The National Encyclopædia


EVOLUTION,

a doctrine which, as applied to the science of life, means that all the species of living beings, both animal and vegetable, have not been originally created as we see them, but are derived from ancestors of lower and simpler organization than themselves, by a process of descent with gradual modification; that all species, however different they may now be, are descended from the same or perfectly similar ancestors, which, like the simplest living beings now known to exist, were minute gelatinous masses, without organization or structure.

The doctrine of evolution is much older than the Darwinian controversy, but its prominence in recent years is chiefly due to the importance attached to it by Mr. Darwin in his work on the "Origin of Species,' in which he states his belief that 'animals are descended from at most only four or five progenitors, and plants from an equal or lesser number. Analogy would lead me one step further, namely to the belief that all animals and plants have descended from some one prototype.'

It is obvious that, carried as far back as the theory possibly can be, in cannot dispense with the necessity for a Creative Power.

Taking the origin of species by evolution as proved, and taking the known laws of life as his data, Darwin's theory is an attempt to explain the process of evolution by purely physical causation. The theory, in outline, is this: -- All organisms are more or less variable; no two leaves in a forest are exactly alike, and the differences are often great enough to be quite conspicuous, as in the familiar case of human faces. At the same time, these variations tend to become hereditary. Now, if any variation is such as to give its owner any advantage over other individuals of the same species, the owner of such a 'favourable variation' will be more likely than less favoured individuals to win a place in the struggle of life, and to leave offspring. These offspring will tend to inherit the favourable variation that caused their parent to survive, and the same competition will go on among them. Those which possess the favourable variation in the highest degree will again survive, and the improvement will go on progressing and accumulating through generations. This preservation of favourable variations is what Darwin calls 'natural selection.'

In supporting his theory, Darwin rests much on the difficulty of distinguishing between varieties and species, and on the changes which are observed to result from cultivation and domestication. He dwells on the selection which man makes in order to produce new breeds or varieties, and supposes a similar selection to take place in nature in the 'struggle for life' which all plants and animals must undergo, not only against those other creatures which seem to make them their food, but still more in a competition with those which seek the same nutriment with themselves. At Nature's feast there is clearly no room for all, so many being born that only a fraction of the entire number can survive and leave offspring. There is therefore a 'struggle for existence,' and the race is on the whole to the swift, and the battle to the strong. In this 'struggle' -- which underlies the whole Darwinian theory -- the stronger, or those which possess anything peculiarly favourable in the organization, must overcome the weaker, and these must therefore cease to exist. Thus a slight variation, such as often takes place, may be perpetuated, and the possessors of any advantage in the means of procuring food, or in the powers of offence or defence, may entirely displace their less favoured congeners. It is undoubtedly possible to produce, and with care to perpetuate, remarkable modifications in cultivated plants and domestic animals; and Darwin asks if it can be thought improbable that other variations useful in some way to each being in the great and complex battle of life should sometimes occur in the course of thousands of generations? And if such occur, can we doubt that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind? In this way Mr. Darwin supposes new variations to be continually taking place, but the greater number of these speedily to become extinct; whilst others, becoming perpetuated, and perhaps causing the extinction of the original forms, again give rise to other forms, until some of them have so widely diverged that all traces of the common origin are lost.

The theory of evolution is no doubt unlike anything in our experience, but the same is true of any possible theory of the origin of species; and of all possible theories of the origin of species, that of evolution is the least out of harmony with the ordinary facts of experience. The origin of species is a matter of inference, but the origin of individual organisms is a matter of observation. Every living organism has been evolved out of a perfectly simple germ, in which the microscope shows no vestige of structure; and it would seem more consistent with this fact to believe that species also have been developed by descent with modification from perfectly simple ancestral forms, than to believe that they have been created all at once just as we see them.

not a lamprey, but it'll doIt is obvious that, carried as far back as the theory possibly can be, in cannot dispense with the necessity for a Creative Power. It certainly, however, attempts to account for the facts of vital organization without the agency of an organizing intelligence, and in this respect the theory as propounded by Darwin appears paradoxical. No greater paradox can well be imagined than to maintain that all the wonderful adaptations of the animal frame -- of the wing for flight, of the ear for hearing, and of the eye for seeing -- are in no way due to intelligence, but to the action of blind unintelligent forces. Yet the Darwinian theory implies this. Seeming paradoxes, however, have sometimes proved to be true; and when a theory is supported by such authorities as Darwin, Wallace, Huxley, and Tyndall, it deserves a respectful consideration with which no prejudices of any kind ought to interfere.

The principal replies to the Darwinian theory of the origin of species by evolution from the lowest to the highest forms of life, have come from Agassiz, Mr. Mivart, Mr. Murphy, and Professor Cope of America. The first and most natural objection is the absence of any evidence of a transitional state. Animals known and described in the most ancient times are still in existence, exhibiting to this day the same characters of old. The oldest geological evidence shows that certain classes of animals have been superseded by others, but the gradual evolution from a lower to a higher class of organization cannot be traced -- owing, Mr. Darwin says, to the imperfection of the geological record; an imperfection, however, which geologists decline to admit. Granting the evolution of species, then, in the first place variations have occurred which no theory of spontaneous and unguided variation is sufficient to account for; in the second place, it is asserted that natural selection among small spontaneous variations is incapable of acting to the extent required; and in the third place, that even if these causes were adequate in respect of magnitude, there are still large classes of facts which contradict the theory.

As to the first, one of the greatest difficulties of Darwin's theory is that of accounting for the origin of a co-ordinated structure, that is, of a structure in which a number of parts are adapted to each other. The most remarkable of all instances of co-ordination of parts, or in other words of complex adaptation, are the organs of the higher senses, the eye and the ear. Variations in such a complicated organ as the eye, in order to be improving at all, must be favourable in at least two opposite directions at once -- both in respect of the nerves which contract and of those which open the pupil; and such coincidences of accidental favourable variation are incredible in the highest degree. Indefinite and equal variability in all directions alike do not appear to be a law of nature; for the lamprey has but one nostril, while other vertebrates have two. Some animals, too, such as the chameleon and the ermine, have the singular power of changing their colour -- a power of great and special value to its possessors; so much so that once a race of animals formed with this power, there is not doubt is would be preserve and perpetuated by natural selection. But how is it first to be formed? and how many generations without this power would have to live and die before a single individual was born with the slightest tendency to change its colour with the seasons, or in correspondence with surrounding objects? It would seem impossible that such a power could have originated from the slight random spontaneous variations which alone Darwin's theory admits. Again,according to Darwin, no variation can be preserved if not useful to its possessors; and granting his theory of evolution in its entirety, birds must be descended from reptiles, and their wings must be modified forelegs. Now the usefulness of a bird's wing is obvious, but ungrown wings are worse than useless; and how was the long period of transition got over during which the limb was ceasing to be either a foot or hand, without having yet become an organ of flight? Natural selection would have been more likely to destroy than to preserve a race of animals in such a state. A similar difficulty occurs with the fins of fishes, for a fin in its incipient state would be as useless as an ungrown wing; and on any theory of evolution fishes with fins are descended from finless fishes like the lamprey.

In the second place, it may be admitted that natural selection may do in the wild state what artificial selection has done in the domestic state. It may give origin to races or breeds which possess in a higher degree some power or peculiarity of the un-improved stock; for where species are at all variable there will be many individuals that excel the rest in strength, swiftness, and in keenness of eye, ear, or scent, and these, if kept apart, may possibly be perpetuated. But this accounts for comparatively slight changes, and not for the origin of anything like a new structure. It cannot be shown that the most acute and persevering ingenuity is capable of producing even the semblance of a new structure in any breed, and yet it is maintained that this is done by means of small spontaneous unguided variations. Such random variations do not act in the manner or to the extent demanded by the theory; and if they did natural selection would be insufficient to transmit them, for even granting the unlikely supposition that the same particular favourable variation occurred in two animals at once, we have again to suppose that they will be accidentally brought together in order to perpetuate the variation, instead of its being weakened and lost by the crossing of breeds; for it is easy to prove that the variations produced by artificial selection and training are very soon lost when the animals are left to themselves.

The time which has elapsed since the earth was sufficiently cooled to be the abode of living beings, is certainly not more than five hundred millions of years, and probably not more than one hundred millions. Either of these periods so transcends the powers of the imagination that it may at first seem ample for any purpose...

In the third place, even if the causes were adequate, large classes of facts contradict the theory. One of the most conspicuous of all the facts of the organic world is the remarkable variety of characters as between different species and different groups, contrasted with their equally remarkable fixity within species and groups. It is on this fact that all classification depends, and it is the prominence of this fact which has, until late years, caused the belief to be almost universal that species are not only comparatively permanent but absolutely unchangeable. It is difficult to see how natural selection could have transformed a bake fish into a scaly one, but the difficulty is indefinitely increased by the fact that there are among fishes, besides those which have the skin naked, four distinct types of scales, each of which is characteristic of entire groups of fishes. If Darwin's theory be true, the form and structure of the scales should be a comparatively unvarying character, and the covering of all fishes should be nearly alike, as is the case with flying birds. The same difficulty occurs among plants and flowers. There is great diversity in the form of leaves; and yet how can one form be more favourable than another to the life of the plant? The prickles of the holly, which a Darwinian may argue have been produced by natural selection, certainly protect it from being eaten by cattle; but there is no such apparent reason to account for the various characteristic forms of the leaves of the lime tree, the oak, the ash, and the sycamore. Mr. Mivart and Professor Cope have independently gathered together a mass of facts of this nature, for which our space will not allow even the enumeration, but which certainly appear fatal to Darwinism, so far as the theory asserts the origin of the most highly cultured species to have been entirely through random unguided evolutions from the lowest organism.

Finally, if all other objections to Darwin's theory were satisfactorily answered, the vital one remains, that geological time is not long enough for the production of the highest forms out of the lowest by the gradual accumulation of slight variations. Sir William Thomson has calculated, from the mathematical laws of the cooling of heated masses, that the time which has elapsed since the earth was sufficiently cooled to be the abode of living beings, is certainly not more than five hundred millions of years, and probably not more than one hundred millions. Either of these periods so transcends the powers of the imagination that it may at first seem ample for any purpose. But let us compare it with the period demanded by Darwin's theory. Mr. Mivart says that no distinct species could have been formed and established as such by any process of natural selection in less than a thousand years. If then, says Mr. Murphy, it takes this period to form a species, it ought to take about ten times as long to form a genus, a hundred times as long to form a tribe, and so on, the periods increasing in geometrical ratio as we go on to wider and wider groups, separated by increasingly greater differences. If, for instance, it took a thousand years to develop the lion out of the original stock of the cat genus, it should then take ten thousand years to develop the cats out of the original stock of the tribe to which cats and dogs alike belong, and one hundred thousand years to develop this out of the original stock of the carnivorous order. To develop this out of the original stock of the placental mammals would take a million years, and ten millions to develop this out of the original stock of all the mammalia. To develop this first mammal out of a newt must have required probably a hundred times this, or a thousand million years; and to develop the first newt out of a fish a thousand millions more, and it must have taken at least as long a period for a fish with fins and jaws to be developed out of a fish like the lamprey, which has neither. It is perhaps not too much to say ten thousand million years as the time needed to develop a fish like the lamprey out of such a fish as the amphioxus, which has white blood and no distinct heart; a hundred thousand million years to develop this out of an animal resembling the ascidian larvae, and at least as much more to develop this form out of those minute gelatinous masses without structure, which are the simplest of all living beings. We thus conclude that the time needed for the evolution of the highest forms of life out of the lowest would probably require, on the Darwinian theory, more than two hundred thousand million years, while the utmost possible duration of geological time, according to Sir Wm. Thomson, is not more than one four-hundredth of this.

It appears difficult to resist the conclusion, that the variations by which new species and new classes are formed are not fortuitous or at random, but take place according to a pre-determined plan; and that the evolution of living being is guided by an Intelligence whose beneficent purposes are best served by an endless variety in both the useful and the beautiful.