Part 5

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.

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. 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.