Popular Science Monthly/Volume 17/June 1880/The Rate of Animal Development
|THE RATE OF ANIMAL DEVELOPMENT.|
By J. W. SLATER.
"Consider young ducks."
ONE of the attempts which have been made to establish the existence of a "great gulf" between man and beast may be pronounced exceptionally curious as an instance alike of careless and defective observation and of rash conclusions. That by such arguments men of eminence could really mislead themselves, and succeed for a length of time in misleading the outside public, is deeply humiliating. Professor St. George Mivart suggests that a book should be written on the "stupidity of animals." We are far from denying that such a work would be useful; but, should the needful companion volume on the "stupidity of man" make its appearance in due course, it might not unfittingly open with the reasoning we are about to quote.
To begin, then: the slow bodily development of the human infant and its prolonged helplessness are matters far too familiar to require proof, or even illustration. No less familiar and universally admitted is the rapidity with which foals, calves, lambs, kids, chickens, and ducklings acquire the use of their limbs and other organs. These facts could not fail to come under the notice even of the most careless observers. But, who could have imagined that the said facts would be, without further inquiry, at once seized hold of as a theme for stilted declamation, and be elevated to the rank of a fundamental distinction between man and the lower animals? Yet this strange error has actually been committed, not merely by men of words, like Addison, Paley, and Whewell—which is surely sad enough—but even by a man of things, like Sir Humphry Davy. The great chemist attempts to show that man does not use his limbs instinctively, like other animals. Says he:
"Man is so constituted that his muscles acquire their power by habit, but in the colt and the chicken the limbs are formed with the power of motion, and these animals walk as soon as they have quitted the womb or the egg.
"Physicus. I think I have observed that birds learn to fly and acquire the use of their wings by continued efforts in the same manner as a child does that of his limbs.
"Ornither. I can not agree with you. Young birds can not fly as soon as they are hatched, because they have no wing-feathers; but, as soon as these are developed, and even before they are perfectly strong, they use their wings, fly, and quit the nest without any education from their parents."
Very similar assertions are found in a laborious attempt made by the late Professor Whewell to set aside the palpable fact that man, like every other animal, has an instinctive—or we might perhaps better say an hereditary—knowledge of the functions of his voluntary organs.
Said the Professor: "The child learns to distinguish forms and positions by a repeated and incessant use of his hands and eyes; he learns to walk, to run, and to leap by slow and laborious degrees; he distinguishes one man from another and one animal from another only after repeated mistakes. Nor can we conceive this to be otherwise. How should the child know at once what muscles he is to exert that he may stand and not fall, till he has often tried? How should he learn to direct his attention to the differences of different faces and persons till he is roused by some memory, or hope which implies memory? It seems to me as if the sensations could not, without considerable practice, be rightly referred to ideas of space, force, resemblance, and the like. Yet that which thus appears impossible is, in fact, done by animals. The lamb, almost immediately after its birth, follows its mother, accommodating the action of its muscles to the form of the ground. The chick just emerged from the shell picks up a minute insect, directing its beak with the greatest accuracy. Even the human infant seeks the breast and exerts its muscles in sucking almost as soon as it is born."
So, after all, "that which thus appears impossible" is, in fact, done not by "animals" only, but by man also! The concession contained in the last sentence is simply fatal to what has gone before. To be consistent the learned Professor ought by all means to have asserted that an infant learns to suck only "by slow and laborious degrees," and after its sensations have been rightly referred to appropriate "ideas." It would scarcely be a more unwarrantable assumption than those he has indulged in abundantly in the course of his argument.
In the same vein as Davy and Whewell, teleologists and natural theologians, when enlarging upon the marvels of instinct, have seldom failed to "trot out" the colt, the calf, or the lamb, to invite our consideration to the chickens and the "young ducks," and to erect upon the precocity of these creatures—as compared with the tedious development of our own species—a fancied wall of demarkation between man and beast. Had they been really actuated by a scientific spirit, they would have felt it their bounden duty to ascertain whether all the lower animals were, in contrast to man, able to use their limbs soon after their birth. Had they done so, they might have met with evidence similar to what is thus given by an actual observer in describing an infant orang-outang which had come into his possession: "The Mias, like a very young baby, lying on its back quite helpless, rolling lazily from side to side, stretching out his hands into the air, wishing to grasp something, but hardly able to guide its fingers to any definite object, and when dissatisfied opening wide its almost toothless mouth, and expressing its wants by an almost infantile scream. . . . When I had had it for about a month it began to exhibit some signs of learning to run alone. When laid upon the floor it would push itself along by its legs, or roll over, and thus make an unwieldy progression. When lying in the box it would lift itself up to the edge into almost an erect position, and once or twice succeeded in tumbling over."
Thus we see that, the nearer brutes approach to man in their structure, the more gradual is their development. The process which in the colt and the lamb is contracted so as to escape observation is here shown at very considerable length. That the child, especially in the higher races of mankind, makes a still more gradual progress, is plainly a mere question of degree.
The young ape which Mr. Wallace observed was, beyond all reasonable dispute, acquiring the use of its limbs precisely in the same manner as a human child. If the latter learns, by slow and laborious degrees, what muscles he must exert in order to effect any desired movement, so does the young ape. If the child can not judge of the position and distance of objects, till it has by considerable practice learned to refer its sensations to appropriate "ideas," the same must be said of the young Mias. But, if the young apes, and, indeed, all other young animals, inherit from their forefathers a latent knowledge of the use of their organs, which is called into activity as soon as their muscular and nervous systems are sufficiently developed, the same holds good of the human infant.
Of course, it would be unfair to demand of such men as Professor Whewell that, before theorizing and dogmatizing, they should go forth to the forests of Borneo in search of facts. As for Davy, his splendid achievements in chemistry may cover his failure in biology. But surely every man in Europe, though he may never have met with infant apes, must have seen how kittens, when beginning to walk, totter, stagger, and roll over, just like young children; how they pat at, and endeavor to touch, objects beyond their reach; and how, even after the forelegs have gained a considerable degree of firmness and obey volition, the hinder extremities remain feeble, and are often for a time trailed helplessly along. Thus, then, we see that in the mammalia, instead of man standing alone, sharply contrasted to the rest of the class, he merely occupies one extremity of a series toward the other end of which stand our much-talked-of friends the lamb and the foal, while the carnivorous animals and the apes occupy intermediate positions. Some very plain reasons why this should be the case will follow in due course.
But what are the facts concerning birds? Are they all able, as soon as hatched, to direct the beak with perfect accuracy, to select suitable nourishment, and to flutter about awaiting merely the growth of their wing-feathers before they can take flight? Davy's "Ornither" must have been either a willful sophist or a most egregious goose. Had he been an accurate and conscientious observer, he must have been aware that what he predicates of birds in general is true, in any sense, merely of the Gallinæ, Grallæ, Anseres, and Struthiones, and assuredly not of the Passeres, Picariæ, Columbæ, Psittaci, and Raptores. Did any of the authors to whom we have been referring, before indulging in platitudes on young ducks, ever take the trouble to "consider" young hawks, young thrushes, or young canaries? Had they done so they would have seen that such nestlings, instead of being able to "direct the beak with the greatest accuracy," can merely sit in the nest with open mouth waiting to be fed! A young canary, so far from being able to stand or walk, seldom fails to break its legs if startled and induced by fright to attempt leaving the nest. Such facts as these are known to every bird-fancier—nay, we might say to every rustic youth, who has ever robbed a nest and has attempted to bring up the callow young by hand. They are not known, it appears, to men of erudition. It was, we think, the Prime Minister of Gustavus Adolphus, of Sweden, who said to his son, "Thou knowest not with how little wisdom the world is governed." In like manner, and even more truth, it might be said that we know not with how little accurate thorough knowledge books are compiled, the world is misinstructed, and imposing reputations are built up.
We do not demand original observation from Professor Whewell. Every one knows that the possessors of inherited wealth are apt to despise the man who has acquired a fortune by his own exertions. But there is a class of men—more numerous, we fear, in England than in any other civilized country—who, with a still more unjustifiable prejudice, contemn all knowledge that has not been derived from books, and scorn original research and discovery. Still it is strange that none of these writers should have met with the following observation from Gilbert White: "On the 5th of July, 1775, I again untiled part of the roof over the nest of a swift. The squab young we brought down and placed upon the grass-plot, where they tumbled about and were as helpless as a new-born child. When we contemplated their naked bodies, their unwieldy, disproportionate abdomina, and their heads too heavy for their necks to support, we could not but marvel."
Davy and Whewell might, further, have found in Erasmus Darwin's "Zoönomia" some remarks on the different stages of maturity which animals of different species have reached when they are first brought into the world. The author uses these very words: "The chicks of the pheasant and the partridge have more perfect plumage, more perfect eyes, and greater aptitude for walking, than the callow nestlings of the dove or the wren. It is only necessary to show the first their food and teach them how to pick, while the latter for days obtrude a gaping mouth." Would it have been too much trouble for a man of such extensive reading as Professor Whewell to have run his eyes over the passage above quoted? Being, moreover, a German scholar—at least to the extent of an occasional mistranslation from the language the Professor might have read that Lorenz Oken divided the class Birds into two main subdivisions, nest-sitters and nest-quitters (nest-hocker und nest-flüchter), according as when hatched they remain helpless in the nest, or are at once able to run about and seek food for themselves.
Davy, by the mouth of "Ornither," gives a very lame explanation of the fact that the majority of birds can not fly as soon as hatched. Before they can take flight they have to await not alone the growth of their wing-feathers, but the simultaneous development of the muscles. The Raptores, Passeres, etc., are, as we have already seen, unable to walk as well as fly. Does this inability depend upon the want of feathers? The fact that parent-birds educate their young is clearly established by the interesting observations of Dr. C. Abbott.
In the case of birds of prey the process of education is somewhat prolonged, even after leaving the nest. It is thought by many that Deuteronomy xxxii., v. 11, is a description of the manner in which eagles train their young to fly; "stirring up" the nest, i. e., shaking and disturbing it so as to compel the nestlings to leave their cradle; "fluttering" over them "and bearing them on her wings"—that is to say, following and intercepting their downward movement, and aiding them to reascend.
Thus we see that the condition of the young of the lower animals is, after all, analogous to that of the human infant. The child, indeed, is still slower in learning to walk than the kitten or the young ape, not because he has to learn in a different manner, but because the development of his muscles and joints is much more gradual; because his head is relatively heavier; because he has to support himself on one pair of limbs only, thus rendering his base much narrower and his center of gravity higher from the ground; and because, as we have already pointed out in the case of the kitten, the hinder extremities gain strength more slowly than the anterior.
Surely, therefore, the helplessness of the human infant can no longer be regarded as an exceptional phenomenon, and all conclusions based upon it by rhetoricians may be safely dismissed to dream-land, whence they came.—Journal of Science.
- "Lessons from Nature."
- To speak of acquiring a power by habit is scarcely rational. The power must exist before the habit can be formed.
- Collected "Works," vol. ix. "Salmonia," p. 105.
- "Philosophy of the Inductive Sciences," ii., p. 616.
- A. R. Wallace, "Malay Archipelago," p. 45.
- "Natural History of Selborne," Letter XXI.
- Vol. i., pp. 187-194.
- "Quarterly Journal of Science," vol. vi., p. 361.