Read Ebook: Essays of a Biologist by Huxley Julian

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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.

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 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.

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.

This has meant, among other things, that for the first time in biological history there has been an aggregation 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 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 supr?me" of human destiny, will eventually have "fait entrer dans l'homme tant d'azur qu'elle a supprim? 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.

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 , secondly by their aggregation; and this has been accompanied by a 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.

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.

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.

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.

The process will take time, for, whatever theory of variation we may hold--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 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.

This will of course be true only so far as the general conditions of the environment remain within certain limits: it is probable that too great reductions of temperature or moisture on the surface of the earth would lead to a gradual reversal of progress before the final extinction of life. Up to the present, however, it is clear that such conditions have not occurred, or, possibly, have occurred only for short periods. The general state has been one in which steady, slow progress has been achieved. Progress, like adaptation, is in pre-human evolution almost entirely the resultant of blind chance and blind necessity.

What corollaries and conclusions may be drawn from the establishment of the fact of biological progress? In the first place, it permits us to treat human progress as a special case of a more general process. Biologically speaking, the human species is young--not perhaps still in infancy, but certainly not yet attained to any stable maturity. The conception, common enough in much traditional thought, that man as a species is old, far removed from all pristine vigour and power, is demonstrably untrue. The genus Homo has not yet adapted itself to the new conditions and the new possibilities arising out of the acquisition of reason and tradition. Its history so far is a record of experiment after experiment. From a period so short and so empirical it is impossible to deduce any general law of progress. In certain respects, as we shall see more in detail later, there has been advance; in others, the species has been stationary. But whether humanity in this or that particular has progressed is for the moment comparatively immaterial. Humanity is part of life, a product of life's movement; and in life as a whole there is progress.

What is more, there was progress before man ever appeared on the earth, and its reality would have been in no way impaired even if he had never come into being. His rise only continued, modified, and accelerated a process that had been in operation since the dawn of life.

Here we find, in the intellectual sphere at least, that assurance which men have been seeking from the first. We see revealed, in the fact of evolutionary progress, that the forces of nature conspire together to produce results which have value in our eyes, that man has no right to feel helpless or without support in a cold and meaningless cosmos, to believe that he must face and fight forces which are definitively hostile. Although he must attack the problems of existence in a new way, yet his face is set in the same direction as the main tide of evolving life, and his highest destiny, the end towards which he has so long perceived that he must strive, is to extend to new possibilities the process with which, for all these millions of years, nature has already been busy, to introduce less and less wasteful methods, to accelerate by means of his consciousness what in the past has been the work of blind unconscious forces. "In la sua volontade ? nostra pace."

For this is one of the most remarkable facts of evolution--that consciousness, until a very late period, has played in it a negligible part. Indeed the rise of consciousness to become a factor of importance in evolution has been one of the most notable single items of progress. Darwin gave the deathblow to teleology by showing that apparently purposive structures could arise by means of a non-purposive mechanism. "Purpose" is a term invented to denote a particular operation of the human mind, and should only be used where a psychological basis may reasonably be postulated. On the other hand, a result can be attained by conscious purpose without the waste of time and of living material needed by the indirect method of natural selection; and thus the substitution of purposed for unpurposed progress is itself a step in progress.

As another corollary of our concept of progress, it follows that we can and should consider, not only the direction of any evolutionary process, but also its rate.

An evolutionary process, if it is to be considered progressive, must have a component in one particular direction--a direction which we have already defined. But this is not all; for even if it be moving in the right direction, and yet be moving extremely slowly, it may, if it have any interaction with a much more rapid progressive movement, actually exert a drag on this; its relative motion--relative to the main current of progress--will be backwards, and we may have to class it as the reverse of progressive. For example, the interaction of carnivore and herbivore, pursuer and pursued, led during the development of the vertebrates to the evolution of much that was good--speed, strength, alertness, and acuity of sense--and of many noble types of living things. But with the advent of man, different methods have been introduced, new modes of competition and advance; and the tiger and the wolf not only cease to be agents of progress in its new form, but definitely stand in its way and must be stamped out, or at least reduced to a condition in which they can no longer interfere as active agents in evolution.

Some such considerations as these will help perhaps to resolve various difficulties of ethics--how, for instance, that which seems good to me may seem evil to another. Even the good, if it be a drag on the better, is evil. Expressed thus, the proposition is a paradox; but expressed in terms of direction and relative speed, it is at once intelligible.

But the test of any such general biological theory as I have outlined will be its application to human problems. And here too, I venture to say, the value of biological method is apparent. What we ask, and rightly ask, is whether in the laws of biological progress we can find any principle which we can apply directly to guide us in devising methods for human progress.

I do not propose to follow the example of many rather hasty philosophers and biologists, who have thought that, whenever the study of lower organisms permitted the promulgation of a biological law, such law can be lifted bodily from its context and be applied without modification to human affairs. Man is an organism--but a very exceptional and peculiar organism. Any biological law which epitomizes only facts about the lower creatures is not a general biological law, for general biological laws must take account not only of plants and animals, but of man as well. In practice, however, the simplest method is to frame our biological laws without considering man, and then to see in what way they must be modified if they are to be applied to him.

Man differs biologically from other organisms in the following main ways. First, he has the power of thinking in concepts; in other words, his power of learning by experience is not always conditioned directly by the accidents of his own life, as is the case with animals endowed only with associative memory, but he can, by reaching the general from the special, attain to the possibility of dealing with many more, and more complicated, eventualities. Next, by means of speech, writing, and printing, he has developed a new mode of inheritance. Each community, and indeed humanity as a whole, transmits its peculiarities to later ages by means of tradition, using that word in its largest sense. Physical inheritance of the same type as in all higher animals and plants is the necessary basis, but the distinctive characters of any civilization are based on this new tradition-inheritance. Thirdly, the type of mind which has been evolved in man is much more plastic--a much more elastic and flexible mechanism than any tool previously evolved by life for handling the problems of existence. As a consequence of this we have the substitution of general educability for specific instincts. For the power of performing comparatively few actions smoothly and without trouble, there is exchanged the possibility of a vastly increased range of action, but one which has to be learnt. As another consequence, man has come by the power--impossible to any other organism--of leading what is to all intents and purposes a multiple existence. It is for this very reason difficult to fit man into many of the ordinary biological categories. The physical and mental structure and the mode of life of even the highest of the animals are for all practical purposes a fixed quantity. An ant, for all its delicacy of adjustment, is little less than a sentient cog shaped to fit in just one way into the machinery of the community; a dog, for all his power of learning, is tied down and imprisoned within a rigidity and narrowness of bodily and mental organization difficult for us to imagine.

Man passes freely from one aggregation to another. He can change his nation or his city; he can belong to a dozen organizations--biologically speaking, can be aggregated in a dozen different ways--and play a different part as unit in each. He can follow one profession in the morning, another at night, and be a hobby-horse rider in between.

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