', they mean -- as behaviourists do when they talk of 'responses' -- a basically passive process, entirely controlled by 'the contingencies of the environment'. This may suit their philosophy, but is certainly not in keeping with the evidence which shows, in G. E. Coghill's phrase, that 'the organism acts on the environment before it reacts to it'. [11] Almost from the moment a creature is hatched or born, it lashes out at the environment, be it liquid or solid, with cilia, flagellae, or muscles; it swims, crawls, glides, pulsates; it kicks, yelps, breathes, feeds on the environment. It does not merely adapt to the environment but adapts the environment to its own needs -- it eats and drinks its environment, fights and mates with it, burrows and builds in it; it does not merely 'respond' to the environment, but asks questions by exploring it. Let us remember (Chapter VII, 2) that the 'exploratory drive' is a primary instinct, as basic as hunger and sex, and can occasionally prove even more powerful then these. Countless naturalists, starting with Darwin himself, have shown that curiosity is an instinctual urge in rats, birds, dolphins, monkeys, etc.; and we have seen that it is the main driving force which motivates artists and scientists alike. Thus the exploratory drive is a dominant factor in man's mental evolution; and it has been suggested, by Hardy and others, that it may also be a dominant factor in biological evolution. In this view, evolutionary progress is based on the initiative of some enterprising individuals in the species, who discover a new method of feeding, or self-protection, or some new skill which, spreading by imitation, is incorporated into the species's way of life. To illustrate the process, Hardy cites as an example, one of 'Darwin's finches' on the Galapagos islands, C. pallidus. This remarkable bird pecks holes or crevices into the bark of trees, and 'having excavated, it picks up a cactus spine or twig, one or two inches long, and holding it lengthwise in its beak, pokes it up the crack, dropping the twig to seize the insect as it emerges. . . . Sometimes the bird carries a spine or twig about with it, poking into cracks and crannies as it searches one tree after another.' [12]
After describing a number of similar examples, Hardy suggests that the main causative factor of evolutionary progress is not the selective pressure of the environment, but the initiative of the living organism -- 'the restless, exploring and perceiving animal that discovers new ways of living . . . It is adaptations which are due to the animal's behaviour, to its restless exploration of its surroundings, to its initiative, that distinguish the main diverging lines of evolution . . . giving the lines of runners, climbers, burrowers, swimmers and conquerors of the air.' [13]
One might call this the 'progress-by-initiative' theory of evolution. The pioneers of the species initiate a new habit, a change in behaviour, which spreads through the population and is copied by successive generations -- until a lucky chance-mutation transforms it into a hereditary instinct. Thus the process is initiated by the animal, and the lucky mutation comes only afterwards, as a kind of genetic endorsement which incorporates the new skill into the genetic blueprint. The role of chance has been further reduced; the monkey at the typewriter needs only to go on trying until he hits a pre-specified key.
When I wrote The G
host in the Machine I found this theory rather attractive, but on second thoughts it reveals a crucial flaw, in still relying -- though to a lesser extent than the orthodox theory -- on random mutations to achieve the fantastically complex changes in the nervous system that are needed in order to insert a new habit or skill into the organism's native equipment. The emphasis on initiative, on the active role of the exploring animal remains attractive, but the basic riddle of the ostrich's callosities or the spider's architectural brilliance is left unsolved. From a methodological point of view it seems preferable to assume that the insect-hunting skill of Darwin's finch became impressed on its chromosomes by some unknown process because it was useful -- that is, by Lamarckian inheritance -- instead of invoking once more the Darwinian mantra.
6
Evolution, as seen through human eyes, appears as a shockingly wasteful process. Biologists take it for granted that for every one of the existing one million species, hundreds must have perished in the past; and those lines which have survived seem to have become stagnant, their evolution having come to a standstill in the far-distant past. The principal cause of both extinction and stagnation appears to have been over-specialization with its concomitant loss of adaptability to changes in the environment. Julian Huxley has compared evolution to a maze with an '. . . enormous number of blind alleys with a very occasional path to progress . . . All reptilian lines were blind alleys save two -- one which was transformed into birds, and another which became the mammals. Of the bird stock, all lines came to a dead end; of the mammals all but one -- the one which became man.' [14]
The human paradigm of over-specialization is the pedant, the slave of habit, whose thinking and behaviour move in rigid grooves -- a predestined victim of any unexpected calamity. His equivalent in the animal kingdom is the pathetic koala bear, which specializes in feeding on the leaves of a particular variety of eucalyptus tree and on nothing else; and which has hook-like claws, ideally suited for clinging to the bark of the tree -- and for nothing else. All orthodoxies tend to breed human koalas.
One line of escape from the maze of blind alleys is of particular relevance to our theme: a phenomenon which goes under the name of 'paedomorphosis'. It was described by Garstang in the 1920s, and taken up by several biologists*; but although the existence of the phenomenon is generally accepted, it made little impact on the orthodox theory and is rarely mentioned in the textbooks. It indicates that at certain critical stages evolution can retrace its steps, as it were, along the path which led to the dead end and make a fresh start in a new, more promising direction. The crucial event in this process is the appearance at the foetal, larval or juvenile stage of some useful evolutionary novelty which is carried over into the adult stage of the organism's progeny. The following example will show what is meant:
There is fairly good evidence in favour of the hypothesis that the chordates -- and thus we, the vertebrates -- are descended from the larval stage of some primitive echinoderm, rather like the sea urchin or sea cucumber [echinoderm = 'prickly-skinned']. Now an adult sea cucumber would not be a very inspiring ancestor -- it is a sluggish creature which looks like an ill-stuffed sausage with leathery skin, lying on the sea bottom. But its free-floating larva is a much more promising proposition: unlike the adult sea cucumber, the larva displays bilateral symmetry like a fish; it has a ciliary band -- a forerunner of the nervous system -- and some other sophisticated features not found in the adult animal. We must assume that the sedentary adult residing on the sea bottom had to rely on mobile larvae to spread the species far and wide in the ocean, as plants scatter their seeds in the wind; that the larvae, which had to fend for themselves, exposed to much stronger selective pressures than the adults, gradually became more fish-like; and that eventually they became sexually mature while still in the free-swimming, larval state -- thus giving rise to a new type of animal which never settled on the bottom at all, and altogether eliminated the senile, sedentary cucumber stage from its life history. [16] * Among them Hardy and de Beer in England, Koltsov and Takhtajan in the Soviet Union. [15]
Now this lowering of the age of sexual maturity is a well-known evolutionary phenomenon called neoteny. It has two aspects: the animal starts to breed while still in a larval or juvenile stage; and it never reaches the fully adult stage, which is dropped off -- eliminated from its life cycle ('terminal abbreviation'). Thus the ancestors' juvenile stages of development become the definite condition of their descendants, while the ancestors' mature characteristics have fallen by the roadside. What this amounts to is a process of 'juvenilization'* and de-specialization -- a successful escape from a dead-end in the evolutionary maze. As J. Z. Young wrote, commenting on Garstang's views:
The problem which remains is in fact not 'how have vertebrates been formed by sea-squirts?', but how have vertebrates eliminated the [adult] sea -- squirt stage from their life history? It is wholly reasonable to consider that this has been accomplished by paedomorphis. [17] * A term proposed by Julian Huxley (1952), p. 532.
Sir Gavin de Beer compared the process to the re-winding of a biological clock when evolution is in danger of running down and coming to a standstill: 'A race may become rejuvenated by pushing the adult stage of its individuals off from the end of their ontogenies, and such a race may then radiate out in all directions.' [18]
The record from palaeontology and comparative anatomy does indeed suggest that this retracing of steps to escape from the blind alleys of over-specialization was repeated at each major evolutionary turning point. I have mentioned the evolution of the vertebrates from the larval stage of some primitive echinoderm. Hardy and Koltsov [19] have given numerous other examples and Takhtajan [20] has shown that paedomorphosis is also a common occurrence in the evolution of plant life. Insects have in all likelihood evolved from a millipede-like ancestor -- not, however, from its adult form, whose structure is too specialized, but from its larval form. The conquest of the dry land was pioneered by amphibians whose ancestry can be traced back to some primitive type of lung-breathing fish, whereas the later lines of highly specialized gill-breathing fishes came to a dead end. The examples could be multiplied; but the most striking case of paedomorphosis is the evolution of our own species.
Since Bolk's pioneering work, published in 1926, it is now generally accepted that the human adult resembles the embryo of an ape rather than an adult ape.
In both simian embryo and human adult, the ratio of the weight of the brain to total body weight is disproportionately high. In both, the closing of the sutures between the bones of the skull is retarded to permit the brain to expand. The back-to-front axis though man's head -- i.e., the direction of his line of sight -- is at right angles to his spinal column: a condition which, in apes and other mammals, is found only in the embryonic, not in the adult stage. The same applies to the angle between backbone and uro-genital canal -- which may account for the singularity of the human way of copulating face to face. Other embryonic -- or, to use Bolk's term, foetalized -- characteristics in adult man are: the absence of brow-ridges; the scantiness and late appearance of body hair; pallor of the skin; retarded growth of the teeth, and a number of other features . . . [21]
The 'missing link' between ape and man will probably never be found -- because it was an embryo.
7
Paedomorphosis -- or juvenilization -- thus appears to play an important part in the grand strategy of evolution. It involves a retreat from specialized adult forms to earlier, less committed and more plastic stages in the development of organisms -- followed by a sudden advance in a new direction. It is as if the stream of life had momentarily reversed its course, flowing uphill for a while towards its original source; then opened up a new stream-bed -- leaving the koala bear stranded on his tree like a discarded hypothesis. In other words, we are faced here with the same pattern of reculer pour mieux sauter, 'step back to leap', which we have encountered at the critical turning points in the evolution of science and art. Biological evolution is to a large extent a h
istory of escapes from the blind alleys of over-specialization, the evolution of ideas a series of escapes from the tyranny of mental habits and stagnant routines. In biological evolution the escape is brought about by a retreat from the adult to a juvenile stage as the starting-point for the new line; in mental evolution by a temporary regression to more primitive and uninhibited modes of ideation, followed by the creative forward leap (the equivalent of a sudden burst of 'adaptive radiation'). Thus these two types of progress -- the emergence of evolutionary novelties and the creation of cultural novelties -- reflect the same undoing -- redoing pattern and appear as analogous processes on different levels.
Neither biological evolution nor cultural progress follows a continuous curve. Neither of them is strictly cumulative in the sense of continuing to build where the previous generation had left off. Both progress in the zigzag fashion described in Chapter VIII. The advance of science is continuous only during those periods of consolidation and elaboration which follow a main breakthrough or 'paradigm-change'. Sooner or later, however, consolidation leads to increasing rigidity, orthodoxy, and so into the blind alley of over-specialization -- the equivalent of the Irish elk or the koala bear. But the new theoretical structure which emerges from the breakthrough is not just added to the old edifice; it branches out from the point where the evolution of ideas has taken the wrong turn. The great revolutions in the history of science have a decidedly paedomorphic character. In the history of literature and art, the zigzag course is even more in evidence: we have seen how the periods of cumulative progress within a given 'school' or technique end inevitably in stagnation, mannerism or decadence, until the crisis is resolved by a revolutionary shift in sensibility, emphasis, style.