Fig. 7.—Brain of chimpanzee (a) and of man (b), seen from above, showing the cerebral hemispheres, whole on left, in section on right (after Huxley).
Having looked at some of the important differences between the bodies of man and lower animals, we may venture to ask the still harder question, How far do their minds work like ours? No full answer can be given, yet there are some well ascertained points to judge by. To begin, it is clear that the simple processes of sense, will, and action, are carried on in man by the same bodily machinery as in other high vertebrate animals. How like their organs of sense are, is well illustrated by the anatomist who dissects a bullock’s eye as a substitute for a man’s, to show how the picture of the outer world is thrown by the lenses on the retina or screen, into which spread the end-fibres of the optic nerve leading into the brain. Not but what the touch, sight, and other senses in the various orders of animals have their special differences, as where the eagle’s eyes are focussed to see small objects far beyond man’s range, while the horse’s eyes are so set in his head that they do not converge like ours, and he must practically have two pictures of the two sides of the road to deal with. Such special differences, however, make the general resemblance all the more striking. Next, the nervous system in beast and man shows the same common plan, the brain and spinal cord forming a central nervous organ, to which the sensory nerves convey the messages of the senses, and from which the motor nerves carry the currents causing muscular contraction and movement. The involuntary acts of animals are like our own, as when the sleeping dog draws his leg back if it is touched, much as his master would do, and when awake, both man and beast wink when a finger pretends to strike at their eyes. If we go on to voluntary actions, done with conscious will and thought, the lower creatures can for some distance keep company with mankind. At the Zoological Gardens one may sometimes see a handful of nuts divided between the monkeys inside the bars and the children outside, and it is instructive to notice how nearly both go through the same set of movements, looking, approaching, elbowing, grasping, cracking, munching, swallowing, holding out their hands for more. Up to this level, the monkeys show all the mental likeness to man that their bodily likeness would lead us to expect. Now we know that in the scramble, there passes in the children’s minds a great deal besides the mere sight and feel of the nuts, and the will to take and eat them. Between the sensation and action there takes place thought. To describe it simply, the boy knows a nut by sight, wishes to renew the pleasant taste of former nuts, and directs his hands and mouth to grasp, crack, and eat. But here are complicated mental processes. Knowing a nut by sight, or having an idea of a nut, means that there are grouped together in the child’s mind memories of a number of past sensations, which have so become connected by experience that a particular form and colour, feel and weight, lead to the expectation of a particular flavour. Of what here takes place in the boy’s mind we can judge, though by no means clearly, from what we know about our own thoughts and what others have told us about theirs. What takes place in the monkeys’ minds we can only guess by watching their actions, but these are so like the human as to be most readily explained by considering their brain-work also to be like the human, though less clear and perfect. It seems as though a beast’s idea or thought of an object may be, as our own, a group of remembered sensations compacted into a whole. What makes this the more likely is that when part of the sensations present themselves, the animal seems to judge that the rest must be there also, much as we ourselves are so apt to do. Thus a dog will jump upon a scum-covered stream which it takes for dry land, or when offered a sham biscuit will come for it, turning away when smell and taste prove that the rest of the idea does not agree with what sight suggested.
In much the same way, all people who attend to the proceedings of animals, account for them by faculties more or less like their own. Not only do creatures of all high orders give unmistakable signs of pleasure and pain, but our dealings with the brutes go on the ground of their sharing with us such more complex emotions as fear, affection, anger, nay, even curiosity, jealousy, and revenge. Some of these show themselves in bodily symptoms which are quite human, as every one must admit who has felt the trembling limbs and throbbing heart of a frightened puppy, or looked at the picture in Darwin’s Expression of the Emotions of the chimpanzee who has had his fruit taken from him, and displays his sulkiness by a pout which is a caricature of a child’s. Again, the lower animals show a well-marked will, which like man’s is not simply wish, but the resultant or balance of wishes, so that it is possible for two people calling a dog different ways, or both offering him bones, to distract his will in a way that reminds us of the philosopher’s imaginary ass that died of starvation between its hay and its water. As to the power of memory in brutes, we have all had opportunities of noticing how lasting and exact it is. Some things which the animals remember may be explained simply by their ideas becoming associated through habit, as when the horse betrays its former owner’s ways by stopping at every public-house; this may only mean that the familiar door suggests to the beast the memory of rest, and he stops. But to watch a dog dreaming makes us think that whole trains of ideas from the storehouse of memory are passing before his consciousness, as in our dreams. A memory in which such a revival of the past is possible, is a source of experience whence to extract understanding of the present, and foresight of the future. To make the memory of what has been, the means of controlling what shall be, is the great intellectual faculty in man, and in simple and elementary forms it comes into view among lower creatures. To tell but one of the innumerable animal stories which show expectation and design founded on experience. A certain Mr. Cops, who had a young orang-utan, one day gave it half an orange, put the other half away out of its sight on a high press, and lay down himself on the sofa, but the ape’s movements attracting his attention, he only pretended to go to sleep; the creature came cautiously and satisfied himself of his master being asleep, then climbed up the press, ate the rest of the orange, carefully hid the peel among some shavings in the grate, examined the pretended sleeper again, and then went to lie down on his own bed. Such behaviour is only to be explained by a train of thought involving something of what in ourselves we call reason.
To measure the differences between beast and man is really more difficult than tracing their resemblances. One plain mark of the higher intellectual rank of man is that he is less dependent on instinct than the animals which migrate at a fixed season, or build nests of a fixed and complicated pattern peculiar to their kind. Man has some instincts plainly agreeing with those of inferior animals, such as the child’s untaught movements to ward off danger, and the parental affection which preserves the offspring during the first defenceless period of life. But if man were possessed by a resistless longing to set off wandering southward before winter, or to build a shelter of boughs laid in a particular way, this would be less beneficial to his species than the use of intelligent judgment adapting his actions to climate, supply of food, danger from enemies, and a multitude of circumstances differing from district to district, and changing from year to year. If man’s remote progenitors had instincts like the beavers’ implanted in the very structure of their brain, these instincts have long ago fallen away, displaced by freer and higher reason. Man’s power of accommodating himself to the world he lives in, and even of controlling it, is largely due to his faculty of gaining new knowledge. Yet it must not be overlooked that this faculty is in a less measure possessed by other animals. We may catch them in the act of learning by experience, which is indeed one of the most curious sights in natural history, as when telegraph-wires are set up in a new district, and after the second year partridges no longer kill themselves by flying against them, or where in Canada the wily marten baffles the trapper’s ingenuity, finding out how to get the bait away, even from a new kind of trap, without letting it fall. The faculty of learning by imitation comes out in the apes in an almost human way. The anthropoid ape Mafuka, kept lately in the Zoological Gardens at Dresden, saw how the door of her cage was unlocked, and not only did it herself, but even stole the key and hid it under her arm for future use; after watching the carpenter she seized his bradawl and bored holes with it through the little table she had her meals on; at her meals she not only filled her own cup from the jug, but, what is more remarkable, she carefully stopped pouring before it ran over. The death of this ape had an almost human pathos; when her friend the director of the gardens came to her, she put her arms round his neck, kissed him three times, and then lay down on her bed and giving him her hand fell into her last sleep. One cannot but think that creatures so sagacious must learn in their wild state. Indeed less clever animals seem to some extent to teach their young, birds to sing, wolves to hunt, although it is most difficult for naturalists in such cases to judge what comes by instinct and what is consciously learnt.
Philosophers have tried to draw a hard and fast line between the animal and human mind. The most celebrated of these attempts is Locke’s, where in his Essay concerning Human Understanding he lays it down that beasts indeed have ideas, but are without man’s faculty of forming abstract or general ideas. Now it is true that we have learnt to reason with abstract ideas, such as solidity and fluidity, quantity and quality, vegetable and animal, courage and cowardice; and that there is not the least reason to suppose that such abstractions are formed by dogs or apes. But though the faculty of thus abstracting and generalising is one which rises to the highest flights of philosophic thought, it must be borne in mind that it begins in easy mental acts which seem quite possible to animals. Abstraction is noticing what several thoughts have in common, and neglecting their differences; thus a general idea is obtained by not attending too closely to particulars. The simplest form of this is when only one sense at a time is attended to, as in Locke’s example of the idea of whiteness, as being that which chalk, snow, and milk, agree in. But, to judge by animals’ actions, they also will attend to one sense at a time, as where a bull is excited by anything red. And it is most interesting to watch animals comparing a new object with their recollections or ideas of previous ones, practically recognising in it what is already familiar, and expecting it to behave like other individuals of its class. Cats or monkeys do not require to be shown the use of a fresh rug or cushion, when it is at all like the old one it is put in place of, and the “dog of the regiment” will accept any man in the uniform as a master, whether he has seen him before or not. Thus, the very simplicity of animal thought foreshadows the results of man’s higher abstraction and generalisation. Let us now read a few lines farther in Locke, and we shall see why he concludes that animals have not the power of forming abstract ideas. It is, he says, because they have no use of words or other general signs. But this itself is an easier point and far more worth arguing, than the hard question whether brutes have abstract ideas. In fact the power of speech gives about the clearest distinction that can be drawn between the action of mind in beast and man. It is far more satisfactory than another division attempted by philosophers who lay it down that while other animals have consciousness, man alone has self-consciousness, that is, he not only feels and thinks, but is aware of himself as feeling and thinking. Man, we know, is capable of this self-consciousness, which is cultivated by his being able to talk about himself as he does about other persons; but it has never been proved that animals, who we know are not apt to mistake their own bodies for anything outside, have no consciousness of themselves. When we study the rules of sign-making and language, we really have some means of contrasting the animals with ourselves. Evidently it is by means of language that the human mind has been able to work out and mark the high abstract ideas we deal with so easily; without words, how could we have reached results of combined and compared thought such as momentum, plurality, righteousness? The great mental gap between us and the animals we study is well measured by the difference between their feeble beginnings in calling one another and knowing when they are called, and man’s capacity for perfect speech. It is not merely that the highest anthropoid apes have no speech; they have not the brain-organisation enabling them to acquire even its rudiments. Man’s power of using a word, or even a gesture, as the symbol of a thought and the means of conversing about it, is one of the points where we most plainly see him parting company with all lower species, and starting on his career of conquest through higher intellectual regions.
In the comparison of man with other animals the standard should naturally be the lowest man, or savage. Put the savage is possessed of human reason and speech, while his brain-power, though it has not of itself raised him to civilization, enables him to receive more or less of the education which transforms him into a civilized man. To show how man may have advanced from savagery to civilization is a reasonable task, worked out to some extent in the later chapters of this volume. But there is no such evidence available for crossing the mental gulf that divides the lowest savage from the highest ape. On the whole, the safest conclusion warranted by facts is that the mental machinery of the lower animals is roughly similar to our own, up to a limit. Beyond this limit the human mind opens out into wide ranges of thought and feeling which the beast-mind shows no sign of approaching. If we consider man’s course of life from birth to death, we see that it is, so to speak, founded on functions which he has in common with lower beings. Man, endowed with instinct and capable of learning by experience, drawn by pleasure and driven by pain, must like a beast maintain his life by food and sleep, must save himself by flight, or fight it out with his foes, must propagate his species and care for the next generation. Upon this lower framework of animal life is raised the wondrous edifice of human language, science, art, and law.