Darwin and the Theory of Evolution/Chapter 3
CHAPTER III
THE DESCENT OF MAN, AND OTHER BOOKS
When Darwin wrote the Origin of Species he considered it as little more than an abstract or outline of the subject, to be followed by a series of larger books giving in full the evidence for evolution which he possessed. One of these, "Variations of Animals and Plants under Domestication," he began on January 1, of 1860—less than six weeks after the publication of the Origin—but could not get on with it very rapidly. This partly was because of the great deal of work necessary to correct the successive editions of the Origin, but even more because of illness. At one time Darwin was unable to do anything for seven months, and shorter periods of disability were common. Also, conditions had shown that scientists were having trouble enough comprehending the preliminary book on evolution, so there was no pressing need for a series of larger treatises for a while, at least.
But perhaps the most important factor of all in the delay of the larger books was the great accumulation of data on lines other than evolution, which Darwin felt it his duty to publish. Thus as far back as 1839 he had begun to study the part which insects played in the cross-fertilization of flowers. Every summer he had devoted time to that work, and the accumulation of twenty years of investigation lay on his hands—valuable, indeed, yet doing no good to anyone but himself. Plainly, therefore, it was his duty to publish this material, so that it could be examined by other naturalists and used by them in making still further researches.
Thus it was that in 1862 appeared the Fertilization of Orchids,[1] which two years later was described as the most masterly treatise in any branch of vegetable physiology that had appeared. The group of plants which it treated are remarkable for the devices by which they provide for cross-fertilization by means of the insects which visit them. These provisions were skilful enough in the English forms, but in foreign ones, and particularly those from tropical and semi-tropical countries, the mechanisms were still more highly developed. Thus Darwin found that among one group the various parts of the flower were so accurately developed for cross-fertilization that without the aid of insects not a single plant in the whole group of twenty-nine genera could produce seed. In most cases the insects which come to the flowers for food withdraw the pollen masses only when retreating from the blossom, and, by going to another plant or flower effect a union between the two. Commonly the pollen masses slowly change position while attached to the insects, so as to assume the position proper to contact with the stigma of another flower. During the time necessary for this change the insect almost certainly flies to another plant, so that the necessary cross is accomplished.
The Orchid book was Darwin's first venture into botany and it established his position there as other books had established it in geology and zoology. In 1864 he published a paper on Climbing Plants—an effort which cost him four months of labor. Again illness interfered, and the paper was so badly written, and so obscurely phrased that it received little attention. Eleven years later it was rewritten into a book and became very popular.
In 1868 the first volume of the detailed studies of evolution appeared. Of it Darwin says, "It was a big book, and cost me four years and two months hard labour. It gives all my observations and an immense number of facts collected from various sources, about our domestic productions. In the second volume the causes and laws of variation, inheritance, etc., are discussed as far as our present state of Our knowledge permits. Towards the end of the work I give my well abused hypothesis Of Pangenesis." This, briefly stated, supposes that the countless cells which compose the body of an animal or plant are continually throwing off tiny granules, far too small to be seen even microscopically, that accumulate in the reproductive system. Instead of developing in the next generation they may be transmitted in an inactive or dormant state to several generations, and then suddenly become developed. Various combinations of these granules are supposed to influence their appearance or dormancy in the various generations. As a hypothesis Pangenesis was suggestive but not very satisfactory when put to practice, and it has been discarded in favor of later and more probable ideas.
The next important evolutionary work was the Descent of Man, published in February, 1871. Inasmuch as there is some misunderstanding as to the motive which forced Darwin to say but little of man in the Origin, and delay twelve years before publishing a book on the subject, it is worth while to give his own statement of the case:
… As soon as I had become, in the year 1837 or 1838,[2] convinced that species were mutable productions, I could not avoid the belief that man must come under the same law. Accordingly I collected notes on the subject for my own satisfaction, and not for a long time with any intention of publishing. Although in the Origin of Species the derivation of any particular species is never discussed, yet I thought it best, in order that honourable man should accuse me of concealing my views, to add that by the work "light would be thrown on the origin of man and his history." It would have been useless and injurious to the success of the book to have paraded, without giving any evidence, my convinction with respect to origin.
But when I found that many naturalists fully accepted the doctrine of the evolution of species, it seemed to me advisable to work up such notes as I possessed, and to publish a special treatise on the origin of man. I was the more glad to do so, as it gave me an opportunity of fully discussing sexual selection—a subject which had always greatly interested me. This subject, and that of the variation of our domestic productions, together with the causes and laws of variation, inheritance, and the intercrossing of plants, are the sole subjects which I have been able to write about in full, so as to use all the materials which I have collected. The Descent of Man took me three years to write, but then as usual some of this time was lost by ill health, and some was consumed by preparing new editions and other minor works.
The Descent of Man created an even greater popular stir than did the Origin. The large first edition was quickly sold out; and discussion and ridicule of the book became the fashionable recreation for those who had read arts of it as well as those who had not. The comic paper Punch acted as a mirror of current opinion, which in the main was adverse. One of the Darwin ballads[3] calls to mind more recent things of the same sort in connection with the discovery of great fossil animals in our own country:
They slept in a wood,
Or wherever they could
For they didn’t know how to make beds;
They hadn’t got huts,
They dined upon nuts,
Which they cracked upon each other’s heads.
They hadn’t much scope
For a comb, brush, or soap,
Or towels, or kettle, or fire;
They had no coats nor capes,
For ne'er did these apes
Invent what they didn’t require.
*****
From these though descended,
Our manners are mended.
Though still we can grin and backbite;
We cut up each other,
Be he friend or brother,
And tails are the fashion—at night.
This origination
Is all speculation—
We gamble in various shapes;
So Mr. Darwin
May speculate in
Our ancestors having been apes.
The main contention of Darwin, that man was developed from a lower stock, and so on back to the beginning of life, is too well known today to deserve a great deal of comment. How much natural selection may have affected that development cannot yet be said with certainty—there are too many other possible factors of which we are just beginning to learn. In that time, however, it was less known, and even more apt to excite prejudice. The mere conclusion that the minds of man and the lower animals were very similar was enough to set the theologians agog with excitement; to them it was a direct thrust at the "godliness" of the human intellect.
Indeed, the preachers did have cause for alarm. Not only was Darwin's general conclusion as to man’s ancestry at direct variance with the tenets of "revealed" religion; some of his statements contradicted the strongest arguments on which religion is based. He sees no evidence that it had played, in the remote past, any important role in the development of humanity. "There is no evidence," he says, "that man was aboriginally endowed with the ennobling belief in the existence of an omnipotent God." This was not, of course, a proclamation of atheism or agnosticism; it was not even a question as to the truth of the conception of a god, or of gods. Yet it would cause others to question, to examine the bases for their beliefs, and perhaps even to give some of them up. Of course, one might give up a great many beliefs and still be a Christian, a Mohammedan, or what not, but he could not be orthodox. And it was orthodoxy upon which the preachers depended for their power—or, in many cases, for their jobs.
But the most emphasized, if not the most important, feature of the Descent of Man was the section dealing with Darwin’s hypothesis of sexual selection. This hypothesis held that animals of one sex held a definite preference for certain qualities in the opposite sex. Naturally, under this supposition, the predominant number of matings would be with those individuals possessing the favored characteristics, so that in time those qualities would become established. Thus among birds the more brilliant males, or those with superior voices, were the more successful in courtship, and so left more descendants than did the unfavored ones. Eventually the advantageous coloration would be established as the character of the species, or of a new species.
This hypothesis (it hardly deserves to be called a theory) became extremely popular with the followers of Darwin. It seemed to explain a great number of things, and required only a small acquaintance with the subject and an ordinary amount of common sense to manipuate. Evolutionists actually hunted for multiple examples of favorable characters; the most insignificant features of appearance or structure were assumed to be aids in the struggle for existence. From the arguments of these enthusiasts one would gain the idea that there were no traits in animals that were either useless or harmful, but that every structure and habit had been carefully selected with regard to their usefulness. For a while evolutionists and particularly amateur evolutionists, made a fad of sexual selection, and the more significant features of Darwin's work were slighted.
But the hypothesis contained a great weakness—it depended too much on the accuracy of the human mind as a gauge of the animal mind. It supposed that the thoughts of a man, looking upon the gorgeous plumage of a cock pheasant, were akin to those of the hen pheasant. It made possible the explanation of altogether too many things, and on a basis for which there was but the slightest psychological support. To hold that the minds of a beetle, a bird, an elephant, and a man were similarly affected by similar things was going too far, particularly when there was no way of proving the stand, or of testing it by experiment. Gradually sexual selection lost popularity, and in the reaction dragged with it the theory of natural selection. Indeed, though careful experiments in breeding have demonstrated too clearly for question the efficiency of selection, the part which selection, of whatever kind, played in evolution is far from settled. As Dr. A. F. Shull, one of the leaders among the younger zoologists of America, recently wrote, "There is no marked inclination among leading biologists to attribute to selection in nature, through the struggle for existence, anything but a minor and negative role in evolution."
In the years following 1874 Darwin wrote several books, and in 1879 he supervised the publication of an English version of Dr. Ernst Krause's Life of Erasmus Darwin, adding a sketch of the poet-evolutionist’s habits and character. But people were too much interested in the ideas of a living Darwin to devote much thought to those of a dead member of the same family, and fewer than a thousand copies of the book sold.
In 1881 the aged naturalist published his last book, The Formation of Vegetable Mould, Through the Action of Worms. More than forty years before he had written a preliminary sketch of the subject, and in December of the year he moved to Down he had begun an experiment which was to contribute greatly to the study. Twenty-nine years later, November, 1871, the experiment was completed. Darwin proved that bits of chalk and of harder rock could, in a period of three decades, be buried more than half a foot by the action of earthworms alone. Observations on the buried ruins of Roman towns of Britain showed that their condition was due largely to the action of these same earthworms, which year after year brought earth to the surface in the form of castings. Of the further work in this problem Mr. Brittany says:
Earthworms were not only scrutinized in their out-of-door work, but were kept in confinement and studied. It appears that they swallow earth both to make their burrows and to extract all nutriment it may contain; they will eat almost anything they can get their skin over. From careful calculation it wass shown that worms on an average pass ten tons of soil on an acre of ground through their bodies every year. It is, then, but a truism to say that every bit of soil on the surface of the globe must have passed through their bodies many times. They were discovered to work mainly by night, when hundreds may with care be discerned, with tails fixed in their burrows, prowling round in circles, rapidly retreating into holes, and strongly resisting efforts to extract them. It was found … that they have no sense of hearing, but a most remarkable sensitiveness to vibrations of the earth or even to contact with air in motion.
This book which, like the others achieved a great and unexpected popularity, left Darwin exhausted. "I feel so worn out that I do not suppose I shall ever again give reviewers trouble," he wrote Hooker. Yet for several months he worked on, not with enthusiasm nor with the hope of carrying out another large project, yet with interest. In March and April, 1882, he felt poorly, and the action of his heart became so weak that he was unable to climb the stairs. On April 18 he was well enough to examine a specially interesting plant which had been brought him, but on the following day he died.
- ↑ The full title is, On the Various Contrivances by Which Orchids Are fertilised by Insects.
- ↑ There may be some doubt about the extent of Darwin's conviction at that time. Certain it is that his Journal of Researches, edition of 1839, contains several references to special creation, as is shown in "Darwin as a Naturalist," No. 567, in this Series.
- ↑ Quoted by Bettany, Life of Darwin, p. 124.