Animal Life and Intelligence

by C. Lloyd Morgan

Let us again hear the voice of Darwin himself. "Most male birds," he says, "are highly pugnacious during the breeding season, and some possess weapons especially adapted for fighting with their rivals. But the most pugnacious and the best-armed males rarely or never depend for success solely on their power to drive away or kill their rivals, but have special means for charming the female. With some it is the power of song, or of emitting strange cries, or of producing instrumental music; and the males in consequence differ from the females in their vocal organs or in the structure of certain feathers. From the curiously diversified means for producing various sounds, we gain a high idea of the importance of this means of courtship. Many birds endeavour to charm the females by love-dances or antics, performed on the ground or in the air, and sometimes at prepared places. But ornaments of many kinds, the most brilliant tints, combs and wattles, beautiful plumes, elongated feathers, top-knots, and so forth, are by far the commonest means. In some cases, mere novelty appears to have acted as a charm. The ornaments of the males must be highly important to them, for they have been acquired in not a few cases at the cost of increased danger from enemies, and even at some loss of power in fighting with their rivals[AK].... What, then, are we to conclude from these facts and considerations? Does the male parade his charms with so much pomp and rivalry for no purpose? Are we not justified in believing that the female exerts a choice, and that she receives the addresses of the male who pleases her most?"[AL]

Here again, then, we have the combined action of elimination and selection. And now we may note that selection involves intelligence—involves the play of appetence and choice. Hence it is that, when we come to consider the evolution of human-folk, the principle of elimination is so profoundly modified by the principle of selection. Not only are the weaker eliminated by the inexorable pressure of competition, but we select the more fortunate individuals and heap upon them our favours. This enables us also to soften the rigour of the blinder law; to let the full stress of competitive elimination fall upon the worthless, the idle, the profligate, and the vicious; but to lighten its incidence on the deserving but unfortunate.

Both selection and elimination occurring under nature, but elimination having by far the wider scope, we may now inquire what will be their effect as regards the three modes of variation—advantageous, disadvantageous, and neutral. It must be remembered that these modes are relative and dependent upon circumstances, so that variations, neutral under certain conditions, may become relatively disadvantageous under other conditions. Selection clearly leads to the preservation of advantageous variations alone, and these variations are advantageous in so far as they meet the taste of the selecting organism. For selection depends upon individual choice; and uniformity of selection is entirely dependent upon uniformity in the standard of taste. If, as Darwin contends, the splendid plumage and tuneful notes of male birds are the result of a selection of mates by the hens, there must be a remarkable uniformity of taste among the hens of each particular species, since there is a uniformity of coloration among the cock-birds. It may be said that in all their mental endowments there is greater uniformity among animals than among men; and it is true that individuation has not been carried so far in them as in human-folk. Still, careful observers of animals see in them many signs of individual character; and this uniformity in the standard of taste in each species of birds seems to many naturalists a real difficulty in the way of the acceptance of sexual selection. We shall, however, return to this point. For the present it is clear that selection chooses out advantageous variations, that the advantage is determined by the taste of the selector, and that uniform selection implies uniformity of taste.

Turning to elimination, it is clear that it begins by weeding out, first the more disadvantageous, then the less disadvantageous variations. It leaves both the advantageous and the neutral in possession of the field. I imagine that many, perhaps most, of the variations tabulated by Mr. Wallace and other observers belong to the neutral category. Their fluctuating character seems to indicate that this is so. In any case, they are variations which have so far escaped elimination. And I think they are of great and insufficiently recognized importance. They permit, through interbreeding, of endless experiments in the combination of variations, some of which cannot fail to give favourable results.

It is just possible that it may be asked—If in natural elimination there is nothing more than the weeding out of the unfit and the suppression of disadvantageous variations, where is the possibility of advance? The standard may thus be maintained, but where is the possibility of progress? Such an objection would, however, imply forgetfulness of the fact that all the favourable variations remain to leaven the residual lump. Given a mean, with plus and minus variations: if in any generations the minus variations are got rid of, the mixture of the mean with the plus variations will give a new mean nearer the plus or advantageous end of the scale than the old mean. By how much the favourable variations tend to raise the mean standard, by so much will the race tend to advance. But in this process I see no reason why the neutral variations should be eliminated, except in so far as, in the keen struggle for existence, they become relatively unfavourable.

It is clear, however, that the intercrossing and interbreeding which occurs between average individuals on the one hand, and those possessing favourable variations on the other, while it tends gradually to raise the mean standard, tends also at the same time to reduce the advantageous variations towards the mean. It must tend to check advance by leaps and bounds, and to justify the adage, Natura nil facit per saltum. At the same time, it will probably have a greater tendency to reduce to a mean level neutral variations indefinite in direction than advantageous variations definite in direction. Still, it is a most important factor, and one not to be neglected. It tends to uniformity in the species, and checks individualism. It may act as a salutary brake on what we may figuratively term hasty and ill-advised attempts at progress. And at the same time, it favours repeated new experiments in the combination of variations, occasionally, we may suppose, with happy results.

But it does more than this. It tends to check, and, if the offspring always possessed the blended character of both parents, would be absolutely fatal to, divergence of character within the interbreeding members of a species. And yet no fact is more striking than this divergence of character. It is seen in the diversified products of human selection; for example, among pigeons. It is seen in the freedom of nature. Mr. Wallace gives many examples. "Among our native species," he says, "we see it well marked in the different species of titmice, pipits, and chats. The great titmouse, by its larger size and stronger bill, is adapted to feed on larger insects, and is even said sometimes to kill small and weak birds. The smaller and weaker coal-titmouse has adopted a more vegetarian diet, eating seeds as well as insects, and feeding on the ground as well as among trees. The delicate little blue titmouse, with its very small bill, feeds on the minutest insects and grubs, which it extracts from crevices of bark and from the buds of fruit trees. The marsh-titmouse, again, has received its name from the low and marshy localities it frequents; while the crested titmouse is a Northern bird, frequenting especially pine forests, on the seeds of which trees it partially feeds. Then, again, our three common pipits—the tree-pipit, the meadow-pipit, and the rock-pipit, or sea-lark—have each occupied a distinct place in nature, to which they have become specially adapted, as indicated by the different form and size of the hind toe and claw in each species. So the stone-chat, the whin-chat, and the wheat-ear are all slightly divergent forms of one type, with modifications in the shape of the wing, feet, and bill adapting them to slightly different modes of life."[AM] There is scarcely a genus that does not afford examples of divergent species. The question then naturally occurs—How have these divergent forms escaped the swamping effects of intercrossing?

That perfectly free intercrossing, between any or all of the individuals of a given group of animals, is, so long as the characters of the parents are blended in the offspring, fatal to divergence of character, is undeniable. Through the elimination of less favourable variations, the swiftness, strength, and cunning of a race may be gradually improved. But no form of elimination can possibly differentiate the group into swift, strong, and cunning varieties, distinct from each other, so long as all three varieties freely interbreed, and the characters of the parents blend in the offspring. Elimination may and does give rise to progress in any given group as a group; it does not and cannot give rise to differentiation and divergence, so long as interbreeding with consequent interblending of characters be freely permitted. Whence it inevitably follows, as a matter of simple logic, that where divergence has occurred, intercrossing and interblending must in some way have been lessened or prevented.

Thus a new factor is introduced, that of isolation, or segregation. And there is no questioning the fact that it is of great importance.[AN] Its importance can, indeed, only be denied by denying the swamping effects of intercrossing, and such denial implies the tacit assumption that interbreeding and interblending are held in check by some form of segregation. The isolation explicitly denied is implicitly assumed.

There are several ways in which isolation, or segregation, may be effected. Isolation by geographical barriers is the most obvious. A stretch of water, a mountain ridge, a strip of desert land, may completely, or to a large extent, prevent any intercrossing between members of a species on either side of the barrier. The animals which inhabit the several islands of the Galapagos Archipelago are closely allied, but each island has its particular species or well-marked varieties. Intercrossing between the several varieties on the different islands is prevented, and divergence is thus rendered possible and proceeds unchecked. It is said that in the Zuyder Zee a new variety of herrings, the fry of which are very small compared with open-sea herrings, is being developed. And the salmon introduced into Tasmania seem to be developing a fresh variety with spots on the dorsal fin and a tinge of yellow on the adipose fin. In the wooded valleys of the Sandwich Islands there are allied but distinct species of land-shells. The valleys that are nearest each other furnish the most nearly related forms, and the degree of divergence is roughly measured by the number of miles by which they are separated. Here there is little or no intercrossing between the slow-moving molluscs in adjoining valleys; none at all between those at any distance apart.