Janus: A Summing Up
Page 20
* For a summary of the problems posed by the evolution of the eye see, e.g. Grassé (1973). pp. 176-81 and Wolsky (1976), pp. 106 f.
Equally chilling is the idea that some ancestral reptiles became transformed into birds by the small, step-by-step changes caused by random mutations affecting different organs. In fact one gets goose-pimples at the mere thought of the number of Monod's roulette wheels which must be kept spinning to produce the simultaneous transformation of scales into feathers, solid bones into hollow tubes, the outgrowth of air sacs into various parts of the body, the development of the shoulder muscles and bones to athletic proportions, and so forth. And this re-casting of bodily structure is accompanied by basic changes in the internal systems, including excretion. Birds never spend a penny. Instead of diluting their nitrogenous waste in water, which is a heavy ballast, they excrete it from the kidneys in a semi-solid state though the cloaca. Then there is also the little matter of the transition, by 'blind chance', from the cold-blooded to the warm-blooded condition. There is no end to the specifications which have to be met to make our reptile airborne or to construct a camera eye out of living software.
To conclude this section, here is a less dramatic example of an evolutionary advance -- the seemingly modest step which led to the transformation of the amphibian egg into the reptilian egg. I have described this process in The Ghost in the Machine, and am quoting it again, because its explanation by the Darwinian schema is not only vastly improbable, but logically impossible.
The vertebrates' conquest of dry land started with the evolution of reptiles from some primitive amphibian form. The amphibians reproduced in the water, and their young were aquatic. The decisive novelty of the reptiles was that, unlike amphibians, they laid their eggs on dry land; they no longer depended on the water and were free to roam over the continents. But the unborn reptile inside the egg still needed an aquatic environment: it had to have water or else it would dry up at an early stage. It also needed a lot of food: amphibians hatch as larvae who fend for themselves, whereas reptiles hatch fully developed. So the reptilian egg had to be provided with a large mass of yolk for food, and also with albumen -- the white of egg -- to provide the water. Neither the yolk by itself, nor the egg-white itself, would have had any selective value. Moreover, the egg-white needed a vessel to contain it, otherwise its moisture would have evaporated. So there had to be a shell made of a leathery or limey material, as part of the evolutionary package-deal. But that is not the end of the story. The reptilian embryo, because of this shell, could not get rid of its waste products. The soft-shelled amphibian embryo had the whole pond as a lavatory; the reptilian embryo had to be provided with a kind of bladder. It is called the allantois, and is in some respects the forerunner of the mammalian placenta. But this problem having been solved, the embryo would still remain trapped inside its tough shell; it needed a tool to get out. The embryos of some fishes and amphibians, whose eggs are surrounded by a gelatinous membrane, have glands on their snouts: when the time is ripe, they secrete a chemical which dissolves the membrane. But embryos surrounded by a hard shell need a mechanical tool: thus snakes and lizards have a tooth transformed into a kind of tin-opener, while birds have a caruncle -- a hard outgrowth near the tip of their beaks which serves the same purpose, and is later shed by the adult animal. [27]
Now according to the Darwinian schema, all these changes must have been gradual, each small step caused by a chance mutation. But it is obvious that each step, however small, required simultaneous, interdependent changes affecting all the factors involved in the story. Thus the liquid store in the albumen could not be kept in the egg without the hard shell. But the shell would be useless, in fact murderous, without the allantois and without the tin-opener. Each of these changes, if they had occurred alone, would have been harmful, and the organisms thus affected would have been weeded out by natural selection (or rather, as suggested above, by 'natural elimination'). You cannot have an isolated mutation A, preserve it over an incalculable number of generations until mutation B occurs in the same lineage and so on to C and D. Each single mutation would be wiped off the slate before it could be combined with all the others. They are all interdependent within the organism -- which is a functional whole, and not a mosaic. The doctrine that the coming together of all requisite changes was due to a series of coincidences is an affront not only to common sense but to the basic principles of scientific explanation. In a recently published major work, Professor Pierre Grassé (who, for thirty years, held the chair for evolution at the Sorbonne without losing his Gallic wit) commented:
Where is the gambler, however obsessed with his passion, who would be crazy enough to bet on the roulette of random evolution? The creation, by grains of dust carried by the wind, of Dürer's Melancholia has a probability less infinitesimal than the construction of an eye through the mishaps which might befall the DNA molecule -- mishaps which have no connection whatsoever with the future functions of the eye. Daydreaming is permissible, but science should not succumb to it. [Grassé's italics] [28]
4
When we talk about the evolution of species, we mostly have the emergence of new forms and physical structures in mind, as we see them displayed in museums of natural history. But evolution creates not only new shapes; it also creates new types of behaviour, new instinctual skills which are innate and hereditary. If the forces behind the emergence of new structures are obscure, those behind the evolution of innate skills are shrouded in total darkness. As Nobel laureate Niko Tinbergen lamented: 'The backward position of ethology is striking . . . A genetics of behaviour still has to be developed.' [29]
The reason for this is simple: neo-Darwinism does not possess the theoretical tools to tackle the problem. The only explanation it has to offer for the incredibly complex instinctual skills of animals is that these too are produced by random mutations somehow affecting the neural circuitry in the animal's brain and nervous system, which are then preserved by 'natural selection'. It would be a wholesome exercise for graduate students in biology to repeat this explanatory formula like a Sanskrit mantra while watching a spider constructing its web, a blue-tit shaping its nest, a badger constructing a dam, an oyster-catcher carrying its prey skyward and dropping it on a hard rock, the social activities in the welfare state of the honey-bee, and so on. One could fill a library with illustrations of the staggeringly complex patterns of instinctual activities of various species of animals which defy any explanation in terms of the Darwinian mantra. I shall quote one of the less well-known examples from Tinbergen:
A female of this species [the so-called digger wasp], when about to lay an egg, digs a hole, kills or paralyses a caterpillar, and carries it to the hole, where she stows it away after having deposited an egg on it (phase a). This done, she digs another hole, in which an egg is laid on a new caterpillar. In the meantime, the first egg has hatched and the larva has begun to consume its store of food. The mother wasp now turns her attention again to the first hole (phase b), to which she brings some more moth larvae; then she does the same in the second hole. She returns to the first hole for the third time to bring a final batch of six or seven caterpillars (phase c), after which she closes the hole and leaves it forever. In this way she works in turn at two or even three holes, each in a different phase of development. Baerends investigated the means by which the wasp brought the right amount of food to each hole. He found that the wasp visited all the holes each morning before leaving for the hunting grounds. By changing the contents of the hole and watching the subsequent behaviour of the wasp, he found that (1) by robbing a hole he could force the wasp to bring far more food than usual; and (2) by adding larvae to the hole's contents he could force her to bring less food than usual. [30]
But another wasp, Eumenes amedei, goes still one better. The somewhat gruesome description which follows is borrowed from Darwin Retried by Norman Macbeth: *
The egg is not laid upon or among the caterpillars, as in many allied species. These caterpillars are on
ly partially paralysed, and can still move their claws and champ their jaws. Should one of them feel the nibblings of the tiny grub, it might writhe about and injure the grub. Both the egg and the grub must be protected, and to this end the egg is suspended by a tiny thread of silk fastened to the roof. The caterpillars may wriggle and writhe, but they cannot come near it. When the grub emerges from the egg, it devours its eggshell, then spins for itself a tiny silken ribbon-sheath in which it is enfolded tail-uppermost and with head hanging down. In this retreat it is suspended above the pile of living food. It can lower itself far enough to nibble at the caterpillars. If they stir too violently it can withdraw into its silken sheath, wait until the commotion has subsided, then descend again to its meal. As the grub grows in size and strength, it becomes bolder; the silken retreat is no longer required; it can venture down and live at its ease among the remains of its food. [31] * This brilliant treatise by a Harvard lawyer highlights the shortcomings and inconsistencies of the neo-Darwinian theory. Sir Karl Popper called it a 'most meritorious and really important contribution to the debate'.
At this point, I think, the mantra loses its hypnotic power even over pious neo-Darwinists. As Tinbergen said: 'A genetics of behaviour still has to be developed.' But the synthetic theory is unable to provide the tools for it.
5
How could a doctrine which in effect begged all the basic questions gain general acceptance among biologists and be considered as gospel truth by the public? (The same question might be asked about behaviourism.) Part of the answer is again found in von Bertalanffy:
I think the fact that a theory so vague, so insufficiently verifiable and so far from the criteria otherwise applied in 'hard 'science, has become a dogma, can only be explained on sociological grounds. Society and science have been so steeped in the ideas of mechanism, utilitarianism and the economic concept of free competition, that instead of God Selection was enthroned as ultimate reality. [32]
This is no doubt part of the answer, but other factors also enter into it. First, the theory contained a basic truth: the fossil record testified that evolution was a fact, that Darwin was right and Bishop Wilberforce was wrong, so Darwinism became something of a credo for all enlightened, progressive people, while the details of the theory could be left to the experts.
The experts, however, including Darwin himself, soon ran into trouble. There is a little-known episode in the early history of Darwinism which is pertinent to our theme.* In 1867, eight years after the publication of The Origin of Species, a professor of engineering at Edinburgh University, Fleeming Jenkin, published an article which amounted to a complete refutation of Darwin's theory. [33] Jenkin demonstrated, by an astonishingly simple logical deduction, that no new species could ever arise from chance variations by the mechanisms of heredity accepted at the time. For the theory of heredity, in Darwin's day, was based on the assumption that the native endowment of the newborn was an alloy or 'blend' of the characteristics of the parents, to which blend each parent contributed approximately one half. Darwin's own cousin, Francis Galton, gave a mathematical formulation to this 'law of ancestral inheritance', as it was called. Assuming now that an individual endowed with a useful chance variation (later to be called a random mutation) cropped up within the species, and mated with a normal partner (i.e., with one of the vast majority of the population), then their offspring would inherit only 50 per cent of the useful new characteristic, the grandchildren only 25 per cent, the great-grandchildren 12.5 per cent, and so on, until the hopeful novelty vanished like a drop in the ocean, long before natural selection had a chance to make it spread.
* The following is a condensed version of the account of this episode in The Case of the Midwife Toad, pp. 52 f.
It is remarkable, as Sir Alister Hardy wrote [34], that 'the great brains of the Victorian era' did not notice the basic logical fallacy which Jenkin pointed out. Darwin himself was so shaken that he inserted a whole new chapter in the sixth edition of The Origin, in which he resuscitated the Lamarckian theory of evolution through the inheritance of acquired characteristics which earlier he had described as 'a load of rubbish', and which is still anathema to Darwinists. As his letters to Wallace indicate, he saw no other way out.* But Darwin's followers ignored the master's relapse into the Lamarckian heresy (which, anyway, did not provide the required answers), and during the last decades of the nineteenth century Darwinism had run into a dead end -- although the public was unaware of it. The leading English Darwinist at the time, William Bateson, wrote in retrospect: 'In the study of evolution progress had well-nigh stopped. The more vigorous, perhaps the more prudent, had left this field of science.' [36]
* His son, Francis Darwin, later commented: 'It is not a little remarkable that the criticisms, which my father, as I believe, felt to be the most valuable ever made on his views, should have come, not from a professed naturalist but from a Professor of Engineering, Mr Fleeming Jenkin.' [35] Yet the sixth edition does not even mention his name.
In the year 1900, however, by an unexpected and dramatic turn of events, the crisis was resolved -- or so it seemed at the time; the clouds vanished, and Darwinisin became transformed into neo-Darwinism.
This crucial event was the rediscovery of a paper called 'Experiments in Plant Hybridisation' by the Augustine monk Gregor Mendel, published in 1865, in the Proceedings of the Natural History Society of Brünn (now Brno) in Moravia. Thirty-five years later, long after Mendel's death, this paper was unearthed almost simultaneously and independently, by three biologists in three different countries (Tschermak in Vienna, de Vries in Leyden, Correns in Berlin). Each had been searching the literature for some clue to indicate the way out of the cul-de-sac, and each saw immediately the significance of Mendel's hybrid garden peas -- which, like Newton's apple, were to become an integral part of science-lore. Mendel's experiments showed that the 'units of heredity' -- later to be called genes -- which determined the colour, size, and other features of his plants, did not 'blend' and thus become diluted; they were rather like hard, stable marbles which combined into a variety of mosaic patterns, but preserved their identity and were transmitted unchanged and intact to subsequent generations -- even though the effect of 'recessive' genes was masked if they were paired with 'dominant' ones.
Here, at long last, was the answer to Jenkin's crucial objection. For it could now be assumed that whenever a chance mutation occurred it would not be whittled away through blendings, but would be preserved in successive generations and thus give 'natural selection' a chance to pick and choose.
Now everything was falling into place. Every single factor determining a hereditary trait was contained in a Mendelian gene, and every gene had its allotted place in the chromosomes in the cell-nucleus, like beads on a string. Evolution no longer had any secrets -- or so it seemed. Bateson, instantly cured of his despair when he read Mendel's paper in a railway carriage, gave his youngest son the name Gregory, in honour of the Bohemian monk. 'Only those', he wrote twenty years later, 'who remember the utter darkness before the Mendelian dawn, can appreciate what happened.' [36]
The details of Mendelism do not concern us here, only its impact on the theory of evolution. It turned out to be decisive.
Bateson was the first to show that Mendel's laws of inheritance applied to plant and animal alike. He experimented on poultry; but the favourite experimental subject of the new science of genetics was the small fruit-fly Drosophila melanogaster, which propagates very fast and has only four pairs of chromosomes. This made it possible to apply statistical methods to the study of hereditary variations among large populations of the fly caused by spontaneous or artificially induced mutations (by irradiation, heat, etc.). In its own limited field, the science of genetics was immensely successful, and still is. But it took a long time for the more thoughtful among its practitioners to realize that their labours, while providing new insights into the mechanisms of minor hereditary variations, had little or no relevance to the basic problem of evolution: the origin an
d why and how of the major steps up the evolutionary ladder, the emergence of higher life-forms and new life-styles. In the words of Pierre Grassé who, let us remember, held the chair of evolution for thirty years at the Sorbonne (italics in the original):
Variation is one thing, evolution quite another: this cannot be emphasised strongly enough . . . [37] Let us repeat it once more: mutations do not provide an explanation for the nature or temporal order of the phenomena of evolution; they do not create evolutionary novelties; they cannot account for the precise fitting together of the parts of an organ, and the mutual co-ordination of organs . . . [38] Mutations provide change, but not progress . . . [39] The repertory of mutations, or mutation-spectrum of a species has nothing to do with evolution. The 'Jordanons' (equivalents of mutations) of the whitlow grass (Erophila verna); of the wild pansy (Viola tricolor); of the Plantains (Plantago); of the candytuft (Iberis), which add up to a rich and well-catalogued assortment, are the irrefutable proof of it. When all is said, Erophila verna, Viola tricolor, etc., despite their numerous mutations, do not evolve. This is a fact. The various races of dogs, and of all the other domesticated animals, represent merely the mutation spectrum of the species, manipulated by artificial selection. The same applies to garden plants. Nothing in all this amounts to an evolution. [40]