What is Darwinism?. Charles Russell Hodge

Чтение книги онлайн.

СКАЧАТЬ He assumes the efficiency of physical causes, showing no disposition to resolve them into mind-force, or into the efficiency of the First Cause.

      3. He assumes also the existence of life in the form of one or more primordial germs. He does not adopt the theory of spontaneous generation. What life is he does not attempt to explain, further than to quote (p. 326), with approbation, the definition of Herbert Spencer, who says, "Life depends on, or consists in, the incessant action and reaction of various forces,"—which conveys no very definite idea.

      4. To account for the existence of matter and life, Mr. Darwin admits a Creator. This is done explicitly and repeatedly. Nothing, however, is said of the nature of the Creator and of his relation to the world, further than is implied in the meaning of the word.

      5. From the primordial germ or germs (Mr. Darwin seems to have settled down to the assumption of only one primordial germ), all living organisms, vegetable and animal, including man, on our globe, through all the stages of its history, have descended.

      6. As growth, organization, and reproduction are the functions of physical life, as soon as the primordial germ began to live, it began to grow, to fashion organs however simple, for its nourishment and increase, and for the reproduction, in some way, of living forms like itself. How all living things on earth, including the endless variety of plants, and all the diversity of animals—insects, fishes, birds, the ichthyosaurus, the mastodon, the mammoth, and man—have descended from the primordial animalcule, he thinks, may be accounted for by the operation of the following natural laws, viz.:—

      First, the law of Heredity, or that by which like begets like. The offspring are like the parent.

      Second, the law of Variation, that is, while the offspring are, in all essential characteristics, like their immediate progenitor, they nevertheless vary more or less within narrow limits, from their parent and from each other. Some of these variations are indifferent, some deteriorations, some improvements, that is, they are such as enable the plant or animal to exercise its functions to greater advantage.

      Third, the law of Over Production. All plants and animals tend to increase in a geometrical ratio; and therefore tend to overrun enormously the means of support. If all the seeds of a plant, all the spawn of a fish, were to arrive at maturity, in a very short time the world could not contain them. Hence of necessity arises a struggle for life. Only a few of the myriads born can possibly live.

      Fourth, here comes in the law of Natural Selection, or the Survival of the Fittest. That is, if any individual of a given species of plant or animal happens to have a slight deviation from the normal type, favorable to its success in the struggle for life, it will survive. This variation, by the law of heredity, will be transmitted to its offspring, and by them again to theirs. Soon these favored ones gain the ascendency, and the less favored perish; and the modification becomes established in the species. After a time another and another of such favorable variations occur, with like results. Thus very gradually, great changes of structure are introduced, and not only species, but genera, families, and orders in the vegetable and animal world, are produced. Mr. Darwin says he can set no limit to the changes of structure, habits, instincts, and intelligence, which these simple laws in the course of millions or milliards of centuries may bring into existence. He says, "we cannot comprehend what the figures 60,000,000 really imply, and during this, or perhaps a longer roll of years, the land and waters have everywhere teemed with living creatures, all exposed to the struggle for life, and undergoing change." (p. 354). "Mr. Croll," he tells us, "estimates that about sixty millions of years have elapsed since the Cambrian period, but this, judging from the small amount of organic change since the commencement of the glacial period, seems a very short time for the many and the great mutations of life, which have certainly occurred since the Cambrian formation; and the previous one hundred and forty million years can hardly be considered as sufficient for the development of the varied forms of life which certainly existed toward the close of the Cambrian period." (p. 379). Years in this connection have no meaning. We might as well try to give the distance of the fixed stars in inches. As astronomers are obliged to take the diameter of the earth's orbit as the unit of space, so Darwinians are obliged to take a geological cycle as their unit of duration.

Natural Selection.

       Table of Contents

      As Natural Selection which works so slowly is a main element in Mr. Darwin's theory, it is necessary to understand distinctly what he means by it. On this point he leaves us no room for doubt. On p. 92, he says: "This preservation of favorable variations, and the destruction of injurious variations, I call Natural Selection, or, the Survival of the Fittest." "Owing to the struggle (for life) variations, however slight and from whatever cause proceeding, if they be in any degree profitable to the individuals of a species, in their infinitely complex relations to other organic beings and to their physical conditions of life, will tend to the preservation of such individuals, and will generally be inherited by their offspring. The offspring also will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection, in order to mark its relation to man's power of selection. But the expression often used by Mr. Herbert Spencer of the Survival of the Fittest, is more accurate, and sometimes is equally convenient." (p. 72). "Slow though the progress of selection may be, if feeble man can do so much by artificial selection, I can see no limit to the amount of change, to the beauty and infinite complexity of the co-adaptations between all organic beings, one with another, and with their physical conditions of life, which may be effected in the long course of time by nature's power of selection, or the survival of the fittest." (p. 125). "It may be objected that if organic beings thus tend to rise in the scale, how is it that throughout the world a multitude of the lowest forms still exist; and how is it that in each great class some forms are far more highly developed than others? … On our theory the continuous existence of lowly forms offers no difficulty; for natural selection, or the survival of the fittest, does not necessarily include progressive development, it only takes advantage of such variations as arise and are beneficial to each creature under its complex relations of life. … Geology tells us that some of the lowest forms, the infusoria and rhizopods, have remained for an enormous period in nearly their present state." (p. 145). "The fact of little or no modification having been effected since the glacial period would be of some avail against those who believe in an innate and necessary law of development, but is powerless against the doctrine of natural selection, or the survival of the fittest, which implies only that variations or individual differences of a favorable nature occasionally arise in a few species and are then preserved." (p. 149)

      This process of improvement under the law of natural selection includes not only changes in the organic structure of animals, but also in their instincts and intelligence. On entering on this part of his subject, Mr. Darwin says, "I would premise that I have nothing to do with the origin of the primary mental powers, any more than I have with that of life itself. We are concerned only with the diversities of instinct and of other mental qualities within the same class." (p. 255) He shows that even in a state of nature the instincts of animals of the same species do in some degree vary, and that they are transmitted by inheritance. A mastiff has imparted courage to a greyhound, and a greyhound has transmitted to a shepherd-dog a disposition to hunt hares. Among sporting dogs, the young of the pointer or retriever have been known to point or to retrieve without instruction. "If," he says, "it can be shown that instincts do vary ever so little, then I can see no difficulty in natural selection preserving and continually accumulating variations of instinct to any extent that was profitable. It is thus, as I believe, that all the most complex and wonderful instincts have arisen." (p. 257) He was rather unguarded in saying that he saw no difficulty in accounting for the most wonderful instincts of animals. He admits that he has found very great difficulty. He selects three cases СКАЧАТЬ