Animal Life and Intelligence

by C. Lloyd Morgan

And how does Mr. Darwin meet this difficulty? "It is lessened, or, as I believe, disappears," he says,[JI] "when it is remembered that selection may be applied to the family as well as to the individual. Breeders of cattle wish the flesh and fat to be well marbled together; an animal thus characterized has been slaughtered, but the breeder has gone with confidence to the same stock, and has succeeded. Such faith may be placed in the power of selection, that a breed of cattle always yielding oxen with extraordinarily long horns could, it is probable, be formed by carefully watching which individual bulls and cows, when matched, produced oxen with the longest horns; and yet no one ox would ever have propagated his kind.... Hence we may conclude that slight modifications of structure or of instinct, correlated with the sterile condition of certain members of the community, have proved advantageous; consequently, the fertile males and females have flourished, and transmitted to their fertile offspring a tendency to produce sterile members with the same modifications. This process must have been repeated many times, until that prodigious amount of difference between the fertile and sterile females of the same species has been produced which we see in many social insects."

Now let us apply this illustration to the case of habits intelligently acquired. Instead of the possession of long horns, suppose the performance of some habitual action be observed in the oxen. Then, by carefully watching which individual bulls and cows, when matched, produced oxen which performed this intelligent habitual action, a breed of cattle always yielding oxen which possessed this habit might, on Darwin's principles, be produced. The intelligence of oxen might in this way be enhanced. Such faith may be placed in the power of selection that a breed of cattle always yielding oxen of marked intelligence could, it is possible, be formed by carefully watching which individual bulls and cows, when matched, produced the most intelligent oxen; and yet no ox would ever have propagated its kind. Regarding, then, a nest of ants or bees as a social community, mutually dependent on each other, and subject to natural selection, that community would best escape elimination in which the queen produced two sets of offspring—one set in which the procreative faculty was predominant to the partial exclusion of intelligence, and another in which intelligent activities were predominant to the exclusion of propagation.

It is possible that I have weakened my case by introducing such a difficult problem as the instincts of neuter insects. And I would beg the reader to remember that this is only incidental. What I wish to indicate is that among the many variations to which organisms are subject, there are variations in their intelligent activities; that these are of elimination value, those animals which conspicuously possess them escaping elimination in its several modes; that those survivors which thus escape elimination are likely to hand on, through inheritance, that intelligence which enabled them to survive; that if, throughout a series of generations, such intelligence be applied to some definite end, nervous channels will tend to be definitely established, and the intelligent activity will more and more readily become habitual; that eventually, through the lapsing of intelligence, these habitual activities may become so fixed and stereotyped as to become instinctive; that intelligence has thus been a factor in the establishment of these instinctive activities; that throughout the sequence there is no inheritance of anything individually acquired, the intelligent variations being throughout of germinal origin; and that, therefore, in the origin of instincts, the co-operation of intelligence and the lapsing of intelligence are not excluded on the principles advocated by Professor Weismann.

What, then, is excluded? Any individually acquired increment, either in the intelligence displayed or the stereotyping process. The subject of instinct and of animal intelligence has not at present been considered at any great length by Professor Weismann, but, judging by the general tenor of his writings, I take it that what he demands is definite proof that such individually acquired increment is actually inherited.

As before indicated in the chapter on "Heredity," such proof it is, from the nature of the case, almost impossible to produce. Suppose that we find evidence of a gradually increasing application of intelligence to some important life-activity, or a more and more defined stereotyping of some incompletely habitual or instinctive action; how are we to prove that the increment in either case is due to the inheritance of individual acquisitions, not to the selection of favourable innate (that is to say, germinal) variations? Such a hopeless task may at once be abandoned.

Are we, then, to leave the question as insoluble? I think not. It is still open to us to consider whether there are any cases in which the inheritance of acquired modifications is a more probable hypothesis than the selection of favourable germinal variations. Now, the acquisition of an instinctive dread of man, and the loss of this instinctive timidity under domestication, seem to be of this kind. And yet I doubt whether the evidence on this head is convincing. For the loss of instinctive timidity, Professor Weismann may invoke the aid of panmixia. But if there is truth in what I have already urged on this head, panmixia will not adequately account for the facts. On the other hand, he may contend that the instinctive dread is not due to the inheritance of individually acquired experience, but to the selection of the wilder birds and animals through the persistent elimination of those which are tame. And in support of this view, he may quote Darwin himself, who says,[JJ] "It is surprising, considering the degree of persecution which they have occasionally suffered during the last one or two centuries, that the birds of the Falklands and Galapagos have not become wilder; it shows that the fear of man is not soon acquired." It is questionable, however, whether this persecution, admittedly occasional, can have much elimination value. There is, however, the element of imitation and instruction to be taken into account, and the difficulty of proving that the timidity is really instinctive. It has frequently been observed that birds become, after a while, quite fearless of trains. Here elimination is practically excluded; but it has to be proved that this fearlessness is truly instinctive. Professor Eimer says,[JK] "In my garden every sparrow and every crow know me from afar because I persecute these birds. Once, in the presence of a friend, I shot a crow from the roof of my house, while the pigeons and starlings on the same roof, to the great astonishment of my friend, to whom I had predicted it, remained perfectly quiet. They had learned by frequent experience at what my gun was aimed, and knew that it did not threaten them." There is nothing in this interesting observation, however, to show that what the pigeons had learnt had, by inherited experience, become instinctive. And Professor Weismann will not, in all probability, be prepared to accept as a logical inference "that this instinct of fear, because it can be dispelled by experience, must be founded on inherited, acquired experience."[JL]

Fully admitting, then, that this is a matter of relative probability, and that the observations and inferences in this matter are not by themselves convincing, I still think that the balance of probability is here on the side of some inheritance of experience. Take next such an instinctive habit as that which dogs display of turning round in a narrow circle ere they lie down. In its origin the instinct probably arose with the object of preparing a couch in the long grass. Now, is this habit of elimination value? Can we suppose that it arose through the elimination of those ancestral animals which failed to perform this habit? I find it difficult to accept this view, though it is just possible that the animals which did this thereby escaped the observation of their enemies. It is also possible that this originally was a merely purposeless habit, a strange trick of manner, which has been inherited, and rendered constant and fixed. Here again, however, I think the balance of probability is that the habit was intelligently acquired and inherited.

I have before drawn attention to the more or less incompletely instinctive avoidance, by birds and lizards, of insects with warning coloration. That the avoidance is not perfectly instinctive is shown by the fact that young birds sometimes taste these caterpillars or insects. But a very small basis of experience, often a single case, is sufficient to establish the association. And in young chicks the avoidance of bees and wasps seems to be perfectly instinctive. The effects on the young birds, however, can hardly be of elimination value. Mr. Poulton offered unpalatable insects "to animals from which all other food was withheld. Under these circumstances, the insects were eaten, although often after many attempts, and evidently with the most intense disgust."[JM] I have caused bees to sting young chickens; the result was extreme discomfort, but in no cases permanent injury or death. If, then, the instinct is not of elimination value, that is to say, not such as to save the possessors from elimination, how can it have been established by natural selection? And if not due to natural selection, to what can it be due, save inherited antipathy?

Natural selection is such a far-reaching and ubiquitous factor in organic evolution, that it is not likely that many cases can be found in which the play of elimination can be rigidly excluded. But there are not a few in which elimination does not appear to be the most important factor. Mr. G. L. Grant has recently observed that the sparrows near Auckland, New Zealand, have taken to burrowing holes in sand-cliffs, like the sand-martin. The cliff-swallow of the Eastern United States has almost ceased to build nests in the cliffs, like its progenitors, and now avails itself of the protection afforded by the eaves of houses. The surviving beavers in Europe are said to have abandoned the instinct of building huts and dams. The race being no longer sufficiently numerous to live in communities, the survivors live in deep burrows. In Russian Lapland, under the persecution of hunters, the reindeer are reported to be abandoning the tundras, or open lichen-covered tracts, for the forests. The kea (Nestor notabilis), a brush-tongued parrot of New Zealand, which normally feeds on honey, fruits, and berries, has, since the introduction of sheep, taken to a carnivorous diet. It is said to have begun by pecking at the sheep-skins hung out to dry; subsequently it began to attack living sheep; and now it has learnt to tear its way down to the fat which surrounds the kidneys. This habit, far from being the result of elimination, is rapidly leading to the elimination of the bird that has so strangely adopted it.

Now, although in these cases elimination has, I think, been a quite subordinate factor, I do not adduce them as convincing evidence that acquired habits are hereditary. Instruction and imitation in each successive generation may well have come into play. There is no proof that they are even incompletely instinctive. But I think that these are the kinds of activities, renewed and careful observations and, if possible, experiments on which, may lead to more decisive results. It would probably not be difficult to ascertain how far the carnivorous habit of the kea has become hereditary, and how far it is performed in the absence of instruction and without the possibility of imitation.