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EVOLUTION: AT THE MIND’S CINEMA

I turn the handle and the story starts:

Reel after reel is all astronomy,

Till life, enkindled in a niche of sky,

Leaps on the stage to play a million parts.

Life leaves the slime and through all ocean darts;

She conquers earth, and raises wings to fly;

Then spirit blooms, and learns how not to die,—

Nesting beyond the grave in others’ hearts.

—I turn the handle: other men like me

Have made the film: and now I sit and look

In quiet, privileged like Divinity

To read the roaring world as in a book.

If this thy past, where shall thy future climb,

O Spirit, built of Elements and Time!

Munich, Jan. 1923.

PROGRESS, BIOLOGICAL AND OTHER

“Usus et impigrae simul experientia mentis

Paulatim docuit pedetemtim progredientes.”

—Lucretius.

“As natural selection works solely by and for the good of each being, all corporeal and mental environments will tend to progress towards perfection.”

—Charles Darwin.

“Social progress means the checking of the cosmic process at every step and the substitution for it of another which may be called the ethical process.”

—T. H. Huxley.

“It is probable that what hindered Kant from broaching his theory of progress with as much confidence as Condorcet was his perception that nothing could be decisively affirmed about the course of civilization until the laws of its movement had been discovered. He saw that this was a matter for future scientific investigation.”

—J. B. Bury.

What is the most fundamental need of man? It would be interesting to conduct a plebiscite of such a question, a plebiscite of the same sort that was conducted by one of the French newspapers some years ago, to discover the opinions of its readers as to who was the greatest Frenchman of the century.

When I say the most fundamental need of man, I do not mean those basic needs for food and drink and shelter which he shares with the animals: I mean the most fundamental to him as man, as an organism differing from all other organisms in the power of thought, in reflection and self-consciousness. What variety of answers would be given, I dare not guess; but I hazard the belief that the majority, if the suggestion were put before them, would agree that his deepest need was to discover something, some being or power, some force or tendency, which was moulding the destinies of the world—something not himself, greater than himself, with which he yet felt that he could harmonize his nature, in which he could repose his doubts, through faith in which he could achieve confidence and hope.

That need has been felt by all those to whom life has been more than a problem of the unreflective satisfaction of instincts and desires—however pure those instincts, or beautiful those desires; it has been felt by all in whom the problem of existence has been apprehended by intellect and disinterested imagination.

I say all. There may be rare creatures who, secure in strength of body and mind and in unhampered unfolding of their faculties, possess a confidence by which this need is never felt. They are like those whom Wordsworth drew for us in the “Ode to Duty”:—

“There are who ask not if thine eye

Be on them; who, in love and truth,

Where no misgiving is, rely

Upon the genial sense of youth:

Glad hearts! without reproach or blot;

Who do thy work and know it not.”

But such are rare; or should we say that their type of mind, though not uncommon in the earlier years of life, only by the rarest chance achieves its course without a descent into that vale where the finite human intellect grapples unequally with infinite problems?

The need has been felt in all ages and in all countries; and the answers, the partial satisfactions of the needs which have been found by the mind of men, are correspondingly diverse.

Savages have endowed the objects around them, living and inanimate, with supernatural qualities. At a higher grade of development they have created gods made with hands, visible images of their fears or their desires, by whose worship and service they assuaged the urgent need within their breast. Still later, turning from such crudity, they became servants and worshippers of unseen gods, conceived under the form of persons, but persons transcending human personality, beings in whom was vested the control of man and of the world.

Up to this point there had been an increase of spirituality in the constructions by which human thought satisfied its need; none the less, the ideas underlying the mode of these constructions had not materially altered. As Voltaire so pungently put it, man had created God in his own image.

What remains? there remains to search in the external world, to find there if possible a foundation of fact for the belief drawn from the inner world of mind, to test the conceptions of a supreme being or supereminent power against ever more and more touchstones of reality, until the most sceptical shall acknowledge that the final construction represents, with whatever degree of incompleteness, yet not a mere fragment educed to fill a void, however inevitable, to satisfy a longing, however natural, but the summary and essence of a body of verifiable fact, having an existence independent of the wishes or ideals of mankind.

It was the striving after some such certainty that led Matthew Arnold to his famous definition of God as “something, not ourselves, which makes for righteousness.” Dissatisfaction with the assertion that belief in a very special and undemonstrable form of Divinity was necessary as an act of faith has, in a large measure, helped the widespread revulsion against orthodox Christianity. It was the need for some external, ascertainable basis for belief which led such different minds as William James and H. G. Wells to approach religion, and in such diverse ways as in the “Varieties of Religious Experience” and in “God the Invisible King.” It is this same need which is leading the representatives of Christianity to lay ever greater stress upon the reality and pragmatic value of the religious experience, less and less upon dogmas and creeds.

It will be my attempt in this brief paper to show how the facts of evolutionary biology provide us, in the shape of a verifiable doctrine of progress, with one of the elements most essential to any such externally-grounded conception of God, to any construction which shall be able to serve as permanent satisfaction of that deepest need whereof we have spoken.

Any such construction must take account of many separate parts of reality. In the first place, it must consider those realities inherent in the mind of man: his desire for goodness; the sense of value which all agree is attached to certain experiences of mystics and to certain religious emotions; his ideals and their importance for the conduct of life. But in the second place it must consider those realities which are independent of man and of his mind—the ascertainable body of hard fact, those things which existed before ever he existed, which would exist were he to disappear, with which he must struggle as best he may. Lastly, there is the need for intermediation between the one and the other reality, between the inner felt and the outer known.

Mr. Wells,[1] if you remember, erected a new trinitarianism, which in broad outlines corresponded with this division. With his particular construction, I do not in many respects agree. But that some form of trinitarianism is a reasonably natural method of symbolizing the inevitable tripleness of inner experience, outer fact, and their interrelation is obvious enough. In the particular trinitarianism of Christianity, the reality apprehended to exist behind the forces of Nature is called the Father, the upspringing force within the mind of man, especially when it seems to transcend individuality and to overflow into what we designate as the mystical, is called the Holy Ghost, and the activity, personal or vicarious, which mediates between the individual and the rest of the universe, reconciling his incompleteness and his failures with its apparent sternness and inexorableness, is called the Son.

Some men lay more weight on one of these aspects than on the others. I know a clergyman of the Church of England who, on being reproached during a theological argument with failure to pay sufficient respect to the doctrine of God the Father, replied: “I am not interested in God the Father”; and I know intellectually-minded men who wish to reject the validity of all religious experience because their minds are so made that they pay more attention to external fact and because their reason refuses to let them agree with the interpretations of fact propounded by most religious bodies. But, for a properly balanced construction, for the finding of something which shall serve not as the basis of a creed for this or that sect, but of a creed for humanity, of something which instead of dividing shall unite, we need all aspects.

The idea of Progress constitutes, as I hope to show, the most important element in the first part of our construction—that which attempts to synthesize the facts of Nature; and besides, no inconsiderable portion of the third, the interrelation of inner and outer.

Readers of Bury’s interesting book on the Idea of Progress[2] will perhaps, with me, have been surprised at the modernity of that conception. He shows how, in antiquity, the idea was never a dominant one, and further that the adumbrations made of it all lacked some element without which it cannot be styled progress in the sense in which that word is used to-day.

Not indeed till the late Renaissance can we say that the idea of Progress became in any real sense incorporated with the common thought of Western civilization. From then to the present it has suffered many vicissitudes. Starting in the XVIIth century as little more than a consciousness of the superiority of the present over the past, in the XVIIIth it changed to a dogma, its adherents claiming that there existed a “Law of Progress” leading inevitably to the perfectioning of humanity. In the XIXth century the dogma was questioned, and thinkers began to put it to the test—the test of comparing theory with historical fact. A new lease of life, however, was given to the idea of a law of progress by the evolution theory; but finally, of late years, there has been a marked reaction, leading not only to a denial of any such inevitable law, but often to a questioning of the very existence of Progress in any shape or form.

It is the business of the philosopher and of the biologist to see whether this scepticism be justified, and to find out by a more scientific approach how much of the doctrine of Progress is valid. To the layman it would seem inevitable, once the validity of the evolution theory was granted, to concede the fact of Progress in some form or another. If we accept the doctrine of evolution, we are bound to believe that man has arisen from mammals, terrestrial from aquatic forms, vertebrates from invertebrates, multicellular from unicellular, and in general the larger and the more complex from the smaller and simpler. To the average man it will appear indisputable that a man is higher than a worm or a polyp, an insect higher than a protozoan, even if he cannot exactly define in what resides this highness or lowness of organic types.

It is, curiously enough, among the professional biologists that objectors to the notion of biological progress and to its corollary, the distinction of higher and lower forms of life, have chiefly been found. I say curiously enough, and yet to a dispassionate observer it is perhaps not so curious, but only one further instance of that common human failing, the inability to see woods because of the trees that compose them.

That is as it may be. Our best course will be to start by examining some of the chief objections to the idea of biological progress, in order to see if they involve errors of thought which we may then avoid.

The most widespread of all the objections raised may, I think, be fairly put as follows: “The fundamental attribute of living beings is adaptation to environment. A man is not better adapted to his environment than the flea which lives upon him as a parasite, or than the bacillus which kills him, nor is a bird better adapted to air than a jelly-fish to water; therefore we have no right to speak of one as higher than the other, or to regard the transition from one type to another as involving progress.”

A second class of objector is prepared to admit that there has been an increase of complexity, an increase in the degree of organization during evolution, but refuses to allow that increase of complexity has any value in itself, whether biological or philosophical, and accordingly refuses to dignify this trend towards greater complexity by the name of progress.

Yet a third difficulty is raised by those who ask us to fix our attention on forms of life like Lingula, the lamp-shell, which, though millions of years elapse, do not evolve. If there exists a Law of Progress, they say, how is it that such creatures are exempt from its operations?

Finally, a somewhat similar attitude is adopted by those who refuse to grant that evolution can involve progress when it has, as we know, brought about well-nigh innumerable degenerations. Granted, for instance, they would say, that the average Crustacean is in many ways an improvement upon the simple form of life from which we must suppose that it arose, yet we know that within the group of Crustacea there are several lines of descent which have led to the production of parasitic forms—animals in which the activity and complex organization of the ancestral type has been sacrificed, and as end-product we are presented with a hateful being, an almost shapeless mass consisting of little else but over-developed reproductive organs and mechanisms for sucking nutriment from its unfortunate host. Such a result is revealed to us in the Crustacean form Sacculina, and is paralleled by countless other examples in almost every class of animals. The degradation of parasites and sedentary types is equally a product of the evolutionary process with the genesis of the ant, the bird or the human being; how then can we call the evolutionary process progressive?

These are important objections. Can they be met? In the broadest way they can and must be met by the only possible method, the method of Science, which consists in examining facts objectively, and by drawing conclusions not a priori, but a posteriori. A law of Nature is not (and I wonder how often this fallacy has been exploded, only to reappear next day)—a law of Nature is not something revealed, not something absolute, not something imposed on phenomena from without or from above; it is no more and no less than a summing-up, in generalized form, of our own observations of phenomena; it is an epitome of fact from which we can draw several conclusions. By beginning in this way from the very beginning, by examining the basis of our mode of thinking in natural science, only thus are we enabled to see at one and the same moment how to investigate the question of progress on the constructive side, and how to neutralize the force of the objections to the idea.

Questions of fact are simple to deal with. It is indubitable that some forms of life remain stationary and unevolving for secular periods; it is equally indubitable that degeneration is widespread in evolution. These are facts. But we are not therefore called upon to deny the possibility of progress. To do so would be to fall into the error of reasoning which we have already condemned. It remains for us to take these facts into account when examining the totality of facts concerning organic life, and to see whether, in spite of them, we cannot discover a series of other facts, a movement in phenomena, which may still legitimately be called progress. To deny progress because of degeneration is really no more legitimate than to assert that, because each wave runs back after it has broken, therefore the tide can never rise.

Similarly with the first two objections. If the degree of adaptation has not increased during evolution, then it is clear that progress does not consist in increase in adaptation. But it does not follow that progress does not exist; it may quite well consist in an increase of other qualities. So with complexity. Complexity has increased, but increase in complexity is not progress, say the objectors. Granted: but may there not be something else which has increased besides mere complexity?

No; the remedy for all our difficulties, and indeed the only way in which we can arrive at the possibility of saying whether biological progress exists or no, is to adopt the positive method.

Let us then begin our survey of biological evolution in the endeavour to find whether or no progress is visible there. To start with, we must be clear what are the sources of our knowledge on the subject.

Direct observation of progressive evolution has, of course, not yet been possible in the period—biologically negligible—in which man has directed his attention to the problem; and historical record is also absent. The best available evidence is that of paleontology: here the relative positions of the layers of the earth’s crust enable us to deduce their temporal sequence—and naturally, that of the organisms whose fossil remains they embalm—with a great deal of accuracy.[3]

We can scarcely ever observe the direct transition from the forms of life in an older to those in a younger stratum, nor can we absolutely prove their genetic relationship. But in a vast number of cases it is abundantly clear that the later type of organization is descended from the former—that a group of forms in the younger stratum had its origin in one or more species of the group to which the forms in the older stratum belong. Sometimes, however, as in many groups of mammals, the gaps are few and small, the seriation almost complete. In any event we have here evidence which, so far as it goes, is perfectly admissible for the main lines and for many of the smaller branches of evolutionary descent.

Unfortunately, it does not go very far—or, we had better say, it is of restricted application. By the time we find well-preserved fossils in the rocks, the main groups of the animal kingdom and their chief subdivisions had been already differentiated, with the one important exception of the vertebrates; while time, heat, and pressure have so modified the earlier strata as to destroy the fossil forefathers of insects, molluscs, crustacea, and the rest, which they must have contained.

Within the vertebrate stock, then, we can learn a great deal from the semi-direct methods of paleontology: but for the history of the other groups and for their origin and interrelations, we are driven back upon comparative anatomy and embryology, into another field of more circumstantial evidence. When, for instance, we find that the fore-limbs of bat, bird, whale, horse, and man, although so different in function and in detail of structure, are yet built upon the same general plan, and upon a plan wholly different from that of the limbs, say, of a spider or an insect, we must either deny reason and say that this similarity means nothing; or assume that its cause is supernatural, outside the province of science, that it is the expression of some eternal Idea, or some plan of a personal creator (in which case, be it noted, the idea or the plan often appears to our intellect as unreasonable and indeed stupid); or finally that it implies community of origin with later divergence of development. When we are dealing with the smaller sub-divisions of some larger group, this method too gives us information of the same order of accuracy as does paleontology: but when we try to understand the relationships of these larger groups, then we are forced to renounce any claim to detailed knowledge. In broad outline, however, a great deal still remains, and this broad outline we can employ for our valuation of the whole sweep of biological progress, just as we can use the greater accuracy of vertebrate paleontology and comparative morphology to fill in the detail within a restricted field of its operation. From these various evidences, direct and indirect, we can paint for ourselves a picture of the evolution of life which, in spite of inevitable gaps and errors, is in its main features adequate and true.

Let us not be misled by the fact that disputes can and justifiably do arise over details: as Professor Bateson put it recently[4]:—

“If the broad lines do not hold, then we must sink into irrationality or turn to flagrant supernaturalism.”

Let us then remind ourselves of some of these broad lines.

We know that there was a time when the earth, hot and fiery, could not have been the abode of life. Of the first origins of life we know nothing and guess little. What we can justifiably surmise is that the protoplasm of the original organisms was not yet differentiated into cytoplasm and nucleus, and that sexuality had not yet arisen. The bacteria, however specialized in other ways, are still in this primitive condition.

Later, we can with great probability infer that the independent units into which the stuff of life was subdivided reached a size which, though still minute, was at least not beyond or even close to the limits of microscopic vision; they were further provided with a nucleus, and occasionally underwent sexual fusion. In other words, they showed an organization which we call cellular; they were free-living cells. Such unicellular creatures must have been at one epoch sole inhabitants of the earth, and diverged into the most manifold types of structure and modes of life. Such of them as led an animal as opposed to a plant type of existence would be classified under the Protozoa or unicellular animals.[5]

The colonial habit gives advantages of increased size and greater rapidity of motion, of which many Protozoa have availed themselves. A colonial existence once attained, division of labour, at first between the germinal and the somatic, later between different types of somatic units, will be a further advantage. Such organisms, of which we cannot say definitely whether they are compound aggregates or single wholes, would represent the most natural link between the unicellular Protozoan and the rest of the animal kingdom, the multicellular forms or Metazoa. And indeed such organisms exist at the present day—organisms such as Volvox, Zoothamnium, Proterospongia, and Myxidium—as adjuvant and confirmatory of our reasonable faith.

The multicellular organisms appear to have originated twice over, by divergent routes. There are the true Metazoa, to which belong all the higher types, and the Parazoa or sponges, which have never passed beyond a very primitive type of structure. Both start as simple sacs, whose walls are formed from two primary sheets or layers of cells. Leaving sponges out of account, the Hydroid polyps are the simplest representative of this grade of structure, while some of the Jelly-fish and Siphonophores have attained the utmost limit of its inherent possibilities.

The next great step was the intercalation of a third primary layer between the other two. The result of this, the so-called triploblastic type of organization, gives the ground-plan for all subsequent organizations; and later evolution consists mainly in the evolution of this ground-plan.

In other words, we can now pass from the consideration of the general plan of life’s architecture to that of its details. During the next great tract of time, that which was novel in life (for we must not be guilty of a petitio principii in yet speaking of “advance” or “progress”) was brought about in two main ways—by an increase in the size of organisms, and by an increase in the efficiency of their working.

The simplest Metazoa, such as the polyps, as well as the simplest three-layered forms, such as the free-living flat-worms, are all small, composed of an amount of material comparable with that contained in a single one of our hairs. In every group of Metazoa, increase of size is one of the main features that accompanies specialization, and the more specialized groups possess a higher average size than the less.

A jelly-fish against a polyp; a cuttle-fish against a primitive mollusc; a vertebrate against its chordate ancestor; the giant reptiles of the late secondary period against their forbears; a horse against Phenacodus; man against the earliest primates—over and over again does size increase with the march of time.

Not only this, but when there occurs aggregation of individuals to form units of a higher order, as in bees and ants and termites, and in man himself, there too increase of size in the new units thus produced is one of the most notable features. Is not human history in large measure the history of the increase in size of social units?

But size alone is not enough; there is also a definite improvement of the details of life’s mechanism—partly revealed as improvement in the efficiency of the parts themselves, partly in the adjustment of the parts to each other, and their subordination to the needs of the whole.

It is scarcely necessary to detail the improvements in efficiency of different organs during evolution: such are universally familiar. But a few examples will point my moral. The lowest three-layered forms have no circulatory system; this, rendered necessary later by increase of size, shows a gradual differentiation of parts in evolution. The exquisite machinery of our heart is directly descended from a minute pulsating ventral vessel such as that seen in Amphioxus. Protection and support are better cared for in insect than in worm, in mammal than in lamprey. But the most spectacular improvement of function, the most important of all the directional movements in evolution has been that affecting the nervous system and the sense-organs associated with it. Few people who have not gone carefully into the subject realize how imprisoned and windowless are the existences led by lower forms of life.

Even such physically well-organized creatures as Crustacea stand at an amazingly low mental level. The other day I was reading a careful account of experiments on the behaviour of crabs. The method by which the sexes recognize each other is so crude that I am not sure whether it deserves the term recognition at all. Before mating, which takes place immediately after a moult, the female is carried about for some time in the claws of the male. The mature males will attempt to lift up and carry off any members of the same species, male or female: but the only ones which will permit themselves to be thus carried about are females just before moulting. Hence by a general instinct to lift any members of the same species on the part of the males, and on the part of the females an instinct to allow themselves to be lifted when in the physiological condition which precedes moulting, the required end is brought about. But of any mental operation such as is involved in sex-recognition in man or any other mammal, there is no evidence.

Fish, to take another example, possess associative memory; they can learn. But they learn very slowly, and learn only the simplest things. The jump from their powers of memory to those of a dog, who can be trained comparatively quickly to carry out complicated tricks, is as great as the further jump from the powers of a dog to those of a man capable of learning a page of print by heart in two or three readings.

The first organs connected with mind to become elaborated are the organs of sense: but such receptor organs are useless to their possessor, however elaborate, unless put into relation with proper effector organs—organs for action, whether locomotor or secretory. So that the first steps are the elaboration of sense-organs, the increase of efficiency of muscles and glands, and, equally essential, the construction of an improved “adjustor system,” whereby the stimulus falling on the sense-organ may be translated into action and into the right kind of action. This adjustor mechanism is the central nervous system. Most of the further history of organisms may be summed up in one phrase—the evolution of adjustor mechanisms.

At first, it is chiefly of importance to be brought into relation with more and more of the happenings of the outer world, to be able to see and hear and feel and smell more and more delicately; and to react upon the outer world more and more efficiently and powerfully, to be able to move and to handle matter more quickly and with finer and finer adjustment.

But unless the adjustor mechanism be improved, this process soon tends to a limit. I may illustrate my meaning by a simple supposition. Suppose an organism capable of very little beyond reflexes and instincts and with but a scanty dose of associative power: of what conceivable use to it would be a telescope or a telephone? Man obtains a biological advantage from such accessory sense-organs in that, when thus apprised of events at a distance, he is enabled to plan out courses of action to meet the events which he imagines are going to overtake him: but both planning and imagination are entirely functions of an adjustor mechanism, and without such a mechanism, great enlargement of sensory power would only result in an organism reacting too often and unnecessarily to events in its environment.

There is, in fact, an obvious limit to the perfection which can be attained by receptor and effector organs. Striated muscles, the modelling of the skeleton and joints for speed in a horse or greyhound, the eye and ear of higher vertebrates, the mammalian sense of smell—no doubt it would be possible for life to have produced more perfect and more efficient mechanisms—but not, apparently, mechanisms much more perfect or much more efficient. They stand near the limit of biological efficiency.

There thus comes a time when it is impossible or extremely difficult to give an organism advantage in the struggle by improving its sense-organs or its locomotor system, or indeed any of its general physical construction, whereas it is still possible to confer the most important advantages upon it by means of improvements in the adjustor mechanism, improvements which involve and imply improvements of mind.

This stage was reached by mammals and birds quite early in the Tertiary period; and one of the most striking spectacles of biology, revealed in the fossils of successive strata, is to see Mind coming into its own after this epoch. Over and over again a group of animals is seen to appear and spread, only to be extinguished and replaced by another type which to all outward appearance is similar, no better adapted to the conditions of life. But the two types differ in one point: the later possessed a larger brain, and so, from all analogy, a better mind. Or, to take another example, man differs from the lower animals in no notable physical specialization except the upright posture.

After this critical point in the evolution of organisms was reached, further development has consisted chiefly in the development of mind: and this has meant, from the objective, purely biological standpoint, the possibility of summing-up ever more and more power and fine adjustment of response in the present, in the single act.[6]

The first main function of the improved adjustor mechanism was to make ever more complicated actions possible; but this again tended speedily to a limit. The next step was to make it possible for the past to act in the present. Through associative memory, present behaviour is modified by past experience. What this has meant to organisms can be realized if we reflect that certain terms which can justly be applied to a mammal or a bird have no real meaning if applied to lower forms. If we speak of a cunning wolf or a wary crow, we imply that their life has taught them new qualities; but it is nonsense to talk of a cunning crab, and, though we might properly ascribe wariness to a trout, I would not like to speak of a wary Amoeba. In the same way we can justifiably say that one dog is affectionate, another intelligent: but to speak of an affectionate earthworm or an intelligent snail has no more proper significance than it would be to say that a dog was intellectual or religious.

Quickness of learning then became of importance; but so long as the faculty of generalizing is absent, associative memory, although liberating organisms from the prison of a fixed and inherited mental constitution, still pins them down to the accidental and the particular; an organism can only learn to react to those particular experiences which chance has decreed that it should have had.

The next and last salient step in evolution was a double one. Which of its two parts came first is hard to say; probably they acted reciprocally throughout. This step was, on the one hand, the attainment of the power of generalization—of reason, concept-formation, or what you will—and on the other the origin of tradition, which in its turn was made possible by the acquisition of speech and of a gregarious mode of life. By these means, the human species and its evolving ancestors were gradually enabled, first, to free experience ever more and more from the accidental and to store what was essential; and, secondly, to bring gradually more and more of the experience of the whole race to bear upon the present problem, and to plan further and further ahead, and on a larger and larger scale.

This has meant, among other things, that for the first time in biological history there has been an aggregation (in the technical biological sense) of minds. Over and over again in evolution does the process of aggregation appear.[7] It is an advantage, for at one jump it lands life on a new level of size, with new possibilities of division of labour and specialization. It appears in the aggregation of Protozoa to form the colonial ancestor of all higher, many-celled forms. It appears again on this new level in the aggregation of hydroid polyps, of polyzoa, of ascidians, and especially in the beautiful floating Siphonophora, in which the polyp-like units (themselves historically aggregates of cells) have become so subordinate in relation to the whole that they can often scarcely be recognized as individuals, and the individuality of the aggregate is much more marked than that of its components. It appears in a new way in the Termites and in the social Hymenoptera—ants, bees, and wasps. Here the bonds uniting the members of the aggregate are not physical but mental, their sense-impressions and instincts; but the principle is identical throughout. Finally in man we have not merely aggregation of physical individuals held together by mental bonds, but aggregation of minds as well as of physical individuals.

In many mammals and birds, each generation can extend its influence on to the next, and the experience of the parents is in part made available to the offspring. But never until the origin of speech was it possible for a whole series of generations to be linked together by experience, never could experience be cumulative, never could one mind know what another mind, remote in time, had been thinking or feeling. Biologically, evolution since the time of origin of this new process has consisted essentially in the enlargement and specialization of aggregations of minds, and the improvement of the tradition which constitutes the mode of inheritance for these aggregations—that tradition which, like Hugo’s “Nef magique et suprême” of human destiny, will eventually have “fait entrer dans l’homme tant d’azur qu’elle a supprimé les patries.”

It will, I hope, have been clear, even from the few examples which I have given, that there has been a main direction in evolution. At the close of the paper I shall try to point out that since motion in this direction has led to the production of an increasing intensity of qualities which we are unanimous in calling valuable, since in other words the application of our scale of values tends in the same direction as has the march of evolutionary history, that therefore we are justified in calling this direction progressive, and indeed logically compelled to give to motion in this direction a name which, like progress, implies the idea of value.

I shall therefore, from now on, use the term biological progress to denote movement in the direction which we have sketched in outline, and shall shortly proceed to define more accurately. In so doing, I perhaps beg the question, to be proved I hope later, as to whether the observed direction is progressive: but I no longer beg the question of whether evolution is a directional process. However we may argue on the facts, the facts remain: and the facts are that there has been an increase in certain qualities of organisms, both physical and mental, during geological time.

Meanwhile, let it be remembered, the simplest forms have survived side by side with the more complex, the less specialized with the more specialized. Even when we can trace a causal relation between the rise of one group and the decay of another, as with the mammals and birds on the one hand, and the reptiles on the other, even then numbers of the defeated group continue to exist. Thus, in broad terms, evolution is not a transformation, be it progressive or no, of the whole of living matter, but of a part of it.

I will endeavour to sum up, in brief, what seem to me the salient points of that process, a sketch of which, inevitably hasty and inadequate, I have just tried to give.

During the time of life’s existence on this planet, there has been an increase, both in the average and far more in the upper level, of certain attributes of living things.

In the first place there has been an increase in their size, brought about by two methods, first by the increase of size of the units of life themselves (cells, metazoan individuals, communities), secondly by their aggregation; and this has been accompanied by a (very roughly) parallel increase in the duration of life.

Next, there has been an increase in their complexity; and this in its turn depends upon the fact that a division of labour has been brought about between the parts of organisms, each part becoming specialized for greater efficiency in the performance of some particular function. In the fewest words, the separate bits of machinery of which organisms are composed have become more efficient.

In the third place, there has been an increase in the harmony of these parts, and consequently in the unity of the whole. Delicate mechanisms for co-ordination have been developed, and arrangements whereby one portion becomes dominant over the rest, and so a material basis for unification is given.

In the fourth place, there has been an increase of self-regulation. The outer environment changes from month to month, from hour to hour. The more complex products of evolution are in high degree exempt from the consequences of these changes, through being the possessors of a constant internal environment which, beyond the narrowest limits, it is most difficult to alter.

Fifthly, there has been an increase in the possibility of bringing past experience to bear on present problems. At the base is the power of modifying normal reactions with repetition; then come some simple degrees of memory; then associative memory, as in birds and mammals, for whom most reactions are not given in the inherited constitution, but must be learnt; then rational memory, in which the power of generalization liberates life from blind dependence upon the local and the accidental; and finally tradition, whereby the amount of experience available to the developing race is not constituted merely by the isolated and limited experiences of its members, but by their sum. More and more of the past becomes directly operative in the present; further and further into the future can the aim of the present extend.

Finally we can conclude with a high degree of certainty that the psychical faculties—of knowing, feeling, and willing—have increased in intensity, and also in their relative importance for the life of the individual organism.

We have condensed our summary into these six general statements; if we wish to reach a still more general form, the most general form possible, we can redistil it thus: During the course of evolution in time, there has been an increase in the control exerted by organisms over their environment, and in their independence with regard to it; there has been an increase in the harmony of the parts of organisms; and there has been an increase in the psychical powers of organisms, an increase of willing, of feeling, and of knowing.

This increase has not been universal; many organisms have remained stationary or have even regressed; many have shown increase in one particular but not in others. But the upper level of these properties of living matter has been continually raised, their average has continually increased. It is to this increase, continuous during evolutionary time, in the average and especially in the upper level of these properties that, I venture to think, the term biological progress can be properly applied.

Used thus it is no more an a priori or an undefined concept. It is a name for a complicated set of actual phenomena, and if, with progress thus defined, we were to speak of a law of progress in evolution, we should be using the term law in a perfectly legitimate way, as denoting a generalization based on observed facts, and not as pre-supposing any vitalistic principle of perfectibility, any necessary and mysterious tendency of organisms to advance independently of circumstances.

The gas laws state that the pressure of a gas kept at constant volume increases in a particular way with increase of temperature. Now the pressure of a confined gas depends on the rate at which its particles bombard the walls in which they are contained, and the speed at which they are travelling. In a gas whose temperature is raised, many particles will, at any given moment, be travelling more slowly than the average rate when it was cooler, many even which had been travelling fast may now be travelling slowly. None the less, the average speed of all the particles is greater; and this and nothing else is what with perfect justification we sum up as our law.

In biological evolution, some organisms degenerate, some remain stationary, but the average of certain properties, and more especially their upper level, increases; and this tendency for certain properties to become more marked, this and nothing else, is what we sum up and generalize, again with perfect justification, as the law of biological progress.

The mechanism of biological progress demands a word: for it is noticeable that a mere fact, however well attested, makes a very different kind of impression from a fact explained and brought into relation with the rest of our knowledge. The impression is either less powerful; or else, an explanation being sought for, an erroneous one is found. It was Darwin’s great merit that, not content with the piling up of evidence in favour of the reality of Evolution, he at the same time advanced a theory which made it at least possible to understand how Evolution could have come to pass as a natural process. The effect was multiplicative on men’s minds, not merely additive, for facts are too bulky to be lugged about conveniently except on wheels of theory.

The fact of biological progress has struck many observers. Some have been content to believe that the single magic formula of “Natural Selection” would explain it adequately and without further trouble, forgetting that there must be at least some points of difference between a natural selection producing a degenerate type and natural selection leading to progress. Some biologists have lumped it, together with all other evolutionary processes which seem to show us a development along predetermined lines, under the head of orthogenesis—the (hypothetical!) tendency of organisms to unfold just one type of hidden potentiality. Bergson has been particularly struck with it: refuses to allow that it can have anything to do with Natural Selection or any determinist process, and ascribes it to his élan vital.

Here, as so often elsewhere, Bergson reveals himself as a good poet but a bad scientist. His intellectual vision of evolution as a fact, as something happening, something whole, to be apprehended in a unitary way—that is unsurpassed. He seems to see it as vividly as you or I might see a hundred yards race, holding its different incidents and movements all in his mind together to form one picture. But he then goes on to give a symbolic description of what he sees—and then thinks that his symbols will serve in place of analytic explanations. There is an “urge of life”; and it is, as a matter of fact, urging life up the steps of progress. But to say that biological progress is explained by the élan vital is to say that the movement of a train is “explained” by an élan locomotif of the engine: it is to fall into the error, so often condemned in scientists by philosophers, and ridiculed in both by satirists, of hanging or at least disposing of a difficulty by giving it a long name.

Let us think of the condition of life on earth at any given moment of her evolution. Certain possibilities have been realized by her—others have not. To take a trenchant example, before the Carboniferous or thereabouts, the vertebrates had not realized their possibilities of terrestrial existence—nearly half the globe’s surface lay waiting to be colonized by backboned animals. The earth’s surface was conquered then—but the air remained unsubdued before the mid-Secondary. In every period, there must be not only actual gaps unfilled in the economy of nature—such and such an animal is without parasites, such and such a hot spring or salt lake is without tenants; but also improvements can be made in existing types of organization—a tapeworm could be more firmly attached, a salt-lake shrimp could tolerate an even higher concentration of brine.

These two sorts of possibilities really overlap. For instance, an increased efficiency of vision must be an improvement in pre-existing structures and creatures; it also involves the conquest of new regions of environment, and so in a real sense the occupation of a new biological niche.

In any case, the changes which would confer advantage in the struggle for existence may take place in any direction—with, or against, or at right angles to the stream of progress. By means of those which march with that stream, the upper level of life’s attainment is raised. But the struggle still goes on: and again, starting from this new condition, there will be variations in every direction which will have survival value, and some of these will be progressive; and so the upper level will be once more raised.

The process will take time, for, whatever theory of variation we may hold[8]—the old idea of small continuous variations; or that of large mutations big enough to produce new species at one jump; or the most probable theory of numerous small mutations—they one and all must grant that the largest variation occurring at one time in a living species is infinitesimal in comparison with the secular changes of evolution.

There will further be a premium upon progressive changes, since a progressive change will generally land its possessor in virgin soil, so to speak; if not in an actually new physical environment, then in a biologically new situation. The placental mammal occupies the same dry land as did the wonderful reptilian types of the Secondary epoch. But constant temperature and embryonic nutrition within its mother provide delicately adjusted conditions in the early phases of development which in their turn enabled a more elaborate and more delicately responding brain machinery to be constructed in development, and so advanced their possessors on to new shores of control and independence.

There will thus be a constant biological pressure (to use a term which, though still symbolic, a mere analogy, is less misleading and question-begging than élan vital) tending to push some of life on to new levels of attainment, new steps in progress, because any variations in that direction will have selection value, a selection value above the ordinary. And the process will be a gradual one, because variations are not very large; so that life no more realizes all potentialities of progress at once than did the United States or any other new country receive a uniform population over all its extent as soon as it was discovered, but had its people move in from the coasts in a regular and orderly advance.

There are plenty of parallels from human affairs. Indeed, the evolutionist can often gain valuable light on his subject, on what one may call the economics of the process, by turning to study the development of human inventions and machines. There, although the ways in which variations arise, and the way they are transmitted, are different from those of organic evolution, yet the type of “pressure,” the perpetual struggle, and the advantage of certain kinds of variation therein—these are in essence really similar.

What could be more striking than the parallel between the rise of the mammals to dominance over the reptiles, and the rise of the motor vehicle to dominance over that drawn by horses?

In both cases, a comparatively long period in which the new type is in a precarious and experimental stage, only just managing to exist, of small size and rare occurrence, and in no real sense a serious rival to its old-established competitors. Then, suddenly, a change. It reaches a level at which it can effectively compete with them. What happens? In the case both of man-made machine and evolving vertebrate group, there is first a sudden increase in numbers of the new, a corresponding decrease in numbers of the old type. The upper level of size of the new type also begins to increase, and it begins to split up into a great number of differentiated sub-types. Some of these sub-types become extinct, others, on the other hand, are gradually improved, while still others undergo such rapid change as to merit the style of new sub-types. The upper level of size, complexity, and efficiency increase, both in animal and machine.

It is as well to remember that survival-value means only what it says. A variation with survival-value helps its possessors to survive: it is not the best possible variation of the kind. In the developing motor-car, the substitution of four for one or two cylinders was a great improvement. It had “survival-value”; and not until the majority of cars came to be four-cylindered was the additional advantage of six or eight cylinders large enough to bring them into existence as dominant types.

To the interrelated evolution of carnivore and herbivore, again, leading to increase of size and speed in both, of wariness in one, of tooth and claw in the other, we have again a close parallel in the interrelated evolution of armour-plating and of projectiles. Here again the process is gradual. We can further see that the sudden “development” of full modern armour on the first iron-clad would have been actually disadvantageous, since it would have reduced its speed relatively to other less heavily protected ships, without conferring any corresponding benefit in the way of defence against the comparatively inefficient projectiles of the day. Only when the range and piercing power of the projectiles increased did increase of armour become imperative.

To resume our pressure analogy, the natural increase of all organisms leads to a “biological pressure.” So long as a species remains unchanged, so long must it stay subjected to the full force of this pressure. But if it changes in such a way that it can occupy a new niche in environment, it is expanding into a vacuum or a region of lower pressure. Natural increase soon fills this up to the same level of pressure, and conditions thus become favourable for expansion into new low-pressure areas previously out of reach of the normal range of variation. Variation towards such “low-pressure” regions may be progressive, retrogressive, or neutral: but it is obvious that at each stage of evolution there will always be a low-pressure fringe, representing a considerable fraction of the “low-pressure” area within the range of variability, the occupation of which would be biologically progressive.

Thus from the well-established biological premisses of (1) the tendency to geometrical increase with consequent struggle for existence, (2) some form of inherited variability, we can deduce as necessary consequence, not only the familiar but none the less fundamental fact of Natural Selection, but also the almost neglected fact that a certain fraction of the guiding force of Natural Selection will inevitably be pushing organisms into changes that are progressive.