A History of Evolution/Chapter 4
CHAPTER IV.
EVOLUTION AND THE GREAT NATURALISTS.
One of the outstanding figures of zoology, and for that matter, of all natural science is Carl von Linne, more commonly known as Carolus Linnaeus[1]. For many years naturalists had been struggling to establish a satisfactory system of naming and arranging the various forms of animals, plants and fossils, but without very definite or satisfactory results. Linnaeus devised a very simple method of naming organisms—one that is followed almost without modification even today. He chose Latin and ancient Greek as the languages in which the names should be cast, primarily because both of them were more or less familiar to all students of his day, and neither was an important language of modern times. The name itself was in two parts, one denoting the particular species, the other the group to which that species belonged. Thus the common chipping sparrow is Spizella socialis, just as a man is William Jones, or James Thompson. The only difference is that in Linnaeus' system of naming, the family name comes first; if the same plan were used in human names William Jones would become Jones William. This may sound awkward, but as a matter of fact it is extremely convenient, just as in a directory or telephone book it is convenient to have the family name given first.
In the early editions of Linnaeus' great work, the "Systema Naturae" (System of Nature), published from 1735 to 1751, the great naturalist stated specifically that he believed in the absolute fixity of species from the time of their creation, according to the literal interpretation of Genesis. But Linnaeus was too close a student to hold this idea for long, and in his edition of 1762 we find him expressing the opinion that many new species arose from the interbreeding of those originally created. However, he maintained that only species originated in this manner, and attributed the more general resemblances of animals and plants to similarities of form implanted by the Creator. Plainly, therefore, Linnaeus was at heart a believer in special creation in a very slightly restricted sense, and was by no means as progressive in this respect as the old Greek philosopher Aristotle.
Foremost among the contemporaries of Linnaeus was George Buffon, (1707–1788), the Frenchman whom Osborn has called the "naturalist founder of the modern applied form of the evolutionary theory." During his early work Buffon held essentially the same views as his contemporary, Linnaeus, stating that the species of animals were separated by a gap which could not be bridged, and that everywhere were evidences of "the Creator, dictating his simple but beautiful laws and impressing upon each species its immutable characters."
As early as 1755, however, Buffon found that his studies in comparative anatomy placed many difficulties in the way of these "simple but beautiful laws" and "immutable characters." He calls attention to the fact that the pig is plainly the "compound of other animals," possessing many parts for which it has no use, and concludes that "Nature is far from subjecting herself to final causes in the formation of her creatures," and that by continually searching for such causes men "deprive philosophy of its true character, and misrepresent its object, which consists in the knowledge of the 'how' of things." In 1761 he acknowledged a belief in the frequent modification of species, but believed that some animals were much more subject to variation than others. He understood the struggle for existence, with its consequent elimination of the species least capable of living under unfavorable circumstances, and stated it very clearly.
One of the most interesting portions of Buffon's evolutionary philosophy was his belief that external conditions could directly modify the structure of animals and plants, and that these modifications were hereditary. This was, in essence, the theory of transmission of acquired characters—a theory which was to be greatly elaborated by one of Buffon's successors, and which was to cause trouble among evolutionists for many decades. Buffon applied it particularly to the animals of the western hemisphere, showing how they were changed by climate, food, etc., so that eventually animals coming from the eastern hemisphere to the western[2] would become new species. In this connection he emphasizes the fact, also pointed out by Kant, that man must study the changes taking place in his own period in order to understand those which has been accomplished in the past, and might be accomplished in the future.
Even at the time when he believed most thoroughly in evolution and variation, Buffon was troubled by the Bible account of creation, and wavered between the two. Some time after 1766 he abandoned his advanced stand on evolution, and concluded that species were neither static nor changeable, but instead that "specific types could assume a great variety of forms[3]," and that no definite assertions might be made regarding the origin of any particular animal or plant.
One cannot but wonder what was the cause for Buffon's confusion and changes of attitude. From special creationist to radical evolutionist, and then to conservative occupying a position halfway between was a remarkable mental evolution to be covered in the space of less than sixty years. What was the cause of it?
The answer to this question is not a difficult one. Buffon was a pioneer, and not an overly courageous one. He was staggered by the immensity of the problem which he was trying to solve, and at the same time, fettered by the orthodox ideas of his day. And back of those ideas, as Buffon well knew, there was power—power of the church, of society, and of the scientific world. And neither the church, society, nor science was ready to accept the doctrine of descent, of organic evolution. Linnaeus, as we have seen, was easily the greatest and most influential zoologist of his day, and was at the same time a strong anti-evolutionist. His influence was so great that Buffon could hardly have escaped it, and this probably added to the difficulties of the vacillating evolutionist.
And so, when we considered the difficulties under which Buffon worked, we are not surprised that he found it hard to discover what his ideas on evolution should finally be. He was evidently no hero, willing to become a martyr for science, nor yet a dogmatist, willing to lay his own ideas down as law. Instead of ridiculing him for his indecision, therefore, we should sympathize with him because of his difficulties. Probably few of us would say or write very revolutionary things if we were loaded down with half-shed orthodoxy, and threatened by social and scientific ostracism in case we made a departure from the well beaten path.
The next important figure in evolution is Erasmus Darwin, grandfather of the great Charles Darwin. He was a country physician, a poet, and a very accurate naturalist, but unfortunately buried his ideas in volumes of verse and of combined medicine and philosophy. He believed in the spontaneous origin of the lower animals, but maintained that all of the higher forms were products of natural reproduction. The transition from water-to-land-dwelling animals he illustrated, not by fanciful creations, but by the classic example of the development of the frog, which begins life as a legless tadpole, and ends it as an animal incapable of breathing under water.
To man Dr. Darwin gave much attention, devoting a whole canto to the human hand—"The hand, first gift of Heaven!"—and outlining the development of man's various faculties. Farther on he describes the struggle for existence in lines which remind one of Tennyson's description of nature, except that they lack Tennyson's inevitable syrupiness. Evidently, however, Darwin fails to connect this struggle with its obvious result, the survival of the fittest.
Dr. Darwin's theory of evolution differed from that of Buffon in at least one important respect. Nowhere does he stress the direct influence of environment in the production of variations; on the contrary, he maintained that modifications spring from the reactions of the organism. In this he clearly stated the theory which is generally known as Lamarck's version of the theory of the transmission of acquired characters. In fact, he carried his ideas much farther than did Lamarck, attributing to plants the attribute of sendibility, and supposed their evolution to be due to their own efforts toward the development of certain characters. Adaptations, which Aristotle had believed to be caused by a definite plan, Dr. Darwin interpreted in a purely naturalistic manner. The Creator had, at the beginning, endowed organisms with the power to change and develop, and that power was handed down from one generation to another until it was possessed by every animal and plant. This power was the cause of all variation, adaptation, and evolution, and there was no further divine interference. Dr. Darwin did not see any great, all-encompassing plan of improvement, such as is postulated by the teleologists of today; to him everything was the logical and necessary outcome of the original powers of living things. In this, as we shall see, he believed essentially as do modern evolutionists who do not see in the laws of the universe any necessity for abandoning religion, but who at the same time do not believe in a highly personal god who, as one theologian expressed it recently, "works out His divine will through the processes of evolution."
Dr. Darwin was author of two other distinctly modern ideas, among the most important of his entire work. The first of these is that all living things are descended from a single original living mass, or "filament"—that every living thing on the earth is related to every other living thing. The second is that the process of evolution is almost inconceivably slow, and that millions upon millions of years have been necessary for it. The first idea, while quite conceivably true, can never be proved definitely, but the second has been demonstrated over and over again. Just how many millions we shall allow is, of course, undetermined; some authorities demand sixty; others say that eight hundred is a figure none too large. In this series of books the larger figure is adopted, not because we are certain that it is right, but because it seems to fit more closely with the facts of evolution than do the smaller ones. How fully Dr. Darwin was a prophet of modern scientific chronology we are just beginning to recognize.
The leadership in evolution, which for a time had gone to England, was soon given back to France. The new champion of the theory was Jean Baptiste Lamarck (1744–1829), one of the most pathetic figures in the entire history of zoology. He was a brilliant man, and a skilled zoologist, but because he was courageous, blind, and desperately poor, he suffered little less than martyrdom throughout much of his life, and was given, but scant attention by his contemporaries. Baron Cuvier, rich, talented, and a member of the elite of the nation, dominated French zoology. He was a desperate reactionary, holding out for a literal acceptance of the Bible account of special creation, and ridiculed not only the theories of Lamarck, but the whole conception of evolution. For years he blocked the progress along all lines but his own restricted field of anatomy, and waged bitter warfare on anyone who dared to oppose him. And so the blind Lamarck lived in poverty and obscurity, neglected by both scientists and those who knew nothing of zoology. And through this he stood faithfully by the ideas which he believed but was too poor and unknown to defend.
Lamarck first held to the old teaching that species were fixed, and could neither change nor be changed. But as he learned more his views changed, and in 1809 he published a book stating his interpretation of evolution. One of his principal ideas was that the effects of the use or disuse of any part of the body may be passed on from parent to children until they finally become parts of the animal's make-up. It is well known that an arm that is never used becomes weak; that a muscle which is constantly at work becomes strong and large. Lamarck supposed that this increase or decrease in size could be inherited, and thus races with short, thin arms, or heavy powerful muscles could be developed. This is the "theory of inheritance of acquired characteristics" again, first formulated by Erasmus Darwin. Just how much there is to this theory no one has been able to say; some believe it to be worthless while others, particularly those who study fossil animals, think that it possesses a certain amount of truth.
Lamarck was, as we have said, a conscientious scientist, and made use of his own accurate observations insofar as this was possible. But when he became blind, dictating his books to his daughter in order to get them written, observation was clearly out of the question. In its stead the great naturalist was forced to rely upon the reports of other observers, and those reports were none too reliable. The obvious weakness of some of his second-hand facts reacted very unfavorably upon the whole work of Lamarck, and gave his opponents abundant weapons for their attacks upon his opinions.
But in spite of these handicaps, Lamarck did a very important work. He not only stated his own position very clearly, marshalling such facts as were at his disposal to its support; he devised a branching system of animal descent which approximated the modern "evolutionary tree" and represented far more truly than did the Aristotelian chain the true state of things. He argued strongly and clearly against the fallacious doctrine of special creations and numerous geologic catastrophes which, supposedly, annihilated all of the life on earth at the particular times of their occurrence and made a long series of new creations necessary.
Perhaps the greatest of all Lamarck's achievements was his clear statements of the problems of evolution. As one writer has said, he asked every one of the big, important questions which later evolutionists have had to answer, and by the clear phrasing of his questions, made the answers thereto the more easy.
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In all France there was only one man who was willing to champion this blind naturalist in his stand for evolution. Geoffrey St.-Hilaire was at first a follower of Buffon, but he later became convinced of the value of Lamarck's work, and even went so far in his belief as to champion Lamarck in a public debate with the great Cuvier. Despite the fact that the debate brought a certain fame to St.-Hilaire, he was judged the loser, and the affair was hailed as a great and conclusive victory for those who upheld the theory of special creation.
Although St.-Hilaire believed in the truth of organic evolution, he did not wholly agree with Lamarck. He supposed that environment—that is, surrounding conditions—determined the changes that took place in animals, and preceded some of the most modern of evolutionists by teaching that one species might arise suddenly from an earlier one, without any intermediate forms. As a result of these sudden changes, it was, said St.-Hilaire, often unnecessary to produce the "missing links" over which adverse critics made such a to-do. It Was also unnecessary to show why variations would not be wiped out before they were firmly established. According to his hypothesis, each new form was complete, and no amount of normal interbreeding with other forms would produce fertile hybrids between the two.
We now come to one of the most interesting, and most remarkable of evolutionists. Johann Wolfgang Goethe (1749–1832) was an anatomist, a philosopher, and a great poet, and thus brought to the problem of organic evolution a breadth of vision equalled by but few of the workers who preceded him. As Osborn states:
"The brilliant early achievements of Goethe in science afford another illustration of the union of imagination and powers of observation as the essential characteristics of the naturalist. When he took his journey into Italy, and the poetic instinct began to predominate over the scientific, science lost a disciple who would have ranked among the very highest, if not the highest. Of this time Goethe says: 'I have abandoned my master Loder for my friend Schiller, and Linnaeus for Shakespeare.' Yet Goethe, in the midst of poetry, never lost his passion or scientific studies. He seems to have felt instinctively that what contemporary science needed was not only observation, but generalization."[4]
Goethe derived much of his inspiration from Buffon and the German natural philosophers. Unfortunately he never discovered the works of Lamarck, although he anticipated that scientist in some of his work with plants. There can be little doubt that, had Goethe discovered the "Philosophie Zoologique," he would have accepted its principal doctrine, and would have proclaimed them with a vigor that would have overcome even the antagonism of Cuvier. As it was, he confined his theory to the idea of the "unity of type," making it the chief basis for his conception of evolution. In his own words, this theory enabled him to "assert, without hesitation, that all the more perfect organic natures, such as fishes, amphibious animals, birds, mammals, and man at the head of the list, were all formed upon one original type, which varies only more or less in parts which are none the less permanent, and which still daily changes and modifies its form by propagation."
Akin to Goethe, in some respects, was Gottfried Treviranus (1776–1837), a German naturalist who was a contemporary of St.-Hilaire, Goethe, and Lamarck. Like the German natural philosophers, he considered life as the result of chemical and mechanical processes, and protested whole-heartedly against purely speculative work, calling it "dreams and visions." At the same time, he complained that most of botany and zoology was made up of dry registers of names and that the work of many naturalists consisted of the "spirit killing * * * reading and writing of compilations." Treviranus believed that it was quite within the abilities of man to discover the basic philosophy of nature, largely by the use of working hypotheses as a means of aiding the investigator in attaining the actual facts.
In view of Treviranus' modern stand on the study of animal life, and the interpretation of ascertained facts, we might well expect him to show an equal modernity in his conception of evolution. But in this we are to be disappointed. As soon as he departed from his principles of biology, and attempted to apply those principles to the development of animal life, Treviranus became victim to those same "dreams and visions" against which he protested so strongly. He depended very largely upon the work of Buffon, and believed that modification of form was due entirely to environment. He revived the ancient doctrine of spontaneous generation of living things, or abiogenesis, stating his belief very clearly.
All of this shows that Treviranus, although an ardent believer in evolution, added very little to the idea. In his ideas of the factors of volution he did not advance beyond Buffon; in his ideas of descent he was less clear and accurate than his contemporary, Lamarck. But in his more general work, particularly in defining and organizing the science of biology, he rendered great service to future zoologists and evolutionists. And such service, slight though it was, was of value. During the early part of the nineteenth century the doctrine of evolution needed all the support that could be given it, and even a mistaken scientist was a valuable defender of a struggling cause.
Thus for more than two thousand years the theory of organic evolution had been growing. Philosophers, country doctors, poets, and naturalists had contributed their share to its volume, its character, and its support. But as yet is was little more than an idea in the rough, waiting for some one to refine it, to put it into clear and unmistakable language, and to back it up by evidence secured directly from studies made on living animals and plants. It might have been compared to a piece of waiting for someone to forge it into a key—a key that would open the doors of conventional thought and old-fashioned restriction, and thereby give an insight into life and life's history that would revolutionize human thought, and help in a better understanding between man and man, and man and beast.
- ↑ Carl von Linne was the greatest naturalist of eighteenth century Sweden. He lived from 1707 to 1778, and for many years was professor at the University of Upsala.
- ↑ In Buffon's day the Americas were still the "New World," and it was customary with naturalists of the time to consider it new, not only in discovery, but in its plant and animal inhabitants. For them, the animals of America came from the Old World, just as did its white settlers; the idea of opposite migrations was quite unheard of. How different this conception was from the actual state of affairs can be seen by reference to such books as Osborn's "Age of Mammals."
- ↑ Osborn, op. cit. p. 138.
- ↑ Op. cit., pp. 181–182. The need of which Dr. Osborn speaks was not by any means confined to science of Goethe's time. The great characteristic of modern paleontology, for example, is observation without either generalization or philosophy. It is for this reason that the science of fossils has yielded relatively meagre data on evolution.