A first book in organic evolution

by D. Kerfoot Shute

Through the theory of evolution it can readily be understood why the anatomical characters of the anthropoid apes and of man are so very closely alike. They have a common origin, and are blood relations—the one group of animals having specialized from common ancestors in one direction (obliquely), and the other group having specialized in another (straight) direction. (Vid. [Diagram of Development].)

Man, in his individual development from a fertilized ovum, comes from a source infinitely lower than the ape. Why, therefore, should he feel such reluctance to believe that he has passed, during geologic ages, through the phase of generalized simian ancestors? Is there not much more of hope in the knowledge that he has risen higher and higher through the æons of the past than in the belief that he was created an innocent and noble character and then fell to utter wretchedness through great temptation? The motto of evolution is Excelsior. For it shows that the human race, through all the incalculable ages of the past, has risen to higher and higher levels,—to nobler and nobler phases of being. His progress in the almost infinite past suggests the hope that he will mount higher and higher towards perfection during the limitless future. Not only may we hope that there will be boundless improvement of the human race, but boundless evolution of each individual human being as well. Evolution’s motto for each individual may also be Excelsior. And, therefore, may we say with some assurance of hope that love, while kissing the pathetic lips of death, need not entertain in vain the splendid hope of immortality. For if there be no immortality of personal consciousness, then the evolution of the cosmos, of man, of the highest mind in man, have no intelligible meaning for us; they are unfathomable enigmas—idiot stories without meaning.

Man, in specializing along certain lines since separating from the ancestral simian stock, has displayed more and more that structure of his skeleton and of the soft parts molded upon it that is best adapted to the needs of the mind resident within him. His bones are not merely the jointed framework of an animal, but a framework adapted to that erect attitude which so befits his intellectual nature. His feet are not the climbing and grasping feet of the ape, but organs for giving firmness to the tread and dignity to the bearing of a creature capable of high thought. The arms and hands are not for strength alone, for these members are much stronger in many a brute; but they also give greater expression and power to the thoughts that come from within. The hands possess such molding of fingers, thumbs, and palms, such delicacy for tactile impressions, and such capacity for nice adjustments, that they are not alone used for feeding the mouth and fighting antagonists; but they also contribute pre-eminently to the desires of a large mind, and are the efficient servants of its promptings. As Dana well says, “The face, with its expressive features, is formed so as to respond not solely to the emotions of pleasure and pain, but to shades of sentiment and interacting sympathies the most varied, high as heaven and low as earth,—ay, lower, in debased human nature; the whole being, body, limbs, and head, with eyes looking, not towards the earth, but beyond an infinite horizon, is a majestic expression of the divine feature in man and of the infinitude of his aspirations.”

But it is well to remember that man’s structure is riddled with evidences that he passed from an ancestral, quadrupedal condition, through the semi-erect to his present upright posture, slowly and laboriously. His erect attitude, geologically speaking, is a very recent accomplishment, and his anatomy, therefore, reveals many imperfect adaptations to his newly acquired posture. These imperfect adaptations are the sources of many grave diseases in mankind. It would require too technical a knowledge of anatomy to explain these imperfect adaptations, and I will therefore simply mention rupture and uterine displacements as due to imperfect adaptations to the upright attitude.

The common origin of man and the ape accounts for many interesting and otherwise inexplicable facts in anatomy. There is, for instance, a muscle that is normally present in the orang-outang known as the Opponens Hallucis. This muscle enables the orang to oppose his big toe to the other toes, just as we can oppose our thumb to the other fingers of our hand. This muscle is absent from the foot of man ordinarily. But occasionally it is found in man, in the dissecting-room, as a rarity—as an anomaly. The question naturally arises, why should this muscle be present normally in the orang and absent normally in man, occurring in the latter only as an abnormality? The theory of evolution gives the only rational answer. The man-like, ape-like generalized ancestors of man and the orang possessed this muscle, which was useful to them in grasping the branches of the trees among which they lived. These ancestors used the feet and hands alike for purposes of grasping (prehension) and locomotion. But those descendants that evolved more and more man-ward used the feet more for purposes of locomotion and less for grasping, while they used the hands more for grasping and less for locomotion, until, finally, man was created—a creature that uses his feet exclusively for locomotion, and the hands entirely for grasping. Through disuse, therefore, the opponens hallucis gradually disappeared in man; so that now it occurs only as a rare abnormality. The hereditary units that make this muscle still lie dormant in most men are usually so weak, through disuse, that they do not develop. Some unusual stimulus occasionally causes the latent hereditary units to develop and makes it appear in man. The same is the case with many other muscles and structures that are normal in the modern anthropoid apes, and only occur as rarities in man. The appearance of those muscles in man are instances of atavism, i. e., reversions to conditions that were normal in the ancestors of man and the apes, as they are still normal in the latter.

USELESS SCAFFOLDING LEFT IN THE BODY.

Man, in his post-natal growth, as well as during his embryological development, exhibits reminiscences of his animal ancestry. In the structure and movement of the new-born babe, as well as in the adult frame, we find continuous witnesses to the ancient animal strain.

On the theory that men in bygone ages were closely allied to simian creatures in habit as well as structure; that they led an arboreal life; and that, like the baby-monkeys to-day, the baby-men of other ages clung to their mothers as they climbed among the trees, Dr. Louis Robinson predicted that a baby’s power for grasping would likely be found to equal that of a young monkey which had reached a corresponding period of growth. He tested a large number of new-born infants in reference to this power by extending his finger or a cane, to imitate the branch of a tree, and observed how long they would hang there without any other support ([Plate XI]). He made experiments on about sixty children under a month old. About thirty of the children experimented upon were not over an hour old. Dr. Robinson states that each of the infants, with two exceptions, was able to hang to the finger or cane by its hands, like an acrobat from a horizontal bar, and sustain the whole weight of its body for at least ten seconds. Twelve of the infants, less than an hour old, held on for half a minute before the grasp relaxed; while four of this age held on for one minute. Over fifty of the infants when four days old could continue the grip for half a minute. Three weeks after birth the faculty for holding on reached its maximum, for at this age several succeeded in hanging on for a minute and a half; two held on for over two minutes; and one infant held on over two minutes and a half. One infant that was less than an hour old hung by both hands to Dr. Robinson’s finger for ten seconds, and then deliberately let go with his right hand, as if to seek a better hold, and continued his grasp with the left hand only, for five seconds longer. In none of these experiments did the limbs of the infants hang down in the attitude of the erect position, but the thighs were invariably in the baby-monkey attitude, at right angles to the body. The doctor says that this attitude and the disproportionately large development of the arms compared with the legs give the photographs of the infants a striking resemblance to a well-known picture of the celebrated chimpanzee, Sally, at the Zoölogical Garden in London. In these experiments the infants very seldom gave any sign of distress, and uttered no cry until the grasp began to give way. The fact that the flexor muscles of the forearm of a new-born infant show such remarkable strength while the other parts of the muscular system are so conspicuously weak and flaccid,—that they are able to perform a feat of muscular strength that will tax the powers of many a healthy adult,—can be explained only on the theory of inherited instinct from simian ancestors that lived in trees. This instinct is no longer useful to an infant. It is a vestigial instinct, a useless scaffolding in its life history.