10.1.1.
When some of the débris orbiting a nascent sun coalesced to form planet Earth the most experientially advanced organism upon it was a small molecule. Today, some 4,500 million years later, it is a human being. In general terms, how did the one evolve from the other? Our current orthodoxy has its confident answer: it evolved via a long series of small accretive changes, in which process nothing more was involved than the laws and forces of physics and chemistry as conventionally understood. At one end of the evolutionary process we have our own experience - our perceptions, thoughts, feelings, volitions, imaginings, memories etc.. At the other, the inanimate world as conceived by our current mathematico-mechanistic physics. And according to orthodoxy the one is no more than the other operating in ultra-complex situations that it has itself built up over the aeons.

10.1.2.
Not surprisingly, there have always existed biologists who have refused to accept this answer, rightly regarding it as self-evidently absurd. However, the great majority of these have no quarrel with orthodox physics; no less than the materialists they accept this as a substantially true account of the insentient, inanimate world. But a minority of them invoke some other substance (mind) not at work in this world, and hence peculiar to living things, to account for life. And they generally endow this with some built-in nisus or teleological urge in order to account for what, to us humans, seems the outstanding attribute of evolution: the tendency of the biological world to give rise to ever more experientially complex organisms with the passage of time. These biologists are the dualists or vitalists, and I need hardly say that the irremediable shortcomings of their theories have countless times shown them to be only marginally less absurd than those of mechanistic orthodoxy. Which is only what one might expect; once mechanistic physics (and in the rare instances when it succeeds in saying anything physically meaningful, our mathematically dominated 'new' physics is still purely mechanistic) has been accepted as a substantially true account of the physical world, of necessity, living organisms and their evolution present an insoluble problem.

10.1.3.
More intellectually respectable are the organicists or Systems Theorists. These have proposed no new physics, but in view of the obvious fact that mere mechanically determined feedback is ludicrously incapable of accounting for living organisms, to say nothing of their evolution, they claim that this gives biologists the right to formulate their own basic laws, grounded on the biological facts, independently of physical laws, and to leave to future generations any ontological reconciliation of the two sets. The essence of this organismic position is the claim that a whole, qua whole, must somehow, as a superordinate entity in its own right, act back upon the parts in such way as to bias their movements towards maintaining itself as a viable system. In our present state of knowledge, the organicist claims, one just has to accept this as an empirically established fact. We have already (4.5.3.) provided one quote from Errol E. Harris on this; here is another:

 

“It [the cell] is no mere aggregate of chemical compounds or of synthetic processes in equilibrium (though, of course, it is both), but is a systematically structured, organised and temporally ordered web of chemical interaction regulating itself for self-maintenance and displaying an (as yet) scientifically inexplicable nisus towards order and elaboration of coherent structure that runs counter to thermodynamic probability."¹

There are hundreds, if not thousands, of quotes saying essentially the same thing in different words. We will content ourselves with two from Paul Weiss²:

 

“Thus, in contrast to the infinite number of possible interactions and combinations among its constituent units which could take place in a mere complex, in the living system only an extremely restricted selection from that grab-bag of opportunities for chemical processes is being realized at any one moment – a selection which can be understood solely in its bearing on the concerted harmonious performance of a task by the complex as a whole. This is the feature that distinguishes a living system from a dead body ...”

“ ... the acknowledgement of field continua as ordering principles in systems on the integral level is as valid and indispensable as is the practical acceptance, on the differential level, of discrete singularities within these continua, whether sub-atomic particles, atoms, molecules, molecular assemblies, organelles, cells, or cell assemblies ... I have yet to encounter any phenomena in the living system which could be adequately described without reference to such a dualistic scheme.”

It is worth emphasising here that if the organicist contended that the ultimate parts of organisms are much as the physicist conceives them, he would be talking nonsense. It is just because he is contending that physics has not yet attained to a true understanding of these parts that the organicist can legitimately make the claims he does. As for evolution, since the wholeness of any organism, however complex, is just a natural attribute like any other, there is no reason why, in conjunction with genetic mutation, replicative reproduction and Darwinian selection, more complex wholes, if they possess some survival advantage - as in some classes of organism they frequently do - should not evolve on to increasingly elaborate levels of complexity.

10.1.4.
The next level in the ascent towards truth is defined by those organicists who, from such attributes of living organisms as memory, habit, and instinct, and the recapitulation of phylogeny in ontogeny, postulate that the past is still in some way active, and exerts a force directly on the present organism: that is, by definition of a force, causes the material particles of which the organism is made to accelerate. Physical orthodoxy acknowledges no such force - gravitation, electromagnetic attractions and repulsions, and nuclear forces, strong and weak, making up its whole inventory. By invoking a still active past, every thinker of this persuasion - from Herbart, through von Hartmann, Bergson and Geley to Rupert Sheldrake – has certainly taken a step in the right direction; but because none has ever succeeded in constructing a physics which coherently incorporates this active past, none has succeeded in formulating a remotely satisfactory theory of how the past could act within the present.

10.1.5.
We, of course, claim to have done precisely this; that is, as outlined in the preceding chapters, developed this true or noumenal - as opposed to merely phenomenal - physics: a physics in which, above all, the past persists, and which, through sympathic association and mnemic causation, is active in the physical present. From a physical world so conceived the whole biological world from pre-cellular organisms to the advent of homo sapiens, can be rationally derived. And it is such a derivation - inevitably in the most general terms - that is attempted in this and the three following chapters. Now, despite the fact that conventional biological wisdom, as embodied in Neo-Darwinism, is unable to furnish a rationally coherent account of even the simplest living organism, this has proved no hindrance to its unearthing a vast, detailed, precisely formulated and – albeit on a naively realistic conceptual level - systematically organised body of observational and experimental fact. So much is this the case, that what I am advancing as a true account of experiential evolution may legitimately be viewed as a synthesis of noumenal physics and Neo-Darwinism: that is, Neo-Darwinism incorporated within an ontologically coherent conceptual schema. We may therefore take the great truths of Neo-Darwinism as read and concentrate on everything that conventional biology, grounded as it is on a radically false physics, is incapable of explaining: basically, all those essential attributes of living organisms and their evolution that derive from the preserved past, sympathic association, mnemic causation, and paraphysical sequences. This perfectly exemplifies what I wrote earlier (2.4.) about cosmology's two methods - ontology (metaphysics) and science – complementing one another: the strengths of each compensating for the other’s deficiencies.

 

THE COMPLEXIFICATION OF EXPERIENCE

10.2.1.
A point worth making at the outset is that complexity, as such, causes nature no problems. As organisms grow more complex they show no sign of an increasing tendency to break down. Complex organisms function as naturally as simple - a cat no less efficiently than a cucumber. All this is rooted in the fact that there is no limit to the number of qualification sequences that sympathic association and mnemic causation are capable of ordering.

10.2.2.
With this in mind, how, in broad terms, do we account for the evolving complexity of experience from small molecules to human beings? We account for it in terms of only five basic parameters.
Firstly, of course, there is all that arises as a consequence of our noumenal physics: qualification sequences, a preserved past, its sympathic association with the ongoing present, mnemic causation, and paraphysical sequences.
Secondly, Darwinian selection. All successful species live by responding to their environment – part inanimate, part composed of members of their own and other species – in such way as to at least maintain their numbers. That is, all species are obliged to create a viable ecological niche, or perish.
Thirdly, breeding true. Organisms must be able to reproduce replicatively: to produce offspring which closely resemble themselves in all respects. Otherwise no changes, however advantageous, could be passed on down the generations.
Fourthly, intra-specific variation. The members of a species, while resembling one another in all essential respects, must yet exhibit within these limits, considerable variation. Otherwise, there would be nothing for selection to work on by way of adapting a species to changing environmental conditions.
Fifthly, environmental variation. All over the planet, owing fundamentally to plate tectonics, but subsidiarily to the activities of living organisms, the inanimate environment, solid, liquid, and gaseous is in a constant state of change, gradual or rapid, minor or major. Temperature and precipitation, the chemical constitution of the atmosphere, the land/sea interface, volcanic and seismic activity, mountain building and so forth - fluctuations in these parameters give rise in course of time, at innumerable geographical locations, to many significant changes. Species must respond adaptively to such changes or perish, thereby producing yet further changes in the environment of other species belonging to the same ecosystem.

10.2.3.
With these five parameters at work there is certainly no need whatever to postulate some inbuilt orthogenetic nisus driving life on to ever greater complexity. Certainly, we owe the very possibility of experiential complexity to a physical world such as I am postulating. A physical world as conceived by orthodoxy could not conceivably give rise to even the simplest living organism. But this in no way implies that in our system there is any inbuilt evolutionary drive towards greater complexity. The opposite if anything, since the outstanding consequence of sympathic association and mnemic causation is repetition not innovation – as we see in such universal dispositions as instinct and habit. What our noumenal physics does imply is that organisms can comfortably exist, and consolidate themselves as a species, at any level of experiential complexity. Inevitably, therefore, they are sometimes only a small step away from an eco-niche requiring yet greater experiential complexity. What causes this step to be taken?

10.2.4.
To answer this satisfactorily, we must bear in mind a number of basic parameters germane to all such situations. Firstly, that the sole necessary requirement for the establishment of a new species is its viability in the face of Darwinian selection pressures. Secondly, that complexity of experience is only one among innumerable biological attributes making for such viability. Thirdly, that every new species arises as a result of an accumulation of small changes to some already existing species. From this it follows that new heights of experiential complexity must arise as a consequence of small changes (mutations) to the genome of a species whose viability is grounded on experiential complexity. The basic cause of the arising of new species is environmental change of one kind or another – topographical, climatic, or biological. No environment is unchanging: there are only degrees of change, in terms of magnitude, range or rapidity. But whatever the cause, to such changes all species of the ecosystem affected must adapt or perish. And such adaptation occurs as a result of Darwinian selection acting upon the variations among the members of a species, these phenotypal variations being, themselves, the consequence of small genotypal mutations. The phenotypal variants within this gene pool offering the greatest survival advantage under these changed conditions may well be significantly different from those which offered it under the old. As a consequence they will gradually replace these as the species’ norm. Sometimes, to such an extent that the old species, as an interbreeding pool, splits into two. That is, a new species is born. And it will sometimes be the case that among species whose viability is grounded in complexity of experience, there will arise in this way new species that are experiencing more complexly than the old. Clearly, it is inherently probable that a wider range of perception, a more varied behavioural repertoire, a richer collaboration between perception and memory, more accurate anticipation, and so on, may all offer better chances of survival for an organism whose viability is predicated upon experiential complexity.

10.2.5.
Further, it is an attribute of experiential complexity that it tends to feed on itself – that is, that a degree of positive feedback is inherent in it. In an ecosystem, every species is part of the environment of every other, changes in one species resulting in changes in others, a whole wave of species changes tending to spread through the ecosystem until it has settled into a new stability. And much of this interdependence is of a competitive nature – in the struggle for available resources, or even in the direct conflict of predator and prey. Any increase in experiential complexity of one species opens up a new eco-niche for any other species of the ecosystem sufficiently advanced experientially to advance the further step needed to take advantage of this increase.

10.2.6.
When we say that experiential complexity evolves we mean only that, as a general trend, the planet at any time will contain a species more experientially complex than any existing at an earlier. These most experientially complex species of their time constitute only a tiny minority of species. The only essential attribute of any successful species is viability – the ability to maintain its numbers. And there are innumerable ways of doing that; experiential complexity being but one of innumerable biological parameters constituting the functional core of an eco-niche. Nor, if we traced the evolution of humans from small organic molecules, would it be through these most experientially complex species of their day. In many cases a certain evolutionary line is prevented from evolving beyond a certain level of complexity. All species arise by gradual steps from pre-existing species of the same anatomical and physiological groundplan; and this may be such as to place a definite ceiling on their experiential complexity. As we shall be seeing in some detail in the following three chapters, the physical underpinning of ever more complex experience is an increasingly complex nervous system. And one essential attribute of such complexity is sheer number of nerve cells. But large nervous systems require an internal skeleton to support and maintain them effectively. Hence, invertebrate animals cannot evolve large nervous systems, the large marine molluscs being by far the most experientially complex organisms that nature can produce in this direction. With this minor exception, all higher complexification of experience is confined to the vertebrate phylum. And here, again, we shall find that there are many kinds of eco-niche whose nature either puts an upper limit on experiential complexity, or where greater experiential complexity has little if any survival advantage. This last is particularly the case where selection pressures are low. We have said that environmental change is the greatest stimulus to evolution, but such change tends to be much greater, more frequent, and more diverse on land than in the ocean. As a result, the evolution of experiential complexity has been largely confined to the land dwelling vertebrates.

 

EVOLUTION OF REPLICATIVE REPRODUCTION

FIRST STAGE

10.3.1.
We have seen (10.2.2.) that the evolution of experience from molecule to man has five basic causal parameters: mnemic causation, Darwinian selection, intraspecific variation, replicative reproduction, and environmental change. Now, the earliest self-reproducing cells are generally regarded as having evolved by around 3800 m.y.b.p.¹– that is, some 700 million years after the formation of the Earth. According to our theory, mnemic causation and environmental change would obviously have been factors operating from the start. Also it seems natural enough that as soon as individual metabolic complexes began to form there would inevitably be some kind of passive competition among them for nutrients and otherwise favourable locations. Likewise, that, although there were no species, the various pre-biota composed of numerous individual metabolic complexes would exhibit all manner of minute variations. But what of replicative reproduction?

10.3.2.
Without replicative reproduction how can any change to an organism be passed on to its progeny, generation by generation? We know now that at the heart of replicative reproduction lies the genetic code, based on a precise unvarying relationship between the constituent units of proteins and nucleic acids. But such a code, or anything resembling it, could not possibly have been incorporated into those elementary metabolic systems with which, we are claiming, life on Earth began. A first, primitive version of the genetic code finally evolved some 700 million years later. But since replicative reproduction is an essential ingredient of organic evolution, and since it would seem to require, in however crude a form, the genetic code, how could such an evolution have possibly been achieved? There is only one answer worthy of consideration. Although the genetic code is an essential ingredient of all replicative reproduction above the most rudimentary level, it is not the only ingredient. And it is owing to the operation of these other ingredients that a primitive version of the genetic code was enabled to evolve. So we are claiming that, like the other four evolutionary parameters, replicative reproduction, if only as no more than a vague tendency, was operative right from the formation of the Earth.

10.3.3.
Our five basic evolutionary parameters are far from being mutually exclusive. They are simply five outstanding general features of the one evolutionary process, and, as such, overlap in their effects. In this particular case it is, above all, mnemic causation, present from the formation of the Earth, which contributes so decisively to replicative reproduction. As we saw in Chapter 9, mnemic causation, based upon sympathic association between past and present experience, is, at bottom, no more than a question of the physical forces which contributed to past rhythmic unities, modifying present physical forces in such way as to reproduce these unities in the present. Its whole general tendency is thus to reproduce past order in the present. It is therefore essentially replicative in nature. It is also essentially constructive, not, as we have pointed out, because it contains some “urge to greater unities” but only because, through its ability in the face of general dissipative tendencies to maintain an established unity throughout a succession of individual organisms, it provides a basis upon which slightly more complex unities can arise – which, in turn perform the same role for unities yet more complex, and so on indefinitely. This effect of mnemic causation, at once both constructive and replicative, is present from the start of life on Earth; of course, since, without it, life could never have arisen. Before attempting to reconstruct the role mnemic causation must have played in precellular evolution, we shall first glance at the central feature of the role it plays in morphogenesis.

10.3.4.
The essential role of the genome in morphogenesis is to enable the cellular – fundamentally proteinic – processes to produce a new protein at exactly the time and place it is needed in the whole developmental process. And what triggers any such instance is the metabolic context. For orthodoxy, this context is, of course, purely physical. For us, it is both physical and psychical, having in addition a past component at least as important as the physical present. This past component, as we have just seen, is essentially a tendency – embodied in mnemic causation – to replicate the past. In the normal healthy embryo, these two components operate, of course, in near-perfect constructive collaboration. When the embryo is interfered with, these two operational contexts are no longer harmonious, and then, what the two produce between them may no longer make biological sense. But in the normal course of nature such interference is reduced to a minimum, the whole morphogenetic process taking place in an undisturbed, nutrient rich medium provided by egg or womb.

10.3.5.
Here, we are concerned only with the evolution of the genetic code up to the arrival of its first crude version in around 3800 m.y.b.p. The morphogenetic process with which science is almost wholly concerned is that of multicellular organisms. But the first multicellular organisms did not appear on Earth until some 800 m.y.b.p. But stiil, the latter can legitimately be viewed as a more elaborate version of the former, the role of the genome being just the same: to provide proteins as and when they are needed at that dual developmental context – composed of both physical and mnemic forces. This general situation applies essentially throughout, and we are concerned here only with its first, rudimentary version. It is perhaps worth mentioning here the great steps taken along the evolutionary pathway and the times at which they occurred.
Formation of planet Earth: c. 4600m.y.b.p.
Advent of the first primitive cell, complete with rudimentary genome: c. 3800 m.y.b.p.
Advent of photosynthetic bacteria: c. 3200 m.y.b.p.
Development of aerobic photosynthesis: c. 2300 m.y.b.p.
Oxygenation of atmosphere: c. 2000 m.y.b.p.
Advent of unicellular eurkaryotes: c. 1400 m.y.b.p.
Development of sexual reproduction: c. 1200 m.y.b.p.
Advent of first multicellular organisms: c. 800 m.y.b.p.
Advent of first elaborate multicellular organisms: c. 600 m.y.b.p.

10.3.6.
Our immediate task, then, is to show how, on the primordial Earth, this essential morphogenetic situation of a primitive genome evolved via successively closer approximations. But in order to render such an account intelligible we must first point out certain basic biochemical conditions which had to be fulfilled in order that there might evolve ever more complex syntheses of metabolic processes. Proteins are by far the most important macromolecular constituents of living organisms. So that the evolution of life centrally involved the emergence first, of amino acids; then their polymerisation into chains of varying length, known as polypeptides, the longest and most elaborate of which are the proteins. These polypeptides evolved within increasingly elaborate self-sustaining systems of metabolic processes of which they were (and still are) the principal macromolecular constituents. All the other macromolecular constituents of metabolic systems are intimately dependent upon polypeptides, more particularly proteins, both for their advent, either by manufacture or incorporation, and their subsequent functioning.

10.3.7.
Now, as is well known, this whole process of polymerisation is endergonic (energy requiring). At the outset of organic evolution – the synthesis of the monomers themselves - the energy source was physical: ultra violet light, lightning, volcanic activity, etc. But this would be far too crude and sporadic for elaborately organised biochemical systems. At this level, the energy of polymerisation is obtained from coupled exergonic (energy yielding) chemical reactions. Today, throughout virtually the whole organic world, the energy of polymerisation and constructive metabolism generally is obtained from the coupled breaking of one of the two terminal “high-energy” pyrophosphate bonds of ATP (adenosine triphosphate). What is effectively a water molecule (H₂O) is lost by the two monomers – OH from one and H from the other; and in an essentially two-step process involving a double-headed intermediate, the energy for this endergonic condensation is supplied by the exergonic hydrolysis of the high-energy pyrophosphate bond, the OH becoming attached to one of the phosphate groups, and the H to the other. But this presupposes an already well-advanced biochemistry. So that a gulf of some hundreds of millions of years lies between the primordial stage where the energy for biosynthesis was supplied by physical energy sources, and the evolutionary level when it was first supplied by ATP. This implies a long period when metabolism must have depended on more chemically elementary sources of energy.

10.3.8.
By far the most outstanding candidate for this role is the thioester bond: that between thiols (R' - SH) and carboxylic - more particularly amino – acids (R-COOH). Between the reactants a ‘water molecule’ (H + OH) is lost, and a highly endergonic bond (S~C) is formed between the sulphur and carbon atoms. Bacteria exist, even today, where peptides are synthesised from amino acid thioesters. The main objection to the thioester bond fulfilling this role is its highly endergonic nature. However, in recent years, this objection has lost much of its cogency with the discovery of deep-sea hydrothermal vents, situated as these are in hot highly acidic, sulphur-rich waters closely surrounded by much colder water rich in the molecular constituents of life². These vents are now seen as constituting one of the most favourable kinds of birthplace for life on Earth. The main evolutionary role of the thioesters was essentially the same as ATP at a later date: to supply, in coupled reactions, by the hydrolytic breaking of the thioester bond, the energy of polymerisation through condensation (effectively the loss of a water molecule) between two amino acids. So we are suggesting that the principal energy source for all the ongoing polymerisation of the metabolic systems that constituted primordial life was the S~C thioester bond.

10.3.9.
The principal components of these metabolic systems would have been peptides of a wide range of polymerisation, though all short in comparison with today’s proteins. We must never lose sight of the fact that the basic nature of living systems is that they are not producing anything but themselves: each part, qua part, is a means to an end, that end being the maintainance of the whole system of processes in the face of an environment whose constant tendency is to erode it. The role of sympathic association and mnemic causation in all this is fundamental. What are being sympathically associated are experiences – each of which is a unity, and therefore something more than the merely arithmetical sum of its parts. Mnemic causation, the force making for the reemergence of the past in the present proceeds from such experiential unities. It is the life force, since, without it there would be no life. Each polypeptide fulfilled some vital function in the whole system. Preeminent among such functions was that of organic catalyst (enzyme). All the chemical reactions within the system were mediated by enzymes, the enzyme attaching to both reactants in such way as to render their reaction as smoothly efficient as possible. Moreover, as parts of the whole, they responded mnemically to the dictates of the state of the whole – effecting the reaction or not effecting it as the case might be.

10.3.10.
We are now in a position to return to direct engagement with our theme of replicative reproduction in the epoch before even a rudimentary version of the genetic code had evolved. Our first concern must be with those parameters, if any existed, which made for replicative reproduction, and hence the preservation of systemic complexity, after the demise of the individual systems which possessed them. Clearly, these must have centred upon mnemic causation, whose very nature it is to preserve or bebuild the past in the present. Now, in the necessary absence of bacteria, the death of a particular metabolic system from whatever cause must have been of a very different nature from the death of a higher organism. Presumably, causes of death were the exhaustion of customary sources of nutrients (individual hydrothermal vents possessed only a limited life span); sudden cataclysms born of seismic activity or the impact of large extraterrestrial bodies; poisoning by environmental increase of destructive substances; sudden large changes in ambient temperature; and, constituting a special case³, ingestion by some other metabolic complex. Under such modes of assault the metabolic system would have been radically disrupted, with disintegration of sorts setting in. In a way strange to us, these fragments of disintegration would also have played the role of germ cells. The fragments would have consisted of complexes of polypeptides, and the more such fragments resembled earlier stages of the disintegrated synthesis, the more likely, if the environment were favourable, they would be to grow back, under the influence of mnemic causation, to this original synthesis. For a new metabolic system to develop it would not have been necessary to begin all over again from scratch, at the monomeric level. Other things being equal, the more rapidly, accurately and abundantly a metabolic system, on disintegration, could grow back into what, in all structural and functional interrelationships, is effectively itself, the greater the chance for Darwinian selection to operate in favour of the multiplication of instances of that particular system.

10.3.11.
Such being the case, there are a number of obvious ways in which this relation between metabolic system and offspring might evolve. All of these would be changes in the parent ‘organism’ such as to favour accuracy, rapidity, and abundance of offspring. Perhaps the first to evolve would be a parent metabolic system which tended to disintegrate in such way as to include among the fragments some earlier stage or stages of its own development. The whole tendency of mnemic causation would then be to repeat the subsequent developmental stages, especially if environmental conditions were similar – in effect, to reproduce the parent complex. The next evolutionary step would be not to wait for the fragmentation of ‘death’ but for the metabolic complex to develop in such way that from time to time some part of it constituting an earlier stage of development would ‘bud off’ from it and so lead an independent life, governed as always by mnemic causation with its tendency to reproduce past experience - an experience being some particular ordered process. Finally, there would be no need for a parent organism to restrict itself to one such offspring; a whole type of metabolism could evolve which included such continuous production of offspring as among its principal activities. We envisage that it was at about this evolutionary stage when nucleoside base pairing, with its potential for carrying replicative reproduction to an altogether higher order of accuracy ubiquity and complexity entered the situation.

 

EVOLUTION OF REPLICATIVE REPRODUCTION

SECOND STAGE

10.4.1.
The genetic code consists essentially of very precise relationships between the monomeric constituents of proteins and those of nucleic acids. Our metabolic complexes are essentially composed of polypeptides – which may be regarded as the same as proteins in all respects save only in the lesser number of amino acids composing them. But how did nucleic acids enter these systems? We have already noted that virtually all the energy of the living world is supplied by the hydrolysis of one or more of the phosphate bonds of ATP. But ATP – adenosine triphosphate – derives directly from adenosine diphosphate (ADP), which, equally directly, derives from adenosine monophosphate (AMP). The difference is just whether one, two, or three phosphate groups are serially attached to the adenosine. And adenosine itself is composed of the nucleobase adenine attached to a molecule of the sugar, ribose. Furthermore, all this applies equally to the other three nucleobases involved in the structure of ribonucleic acid (RNA): that is, the other purine, guanine, and the two pyramidines, cytosine and uracil. And although adenine is that one of the four most engaged in general metabolism, the other three are also significantly involved; and indeed, might just as well as adenine, have assumed the primary role in energy production. Indeed, at the much earlier stage of evolution with which we are presently concerned, the role of energy producer might well have been more equally shared among them than it is today.

10.4.2.
So we see that there is much in common between the molecules most intimately involved in energy production in living organisms, and those involved in replicative reproduction. We suggest, then, that it was in the first role, as providing an energy source superior to the thioester bond, that the phosphates and the nucleobases first became an intimate part of metabolic complexes, entering into all manner of constructive processes with the major constituents of these complexes - the polypeptides. All this provided an essential functional preliminary to the emergence of their second and momentous role of raising replicative reproduction, with its high responsiveness to Darwinian selection, to an altogether higher order of complexity.

10.4.3.
One major difference between the polymerisation of nucleobases (RNA) and that of amino acids (proteins) is that, whereas in the proteins each amino acid unit is directly bonded to both its neighbours, this is not the case for RNA. Here, the bonded units of the polymeric chain are not the bases at all. Instead, the chain is composed of alternating units of ribose and phosphate molecules. Each molecule of ribose is bonded to a base. However, the double strand is formed by bonds between bases, with each purine bonded to a pyramidine: adenine⇔uracil and guanine⇔cytosine. This, of course, is the complementary base pairing on which this whole vast contribution to replicative reproduction, and hence to biological evolution, ultimately depends. It means that, given a single strand of RNA, a complementary strand can form on it. Then, when this is unravelled into two single strands, a complementary strand can form on both of these, giving two versions of the original. And so on, doubling in number at each generation. This is the first root process of precise replicative reproduction, but its great importance lies not in itself but only in its providing a necessary basis for a second process. This is the rigidly unvarying attachment of amino acids to small groups of the nucleobases composing RNA, such that the precise replication of these also entails the precise replication of the amino acids attached to them. So that monomer by monomer the polypeptides can be as precisely replicated as the RNA strands themselves. Hence, the replicative properties of RNA are supremely important for life, not because they replicate RNA, but only because, through simple association, they allow of the replication of polypeptides - ultimately, of proteins.

10.4.4.
Needless to say, although this process could hardly be simpler in its general nature, in detailed feature it is far from simple. But most of its details are now well known – in so far, that is, as anything conceived in mechanistic terms can be said to be well known – and it is no part of this work to present them in noumenal terms in systematic detail. It is enough to understand that mnemic causation is operative throughout, maintaining orderly process on a level of complexity utterly beyond the powers of physical forces as conventionally understood, to create and sustain. Because of the strong selective pressures to which the replicative reproduction of any species of organism must be subject, there is every reason why this RNA – polypeptide relationship should evolve in terms of precision, rapidity, abundance and complexity, from its first crude beginnings some 3800 m.y.b.p. to the DNA – protein relationship constituting the genetic code as we have it today. Again, we shall make no attempt to trace this evolution, which is best left to the specialist. We simply contend that any empirical facts unearthed by the scientists can only be grasped as contributions to a rationally ordered system of processes within a context of sympathic association and mnemic causation. However, before we leave this topic, there are one or two general observations which should perhaps be made.

10.4.5.
In the polypeptide-RNA relationship it is overwhelmingly the polypeptide which is the active partner, and the RNA the passive. The whole replicative process is organised and monitored by enzymes. And if our contention is correct that all the constituents of RNA gradually infiltrated a metabolic system all of whose catalysts were polypeptides and many of whose substrates contained amino acids as prominent constituents, this is just what we would expect. In any case it is precisely the unchanging nature of RNA which, second only to its base pairing propensities, makes it an ideal material basis for replicative reproduction. The assembly of RNA from its constituent ribose, phosphate, purine, and pyrimidine molecules is effected entirely by enzymes. Most interesting of all, each step in the translation of RNA into protein is initiated by an ezyme known as tRNA synthetase. The substrate to which this binds is one of the twenty out of hundreds of amino acids that are constituents of protein. It then attaches this amino acid to a relatively short length of RNA, known as a transfer RNA (tRNA) molecule, containing the complement of one of the amino acid’s codons (anticodon). This engages with the codon, whilst simultaneously the amino acid is being bonded into its corresponding place in the growing peptide chain. But there is some hard evidence⁴ that it is the more detailed nature of this process which determines why only twenty – not necessarily the most common – of the hundreds of amino acids that exist, are constituents of protein. It seems that the tRNA under the influence of the tRNA synthetase folds up in such a way that the anticodon, the fourth nucleotide from the 3’ end (acceptor stem) of the tRNA molecule, and the tRNA synthetase form a pocket into which the substrate amino acid fits. Subsequent research has produced some evidence that no amino acid which is not a constituent of protein will fit into such a pocket. Since twenty amino acids are sufficient to give rise to a human being, life doesn’t seem to have been seriously affected by this limitation.

NOTES
1 m.y.b.p. stands for million years before present.
2 A significant proportion of these dissolved nutrients would have come from outer space as ingredients of comets and meteoroids.
3. Because sometimes, far from dying – that is, disintegrating - the ingested complex begins a new and viable life as an endosymbiont within the ingesting organism.
4. See: Shimizu M. Molecular basis for the genetic code. Journal of Molecular Evolution 18:297-303; 1982

chapter 11

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Theory of the Universe