|March 20, 2012||Filled under All text of Paley Natural Theology, Chapter 18||
The order may not be very obvious, by which I place instincts next to relations. But I consider them as a species of relation. They contribute, along with the animal organization, to a joint effect, in which view they are related to that organization. In many cases, they refer from one animal to another animal; and when this is the case, become strictly relations in a second point of view.
An instinct is a propensity prior to experience, and independent of instruction. We contend, that it is by instinct that the sexes of animals seek each other; that animals cherish their offspring; that the young quadruped is directed to the teat of its dam; that birds build their nests, and brood with so much patience upon their eggs; that insects which do not sit upon their eggs, deposit them in those particular situations, in which the young, when hatched, find their appropriate food; that it is instinct which carries the salmon, and some other fish, out of the sea into rivers, for the purpose of shedding their spawn in fresh water.
We may select out of this catalogue the incubation of eggs. I entertain no doubt, but that a couple of sparrows hatched in an oven, and kept separate from the rest of their species, would proceed as other sparrows do, in every office which related to the production and preservation of their brood. Assuming this fact, the thing is inexplicable upon any other hypothesis than that of an instinct impressed upon the constitution of the animal. For, first, what should induce the female bird to prepare a nest before she lays her eggs? It is in vain to suppose her to be possessed of the faculty of reasoning; for no reasoning will reach the case. The fulness or distention which she might fee in a particular part of her body, from the growth and solidity of the egg within her, could not possibly inform her, that she was about to produce something, which, when produced, was to be preserved and taken care of. Prior to experience, there was nothing to lead to this inference, or to this suspicion. The analogy was all against it; for, in every other instance, what issued from the body, was cast out rejected.
But, secondly, let us suppose the egg to be produced into day; how should birds know that their eggs contain their young? there is nothing, either in the aspect, or in the internal composition of an egg, which could lead even the most daring imagination to conjecture, that it was hereafter to turn out from under its shell, a living, perfect bird. The form of the egg bears not the rudiments of a resemblance to that of the bird. Inspecting its contents, we find still less reason, if possible, to look for the result which actually takes place. If we should go so far, as from the appearance of order and distinction in the disposition of the liquid substances which we noticed in the egg, to guess that it might be designed for the abode and nutriment of an animal, (which would be a very bold hypothesis,) we should expect a tadpole dabbling in the slime, much rather than a dry winged, feathered creature; a compound of parts and properties impossible to be used in a state of confinement in the egg, and bearing no conceivable relation, either in quality or material, to anything observed in it. From the white of an egg, would any one look for the feather of a goldfinch? or expect from a simple uniform mucilage, the most complicated of all machines, the most diversified of all collections of substances? nor would the process of incubation, for sometime at least lead us to suspect the event. Who that saw red streaks shooting in the fine membrane which divides the white from the yolk, would suppose that these were about to become bones and limbs? Who that espied two discolored points first making their appearance in the cicatrix, would have had the courage to predict, that these points were to grow into the heart and head of a bird? It is difficult to strip the mind of its experience. It is difficult to resuscitate surprise, when familiarity has once laid the sentiment asleep. But could we forget all that we know, and which our sparrows never knew, about oviparous generation: could we divest ourselves of every information, but what we derive from reasoning upon the appearance or quality discovered in the objects presented to us, I am convinced that Harlequin coming out of an egg upon the stage, is not more astonishing to a child, than the hatching of a chicken both would be, and ought to be, to a philosopher.
But admit the sparrow by some means to know, that within that egg was concealed the principle of a future bird, from what chemist was she to learn, that warmth was necessary to bring it to maturity, or that the degree of warmth, imparted by the temperature of her own body, was the degree required?
To suppose, therefore, that the female bird acts in this process from a sagacity and reason of her own, is to suppose her to arrive at conclusions which there are no premises to justify. If our sparrow, sitting upon her eggs, expect young sparrows to come out of them, she forms, I will venture to say, a wild and extravagant expectation, in opposition to present appearances, and to probability. She must have penetrated into the order of nature, farther than any faculties of ours will carry us; and it hath been well observed, that this deep sagacity, if it be sagacity, subsists in conjunction with great stupidity, even in relation to the same subject. “A chemical operation,” says Addison, “could not be followed with greater art or diligence, than is seen in hatching a chicken; yet is the process carried on without the least glimmering of thought or common sense. The hen will mistake a piece of chalk for an egg; is insensible of the increase or diminution of their number; does not distinguish between her own and those of another species; is frightened when her supposititious breed of ducklings take the water.”
But it will be said, that what reason could not do for the bird, observation, or instruction, or tradition, might. Now, if it be true, that a couple of sparrows, brought up from the first in a state of separation from all other birds, would build their nest, and brood upon their eggs, then there is an end of this solution. What can be the traditionary knowledge of a chicken hatched in an oven?
Of young birds taken in their nests, a few species breed when kept in cages; and they which do so, build their nests nearly in the same manner as in the wild state, and sit upon their eggs. This is sufficient to prove an instinct, without having recourse to experiments upon birds hatched by artificial heat, and deprived from their birth of all communication with their species; for we can hardly bring ourselves to believe, that the parent bird informed her unfledged pupil of the history of her gestation, her timely preparation of a nest, her exclusion of the eggs, her long incubation, and of the joyful eruption at last of her expected offspring; all which the bird in the cage must have learned in her infancy, if we resolve her conduct into institution.
Unless we will rather suppose, that she remembers her own escape from the egg; had attentively observed the conformation of the nest in which she was nurtured; and had treasured up her remarks for future imitation: which is not only extremely improbable, (for who, that sees a brood of callow birds in their nest, can believe that they are taking a plan of their habitation?) but leaves unaccounted for, one principal part of the difficulty, “the preparation of the nest before the laying of the egg.” This she could not gain from observation in her infancy.
It is remarkable also, that the hen sits upon eggs which she has laid without any communication with the male, and which are therefore necessarily unfruitful; that secret she is not let into. Yet, if incubation had been a subject of instruction or of tradition, it should seem that this distinction would have formed part of the lesson; whereas the instinct of nature is calculated for a state of nature; the exception here alluded to taking place chiefly, if not solely, amongst domesticated fowls, in which nature is forced out of her course.
There is another case of oviparous economy, which is still less likely to be the effect of education than it is even in birds, namely that of moths and butterflies, which deposit their eggs in the precise substance, that of a cabbage for example, from which, not the butterfly herself, but the caterpillar which is to issue from her egg, draws its appropriate food. The butterfly cannot taste the cabbage. Cabbage is no food for her; yet in the cabbage, not by chance, but studiously and electively, she lays her eggs. There are, amongst many other kinds, the willow caterpillar, and the cabbage caterpillar: but we never find upon a willow the caterpillar which eats the cabbage; nor upon the converse. This choice, as appears to me, cannot in the butterfly proceed from instruction. She had no teacher in her caterpillar state. She never knew her parent. I do not see, therefore, how knowledge, acquired by experience, if it ever were such, could be transmitted from one generation to another. There is no opportunity either for instruction or imitation. The parent race is gone, before the new brood is hatched. And if it be original reasoning in the butterfly, it is profound reasoning indeed. She must remember her caterpillar state, its tastes and habits; of which memory she shows no signs whatever. She must conclude from analogy, for here her recollection cannot serve her, that the little round body which drops from her abdomen, will at a future period produce a living creature, not like herself, but like the caterpillar, which she remembers herself once to have been. Under the influence of these reflections, she goes about to make provision for an order of things, which she concludes will, sometimes or other, take place. And it is to be observed, that not a few out of many, but that all butterflies argue thus, all draw this conclusion; all act upon it85.
But suppose the address, and the selection, and the plan, which we perceive in the preparations which many irrational animals make for their young, to be traced to some probable origin; still there is left to be accounted for, that which is the source and foundation of these phenomena, that which sets the whole at work, the ??????, the parental affection, which I contend to be inexplicable upon any other hypothesis than that of instinct.
For we shall hardly, I imagine, in brutes, refer their conduct towards their offspring to a sense of duty, or of decency, a care of reputation, a compliance with public manners, with public laws, or with rules of life built upon a long experience of their utility. And all attempts to account for the parental affection form association, I think, fail. With what is it associated? Most immediately with the throes of parturition, that is, with pain, and terror, and disease. The more remote, but not less strong association, that which depends upon analogy, is all against it. Everything else, which proceeds from the body, is cast away and rejected.
Not less surprising is the parental instinct of the gad-fly, (Gasterophilus equi) whose larvae are destined to be nourished in the stomach and intestines of the horse! How shall the parent convey them there? By mode truly extraordinary—Flying round the animal she curiously poises her body while she deposits her eggs on the hairs of his skin. Whenever therefore the horse chances to lick the part of his body to which they are attached, they adhere to the tongue, and from thence pass into the stomach and intestines. And what increases our surprise is, that the fly places her eggs almost exclusively on the knee and the shoulder, on those parts the horse is sure to lick.—Paxton.
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