Popular Science Monthly/Volume 11/October 1877/Cosmic and Organic Evolution
|COSMIC AND ORGANIC EVOLUTION|
The evolution of a world is not obviously identical with the evolution of an organism. From one point of view they may be regarded as, to a certain extent, opposite processes. Fully understood, they are different manifestations of one process, affected by very different circumstances. Regarding each as an aggregate which must equally run its course, the special histories of the two are quite unlike. The history of every aggregate consists of two parts, a rise and a. decline. It has its period of growth and its period of decadence. The first consists in a gradual progress from a diffused toward a concentrated state; the second is the return from the concentrated to the diffused state. The process involved in the first period is the integration of the matter of the aggregate, and the dissipation of its motion. In the second period this process is reversed: its matter is disintegrated, and motion is evolved. The first of these processes is termed evolution; the second, dissolution. In theory this is identical in all aggregates, and therefore the life-history of a plant is the same as that of a star.
But, while we may trace and understand the process in the former of these aggregates, and may declare such to be its law as the result of more or less accurate experimental proof, this is not the case with the latter. We see the varied forms of life spring into being and vanish out of being. We may watch them during their entire history, from the moment when they emerge from the imperceptible to that in which they are again lost in the imperceptible. We can observe all the processes of concentration, of differentiation of parts, and of integration of the whole, as well as those of equilibration, of decomposition, and final dissolution. Not so with the planet. Whatever theory may suggest or require, we are forced to confess a profound ignorance of the final destiny of worlds. So far as we are able to observe, the universal tendency of all matter is from the indefinite and homogeneous to the definite and heterogeneous; from a state of unstable to one of stable equilibrium. But this is only the morning of the life of any aggregate. We have no reason to suppose that, in all the myriad worlds of visible space, a single star presents to our gaze a condition representing the evening of its life. In the light of all our knowledge of the heavenly bodies and of the nebulæ, we study with absorbing interest the history of our own planet. From the confused gaseous condition in which it is supposed to have originally been, its motion has been gradually dissipated and its matter integrated, until only a comparatively thin envelope of gas—the atmosphere—remains. The rest has all assumed either the liquid or the solid form, the latter of which presents the nearest approach to complete stable equilibrium. And it can scarcely be doubted that this process still continues, and will continue, until ultimately this omnipresent eremacausis shall also reduce the waters and the atmosphere to the condition of stability and solidification—a state of planetary existence which many suppose our satellite to have already reached.
And may not this same law be called in to explain the heterogeneity of elementary matter, as known to chemistry? If all matter is primordially identical, as so many philosophers have dreamed, is it not philosophical to assume that our sixty-five known elements represent so many states of heterogeneity, so many distinct kinds of primary aggregates, which the matter of our globe and other worlds has taken on in its course from complete homogeneous instability toward its ultimate condition of stable equilibrium, as represented in what we know as solids?
However this may be, it is at least true that, so far as regards purely cosmical processes, the ascending series is the only one observable by us. For the "dead star," be it understood, represents, in the grand cycle of the redistribution of matter and motion, the meridian of its life, and not its close. Complete equilibration is the last act in the drama of evolution, and must be attained before the forces of dissolution commence their work. But we look in vain for any signs of the dissolution of the universe. Whatever theory may require, the fact ever remains that the process which we see going on in our portion of space is the process of evolution only. We see only the integration of matter and the dissipation of motion. We see only the tendency toward the condition of stable equilibrium. We see only the absorption of the gaseous and the establishment of the solid form of matter. All the theories by which it has been sought to compensate for the radiations of luminous bodies have proved mere speculations. We know that the sun is radiating its heat into space; we do not know that space is returning this dissipated motion, either to the sun or to any other centre. We see planets and stars in various stages of their progress toward the stable state; we have no reason to believe that any are in the condition of transition from the stable to the unstable state.
The moon is supposed to have already passed through most, if not all, of its stages from the gaseous to the solid condition. Its atmosphere has been absorbed, its waters have retreated into its interior or perhaps been converted into solids, and all its visible activities have apparently ceased. If there still exist volcanic activities upon it, as certain observations seem to prove, they are probably the only ones, and are themselves declining. Doubtless there are other bodies in our solar system whose equilibration is even more complete than that of the moon—as, perhaps, some asteroids, or the satellites cf the outer planets. They have run their long cosmical course, and have arrived at last at the final state of complete, stable equilibrium. This state is the goal of the whole process of evolution. It must, therefore, be regarded, when viewed from this standpoint, as the state of greatest perfection in the life of every aggregate. Many of the heavenly bodies have certainly advanced far toward this condition, and all are undoubtedly approaching it. But where is the evidence that any have commenced to reverse this process? What star is suspected of being in a state of disintegration? Where in all the universe do we see solids turning into liquids, and liquids into gases? Where and how are the radiations emitted by concentrating bodies being harvested again, and applied to the disintegration of completely integrated matter? In a word, amid all these manifest proofs of evolution, what proof exists of dissolution regarded as a cosmical process? We are bound to confess that there is none. We are justified in its assumption on a priori grounds alone, if at all. The law of the conservation of energy, now so well established in all the departments of physics, must be theoretically extended to the mechanics of space. This law is only another expression for the indestructibility of motion. If no motion can be destroyed, the same quantity must always exist in the universe. And as motion is necessarily nothing more than the local change of material atoms, all the solar and astral radiations must continue for all time to affect the same quantity of matter to the same extent. Hence these radiations cannot be wholly lost. Still, all this may be true, without affecting the question of the dissolution of worlds. The minute fraction of the sun's heat which is intercepted and absorbed by the different bodies of the solar system is utterly insufficient to ever effect their disintegration; and it is continually diminishing as the sun itself approaches the term of its existence: a fortiori, no such results can ever be produced by any of the more remote radiating bodies. All this motion is projected into space, and the history of its future work is wholly beyond our comprehension. It may continue to affect the ethereal atoms pervading space for all eternity, without exerting an appreciable influence upon concentrated matter. Even our right to project the law of conservation into the realms of space, where we daily see motion dissipated but never recomposed, has been called in question. Have we the right to assert that this motion, lost to our system, is not lost to the universe? True Science well knows how here to suspend its judgment, but it also knows how to restrain the hopeless cry of ignorabimus.
Mr. Herbert Spencer is therefore right in making evolution the fundamental principle of philosophy, and regarding dissolution, which is its exact opposite and correlate, as practically of very inferior importance. For, so far as the earth itself and the heavenly bodies are concerned, the very existence of such a process is in doubt. So far as our knowledge of the universe, as such, extends, but one law is anywhere observable, and that is the law of evolution. Indeed, evolution is but the process of which the principle is gravitation. Evolution is the concentration and integration of matter; its tendency is toward the condition of stable equilibrium. The contraction of a body is due to the attraction of its molecules. Gravitation alone can explain this tendency, and gravitation necessarily requires it. Evolution is therefore coextensive with gravitation. Whenever gravitation prevails, evolution must prevail. On the contrary, a condition of dissolution would require the prevalence of a force the reverse of gravitation—a repulsive and expansive force. Our acquaintance with the visible universe reveals no region of space where we can assume the prevalence of such a force. On the contrary, many fixed stars, and even nebulae, afford the strongest evidence of being under the dominion of an attractive force. Not, however, but that there exists in the universe abundant evidence of the possibility and reality of a repulsive or dissolving force. This is found, and with the greatest certainty, within the scope of our daily observation of the facts about us. And in at least one instance it is assumed, with a high degree of proof, to manifest itself in regions beyond the limits of terrestrial influence. I refer to the behavior of the tails of comets at perihelion. But wherever we see this force of repulsion, which alone could effect the dissolution of the aggregates already formed, it is wholly subordinate to the force of attraction which has formed them. Phenomena of this nature are but episodes in the history of a system or of a world. Everywhere the opposite phenomena predominate. Everywhere the force of gravity is evolving new aggregates, and bearing old ones on to their final state of complete equilibration.
Let us now turn to the second branch of our subject, and glance for a moment at the phenomena and laws of organic evolution. The first fact that presents itself is, that its primary condition is the influence of the sun. However it may have been at one period of the history of the earth, when its internal temperature may have been of a nature to favor the development of organic life without the sun's aid, by the earth becoming itself a sort of sun, it may at least be now affirmed that the solar radiations are the sole condition of vital existence on the globe. This fact is so apparent that even savages have generally recognized it, and science has scarcely been able to qualify the popular conception. By the aid of the sun's heat and light the various forms of vegetable and animal life have been evolved. By the same influence, year by year, the buds, and flowers, and leaves, unfold to the elements, and renew their conditions of growth and reproduction. By means of it the waters of the globe are in part converted into vapor and gas, in which state alone they are adapted to the supply of organic beings. By its influence the various organic bodies on the surface of the earth are finally disintegrated, and the materials for new forms and new beings are dissipated into the gaseous form, for recomposition and reutilization. By the same influence the waters of the globe are prevented from solidifying, and made the abode of millions of organic beings. In a word, it is the influence of the sun which alone renders our planet a habitable globe.
But what is the nature of this great and wonderful influence as expressed in the terms of the redistribution of matter? However paradoxical it may seem, it is nevertheless true that the great life creating and life-sustaining force of the sun is cosmologically a disintegrating force, a force of dissolution. Indeed, the solar and sidereal radiations are the only examples which the whole universe presents to us of such a force. It seems strange enough to be compelled to ascribe all the phenomena which have been embodied in the term organic evolution to the action of a force which is the precise opposite of evolution, and which ultimately accomplishes the dissolution of every such aggregate. Yet it is only because the sun is in a state in which its matter is being integrated, and its motion radiated into space, that our earth is capable of producing the forms of organic life. It is only because a portion of this motion, ejected from the sun, is intercepted and absorbed by the earth, by which a portion of its own matter is disintegrated, and its own course of evolution is in so far arrested that the presence of the beings peopling it has been made possible. It is only through cosmical dissolution that organic evolution can go on.
Is life, then, a process of dissolution? Is organic evolution a misnomer? Are the unfolding of the bud, the branching of the tree, the hatching of the egg, the differentiation of the animal—are these but so many steps which concentrated matter is taking toward its final disintegration? Is development the antithesis of evolution? To all these questions a negative answer may, I think, be given. But we have gone far enough to perceive that some broad distinction exists between cosmic and organic evolution. Let us examine this distinction more closely. We know that an organism develops, much like a world, out of an homogeneous and diffused state of its elements. Throughout its course the organic aggregate behaves like other aggregates. From the imperceptible it becomes perceptible. From the diffuse it becomes concentrated. From the indefinite it becomes definite. From the homogeneous it becomes heterogeneous. From the unstable it approaches the stable condition. Segregation, which is the selective process, is more marked in the organic than in the inorganic aggregate. Its parts are differentiated and rendered distinct and definite, while through an increasing dependence between them the whole aggregate becomes more and more firmly integrated or consolidated. Growth, which is increase of bulk, is simply the absorption of diffuse gaseous or liquid materials, which may theoretically be regarded as having originally belonged to the aggregate in its most widely diffused condition. Development, which is increase of structure, is the same process which all aggregates undergo in their transition from the homogeneous and indefinite toward the heterogeneous and definite, under the laws of segregation and the multiplication of effects. Finally, equilibration in organic aggregates is distinct and universal.
Every organism must reach this stage, and that in a comparatively brief period—so brief as to be capable of repeated and easy observation. So plain does this stage of its progress become that it is feared that the predication of a stage of equilibration, not to say dissolution, for inorganic aggregates, is an argument from analogy, where the analogy is taken from a very subordinate class of phenomena, viz., from the observed equilibration of organic aggregates. A universal conclusion is deduced from a particular case; the law of the whole is assumed from that of a part. This, according to Mr. Spencer's own showing in his "Principles of Psychology," is the weakest form of reasoning. It should be admitted, however, that while the doctrine of the ultimate disintegration and dissolution of the celestial bodies rests on very insufficient inductive evidence, there are strong a priori grounds, beyond the domain of science, but clearly within the range of philosophy, which make it a legitimate object for the exercise of the "constructive imagination."
The most important truth which can be called in to aid us in this difficulty and apparent confusion of phenomena is that of the perpetual competitive operation of both the forces of evolution and of dissolution. Both these influences are at all times and in all kinds of aggregates simultaneously at work. The history of every aggregate is that of its struggle with these opposite contending influences. The final equilibration implies this. It is the establishment of equilibrium between just these forces. In the evolution of a star the forces of dissolution are mostly within the aggregate. In that of a star-system they seem to be wholly so. The process of evolution goes on against the inherent tendencies to dissolution. The equilibrium reached is between the attractive or integrating and the repulsive or disintegrating forces. Both are at all times active, and, if the latter at last prevail and the mode of redistribution is reversed, the gravitative influence still continues to oppose its progress. In an organism the disintegrating tendencies are chiefly from without. Everywhere on the globe the sun's influence is tending to prevent the integration of the liquid and gaseous elements. Life is the product of this struggle.
It may be laid down, as a universal law of the redistribution of matter, that organization is the product of the antagonistic tendencies of attraction and repulsion during the period in which the former prevails. Organization is, then, the great distinguishing characteristic of the process of evolution. The organization of the solar system is the result of this competitive struggle between these two agencies. It is the same with an organism. We have, then, at last reached a plane of generalization in which the cosmical and the organic processes may be regarded as parallel and homologous throughout. The active principle which directly results in organization is that which Mr. Spencer denominates segregation, by which the like parts are brought together and unlike parts separated.
The final result of this process is the formation of many distinct and definite parts which are unlike one another—heterogeneous. Each of these definite parts, differing from all the rest in the same aggregate, is, within itself, homogeneous, i. e., consists of a uniform internal structure. The like particles, in consequence of the similarity of their properties, naturally gravitate to the same place. In the case of the earth the atmosphere or gaseous portion forms a uniform envelope around it, due clearly to the nature and homogeneity of its molecular constitution. The waters, for the same reason, form a partial second envelope within this. The hardened crust of solid matter comes next, and in like manner the entire organization of the earth might be explained. Exactly the same process takes place in a living organism. Its various organs, vessels, specialized tissues, and differentiated parts, are the result of this same law of mechanical selection. The difference in the properties of the matter of each is at once the cause of their segregation and of their organic function.
The point at which we have arrived, therefore, is this: Organization is the necessary consequence of the competition of the integrating and disintegrating forces, so long as the former prevail. The influence of the sim upon the matter of the globe is toward its disintegration and dissipation into gas. But for the opposing influence of gravitation, attraction, or concentration, this result would be speedily accomplished. But the resultant of these two antagonistic forces, at a time when their relative power is substantially what it now is on the surface of our globe, is such as to render possible the form of evolution which we denominate organic life. A certain amount of the matter of the globe is in the gaseous form. The gases themselves are differentiated into what we call oxygen, nitrogen, carbonic acid, and aqueous vapor, each of which exerts its special influence in the economy of vital existence, and without any one form of which, so far as we can see, life would be impossible. Another portion of the matter composing the earth exists in the liquid state, the chief form of which is water, of which more than half the weight of all organized beings consists. Evidently without water nothing answering to our conception of life could exist. Of the solid matter of the globe there exists the greatest heterogeneity, and it may be classified in a variety of different ways. Many, though probably by no means all, of the so called distinct substances known to us are of direct value in the formation of organic tissues, and certain of them are clearly indispensable, so far as we understand their office; as, for example, lime, phosphorus, iron, etc., etc. Certain of these substances are crystalline, others colloid in their structure, the latter of which possess peculiar adaptations to the formation of organic tissue. Finally, between the solid and the liquid state there exist all grades of transition, thus adding variety to the organic adaptations.
As the universal law of concentration or integration proceeds to reduce all these varied forms to one, and to cement all in a single homogeneous solid, it is met by the powerful but somewhat irregular and erratic force of the solar radiations, reënforcing the inherent cosmical influences already so far overcome in the evolution of the planet as to have brought it to its given state. The result of this conflict of forces is the condition in which we find our globe. Without the aid of the sun's rays, organic evolution might have been impossible. Without the aid of the cosmical force of concentration, in a certain way counteracting without neutralizing them, it would have equally been impossible. With such a predominance of the one as has probably prevailed in the past, or of the other as will probably prevail in the future, the particular form of evolution required to develop what we know as life seems also beyond the range of scientific probability. A few degrees more either of heat or of cold are sufficient to utterly destroy it. Of the latter, we have a near approach to a positive example in the state of things existing in regions round the poles of the earth's axis. Of the former, artificial proofs are easy, and certain desert regions of the globe constitute partial illustrations, easily completed by the imagination.
We thus learn what a precarious thing life is, within what narrow limits it is circumscribed, upon what slender conditions its possibility depends; contemplating which, we may be appalled to reflect how small a portion of the concentrated matter of space must be presumed to fall under these conditions. For, even if every world in space passes through this organic period, its duration must be ephemeral compared with the vast cycle of its existence.
The important truth that it has been sought to reach by these considerations is, that organic evolution is but one of the minor manifestations of universal evolution. It occurs at a stage of the process when the struggle between the contending forces is very great, if not at its greatest. It is the immediate product of that struggle, and cannot exist when either the one or the other greatly predominates. The force to which we universally ascribe all possibility of life is the force which is tending to disintegrate the matter of the globe by absorbing the motion of the sun. The force which constitutes evolution proper is that which bears down all life and reduces the face of Nature to a desert waste. The interaction of these two forces, where they are suitably proportioned, effects the organization of portions of the matter on the globe, and organization itself is life. The period of greatest organic perfection on a planet is therefore very different from the period of its greatest cosmical perfection, which corresponds with that of complete equilibration. Cosmical evolution is the history of the universe, organic evolution is a transient episode in the life of a paltry planet. We can only console ourselves with the belief that, but for this trifling digression of Nature, no being would have existed capable of formulating the laws of the universe.
Organic evolution must not, however, be restricted to the mere span which the life of an individual represents. To fully comprehend its scope, the conception of the organic aggregate should be extended to embrace all the life, past, present, and future, on the globe. The mysterious process of reproduction, unknown to all other aggregates, has the effect of binding all living organisms into one continuous whole, and giving to all terrestrial life the stamp of unity. The individuals of a race or species do not represent so many distinct aggregates. The qualities of antecedent forms, whether inherited or acquired, are transmitted to subsequent forms, thus conserving, as it were, all the organization previously evolved. Although the dissolution of the individual aggregate takes place, the work of evolution which has been going on within it is passed on to a new generation, to be there continued and again transmitted. The individual, therefore, becomes of comparatively small importance. The real organic aggregate is the race. The race alone is capable of receiving and preserving all the products of organic evolution. Ontogenetic development is lost sight of in the march of phylogenetic development. The individual is merged in the species, the species in the genus, the order, the class, and all are finally swallowed up in the tout ensemble of organized existence. Organic being, as such, is the final term to which the generalization must be carried before the true scope of organic evolution can be adequately grasped by the mind. Individuals perish and are decomposed; species become extinct; genera, families, and whole classes, are swept from the earth. The broadest divisions into which the organic kingdoms of Nature have been classified have each their periods of ascendency and decline. But organic evolution ever continues. Progress in organization is the constant result. It is always, on the whole, the less organized that gives way to the more organized. If the rich and exuberant cryptogamic vegetation of the Carboniferous epoch has dwindled away into the insignificant cryptogamic vegetation of our time, it has been succeeded by a phænogamic vegetation of far higher organization and nobler qualities. If the great saurian dynasty that ruled the Cretaceous age has surrendered its sceptre and disappeared from the stage of terrestrial life, a far higher mammalian dynasty, at whose head man now stands, has taken up that sceptre and is moving on to still loftier heights of organic development.
We have thus arrived at the highest point from which the phenomena of organic evolution can be surveyed. What do we see? We see that, in proportion as our point of view rises, the relative importance of the phenomena of dissolution to those of evolution diminishes. We see that the dissolution of the individual aggregate affects but little the evolution of the race-aggregate, and not at all that of the complete life-aggregate of the globe. We see that, amid all the evanescent forms that surround us, the evolution of life is constant; that of organic being as such there is no dissolution. We thus find the parallelism between cosmic and organic evolution, which at the outset seemed so paradoxical, and afterward so imperfect, to be at last complete. In the one as in the other, the only phenomena which we know to be universal are those of evolution. In the one as in the other, the opposite class of phenomena are wholly subordinate, special, and local. In the one as in the other, the forces of attraction and repulsion, of integration and disintegration, are in perpetual conflict. In the one as in the other, the organization of matter is the result. Just as the doctrine of the ultimate dissolution of the bodies of space rests on a priori deductions alone, unsupported by empirical observation, so must the final disorganization of the life of our globe be inferred from cosmological principles, which transcend the present limits of astronomy and physics. So far as we are capable of penetrating the mysteries of space or of life, we find that evolution is the law of the universe; while the forces which oppose that law, though powerful and ever active, are secondary and subordinate, and only seem to reverse it by the destruction of transient forms. In the genesis of world-systems this counter-evolutionary force consists in the inherent expansive power of diffused matter, or, what amounts to the same thing, in the resistance which such matter offers to the forces of condensation. In the phenomena of life this resistance comes chiefly from the sun, whose thermal radiations tend to dissipate the elements of the globe.
We are thus brought into full view of the deepest truth that underlies the redistribution of matter—the profound antithesis between gravitation and ethereal vibration, which constitute, in the last analysis, the true correlative principles of which evolution and dissolution are the corresponding processes. These are the agencies which are at all times antagonizing each other in all parts of the universe, and whose exact equality in it seems to form a logical tenet of the modern cosmology. A certain golden mean between these forces, but in which the former must predominate, results in organization; star-systems are formed in space, and life is developed out of the planetary elements. Such appears to be the state of all the matter within the range of human observation. For, whatever may be the condition of other worlds or other regions of space, the phenomena of our world and our portion of space belong to the ascending series; and whatever may be the final doom of our planet and our universe, both are now in a state of progress, and are still rejoicing in the morning of creation.