Front Page Titles (by Subject) CHAPTER XVII.: THE LAW OF EVOLUTION CONCLUDED. - First Principles
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CHAPTER XVII.: THE LAW OF EVOLUTION CONCLUDED. - Herbert Spencer, First Principles 
First Principles, 2nd ed. (London: Williams and Norgate, 1867).
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THE LAW OF EVOLUTION CONCLUDED.
§ 139. The conception of Evolution elaborated in the foregoing chapters, is still incomplete. True though it is it is not the whole truth. The transformations which all things undergo during the ascending phases of their existence, we have contemplated under three aspects; and by uniting these three aspects as simultaneously presented, we have formed an approximate idea of the transformations. But there are concomitant changes about which nothing has yet been said; and which, though less conspicuous, are no less essential.
For thus far we have attended only to the re-distribution of Matter, neglecting the accompanying re-distribution of Motion. Distinct or tacit reference has, indeed, repeatedly been made to the dissipation of Motion, that goes on along with the concentration of Matter; and were all Evolution absolutely simple, the total fact would be contained in the proposition that as Motion dissipates Matter concentrates. But while we have recognized the ultimate re-distribution of the Motion, we have passed over its proximate re-distribution. Though something has from time to time been said about the escaping motion, nothing has been said about the motion that does not escape. In proportion as Evolution becomes compound—in proportion as an aggregate retains, for a considerable time, such a quantity of motion as permits secondary re-distributions of its component matter, there necessarily arise secondary re-distributions of its retained motion. As fast as the parts are transformed, there goes on a transformation of the sensible or insensible motion possessed by the parts. The parts cannot become progressively integrated, either individually or as a combination, without their motions, individual or combined, becoming more integrated. There cannot arise among the parts heterogeneities of size, of form, of quality, without there also arising heterogeneities in the amounts and directions of their motions, or the motions of their molecules. And increasing definiteness of the parts implies increasing definiteness of their motions. In short, the rhythmical actions going on in each aggregate, must differentiate and integrate at the same time that the structure does so.
The general theory of this re-distribution of the retained motion, must here be briefly stated. Properly to supplement our conception of Evolution under its material aspect by a conception of Evolution under its dynamical aspect, we have to recognize the source of the integrated motions that arise, and to see how their increased multiformity and definiteness are necessitated. If Evolution is a passage of matter from a diffused to an aggregated state—if while the dispersed units are losing part of the insensible motion which kept them dispersed, there arise among coherent masses of them, any sensible motions with respect to one another; then this sensible motion must previously have existed in the form of insensible motion among the units. If concrete matter arises by the aggregation of diffused matter, then concrete motion arises by the aggregation of diffused motion. That which comes into existence as the movement of masses, implies the cessation of an equivalent molecular movement. While we must leave in the shape of hypothesis the belief that the celestial motions have thus originated, we may see, as a matter of fact, that this is the genesis of all sensible motions on the Earth’s surface. As before shown (§69), the denudation of lands and deposit of new strata, are effected by water in the course of its descent to the sea, or during the arrest of those undulations produced on it by winds; and, as before shown, the elevation of water to the height whence it fell, is due to solar heat, as is also the genesis of those aerial currents which drift it about when evaporated and agitate its surface when condensed. That is to say, the molecular motion of the etherial medium is transformed into the motion of gases, thence into the motion of liquids, and thence into the motion of solids—stages in each of which a certain amount of molecular motion is lost and an equivalent motion of masses gained. It is the same with organic movements. Certain rays issuing from the Sun, enable the plant to reduce special elements existing in gaseous combination around it, to a solid form—enable the plant, that is, to grow and carry, on its functional changes. And since growth, equally with circulation of sap, is a mode of sensible motion, while those rays which have been expended in generating it consist of insensible motions, we have here, too, a transformation of the kind alleged. Animals, derived as their forces are, directly or indirectly, from plants, carry this transformation a step further. The automatic movements of the viscera, together with the voluntary movements of the limbs and body at large, arise at the expense of certain molecular movements throughout the nervous and muscular tissues; and these originally arose at the expense of certain other molecular movements propagated by the Sun to the Earth; so that both the structural and functional motions which organic Evolution displays, are motions of aggregates generated by the arrested motions of units. Even with the aggregates of these aggregates the same rule holds. For among associated men, the progress is ever towards a merging of individual actions in the actions of corporate bodies. While, then, during Evolution, the escaping motion becomes, by perpetually widening dispersion, more disintegrated, the motion that is for a time retained, becomes more integrated; and so, considered dynamically, Evolution is a decrease in the relative movements of parts and an increase in the relative movements of wholes—using the words parts and wholes in their most general senses. The advance is from the motions of simple molecules to the motions of compound molecules; from molecular motions to the motions of masses; and from the motions of smaller masses to the motions of larger masses. The accompanying change towards greater multiformity among the retained motions, takes place under the form of an increased variety of rhythms. We have already seen that all motion is rhythmical, from the infinitesimal vibrations of infinitesimal molecules, up to those vast oscillations between perihelion and aphelion performed by vast celestial bodies. And as the contrast between these extreme cases suggests, a multiplication of rhythms must accompany a multiplication in the degrees and modes of aggregation, and in the relations of the aggregated masses to incident forces. The degree or mode of aggregation will not, indeed, affect the rate or extent of rhythm where the incident force increases as the aggregate increases, which is the case with gravitation: here the only cause of variation in rhythm, is difference of relation to the incident forces; as we see in a pendulum, which, though unaffected in its movements by a change in the weight of the bob, alters its rate of oscillation when taken to the equator. But in all cases where the incident forces do not vary as the masses, every new order of aggregation initiates a new order of rhythm: witness the conclusion drawn from the recent researches into radiant heat and light, that the molecules of different gases have different rates of undulation. So that increased multiformity in the arrangement of matter, necessarily generates increased multiformity of rhythm; both through increased variety in the sizes and forms of aggregates, and through increased variety in their relations to the forces which move them. That these motions as they become more integrated and more heterogeneous, must become more definite, is a proposition that need not detain us. In proportion as any part of an evolving whole segregates and consolidates, and in so doing loses the relative mobility of its components, its aggregate motion must obviously acquire distinctness.
Here, then, to complete our conception of Evolution, we have to contemplate throughout the Cosmos, these metamormorphoses of retained motion that accompany the metamorphoses of component matter. We may do this with comparative brevity: the reader having now become so far familiar with the mode of looking at the facts, that less illustration will suffice. To save space, it will be convenient to deal with the several aspects of the metamorphoses at the same time.
§ 140. Dispersed matter moving, as we see it in a spiral nebula, towards the common centre of gravity, from all points at all distances with all degrees of indirectness, must carry into the nebulous mass eventually formed, innumerable momenta contrasted in their amounts and directions. As the integration progresses, such parts of these momenta as conflict are mutually neutralized, and dissipated as heat. The out-standing rotatory motion, at first having unlike angular velocities at the periphery and at various distances from the centre, has its differences of angular velocity gradually reduced; advancing towards a final state, now nearly reached by the Sun, in which the angular velocity of the whole mass is the same—in which the motion is integrated. So, too, with each planet and satellite. Progress from the motion of a nebulous ring, incoherent and admitting of much relative motion within its mass, to the motion of a dense spheroid, is progress to a motion that is completely integrated. The rotation, and the translation through space, severally become one and indivisible. Meanwhile, there goes on that further integration by which the motions of all the parts of the Solar System are rendered mutually dependent. Locally in each planet and its satellites, and generally in the Sun and the planets, we have a system of simple and compound rhythms, with periodic and secular variations, forming together an integrated set of movements.
The matter which, in its original diffused state, had motions that were confused, indeterminate, or without sharply-marked distinctions, has, during the evolution of the Solar System, acquired definitely heterogeneous motions. The periods of revolution of all the planets and satellites are unlike; as are also their times of rotation. Out of these definitely heterogeneous motions of a simple kind, arise others that are complex, but still definite;—as those produced by the revolutions of satellites compounded with the revolutions of their primaries; as those of which precession is the result; and as those which are known as perturbations. Each additional complexity of structure has caused additional complexity of movements; but still, a definite complexity, as is shown by having calculable results.
§ 141. While the Earth’s surface was molten, the currents in the voluminous atmosphere surrounding it, mainly of ascending heated gases and of descending precipitated liquids, must have been local, numerous, indefinite, and but little distinguished from one another. But as fast as the surface cooled, and solar radiation began to cause appreciable differences of temperature between the equatorial and polar regions, a decided atmospheric circulation from poles to equator and from equator to poles, must have slowly established itself: the vast moving masses of air becoming, at last, trade-winds and other such permanent definite currents. These integrated motions, once comparatively homogeneous, were rendered heterogeneous as great islands and continents arose, to complicate them by periodic winds, caused by the varied heating of wide tracts of land at different seasons. Rhythmical motions of a constant and simple kind, were, by increasing multiformity of the Earth’s surface, differentiated into an involved combination of constant and recurrent rhythmical motions, joined with smaller motions that are irregular.
Parallel changes must have taken place in the motions of water. On a thin crust, admitting of but small elevations and depressions, and therefore of but small lakes and seas, none beyond small local circulations were possible. But along with the formation of continents and oceans, came the vast movements of water from warm latitudes to cold and from cold to warm—movements increasing in amount, in definiteness, and in variety of distribution, as the features of the Earth’s surface became larger and more contrasted. The like holds with drainage waters. The tricklings of insignificant streams over narrow pieces of land, were once the only motions of such waters; but as fast as wide areas came into existence, the motions of many tributaries became massed into the motions of great rivers; and instead of motions very much alike, there arose motions considerably varied.
Nor can we well doubt that the movements in the Earth’s crust itself, have presented an analogous progress. Small, numerous, local, and very much like one another, while the crust was thin, the elevations and subsidences must, as the crust thickened, have extended over larger areas, must have continued for longer eras in the same directions, and must have been made more unlike in different regions by local differences of structure in the crust.
§ 142. In organisms the advance towards a more integrated, heterogeneous, and definite distribution of the retained motion, which accompanies the advance towards a more integrated, heterogeneous, and definite distribution of the component matter, is mainly what we understand as the development of functions. All active functions are either sensible movements, as those produced by contractile organs; or such insensible movements as those propagated through the nerves; or such insensible movements as those by which, in secreting organs, molecular re-arrangements are effected, and new combinations of matter produced. And what we have here to observe is, that during evolution, functions, like structures, become more consolidated individually, as well as more combined with one another, at the same time that they become more multiform and more distinct.
The nutritive juices in animals of low types, move hither and thither through the tissues quite irregularly, as local strains and pressures determine: in the absence of a distinguishable blood and a developed vascular system, there is no definite circulation. But along with the structural evolution which establishes a finished apparatus for distributing blood, there goes on the functional evolution which establishes large and rapid movements of blood, definite in their courses and definitely distinguished as efferent and afferent, and that are heterogeneous not simply in their directions but in their characters—being here divided into gushes and there continuous.
Instance, again, the way in which, accompanying the structural differentiations and integrations of the alimentary canal, there arise differentiations and integrations both of its mechanical movements and its actions of a non-mechanical kind. Along an alimentary canal of a primitive type, there pass, almost uniformly from end to end, waves of constriction. But in a well-organized alimentary canal, the waves of constriction are widely unlike at different parts, in their kinds, strengths, and rapidities. In the mouth they become movements of prehension and mastication—now occurring in quick succession and now ceasing for hours. In the oesophagus these contractions, propulsive in their office, and travelling with considerable speed, take place at intervals during eating, and then do not take place till the next meal. In the stomach another modification of this originally uniform action occurs: the muscular constrictions are powerful, and continue during the long periods that the stomach contains food. Throughout the upper intestines, again, a further difference shows itself—the waves travel along without cessation but are relatively moderate. Finally, in the rectum this rhythm departs in another way from the common type: quiescence lasting for many hours, is followed by a series of strong contractions. Meanwhile, the essential actions which these movements aid, have been growing more definitely heterogeneous. Secretion and absorption are no longer carried on in much the same way from end to end of the tube; but the general function divides into various subordinate functions. The solvents and ferments furnished by the coats of the canal and the appended glands, become widely unlike at upper, middle, and lower parts of the canal; implying different kinds of molecular changes. Here the process is mainly secretory, there it is mainly absorbent, while in other places, as in the œsophagus, neither secretion nor absorption takes place to any appreciable extent. While these and other internal motions, sensible and insensible, are being rendered more various, and severally more consolidated and distinct, there is advancing the integration by which they are united into local groups of motions and a combined system of motions. While the function of alimentation sub-divides, its sub-divisions become co-ordinated, so that muscular and secretory actions go on in concert, and so that excitement of one part of the canal sets up excitement of the rest. Moreover, the whole alimentary function, while it supplies matter for the circulatory and respiratory functions, becomes so integrated with them that it cannot for a moment go on without them. And, as evolution advances, all three of these fundamental functions fall into greater subordination to the nervous functions—depend more and more on the due amount of nervous discharge.
When we trace up the functions of external organs the same truth discloses itself. Microscopic creatures are moved through the water by oscillations of the cilia covering their surfaces; and various larger forms, as the Turbellaria, progress by ciliary action over solid surfaces. These motions of cilia are, in the first place, severally very minute; in the second place they are homogeneous; and in the third place there is but little definiteness in them individually, or in their joint product, which is mostly a mere random change of place not directed to any selected point. Contrasting this ciliary action with the action of developed locomotive organs of whatever kind, we see that instead of innumerable small or unintegrated movements there are a few comparatively large or integrated movements; that actions all alike are replaced by actions partially unlike; and that instead of being very feebly or almost accidentally co-ordinated, their co-ordination is such as to render the motions of the body as a whole, precise. A parallel contrast, less extreme but sufficiently decided, is seen when we pass from the lower types of creatures with limbs to the higher types of creatures with limbs. The legs of a Centipede have motions that are numerous, small, and homogeneous; and are so little integrated that when the creature is divided and sub-divided, the legs belonging to each part propel that part independently. But in one of the higher Annulosa, as a Crab, the relatively few limbs have motions that are comparatively large in their amounts, that are considerably unlike one another, and that are integrated into compound motions of tolerable definiteness.
§ 143. The last illustrations are introductory to illustrations of the kind we class as psychical. They are the physiological aspects of the simpler among those functions which, under a more special and complex aspect, we distinguish as psychological. The phenomena subjectively known as changes in consciousness, are objectively known as nervous excitations and discharges, which science now interprets into modes of motion. Hence, in following up organic evolution, the advance of retained motion in integration, in heterogeneity, and in definiteness, may be expected to show itself alike in the visible nervo-muscular actions and in the correlative mental changes. We may conveniently look at the facts as exhibited during individual evolution, before looking at them as exhibited in general evolution.
The progress of a child in speech, very completely exhibits the transformation. Infantine noises are comparatively homogeneous; alike as being severally long-drawn and nearly uniform from end to end, and as being constantly repeated with but little variation of quality between narrow limits. They are quite un-coordinated—there is no integration of them into compound sounds. They are inarticulate, or without those definite beginnings and endings characterizing the sounds we call words. Progress shows itself first in the multiplication of the inarticulate sounds: the extreme vowels are added to the medium vowels, and the compound to the simple. Presently the movements which form the simpler consonants are achieved, and some of the sounds become sharply cut; but this definiteness is partial, for only initial consonants being used, the sounds end vaguely. While an approach to distinctness thus results, there also results, by combination of different consonants with the same vowels, an increase of heterogeneity; and along with the complete distinctness which terminal consonants give, arises a further great addition to the number of unlike sounds produced. The more difficult consonants and the compound consonants, imperfectly articulated at first, are by and by articulated with precision; and there comes yet another multitude of different and definite words—words that imply many kinds of vocal movements, severally performed with exactness, as well as perfectly integrated into complex groups. The subsequent advance to dissyllables and polysyllables, and to involved combinations of words, shows the still higher degree of integration and heterogeneity eventually reached by these organic motions. The acts of consciousness correlated with these nervo-muscular acts, of course go through parallel phases; and the advance from childhood to maturity yields daily proof that the changes which, on their physical side are nervous processes, and on their mental side are processes of thought, become more various, more defined, more coherent. At first the intellectual functions are very much alike in kind—recognitions and classifications of simple impressions alone go on; but in course of time these functions become multiform. Reasoning grows distinguishable, and eventually we have conscious induction and deduction; deliberate recollection and deliberate imagination are added to simple unguided association of ideas; more special modes of mental action, as those which result in mathematics, music, poetry, arise; and within each of these divisions the mental processes are ever being further differentiated. In definiteness it is the same. The infant makes its observations so inaccurately that it fails to distinguish individuals. The child errs continually in its spelling, its grammar, its arithmetic. The youth forms incorrect judgments on the affairs of life. Only with maturity comes that precise co-ordination in the nervous processes that is implied by a good adjustment of thoughts to things. Lastly, with the integration by which simple mental acts are combined into complex mental acts, it is so likewise. In the nursery you cannot obtain continuous attention—there is inability to form a coherent series of impressions; and there is a parallel inability to unite many co-existent impressions, even of the same order: witness the way in which a child’s remarks on a picture, show that it attends only to the individual objects represented, and never to the picture as a whole. But with advancing years it becomes possible to understand an involved sentence, to follow long trains of reasoning, to hold in one mental grasp numerous concurrent circumstances. The like progressive integration takes place among the mental changes we distinguish as feelings; which in a child act singly, producing impulsiveness, but in an adult act more in concert, producing a comparatively balanced conduct.
After these illustrations supplied by individual evolution, we may deal briefly with those supplied by general evolution, which are analogous to them. A creature of very low intelligence, when aware of some large object in motion near it, makes a spasmodic movement, causing, it may be, a leap or a dart. The perceptions implied are relatively simple, homogeneous, and indefinite: the moving objects are not distinguished in their kinds as injurious or otherwise, as advancing or receding. The actions of escape are similarly all of one kind, have no adjustments of direction, and may bring the creature nearer the source of peril instead of further off. A stage higher, when the dart or the leap is away from danger, we see the nervous changes so far specialized that there results distinction of direction; indicating a greater variety among them, a greater co-ordination or integration of them in each process, and a greater definiteness. In still higher animals that discriminate between enemies and not-enemies, as a bird that flies from a man but not from a cow, the acts of perception have severally become united into more complex wholes, since cognition of certain differential attributes is implied; they have become more multiform, since each additional component impression adds to the number of possible compounds; and they have, by consequence, become more specific in their correspondences with objects—more definite. And then in animals so intelligent that they identify by sight not species only but individuals of a species, the mental changes are yet further distinguished in the same three ways. In the course of human evolution the law is equally manifested. The thoughts of the savage are nothing like so heterogeneous in their kinds as those of the civilized man, whose complex environment presents a multiplicity of new phenomena. His mental acts, too, are much less involved—he has no words for abstract ideas, and is found to be incapable of integrating the elements of such ideas. And in all but simple matters there is none of that precision in his thinking which, among civilized men, leads to the exact conclusions of science. Nor do the emotions fail to exhibit a parallel contrast.
§ 144. How in societies the movements or functions produced by the confluence of individual actions, increase in their amounts, their multiformities, their precision, and their combination, scarcely needs insisting upon after what has been pointed out in foregoing chapters. For the sake of symmetry of statement, however, a typical example or two may be set down.
Take the actions devoted to defence or aggression. At first the military function, undifferentiated from the rest (all men in primitive societies being warriors) is relatively homogeneous, is ill-combined, and is indefinite: savages making a joint attack severally fight independently, in similar ways, and without order. But as societies evolve and the military function becomes separate, we see that while its scale increases, it progresses in multiformity, in definiteness, and in combination. The movements of the thousands of soldiers that replace the tens of warriors, are divided and re-divided in their kinds—here are bodies that manœuvre and fire artillery; there are battalions that fight on foot; and elsewhere are troops that charge on horseback. Within each of these differentiated functions there come others: there are distinct duties discharged by privates, sergeants, captains, colonels, generals, as also by those who constitute the commissariat and those who attend to the wounded. The actions that have thus become comparatively heterogeneous in general and in detail, have simultaneously increased in precision. Accuracy of evolutions is given by perpetual drill; so that in battle, men and the regiments formed of them, are made to take definite positions and perform definite acts at definite times. Once more, there has gone on that integration by which the multiform actions of an army are directed to a single end. By a co-ordinating apparatus having the commander-in-chief for its centre, the charges, and halts, and retreats are duly concerted; and a hundred thousand individual actions are united under one will.
The progress here so clearly marked, is a progress traceable throughout social functions at large. Comparing the rule of a savage chief with that of a civilized government, aided by its subordinate local governments and their officers, down to the police in the streets, we see how, as men have advanced from tribes of tens to nations of millions, the regulative process has grown large in amount; how, guided by written laws, it has passed from vagueness and irregularity to comparative precision; and how it has sub-divided into processes increasingly multiform. Or observing how the barter that goes on among barbarians, differs from our own commercial processes, by which a million’s worth of commodities is distributed daily; by which the relative values of articles immensely varied in kinds and qualities are measured, and the supplies adjusted to the demands; and by which industrial activities of all orders are so combined that each depends on the rest and aids the rest; we see that the kind of action which constitutes trade, has become progressively more vast, more varied, more definite, and more integrated.
§ 145. A finished conception of Evolution we thus find to be one which includes the re-distribution of the retained motion, as well as that of the component matter. This added element of the conception is scarcely, if at all, less important than the other. The movements of the Solar System have for us a significance equal to that which the sizes, forms, and relative distances of its members possess. And of the phenomena presented by an organism, it must be admitted that the combined sensible and insensible actions we call its life, do not yield in interest to its structural traits. Leaving out, however, all implied reference to the way in which these two orders of facts concern us, it is clear that with each re-distribution of matter there necessarily goes a re-distribution of motion; and that the unified knowledge constituting Philosophy, must comprehend both aspects of the transformation.
While, then, we have to contemplate the matter of an evolving aggregate as undergoing, not progressive integration simply, but as simultaneously undergoing various secondary re-distributions; we have also to contemplate the motion of an evolving aggregate, not only as being gradually dissipated, but as passing through many secondary re-distributions on the way towards dissipation. As the structural complexities that arise during compound evolution, are incidental to the progress from the extreme of diffusion to the extreme of concentration; so the functional complexities accompanying them, are incidental to the progress from the greatest quantity of contained motion to the least quantity of contained motion. And we have to state these concomitants of both transformations, as well as their beginnings and ends.
Our formula, therefore, needs an additional clause. To combine this satisfactorily with the clauses as they stand in the last chapter, is scarcely practicable; and for convenience of expression it will be best to change their order. Doing this, and making the requisite addition, the formula finally stands thus:—Evolution is an integration of matter and concomitant dissipation of motion; during which the matter passes from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity; and during which the retained motion undergoes a parallel transformation.