Russel Wallace : Alfred Russell Wallace (sic)
in Relation to Sex" (S186: 1871)
[[p. 177]] Mr. Darwin's reputation already stands so high that it may seem difficult to add to it. Yet this work will undoubtedly do so, and will prove almost equally attractive to the naturalist and the general reader. The two large volumes on Domesticated Animals and Plants caused some little disappointment to those who looked for easy scientific reading; but the present work will have no such drawback. It is throughout written in the author's clearest style, it is not overloaded with detail, it abounds in curious facts and acute reasoning, and it treats of two great subjects of the very highest interest--the nature and origin of man, and the overwhelming importance of sexual influences in moulding and beautifying the animal world.
The few passages devoted to sexual selection in the Origin of Species, led many persons to suppose that it was but a vague hypothesis almost unsupported by direct evidence; and most of its opponents have shown an utter ignorance of, or disbelief in, the whole matter. It will now be seen on what a solid foundation of fact the theory of sexual selection is founded, and how true, as regards this part of his subject at all events, was Mr. Darwin's assertion, that his first volume contained but a mere abstract of the evidence before him, and that he could not be properly judged till the whole mass of facts he had collected were made public. From the reticence with which the sexual relations of animals have been treated in popular works, most of the readers of this book will be astonished to find that a new and inner world of animal life exists, of which they had hitherto had no conception; and that a considerable portion of the form and structure, the weapons, the ornaments, and the colouring of animals, owes its very existence to the separation of the sexes. This new branch of natural history is one of the most striking creations of Mr. Darwin's genius, and it is all his own; and although we believe he imputes far too much to its operation, it must be admitted to have exerted a most powerful influence over the higher forms of life. In the first part of this article we propose to sketch in outline the main facts and arguments adduced, and shall afterwards discuss certain points which seem open to criticism.
Mr. Darwin tells us that he has for many years collected the materials on which this work is mainly founded, without any intention of publishing them, as he did not wish to prejudice the reception of the general doctrine of natural selection. That doctrine has, however, made such rapid and unexpected progress that no danger of this kind any longer exists; and he has therefore put together his materials relating to the origin of man from a lower animal form. Believing that sexual selection has played an important part in differentiating the races of man, he has found it necessary to treat this subject in great detail, which has much increased the bulk of the work.
The first chapter discusses the evidence for the descent of man from some lower form. Not only is man's whole structure comparable, bone by bone and muscle by muscle, with that of other vertebrata, but his close relation to them is shown in a variety of unexpected ways. He is able to receive some animal diseases, as glanders, hydrophobia, &c., showing a close similarity to other animals in blood and tissues. The internal and external parasites of man are of the same families and genera as those of the lower animals. The embryonic development of man is exactly similar to that of other vertebrates, so that at an early period his embryo can hardly be distinguished from theirs; and arteries running in arch-like branches as if to carry blood to branchiæ which are not present in the higher animals, show his affinity to the lower aquatic forms. A little later, the great toe is found standing out from the side of the foot, as it does in the quadrumana. Numerous rudiments occur in man of structures characteristic of lower forms. Many muscles [[p. 178]] regularly present in apes and other quadrupeds occasionally appear in man. The upper part of the infolded lobe of the ear often presents a pointed projection, the rudiment of the pointed and erectile ears of most mammals. The supracondyloid foramen, through which the great nerve of the fore limb passes in quadrumana and carnivora, is absent in man; but it occasionally reappears, with the nerve passing through it; and a careful examination of the remains of prehistoric races shows, that this form was more frequent in ancient times than now.
The mental powers of man are then compared with those of the lower animals, and it is shown that the latter possess the rudiments of them all. The origin of the moral sense is next treated of; and although such eminent writers as Mill, Bain, Herbert Spencer, and Sir John Lubbock, have all given their independent theories on this subject, Mr. Darwin has hit upon a perfectly original view, which is perhaps more satisfactory than any which have preceded it. He maintains that the moral sense arises from the social instincts combined with an active intellect. As soon as the mental faculties became well developed, images of past actions and motives would be incessantly passing through the mind of each individual, and a feeling of dissatisfaction would arise whenever it was perceived that the ever present social instinct had yielded to some other instinct stronger at the time but less enduring. For example, such instincts as hunger, lust, or the desire of vengeance, are immensely strong but are not enduring, and do not leave vivid and easily recalled impressions at all proportionate to their intensity at the time. The feeling of sympathy, the need of companionship, the desire for the approbation of our fellows are, on the other hand, ever present with us, and anything which interfered with these would be a constant source of dissatisfaction. If then a being with a sufficiently active mind to recall past actions and see the effects they have produced were, under the impulse of any of the stronger instincts, to rob, starve, kill or injure those who were necessary to the satisfaction of his social instincts, he would inevitably feel dissatisfied with himself at having allowed his passion for a temporary enjoyment, the force of which he could not realise afterwards, to interfere with the satisfaction of his less intense but more permanent desires and instincts. A repetition of such experiences would lead to the feeling that the one kind of instincts was less important to his welfare than the other. He would class them as passions to be regulated and controlled; and when in spite of his determination to control them he had not done so, he would almost despise himself--would feel remorse--would be rebuked by his conscience. Mr. Darwin shows at some length, that the rudiments of all these instincts and emotions exist in animals; and he argues that the acquisition of speech would greatly increase their power; for when each member of the community could express his feelings and wishes, the opinion of his fellows would go to increase the regret felt at having allowed the temporary to overcome the permanent instinct. The effect of this at first, would be to limit "virtue" to that which was for the benefit of the tribe exclusively. Murder, robbery, and treachery within the limits of the tribe would be infamous, but beyond these limits might be even praiseworthy. Thus infanticide is so often not looked upon as a crime, because it is supposed to be beneficial to the tribe; and no pity has been felt for the sufferings of enemies, of slaves, or even of women. Owing to its great utility to the tribe, courage is always looked upon as the highest virtue; and for the same reason fidelity and self-sacrifice are always highly esteemed. But intemperance and licentiousness are never counted as vices, because they do not immediately concern any one but the individual and his family. Mr. Darwin concludes, that the moral sense is fundamentally identical with the social instincts, and has been developed for the general good of the community, rather than for its greatest happiness. "General good" is defined as "the means by which the greatest possible number of individuals can be reared in full vigour and health, with all their faculties perfect under the conditions to which they are exposed;" and it is quite conceivable that this may not be always identical with "greatest happiness." If so, the present theory will be a step in advance in the history of the utilitarian philosophy.
The manner of development of man from some lower form is next very fully discussed. The extreme variability of every part of man's bodily structure and mental faculties is shown; the effect of changed conditions whether of locality or of habits is proved to be considerable; and arrested developments, reversions, and correlated variations are all shown to obtain in man exactly as they do in the lower animals. Natural selection must have acted on man, because he multiplies rapidly beyond the means of subsistence, because he varies, and because he is exposed to varying external conditions; but Mr. Darwin adopts the views of the present writer, that as soon as man's mind had become moderately developed, the action of natural selection would have been checked, as regards his general structure, and transferred to his mental faculties. It is argued that the advance from animal to man must have taken place before the dispersal of the race over the world; and that in some warm country as large as Australia, New Guinea, or Borneo, "the competition between tribe and tribe would have been sufficient under favourable conditions to have raised man through survival of the fittest, combined with the inherited effects of habit, to his present high position in the organic scale." A separate chapter is devoted to the development of man's intellect, and to the effects of natural selection on civilised nations; and though many of the arguments used are open to criticism, the subject is most interesting, and is discussed with Mr. Darwin's usual clearness and candour.
The next two chapters discuss,--the special affinities of man to certain lower animals, by means of which the line of his genealogy can be traced, and the place and time of his origin approximately determined,--and the nature and probable origin of the several races of man. This last he believes cannot be fully explained without the agency of sexual selection, and this leads to the second part of the work, which treats of sexual differences, their causes and effects, throughout the animal kingdom, in order that the principles deduced from this extensive survey may be applied to explain certain residual phenomena in man.
The subject of sexual selection, occupying nearly five hundred pages, is treated in great detail, and abounds in matter of interest; but only a very brief sketch can here be given of it. The main theory depends upon the fact that there is almost invariably a struggle among the males for the females; a struggle carried on either by actual fighting or by rivalry in voice or in beauty. This struggle is moreover ensured by the circumstance that in most cases the males are ready to breed before the females, male insects emerging sooner from the pupa, and male migratory birds arriving earlier than those of the other sex. From this it results that some males gain the victory over others, and succeed in pairing earlier and with the earliest and most vigorous females. The males are always the most eager, the females generally coy; and Mr. Darwin believes that in almost all cases the female exerts a choice, and rejects those males who please her least. Hence have arisen two sets of [[p. 179]] modifications in male animals: 1. Weapons of various kinds have been developed, owing to those best able to fight having most frequently left progeny to inherit their superiority; 2. Musical organs, bright colours, or ornamental appendages, have been developed, through the females preferring those so gifted or adorned. The laws of inheritance are first discussed; the transmission of characters to the male alone through the female, and the transmission of variations at certain ages to the offspring at the same age, and to one or both sexes. A large portion of the animal kingdom is then passed in review, as respects the differentiation of the sexes and the means by which such differentiation has been produced. This part of the work is illustrated by numerous woodcuts, showing the extraordinary differences of form and structure between the sexes. Many parts of the body have been modified to enable the male to seize and hold the female; and this is adduced as an argument that the female exerts a choice, and has the power of rejecting any particular male. But this hardly seems to follow, for it may well be maintained that when the more active male seizes a female, she cannot escape, and that she has no means of rejecting him and practically never does so.
The males of a considerable number of homopterous and orthopterous insects emit musical sounds by means of very curious and varied apparatus, and there is no doubt that these sounds serve to attract or charm the female. Among most insects the males fight, but neither spiders nor dragonflies have been observed to do so. Among all other insects than lepidoptera, the sexes are as a rule coloured alike or nearly alike, the exceptions being comparatively few; but among butterflies especially, diversity of colour is the rule, the males being almost always most brilliantly or most intensely coloured; and the difference is often so great that the two sexes look like widely different species. Beetles differ more in form than in colour, the males often possessing wonderful horns, spines, or protuberances, immensely long legs or antennæ, or enormous jaws, while in colour they hardly differ at all or are only somewhat brighter. Passing on to the vertebrates, we find that male fishes often fight, and exhibit as much ardour as terrestrial animals; some of them undergo strange changes of form at the breeding season, and some few differ conspicuously from the females in colour, or by the possession of elongated fins, spines, or other appendages. In other cases, although the sexes are usually alike, yet in the breeding season the males acquire new or more vivid colours.
Passing by amphibians and reptiles, among which many curious sexual characters occur, we come to birds, a class which exhibits them in their highest perfection, and which has furnished Mr. Darwin with the most powerful arguments for the complete development of his theory of sexual selection. Almost every imaginable kind of sexual ornament is here to be found. In an immense number of cases male birds are far more beautifully coloured than the females; and besides this, they often possess the most gorgeous developments of ornamental plumage, as in the train of the peacock, the wings of the African night-jar, the tail of the lyre-bird and of the resplendent trogon, the crest of the umbrella-bird, and the breast plumes of the bird-of-paradise. Spurs are also developed upon the legs or the wings, and the male is generally larger, and has a louder or more melodious voice. Among birds is found the first direct proof that the female notices and admires increased brilliancy or beauty of colour, or any novel ornament; and, what is more important, that she exercises choice, rejecting one suitor and choosing another. There is abundant evidence too that the male fully displays all his charms before the females, and some of the facts adduced on this head are most curious and interesting. Mr. Darwin also devotes himself to showing how some of the most marvellous developments of beauty in plumage may have been produced by the constant selection of slight modifications; and he explains in this manner the origin of the eyed train of the peacock, and the wonderfully decorated wings of the Argus pheasant, with an acuteness and success hardly inferior to that which he exhibited when investigating the structure of coral reefs or of orchids. The four chapters on birds would alone demand a lengthy article to do them justice, but as we shall have to return to this subject when we come to criticise some portion of the theory, it will be as well now to pass over the two chapters on the sexual differences and weapons of the mammalia, and devote some little space to a sketch of the concluding chapters, which again treat of man.
The sexual differences of man are stated to be greater than in most species of quadrumana, while in their general features and mode of development man agrees remarkably with those animals, as an example of which we may quote, that whenever the beard differs in colour from the hair on the head, it is always lighter, both in man and monkeys. The law of battle for wives still prevails among some savages, and to this circumstance Mr. Darwin thinks may be traced the undoubted inferiority of woman, not only in bodily strength but also in courage and perseverance, qualities equally necessary to ensure victory. He thinks also that but for the fortunate circumstance that the law of equal transmission of characters to both sexes has commonly prevailed among mammalia, man might have become as much superior to woman in mind as the peacock surpasses the peahen in plumage. Considerable space is devoted to prove that savages think much of personal appearance, admire certain types of form and complexion, and that probably selection of wives and husbands has been an important agent in determining both the racial and the sexual differences of mankind. The evidence adduced, however, seems only to show that the men as a rule ornament themselves more than the women, and that they do so to be admired by their fellow-men quite as much as by the women; and also that men of each race admire all the characteristic features of their own race, and abhor any wide departure from it; the natural effect of which would be to keep the race true, not to favour the production of new races. It is admitted that promiscuous intercourse and infanticide would to a great extent prevent the action of sexual selection; but it would also be rendered nugatory by the fact that among savages no woman remains unmarried, youth and health being amply sufficient charms to procure her a husband. It also seems very uncertain whether any effect would be produced by the more powerful men possessing themselves of a number of the most beautiful women, and rearing on an average a greater number of children, as Mr. Darwin thinks they would do. Where polygamy prevails the number of children to one father may be very large, but will the number to each mother be as large as with the remainder of the tribe who are forced to practise monogamy? This important point is not alluded to. The absence of hair on the body is admitted to be a character that cannot be accounted for by "natural selection," because it cannot be conceived to have been a beneficial variation; but "sexual selection" is supposed to account for it. At an exceedingly early period in our history our semi-human ancestors were hairy, and it is thought that one or both sexes preferred less hair; and any partial nudity that appeared led to a more early or a more constant wedlock, and thus gave an advantage to such individuals and [[p. 180]] their more numerous progeny. The example of monkeys and apes is adduced, many of which have bare skin on the face or on other parts of the body; and the New Zealand proverb, "There is no woman for a hairy man," is thought to bear upon the question. This explanation is by no means satisfactory. The analogy of the quadrumana and of other animals would have some force if there were still hairy and hairless or partially hairless men,--with bare faces and breasts, but hairy backs, for example; but we have to deal with a complete nudity, which has no parallel in the animal kingdom except in cases where "natural selection" has evidently come into play. That a smooth-skinned race like the New Zealanders should object to hairiness is natural; for, as Mr. Darwin says, each race admires its own characteristics carried to a moderate extreme. Hairy races would therefore admire abundant hairiness, just as bearded races now admire fine beards; and any admiration of deficient hairiness would probably be as rare and abnormal as the admiration for partial baldness or scanty hair in women, would be among ourselves. Any individual fancy for such an abnormal peculiarity as deficient hair in a hair-covered animal could produce no effect; and that any such fancy should become general with our semi-human ancestors, and so produce universal nakedness, does not seem at all probable, when we have no evidence of such a result of sexual selection elsewhere in the whole animal kingdom. It is true, that in that early state the struggle for existence would have been severe, and only the best endowed would have survived; but unless we suppose a universal and simultaneous fancy among all the most vigorous and therefore probably the most hairy men for what would be then an unnatural character--deficiency of hair in women--and that this fancy should have persisted in all its force for a long series of generations, it is not easy to see how this severe struggle for existence and survival of the fittest would in any way aid sexual selection in abolishing the hairy covering. On the contrary it seems more likely that it would entirely prevent it. We can hardly therefore impute much influence to sexual selection in the case of man, even as regards less important characters than the loss of hair, because it requires the very same tastes to persist in the majority of the race during a period of long and unknown duration. All analogy teaches us that there would be no such identity of taste in successive generations; and this seems a fatal objection to the belief that any fixed and definite characters could have been produced in man by sexual selection alone.
In his last chapter, Mr. Darwin gives an able summary of the whole argument; and, while regretting that the result he has arrived at will be highly distasteful to many persons, maintains, that the whole evidence leads to the conclusion that man, notwithstanding his noble qualities and his godlike intellect, still bears in his bodily frame the indelible stamp of his lowly origin.
Having thus sketched in outline the theories advanced by our author, and given a summary of the facts by which he supports them, we have now to notice in more detail certain portions of the argument which appear to rest upon an insecure foundation either of logic or of fact.
The first and most obvious objection that will be made to this great work is, that it consists of two books mixed together. The whole of the matter relating to sexual selection among animals, would have formed a fitting third volume in the series of works treating in detail of the origin of species; while the part which treats of man, is an application of those principles to the human race which had hitherto only been discussed as regards other animals and plants, and would have formed a fitting companion volume to the Origin of Species. This rearrangement could easily be effected in a future edition, and would have many advantages; and should a similar suggestion come from other quarters we hope Mr. Darwin will adopt it.
In entering upon a criticism of some portions of these volumes, I am compelled to touch upon certain topics on which I hold, and have published, views differing considerably from those maintained by Mr. Darwin; and I am glad to have this opportunity of showing to what extent a study of his facts and arguments have modified my opinions. Before plunging into the intricate subject of "sexual selection," I must, however, make a few remarks on Mr. Darwin's use of the same term "instinct" for what seem to me very distinct things. He classes as instincts, hunger, self-preservation, the mother's love of her offspring, and the infant's power of sucking. The first is a sensation, the second acquired habit, the third an emotion, the fourth a pleasurable exercise of certain muscles--none of them instinct in the same sense as the cause of the migration of birds, of the building of platforms by apes, of the avoidance of poisonous fruits or the dread of snakes--all of which are specially mentioned as instincts. To go into the question of which of these latter are acquired habits or acquired knowledge, and which are truly instinctive, would lead us too far; but it is certainly not in accordance with our author's usual precision of language on other topics, to use the same term for a simple sensation like hunger--for a faculty which may be experience or may be simple dislike acquired by natural selection, like the avoidance of poisonous fruits--and for all the mental processes involved in a highly complex operation like that of the construction of a bird's nest. It is no doubt mainly due to the poverty of our language that one word has been used for so many distinct things; but as long as this is the case it is hardly possible to avoid confusion of ideas about instinct.
In discussing the subject of sexual selection it would perhaps have been a more convenient, even if a less scientific arrangement, to have treated first of those groups in which the evidence is clearest and most decisive; for Mr. Darwin is often obliged to refer to these in advance to strengthen his argument in the case of those inferior groups in which it is much more difficult to obtain evidence. I shall therefore first consider what is proved in the case of birds.
In birds sexual differences are both more generally the rule and more wonderfully varied in character than in any other class of animals. The males sometimes possess special weapons for fighting together; more frequently they charm the female by vocal or instrumental music; more frequently still they are ornamented with all sorts of crests, wattles, horns, air-sacs, plumes, and lengthened feathers springing from all parts of the body. They are extremely pugnacious; they sing in rivalry, and they perform the most extraordinary antics and dances during the breeding season, exhibiting in the most curious and often unexpected manner all their peculiar adornments before the female. It is proved that in many cases they have a taste for colour and for novelty; and some female domestic birds are shown to have had such a fondness for a peculiarly coloured male as to refuse to pair with any other. When in addition to this we consider that many birds are polygamous, and that in these the sexual differences are almost always greatest, we must admit that sexual selection would necessarily produce an effect in developing weapons, musical organs, or ornaments in one or both sexes. But while sexual selection has thus been doing its work, the still more powerful agency of natural selection has not been in abeyance, but has also modified one or both sexes in accordance with their conditions of life; and these in the case of birds are somewhat different in the two sexes. Whole groups of birds are evidently coloured for protection, resembling the desert sands, or the green leaves, or the [[p. 181]] arctic snows, among which they live; and as we may be sure that variations tending to other colours have appeared in these birds, and as we have no reason to believe that in these groups only the females have been indifferent to such adornment, we must admit that natural selection has here checked the action of sexual selection. There are, however, an immense number of birds in which the female only is of dull brown or green tints, while the male is adorned with the most splendid colours; and there are also a very large number in which both sexes are equally or almost equally brilliant; and, with very rare exceptions, the rule is found to hold that the former class all build open nests, the latter all covered or hidden nests. The bright-coloured female birds are thus concealed while incubating, the dull-coloured are exposed. This very curious relation appeared to me to indicate that natural selection had been more powerful than the laws, whatever they are, which primarily determine the colours of birds; that the females had in one case been prevented from acquiring any considerable portion of the gay colouring of the males because it was hurtful to them, and in the other case had acquired it because, being concealed during incubation, it was no more hurtful to them than to the males. Mr. Darwin objects to this explanation of the facts. He maintains that the "laws of inheritance" determine whether colour or any other ornament appearing in one sex shall be transmitted to that sex only or to both. So far there is nothing to object to. But he goes further, and maintains that this tendency cannot be affected by natural selection, and that if a particular colour-variation begins to be transmitted to both sexes, the mode of transmission cannot, by natural selection, be changed, so that the colour may continue to be transmitted to the male to whom it is useful, but cease to be transmitted to the female to whom it is hurtful. Mr. Darwin admits that the law itself varies very frequently; for he gives numerous instances in which the different species of a genus exhibit all the possible modes of transmission, and as these have all descended from a common ancestor, the law has varied somewhat rapidly. He also says, "The equal transmission of characters to both sexes is the commonest form of inheritance," and we may therefore fairly assume that before diversity arose between the sexes it was the rule for both sexes to vary together. But he believes that, under these circumstances, it would be exceedingly difficult for natural selection to change the male alone, and he gives an imaginary illustration to exhibit this difficulty. He supposes a fancier to wish to make a breed of pigeons in which the males should be pale blue, the females remaining the usual slaty colour; and he says, "All that he could do would be to persevere in selecting every male pigeon which was in the least degree of a paler blue," and to match these with slaty females, the result being, of course, "either a mongrel piebald lot, or more probably the speedy and complete loss of the pale blue colour." But the supposed fancier has here gone quite the wrong way to work. His primary want is, not "blue males," but a breed in which there is a tendency to differentiation of sex. His proper plan, therefore, would be to look over as many sets as possible of the progeny of single pairs of pigeons till he found one in which a differentiation of sex appeared in the right direction, the males being lighter, the females darker, in however slight a degree. Breeding from these again, he would probably in a few generations find a greater differentiation occur, for we know that such changes in the mode of transmission have often occurred in nature; and only when he had obtained a breed in which the sexes were strongly differentiated, variations of colour occurring frequently in the male sex, rarely or not at all in the female, would it be advisable for him to begin selecting for the exact tint of colour he desired in his males. Now, though nature may often do more in the way of selection than man, we can hardly believe that anything can be done by man's selection which may not be done as effectually by natural selection; and as it is admitted that the dull colours of the females sitting on open nests are a protection to them, and also that variations in the mode of transmission frequently occur, what is to prevent the females being modified in the way most advantageous to them for protection, while the males are being modified in the way most advantageous to them, by sexual selection? When the males of a species began to gain bright colours by sexual selection, and these colours were transmitted to the females till they became injurious, it may be fairly assumed that they would be transmitted in somewhat varying degrees, for Mr. Darwin states (p. 177, vol. ii.), that the degree of limitation differs in species of the same group; and as from mere association in the same locality individuals of the same family have a good chance of breeding together, the less brilliant females and more brilliant males of such families would often produce offspring in which the sexual differences were still greater, and these would have the best chance of surviving again to leave offspring. It is true that brilliant males of the same stock with brilliant females would have an equal chance of leaving descendants, but as the females of their families would be at a great disadvantage and would less frequently rear offspring, while the females of the differentiated families would be protected, the latter would soon be in a majority of two to one, and must inevitably supplant the former. This view enables us to understand many facts given by Mr. Darwin which seem difficulties on his own hypothesis. Thus the sexes of Culicidæ and Tabanidæ among flies, differ in the structure of the mouth in accordance with difference of habits; some male Cirrhipedes have lost almost all their external organs, while the female has retained hers; and female glow-worms, as well as many female moths, have lost their wings. Such varied adaptations of one sex alone could only occur if the rule were almost universal, that variations were limited to the sex in which they originally appeared; but we have seen that the contrary is nearer to the truth, and it seems more probable that the phenomenon of strictly limited sexual transmission was actually produced by natural selection as soon as the need arose for a differentiation of the sexes in organization, habits, or economy, than that it is an independent law. It evidently could have been so produced as well as the primary separation of the sexes which Mr. Darwin does not seem to doubt was effected by means of natural selection; and he appears to be unnecessarily depreciating the efficacy of his own first principle when he places limited sexual transmission beyond the range of its power.
Passing now to the lower animals--fishes, and especially insects--the evidence for sexual selection becomes comparatively very weak; and it seems doubtful if we are justified in applying the laws which prevail among the highly organized and emotional birds, to interpret somewhat analogous results in their case. The rivalry between males, either by fighting together or by emitting attractive sounds or odours, undoubtedly acts in the case of insects as well as in the higher animals; but it is quite different with the other form of sexual selection. This depends upon the appreciation of slight differences of colour by the female, and also by her having the power as well as the will to reject such males as are slightly inferior in attractions; and on both these points there is no direct evidence but what tells against Mr. Darwin's view. Thus, he informs us that "fresh females are often found paired with battered, faded, or dingy males," and breeders agree that in the case of the various silk-moths the female exerts no choice whatever, Dr. Wallace of [[p. 182]] Colchester stating that he frequently finds the most vigorous females of Bombyx Cynthia paired with stunted males. But the Bombyces are among the most elegantly coloured of all moths.
From the fact that many male butterflies may be seen pursuing or crowding round the same female, Mr. Darwin concludes that the females prefer one male to another, because, if this were not the case, the pairing must be left to mere chance, and this does not seem to him a probable event. But surely the male who finally obtains the female will be either the most vigorous, or the strongest-winged, or the most patient of the two or three suitors--the one who tires out or beats off the rest. The pairing therefore will not be left to chance, and it is probably by such struggles that the males of almost all butterflies have been rendered much stronger-winged than the females. Throughout the whole of the other orders of insects there is no direct evidence whatever of sexual selection as regards colour; for the colours are generally similar in both sexes, and the particular colours that occur seem to be often determined by the greater or less need of protection. Thus the stinging Hymenoptera are, as a rule, conspicuously coloured; as are large numbers of the Hemiptera, which are protected by their disgusting odour. Coleoptera are almost all palpably protected, either by resembling inanimate objects, by obscurity, by hard coats of mail, or by being distasteful to birds; and those of the two latter categories are almost all conspicuously coloured. It seems to me therefore, much more probable that the colours of insects are due to the same unknown laws which have produced the colours of caterpillars, than that they are due to sexual selection. In caterpillars we have almost all the classes of coloration found in perfect insects. We have protective and conspicuous tints; and among the latter we have spots, streaks, bands, and patterns, perfectly definite in character and of the most brilliantly contrasted hues. We have also many ornamental appendages; beautiful fleshy tubercles or tentacles, hard spines, beautifully coloured hairs arranged in tufts, brushes, starry clusters, or long pencils,--and horns on the head and tail, either single or double, pointed or clubbed. Now if all these beautiful and varied ornaments can be produced and rendered constant in each species, by some unknown cause quite independent of sexual selection, why cannot the same cause produce the colours and many of the ornaments of perfect insects, subjected as they are to so much greater variety of conditions than their larvæ? In the case of butterflies it is a curious fact that the females are often much more variable than the males. The females of Papilio memnon and Diadema auge are perhaps the most variable of all butterflies, consisting of scores of such different insects that they have over and over again been described as distinct species, while in both cases the males are very constant. Had the males been differentiated by sexual selection we should have expected them to be more variable, as they always are among insects as regards largely developed jaws, horns, or other weapons undoubtedly used for sexual purposes. In many groups of butterflies too, the males of the different species of a genus closely resemble each other, while the females differ considerably, so that it often happens that forms considered to be mere varieties as long as the males only are known, become recognised as good species when the females are discovered. This is the case generally in Ornithoptera, several groups of Papilio, Adolias, Diadema; and it is so exactly the reverse of what obtains in birds that we must hesitate to apply the same explanation to the two sets of phenomena.
There are two other difficulties in the way of accepting Mr. Darwin's wide generalization as to the agency of sexual selection in producing the greater part of the colour that adorns the animal world. How are we to believe that the action of an ever varying fancy for any slight change of colour could produce and fix the definite colours and markings which actually characterize species. Successive generations of female birds choosing any little variety of colour that occurred among their suitors would necessarily lead to a speckled or piebald and unstable result, not to the beautifully definite colours and markings we see. To the agency of natural selection there is no such bar. Each variation is unerringly selected or rejected according as it is useful or the reverse; and as conditions change but slowly, modifications will necessarily be carried on and accumulated till they reach their highest point of efficiency. But how can the individual tastes of hundreds of successive generations of female birds produce any such definite or constant effect? Some law of necessary development of colour in certain parts of the body and in certain hues is first required, and then perhaps, in the case of birds, the females might choose the successive improvements as they occurred; though, unless other variations were altogether prevented, it seems just as likely that they would mar the effect the law of development of colour was tending to produce.
The other objection is, that there are signs of such a tendency, which, taken in connection with the cases of caterpillars, of shells, and other very low organisms, may cover the whole ground in the case of insects, and render sexual selection of colour as unnecessary as it is unsupported by direct evidence. In many islands of the Malay Archipelago, species of widely different genera of butterflies differ, in precisely the same way as to colour or form, from allied species in other islands. The same thing occurs to a less degree in other parts of the world. Here we have indications of some local modifying influence which is certainly not sexual selection. So, the production in the males only of certain butterflies, of a peculiar neuration of the wings, of differently formed legs, and especially of groups of peculiarly formed scales only to be detected by microscopical examination, indicate the existence of some laws of development capable of differentiating the sexes other than sexual selection.
On the whole then it seems to me, that the kind of sexual selection which depends on the female preferring certain colours or ornaments in the male, has not been proved to exist in insects. Their colours are probably due to some as yet unknown causes; the differences of the sexes consisting, partly of a greater intensity of colouring in the male, due perhaps to his smaller size and greater vigour, and partly of more or less protective tints acquired by the female alone on account of her slower flight and greater need for protection while depositing her eggs. Many other points of great interest must be passed over, but sufficient has been said to enable the reader fairly to compare the facts and arguments previously adduced by myself with those now set forth by Mr. Darwin, and to form a judgment as to the comparative importance to be attached to sexual selection and the need of protection, in determining the sexual differences of colour in animals.
Having in the first part of this article made some objections to the theory of sexual selection in its application to man, I will now briefly notice Mr. Darwin's account of the probable mode in which man became developed from his brute ancestor. All the evidence goes to show, that the change from brute to man took place in some limited area, probably tropical. Here he lost his hairy covering, acquired his erect form and his wonderful brain, and became so far advanced in the arts and in morals that natural selection ceased to act upon his mere bodily organization. It is also probable that he learnt to speak language, discovered the use of fire, [[p. 183]] and perhaps even of canoes, before he spread over the earth, and before the several races of man were differentiated. The agency through which this vast transformation occurred was the struggle for existence and natural selection--a struggle first with other animals, and when they were surpassed between tribe and tribe; and this alone Mr. Darwin thinks would, under favourable conditions, raise man to his present high position in the organic scale.
In this view there are many difficulties. How is it possible to conceive, that during the enormous interval required to change a quadrumanous, hairy, speechless animal, into erect, smooth-skinned, large-brained, fire-using man, while the struggle for existence was most severe (for by the severity of the struggle alone he was raised), he yet never spread over the earth but remained concentrated in a limited area. Had he spread widely during the process of modification, divergence of character would inevitably have occurred, and we should have had several distinct species of man. Mr. Darwin argues that the fact of man, even at his lowest stage of civilisation and intellect, being able to maintain himself, surrounded by the most powerful and ferocious animals, is due to his large brain, which is thus of the most essential use to him. But almost all herbivorous animals also maintain themselves under similar conditions, with no special endowment of brains; and in South America the apparently helpless and almost idiotic sloth is not exterminated, though exposed to the attacks of pumas, tiger-cats, and harpy-eagles. Man could have acquired very little of his superiority to animals by a struggle with animals. "Natural selection does not produce absolute perfection but only relative perfection." We have to fall back therefore on the struggle with his fellows--family with family, tribe with tribe. But for this to be at all effectual, one of the most essential conditions is a large population inhabiting an extensive area, and this the conditions of the problem deny to us. The vast amount of the superiority of man to his nearest allies is what is so difficult to account for. His absolute erectness of posture, the completeness of his nudity, the harmonious perfection of his hands, the almost infinite capacities of his brain, constitute a series of correlated advances too great to be accounted for by the struggle for existence of an isolated group of apes in a limited area. And Mr. Darwin himself gives hints of unknown causes which may have aided in the work. He says: "An unexplained residuum of change, perhaps a large one, must be left to the assumed uniform action of those unknown agencies which occasionally induce strongly marked and abrupt deviations of structure in our domestic productions." And again: "If these causes, whatever they may be, were to act more uniformly and energetically during a lengthened period (and no reason can be assigned why this should not sometimes occur), the result would probably be, not mere slight differences, but well marked, constant modifications."
In concluding this very imperfect account of one of the most remarkable works in the English language, it may be affirmed, that Mr. Darwin has all but demonstrated the origin of man by descent from some inferior animal form--that he has proved the vast importance of sexual influences in modifying the colours and the structure of the more highly organized animals--and that he has thrown fresh light upon the intricate question of the mode of development of the moral and intellectual nature of man. Yet it must be admitted that there are many difficulties in the detailed application of his views; and it seems probable that these can only be overcome by giving more weight to those unknown laws whose existence he admits, but to which he assigns an altogether subordinate part in determining the development of organic forms.
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RECORD: Darwin, C. R. 1871. The descent of man, and selection in relation to sex. London: John Murray. Volume 1. 1st edition.
REVISION HISTORY: Scanned by John van Wyhe 1.2006; transcribed (double key) by AEL Data 4.2006, corrections by van Wyhe 2.2011, 2.2014. RN7
The copy scanned was kindly provided by The Balfour and Newton Libraries, Cambridge.
[inside front cover]
THE DESCENT OF MAN,
SELECTION IN RELATION TO SEX.
DESCENT OF MAN,
SELECTION IN RELATION TO SEX.
BY CHARLES DARWIN, M.A., F.R.S., &c.
IN TWO VOLUMES.—VOL. I.
JOHN MURRAY, ALBEMARLE STREET.
[The right of Translation is reserved.]
BY THE SAME AUTHOR.
ON THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION; or, THE PRESERVATION OF FAVOURED RACES IN THE STRUGGLE FOR LIFE; Fifth Edition (Tenth Thousand), with Additions and Corrections. 1869. MURRAY.
THE VARIATION OF ANIMALS AND PLANTS UNDER DOMESTICATION. In two vols. With Illustrations. 1868. MURRAY.
ON THE VARIOUS CONTRIVANCES BY WHICH BRITISH AND FOREIGN ORCHIDS ARE FERTILISED BY INSECTS; and on the GOOD EFFECTS OF CROSSING. With numerous Woodcuts. MURRAY.
A NATURALIST'S VOYAGE ROUND THE WORLD; or, A JOURNAL OF RESEARCHES INTO THE NATURAL HISTORY AND GEOLOGY OF THE COUNTRIES visited during the voyage of H.M.S. 'Beagle,' under the command of Captain FITZROY, R.N. Eleventh Thousand. MURRAY.
ON THE STRUCTURE AND DISTRIBUTION OF CORAL REEFS. SMITH, ELDER, & Co.
GEOLOGICAL OBSERVATIONS ON VOLCANIC ISLANDS. SMITH, ELDER, & Co.
GEOLOGICAL OBSERVATIONS ON SOUTH AMERICA. SMITH, ELDER, & Co.
A MONOGRAPH OF THE CIRRIPEDIA. With numerous Illustrations. 2 vols. 8vo. HARDWICKE.
ON THE MOVEMENTS AND HABITS OF CLIMBING PLANTS. With Woodcuts. WILLIAMS & NORGATE.
LONDON: PRINTED BY WILLIAM CLOWES AND SONS, STAMFORD STREET, AND CHARING CROSS.
INTRODUCTION .. .. .. .. .. .. .. .. .. Page 1-5
ON THE DESCENT OF MAN.
THE EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM.
Nature of the evidence bearing on the origin of man — Homologous structures in man and the lower animals — Miscellaneous points of correspondence — Development — Rudimentary structures, muscles, sense-organs, hair, bones, reproductive organs, &c. — The bearing of these three great classes of facts on the origin of man .. .. .. .. .. .. .. .. .. .. .. 9-33
COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS.
The difference in mental power between the highest ape and the lowest savage, immense — Certain instincts in common — The emotions—Curiosity — Imitation—Attention — Memory — Imagination — Reason — Progressive improvement — Tools and weapons used by animals — Language — Self-consciousness — Sense of beauty — Belief in God, spiritual agencies, superstitions
COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS—continued.
The moral sense — Fundamental proposition — The qualities of social animals — Origin of sociability — Struggle between opposed instincts — Man a social animal — The more enduring social instincts
conquer other less persistent instincts—The social virtues alone regarded by savages—The self-regarding virtues acquired at a later stage of development—The importance of the judgment of the members of the same community on conduct—Transmission of moral tendencies—Summary .. .. Page 70-106
ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME LOWER FORM.
Variability of body and mind in man—Inheritance—Causes of variability—Laws of variation the same in man as in the lower animals—Direct action of the conditions of life—Effects of the increased use and disuse of parts—Arrested development—Reversion — Correlated variation — Rate of increase—Checks to increase — Natural selection — Man the most dominant animal in the world — Importance of his corporeal structure — The causes which have led to his becoming erect—Consequent changes of structure—Decrease in size of the canine teeth—Increased size and altered shape of the skull—Nakedness—Absence of a tail—Defenceless condition of man .. .. .. .. 107-157
ON THE DEVELOPMENT OF THE INTELLECTUAL AND MORAL FACULTIES DURING PRIMEVAL AND CIVILISED TIMES.
The advancement of the intellectual powers through natural selection — Importance of imitation—Social and moral faculties — Their development within the limits of the same tribe—Natural selection as affecting civilised nations—Evidence that civilised nations were once barbarous.. .. .. .. .. .. 158-184
ON THE AFFINITIES AND GENEALOGY OF MAN.
Position of man in the animal series—The natural system genealogical — Adaptive characters of slight value — Various small points of resemblance between man and the Quadrumana — Rank of man in the natural system — Birthplace and antiquity
of man — Absence of fossil connecting-links—Lower stages in the genealogy of man, as inferred, firstly from his affinities and secondly from his structure—Early androgyngus condition of the Vertebrata—Conclusion .. .. .. .. Page 185-213.
ON THE RACES OF MAN.
The nature and value of specific characters—Application to the races of man — Arguments in favour of, and opposed to, ranking the so-called races of man as distinct species — Sub-species—Monogenists and polygenists—Convergence of character—Numerous points of resemblance in body and mind between the most distinct races of man—The state of man when he first spread over the earth—Each race not descended from a single pair — The extinction of races—The formation of races—The effects of crossing—Slight influence of the direct action of the conditions of life—Slight or no influence of natural selection—Sexual selection.
PRINCIPLES OF SEXUAL SELECTION.
Secondary sexual characters—Sexual selection—Manner of action — Excess of males — Polygamy — The male alone generally modified through sexual selection—Eagerness of the male—Variability of the male—Choice exerted by the female—Sexual compared with natural selection—Inheritance at corresponding periods of life, at corresponding seasons of the year, and as limited by sex—Relations between the several forms of inheritance—Causes why one sex and the young are not modified through sexual selection—Supplement on the proportional numbers of the two sexes throughout the animal kingdom—On the limitation of the numbers of the two sexes through natural selection
SECONDARY SEXUAL CHARACTERS IN THE LOWER CLASSES OF THE ANIMAL KINGDOM.
These characters absent in the lowest classes—Brilliant colours—Mollusca — Annelids—Crustacea, secondary sexual characters strongly developed; dimorphism; colour; characters not acquired before maturity—Spiders, sexual colours of; stridulation by the males—Myriapoda .. .. .. .. .. .. Page 321-340
SECONDARY SEXUAL CHARACTERS OF INSECTS.
Diversified structures possessed by the males for seizing the females—Differences between the sexes, of which the meaning is not understood — Difference in size between the sexes — Thysanura—Diptera — Hemiptera — Homoptera, musical powers possessed by the males alone — Orthoptera, musical instruments of the males, much diversified in structure; pugnacity; colours—Neuroptera, sexual differences in colour — Hymenoptera, pugnacity and colours—Coleoptera, colours; furnished with great horns, apparently as an ornament; battles; stridulating organs generally common to both sexes.. .. .. .. .. 341-385
INSECTS, continued.—ORDER LEPIDOPTERA.
Courtship of butterflies — Battles — Ticking noise — Colours common to both sexes, or more brilliant in the males — Examples — Not due to the direct action of the conditions of life — Colours adapted for protection — Colours of moths—Display — Perceptive powers of the Lepidoptera — Variability — Causes of the difference in colour between the males and females — Mimickry, female butterflies more brilliantly coloured than the males — Bright colours of caterpillars — Summary and concluding remarks on the secondary sexual characters of insects — Birds and insects compared .. .. .. .. .. .. .. 386-423
THE DESCENT OF MAN;
SELECTION IN RELATION TO SEX.
THE nature of the following work will be best understood by a brief account of how it came to be written. During many years I collected notes on the origin or descent of man, without any intention of publishing on the subject, but rather with the determination not to publish, as I thought that I should thus only add to the prejudices against my views. It seemed to me sufficient to indicate, in the first edition of my 'Origin of Species,' that by this work "light would be thrown on the origin of man and his history;" and this implies that man must be included with other organic beings in any general conclusion respecting his manner of appearance on this earth. Now the case wears a wholly different aspect. When a naturalist like Carl Vogt ventures to say in his address as President of the National Institution of Geneva (1869), "personne, en Europe au moins, n'ose plus soutenir la crèation indèpendante et de toutes pièces, des espèces," it is manifest that at least a large number of naturalists must admit that species are the modified descendants of other species;
VOL. I. B
and this especially holds good with the younger and rising naturalists. The greater number accept the agency of natural selection; though some urge, whether with justice the future must decide, that I have greatly overrated its importance. Of the older and honoured chiefs in natural science, many unfortunately are still opposed to evolution in every form.
In consequence of the views now adopted by most naturalists, and which will ultimately, as in every other case, be followed by other men, I have been led to put together my notes, so as to see how far the general conclusions arrived at in my former works were applicable to man. This seemed all the more desirable as I had never deliberately applied these views to a species taken singly. When we confine our attention to any one form, we are deprived of the weighty arguments derived from the nature of the affinities which connect together whole groups of organisms—their geographical distribution in past and present times, and their geological succession. The homological structure, embryological development, and rudimentary organs of a species, whether it be man or any other animal, to which our attention may be directed, remain to be considered; but these great classes of facts afford, as it appears to me, ample and conclusive evidence in favour of the principle of gradual evolution. The strong support derived from the other arguments should, however, always be kept before the mind.
The sole object of this work is to consider, firstly, whether man, like every other species, is descended from some pre-existing form; secondly, the manner of
his development; and thirdly, the value of the differences between the so-called races of man. As I shall confine myself to these points, it will not be necessary to describe in detail the differences between the several races—an enormous subject which has been fully discussed in many valuable works. The high antiquity of man has recently been demonstrated by the labours of a host of eminent men, beginning with M. Boucher de Perthes; and this is the indispensable basis for understanding his origin. I shall, therefore, take this conclusion for granted, and may refer my readers to the admirable treatises of Sir Charles Lyell, Sir John Lubbock, and others. Nor shall I have occasion to do more than to allude to the amount of difference between man and the anthropomorphous apes; for Prof. Huxley, in the opinion of most competent judges, has conclusively shewn that in every single visible character man differs less from the higher apes than these do from the lower members of the same order of Primates.
This work contains hardly any original facts in regard to man; but as the conclusions at which I arrived, after drawing up a rough draft, appeared to me interesting, I thought that they might interest others. It has often and confidently been asserted, that man's origin can never be known: but ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science. The conclusion that man is the co-descendant with other species of some ancient, lower, and extinct form, is not in any degree new. La-
marck long ago came to this conclusion, which has lately been maintained by several eminent naturalists and philosophers; for instance by Wallace, Huxley, Lyell, Vogt, Lubbock, Büchner, Rolle, &c.,1 and especially by Häckel. This last naturalist, besides his great work, 'Generelle Morphologie' (1866), has recently (1868, with a second edit. in 1870), published his 'Natürliche Schöpfungsgeschichte,' in which he fully discusses the genealogy of man. If this work had appeared before my essay had been written, I should probably never have completed it. Almost all the conclusions at which I have arrived I find confirmed by this naturalist, whose knowledge on many points is much fuller than mine. Wherever I have added any fact or view from Prof. Häckel's writings, I give his authority in the text, other statements I leave as they originally stood in my manuscript, occasionally giving in the foot-notes references to his works, as a confirmation of the more doubtful or interesting points.
During many years it has seemed to me highly probable that sexual selection has played an important part in differentiating the races of man; but in my
1 As the works of the first-named authors are so well known, I need not give the titles; but as those of the latter are less well known in England, I will give them:—'Sechs Vorlesungen über die Darwin'sche Theorie:' zweite Auflage, 1868, von Dr. L. Büchner; translated into French under the title 'Conférences sur la Théorie Darwinienne,' 1869. 'Der Mensch, im Lichte der Darwin' sche Lehre,' 1865, von Dr. F. Rolle. I will not attempt to give references to all the authors who have taken the same side of the question. Thus G. Canestrini has published ('Annuario della Soc. d. Nat.,' Modena, 1867, p. 81) a very curious paper on rudimentary characters, as bearing on the origin of man. Another work has (1869) been published by Dr. Barrago Francesco, bearing in Italian the title of "Man, made in the image of God, was also made in the image of the ape."
'Origin of Species' (first edition, p. 199) I contented myself by merely alluding to this belief. When I came to apply this view to man, I found it indispensable to treat the whole subject in full detail.2 Consequently the second part of the present work, treating of sexual selection, has extended to an inordinate length, compared with the first part; but this could not be avoided.
I had intended adding to the present volumes an essay on the expression of the various emotions by man and the lower animals. My attention was called to this subject many years ago by Sir Charles Bell's admirable work. This illustrious anatomist maintains that man is endowed with certain muscles solely for the sake of expressing his emotions. As this view is obviously opposed to the belief that man is descended from some other and lower form, it was necessary for me to consider it. I likewise wished to ascertain how far the emotions are expressed in the same manner by the different races of man. But owing to the length of the present work, I have thought it better to reserve my essay, which is partially completed, for separate publication.
2 Prof. Häckel is the sole author who, since the publication of the 'Origin,' has discussed, in his various works, in a very able manner, the subject of sexual selection, and has seen its full importance.
THE DESCENT OR ORIGIN OF MAN.
PART I.—THE DESCENT OF MAN.
THE EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM.
Nature of the evidence bearing on the origin of man — Homologous structures in man and the lower animals — Miscellaneous points of correspondence — Development — Rudimentary structures, muscles, sense-organs, hair, bones, reproductive organs, &c. — The bearing of these three great classes of facts on the origin of man.
HE who wishes to decide whether man is the modified descendant of some pre-existing form, would probably first enquire whether man varies, however slightly, in bodily structure and in mental faculties; and if so, whether the variations are transmitted to his offspring in accordance with the laws which prevail with the lower animals; such as that of the transmission of characters to the same age or sex. Again, are the variations the result, as far as our ignorance permits us to judge, of the same general causes, and are they governed by the same general laws, as in the case of other organisms; for instance by correlation, the inherited effects of use and disuse, &c.? Is man subject to similar malconformations, the result of arrested development, of reduplication of parts, &c., and does he display in any of his anomalies reversion to some former and ancient type of structure? It might also naturally be enquired whether man, like so many other animals, has given rise to varieties and sub-races, differing but slightly from each other, or to
races differing so much that they must be classed as doubtful species? How are such races distributed over the world; and how, when crossed, do they react on each other, both in the first and succeeding generations? And so with many other points.
The enquirer would next come to the important point, whether man tends to increase at so rapid a rate, as to lead to occasional severe struggles for existence, and consequently to beneficial variations, whether in body or mind, being preserved, and injurious ones eliminated. Do the races or species of men, whichever term may be applied, encroach on and replace each other, so that some finally become extinct? We shall see that all these questions, as indeed is obvious in respect to most of them, must be answered in the affirmative, in the same manner as with the lower animals. But the several considerations just referred to may be conveniently deferred for a time; and we will first see how far the bodily structure of man shows traces, more or less plain, of his descent from some lower form. In the two succeeding chapters the mental powers of man, in comparison with those of the lower animals, will be considered.
The Bodily Structure of Man.—It is notorious that man is constructed on the same general type or model with other mammals. All the bones in his skeleton can be compared with corresponding bones in a monkey, bat, or seal. So it is with his muscles, nerves, blood-vessels and internal viscera. The brain, the most important of all the organs, follows the same law, as shewn by Huxley and other anatomists. Bischoff,1 who is a hostile witness, admits that every chief fissure and fold
1 'Grosshirnwindungen des Menschen,' 1868, s. 96.
in the brain of man has its analogy in that of the orang; but he adds that at no period of development do their brains perfectly agree; nor could this be expected, for otherwise their mental powers would have been the same. Vulpian2 remarks: "Les différences réelles qui existent entre I'encéphale de l'homme et celui des singes supé rieurs, sont bien minimes. Il ne faut pas se faire d'illusions à cet égard. L'homme est bien plus prés des singes anthropomorphes par les caractéres anatomiques de son cerveau que ceux-ci ne le sont non-seulement des autres mammiféres, mais mêmes de certains quadrumanes, des guenons et des macaques."
But it would be superfluous here to give further details on the correspondence between man and the higher mammals in the structure of the brain and all other parts of the body.
It may, however, be worth while to specify a few points, not directly or obviously connected with structure, by which this correspondence or relationship is well shewn.
Man is liable to receive from the lower animals, and to communicate to them, certain diseases as hydrophobia, variola, the glanders, &c.; and this fact proves the close similarity of their tissues and blood, both in minute structure and composition, far more plainly than does their comparison under the best microscope, or by the aid of the best chemical analysis. Monkeys are liable to many of the same non-contagious diseases as we are; thus Rengger,3 who carefully observed for a long time the Cebus Azaræ in its native land, found it liable to catarrh, with the usual symptoms, and which when
2 'Lec. sur la Phys.' 1866, p. 890, as quoted by M. Dally, 'L'Ordre des Primates et le Transformisme,' 1868, p. 29.
3 'Naturgeschichte der Säugethiere von Paraguay,' 1830, s. 50.
often recurrent led to consumption. These monkeys suffered also from apoplexy, inflammation of the bowels, and cataract in the eye. The younger ones when shedding their milk-teeth often died from fever. Medicines produced the same effect on them as on us. Many kinds of monkeys have a strong taste for tea, coffee, and spirituous liquors: they will also, as I have myself seen, smoke tobacco with pleasure. Brehm asserts that the natives of north-eastern Africa catch the wild baboons by exposing vessels with strong beer, by which they are made drunk. He has seen some of these animals, which he kept in confinement, in this state; and he gives a laughable account of their behaviour and strange grimaces. On the following morning they were very cross and dismal; they held their aching heads with both hands and wore a most pitiable expression: when beer or wine was offered them, they turned away with disgust, but relished the juice of lemons.4 An American monkey, an Ateles, after getting drunk on brandy, would never touch it again, and thus was wiser than many men. These trifling facts prove how similar the nerves of taste must be in monkeys and man, and how similarly their whole nervous system is affected.
Man is infested with internal parasites, sometimes causing fatal effects, and is plagued by external parasites, all of which belong to the same genera or families with those infesting other mammals. Man is subject like other mammals, birds, and even insects, to that mysterious law, which causes certain normal processes, such as gestation, as well as the maturation and duration of various diseases, to follow lunar periods.5 His wounds
4 Brehm, 'Thierleben,' B. i. 1864, s. 75, 86. On the Ateles, s. 105. For other analogous statements, see s. 25, 107.
5 With respect to insects see Dr. Laycock 'On a General Law of Vital Periodicity,' British Association, 1842. Dr. Macculloch, 'Silli-
are repaired by the same process of healing; and the stumps left after the amputation of his limbs occasionally possess, especially during an early embryonic period, some power of regeneration, as in the lowest animals.6
The whole process of that most important function, the reproduction of the species, is strikingly the same in all mammals, from the first act of courtship by the male7 to the birth and nurturing of the young. Monkeys are born in almost as helpless a condition as our own infants; and in certain genera the young differ fully as much in appearance from the adults, as do our children from their full-grown parents.8 It has been urged by some writers as an important distinction, that with man the young arrive at maturity at a much later age than with any other animal: but if we look to the races of mankind which inhabit tropical countries the difference is not great, for the orang is believed not to be adult till the age of from ten to fifteen years.9 Man
man's North American Journal of Science,' vol. xvii. p. 305, has seen a dog suffering from tertian ague.
6 I have given the evidence on this head in my 'Variation of Animals and Plants under Domestication,' vol. ii. p. 15.
7 "Mares e diversis generibus Quadrumanorum sine dubio dignoscunt feminas humanas a maribus. Primum, credo, odoratu, postea aspectu. Mr. Youatt, qui diu in Hortis Zoologicis (Bestiariis) medicus animal-ium erat, vir in rebus observandis cautus et sagax, hoc mihi certissime probavit, et curatores ejusdem loci et alii e ministris confirmaverunt. Sir Andrew Smith et Brehm notabant idem in Cynocephalo. Illustrissimus Cuvier etiam narrat multa de hac re quâ ut opinor nihil turpius potest indicari inter omnia hominibus et Quadrumanis communia. Narrat enim Cynocephalum quendam in furorem incidere aspectu feminarum aliquarum, sed nequaquam accendi tanto furore ab omnibus. Semper eligebat juniores, et dignoscebat in turba, et advocabat voce gestuque."
8 This remark is made with respect to Cynocephalus and the anthropomorphous apes by Geoffroy Saint-Hilaire and F. Cuvier, 'Hist. Nat. des Mammiféres,' tom. i. 1824.
9 Huxley, 'Man's Place in Nature,' 1863, p. 34.
differs from woman in size, bodily strength, hairyness, &c., as well as in mind, in the same manner as do the two sexes of many mammals. It is, in short, scarcely possible to exaggerate the close correspondence in general structure, in the minute structure of the tissues, in chemical composition and in constitution, between man and the higher animals, especially the anthropomorphous apes.
Embryonic Development.—Man is developed from an ovule, about the 125th of an inch in diameter, which differs in no respect from the ovules of other animals. The embryo itself at a very early period can hardly be distinguished from that of other members of the vertebrate kingdom. At this period the arteries run in arch-like branches, as if to carry the blood to branchiæ which are not present in the higher vertebrata, though the slits on the sides of the neck still remain (f, g, fig. 1), marking their former position. At a somewhat later period, when the extremities are developed, "the feet of lizards and mammals," as the illustrious Von Baer remarks, "the wings and feet of birds, no less than the hands and feet of man, all arise from the same fundamental form." It is, says Prof. Huxley,10 "quite in the later stages of development that the young human being presents marked differences from the young ape, while the latter departs as much from the dog in its developments, as the man does. Startling as this last assertion may appear to be, it is demonstrably true."
As some of my readers may never have seen a drawing of an embryo, I have given one of man and another of a dog, at about the same early stage of development,
10 'Man's Place in Nature,' 1863, p. 67.
Fig. 1. Upper figure human embryo, from Ecker. Lower figure that of a dog, from Bischoff.
a. Fore-brain, cerebral hemispheres, &c.
b. Mid-brain, corpora quadrigemina.
c. Hind-brain, cerebellum, medulla oblongata.
f. First visceral arch.
g. Second visceral arch.
H. Vertebral columns and muscles in process of development.
L. Tail or os coccyx.
carefully copied from two works of undoubted accuracy.11
After the foregoing statements made by such high authorities, it would be superfluous on my part to give a number of borrowed details, shewing that the embryo of man closely resembles that of other mammals. It may, however, be added that the human embryo like-wise resembles in various points of structure certain low forms when adult. For instance, the heart at first exists as a simple pulsating vessel; the excreta are voided through a cloacal passage; and the os coccyx projects like a true tail, "extending considerably beyond the rudimentary legs."12 In the embryos of all air-breathing vertebrates, certain glands called the corpora Wolffiana, correspond with and act like the kidneys of mature fishes.13 Even at a later embryonic period, some striking resemblances between man and the lower animals may be observed. Bischoff says that the convolutions of the brain in a human fœtus at the end of the seventh month reach about the same stage of development as in a baboon when adult.14 The great toe, as Prof. Owen remarks,15 "which forms the fulcrum when standing or walking, is perhaps the most characteristic
11 The human embryo (upper fig.) is from Ecker, 'Icones Phys.,' 1851–1859, tab. xxx. fig. 2. This embryo was ten lines in length, so that the drawing is much magnified. The embryo of the dog is from Bischoff, 'Entwicklungsgeschichte des Hunde-Eies,' 1845, tab. xi. fig. 42 B. This drawing is five times magnified, the embryo being 25 days old. The internal viscera have been omitted, and the uterine appendages in both drawings removed. I was directed to these figures by Prof. Huxley, from whose work, 'Man's Place in Nature,' the idea of giving them was taken. Häckel has also given analogous drawings in his 'Schöpfungsgeschichte.'
12 Prof. Wyman in 'Proc. of American Acad, of Sciences,' vol. iv. 1860, p. 17.
13 Owen, 'Anatomy of Vertebrates,' vol. i. p. 533.
14 'Die Grosshirnwindungen des Menschen,' 1868, s. 95.
15 'Anatomy of Vertebrates,' vol. ii. p. 553.
"peculiarity in the human structure;" but in an embryo, about an inch in length, Prof. Wyman16 found "that the great toe was shorter than the others, and, instead of being parallel to them, projected at an angle from the side of the foot, thus corresponding with the permanent condition of this part in the quadrumana." I will conclude with a quotation from Huxley,17 who after asking, does man originate in a different way from a dog, bird, frog or fish? says, "the reply is not doubtful for a moment; without question, the mode of origin and the early stages of the development of man are identical with those of the animals immediately below him in the scale: without a doubt in these respects, he is far nearer to apes, than the apes are to the dog."
Rudiments.—This subject, though not intrinsically more important than the two last, will for several reasons be here treated with more fullness.18 Not one of the higher animals can be named which does not bear some part in a rudimentary condition; and man forms no exception to the rule. Rudimentary organs must be distinguished from those that are nascent; though in some cases the distinction is not eary. The former are either absolutely useless, such as the mammæ of male quadrupeds, or the incisor teeth of ruminants which never cut through the gums; or they are of such slight service to their present possessors, that we cannot suppose that they were developed under the conditions
16 'Proc. Soc. Nat. Hist.' Boston, 1863, vol. ix. p. 185.
17 'Man's Place in Nature,' p. 65.
18 I had written a rough copy of this chapter before reading a valuable paper, "Caratteri rudimentali in ordine all' origine del uomo" ('Annuario della Soc. d. Nat.,' Modena, 1867, p. 81), by G. Canestrini, to which paper I am considerably indebted. Häckel has given admirable discussions on this whole subject, under the title of Dysteleology, in his 'Generelle Morphologie' and 'Schöpfungsgeschichte.'
VOL. I. C
which now exist. Organs in this latter state are not strictly rudimentary, but they are tending in this direction. Nascent organs, on the other hand, though not fully developed, are of high service to their possessors, and are capable of further development. Rudimentary organs are eminently variable; and this is partly intelligible, as they are useless or nearly useless, and consequently are no longer subjected to natural selection. They often become wholly suppressed. When this occurs, they are nevertheless liable to occasional reappearance through reversion; and this is a circumstance well worthy of attention.
Disuse at that period of life, when an organ is chiefly used, and this is generally during maturity, together with inheritance at a corresponding period of life, seem to have been the chief agents in causing organs to become rudimentary. The term "disuse" does not relate merely to the lessened action of muscles, but includes a diminished flow of blood to a part or organ, from being subjected to fewer alternations of pressure, or from becoming in any way less habitually active. Rudiments, however, may occur in one sex of parts normally present in the other sex; and such rudiments, as we shall hereafter see, have often originated in a distinct manner. In some cases organs have been reduced by means of natural selection, from having become injurious to the species under changed habits of life. The process of reduction is probably often aided through the two principles of compensation and economy of growth; but the later stages of reduction, after disuse has done all that can fairly be attributed to it, and when the saving to be effected by the economy of growth would be very small,19 are difficult to understand. The final and com-
19 Some good criticisms on this subject have been given by Messrs. Murie and Mivart, in 'Transact. Zoolog. Soc.' 1869, vol. vii. p. 92.
plete suppression of a part, already useless and much reduced in size, in which case neither compensation nor economy can come into play, is perhaps intelligible by the aid of the hypothesis of pangenesis, and apparently in no other way. But as the whole subject of rudimentary organs has been fully discussed and illustrated in my former works,20 I need here say no more on this head.
Rudiments of various muscles have been observed in many parts of the human body;21 and not a few muscles, which are regularly present in some of the lower animals can occasionally be detected in man in a greatly reduced condition. Every one must have noticed the power which many animals, especially horses, possess of moving or twitching their skin; and this is effected by the panniculus carnosus. Remnants of this muscle in an efficient state are found in various parts of our bodies; for instance, on the forehead, by which the eyebrows are raised. The platysma myoides, which is well developed on the neck, belongs to this system, but cannot be voluntarily brought into action. Prof. Turner, of Edinburgh, has occasionally detected, as he informs me, muscular fasciculi in five different situations, namely in the axillæ, near the scapulæ &c., all of which must be referred to the system of the panniculus. He has also shewn22 that the musculus sternalis or sternalis brutorum, which is not an extension of the rectus abdominalis, but is closely allied to the panniculus, oc-
20 'Variation of Animals and Plants under Domestication,' vol. ii. pp. 317 and 397. See also 'Origin of Species,' 5th edit. p. 535.
21 For instance M. Richard ('Annales des Sciences Nat.' 3rd series, Zoolog. 1852, tom. xviii. p. 13) describes and figures rudiments of what he calls the "muscle pédieux de la main," which he says is sometimes "infiniment petit." Another muscle, called "le tibial postérieur," is generally quite absent in the hand, but appears from time to time in a more or less rudimentary condition.
22 Prof. W. Turner, 'Proc. Royal Soc. Edinburgh,' 1866-67, p. 65.
curred in the proportion of about 3 per cent. in upwards of 600 bodies: he adds, that this muscle affords "an excellent illustration of the statement that occasional and rudimentary structures are especially liable to variation in arrangement."
Some few persons have the power of contracting the superficial muscles on their scalps; and these muscles are in a variable and partially rudimentary condition. M. A. de Candolle has communicated to me a curious instance of the long-continued persistence or inheritance of this power, as well as of its unusual development. He knows a family, in which one member, the present head of a family, could, when a youth, pitch several heavy books from his head by the movement of the scalp alone; and he won wagers by performing this feat. His father, uncle, grandfather, and all his three children possess the same power to the same unusual degree. This family became divided eight generations ago into two branches; so that the head of the above-mentioned branch is cousin in the seventh degree to the head of the other branch. This distant cousin resides in another part of France, and on being asked whether he possessed the same faculty, immediately exhibited his power. This case offers a good illustration how persistently an absolutely useless faculty may be transmitted.
The extrinsic muscles which serve to move the whole external ear, and the intrinsic muscles which move the different parts, all of which belong to the system of the panniculus, are in a rudimentary condition in man; they are also variable in development, or at least in function. I have seen one man who could draw his ears forwards, and another who could draw them backwards;23
23 Canestrini quotes Hyrt. (' Annuario della Soc. dei Naturalisti,' Modena. 1867, p. 97) to the same effect.
and from what one of these persons told me, it is probable that most of us by often touching our ears and thus directing our attention towards them, could by repeated trials recover some power of movement. The faculty of erecting the ears and of directing them to different points of the compass, is no doubt of the highest service to many animals, as they thus perceive the point of danger; but I have never heard of a man who possessed the least power of erecting his ears,—the one movement which might be of use to him. The whole external shell of the ear may be considered a rudiment, together with the various folds and prominences (helix and anti-helix, tragus and anti-tragus, &c.) which in the lower animals strengthen and support the ear when erect, without adding much to its weight. Some authors, however, suppose that the cartilage of the shell serves to transmit vibrations to the acoustic nerve; but Mr. Toynbee,24 after collecting all the known evidence on this head, concludes that the external shell is of no distinct use. The ears of the chimpanzee and organ are curiously like those of man, and I am assured by the keepers in the Zoological Gardens that these animals never move or erect them; so that they are in an equally rudimentary condition, as far as function is concerned, as in man. Why these animals, as well as the progenitors of man, should have lost the power of erecting their ears we cannot say. It may be, though I am not quite satisfied with this view, that owing to their arboreal habits and great strength they were but little exposed to danger, and so during a lengthened period moved their ears but little, and thus gradually lost the power of moving them. This would be a parallel case with that of those large and heavy birds,
24 'The Diseases of the Ear,' by J. Toynbee, F.R.S., 1860, p. 12.
which from inhabiting oceanic islands have not been exposed to the attacks of beasts of prey, and have consequently lost the power of using their wings for flight.
Fig. 2. Human Ear, modelled and drawn by Mr. Woolner.
a. The projecting point.
The celebrated sculptor, Mr. Woolner, informs me of one little peculiarity in the external ear, which he has often observed both in men and women, and of which he perceived the full signification. His attention was first called to the subject whilst at work on his figure of Puck, to which he had given pointed ears. He was thus led to examine the ears of various monkeys, and subsequently more carefully those of man. The peculiarity consists in a little blunt point, projecting from the inwardly folded margin, or helix. Mr. Woolner made an exact model of one such case, and has sent me the accompanying drawing. (Fig.2.) These points not only project inwards, but often a little outwards, so that they are visible when the head is viewed from directly in front or behind. They are variable in size and somewhat in position, standing either a little higher or lower; and they sometimes occur on one ear and not on the other. Now the meaning of these projections is not, I think, doubtful; but it may be thought that they offer too trifling a character to be worth notice. This thought, however, is as false as it is natural. Every character, however slight, must be the result of some definite cause; and if it occurs in many individuals deserves consideration. The helix obviously consists of the extreme margin of the ear folded inwards; and this folding appears to be in some manner connected with the
whole external ear being permanently pressed backwards. In many monkeys, which do not stand high in the order, as baboons and some species of macacus,25 the upper portion of the ear is slightly pointed, and the margin is not at all folded inwards; but if the margin were to be thus folded, a slight point would necessarily project inwards and probably a little outwards. This could actually be observed in a specimen of the Ateles beelzebuth in the Zoological Gardens; and we may safely conclude that it is a similar structure—a vestige of formerly pointed ears—which occasionally reappears in man.
The nictitating membrane, or third eyelid, with its accessory muscles and other structures, is especially well developed in birds, and is of much functional importance to them, as it can be rapidly drawn across the whole eye-ball. It is found in some reptiles and amphibians, and in certain fishes, as in sharks. It is fairly well developed in the two lower divisions of the mammalian series, namely, in the monotremata and marsupials, and in some few of the higher mammals, as in the walrus. But in man, the quadrumana, and most other mammals, it exists, as is admitted by all anatomists, as a mere rudiment, called the semilunar fold.26
The sense of smell is of the highest importance to the greater number of mammals—to some, as the ruminants, in warning them of danger; to others, as the
25 See also some remarks, and the drawings of the ears of the Lemuroidea, in Messrs. Murie and Mivart's excellent paper in 'Transact. Zoolog. Soc.' vol. vii. 1869, pp. 6 and 90.
26 Müller's 'Elements of Physiology,' Eng. translat., 1842, vol. ii. p. 1117. Owen, 'Anatomy of Vertebrates,' vol. iii. p. 260; ibid. on the Walrus, 'Proc. Zoolog. Soc.' November 8th, 1854. See also R. Knox, 'Great Artists and Anatomists,' p. 106. This rudiment apparently is somewhat larger in Negroes and Australians than in Europeans, see Carl Vogt, 'Lectures on Man,' Eng. translat. p. 129.
carnivora, in finding their prey; to others, as the wild boar, for both purposes combined. But the sense of smell is of extremely slight service, if any, even to savages, in whom it is generally more highly developed than in the civilised races. It does not warn them of danger, nor guide them to their food; nor does it prevent the Esquimaux from sleeping in the most fetid atmosphere, nor many savages from eating half-putrid meat. Those who believe in the principle of gradual evolution, will not readily admit that this sense in its present state was originally acquired by man, as he now exists. No doubt he inherits the power in an enfeebled and so far rudimentary condition, from some early progenitor, to whom it was highly serviceable and by whom it was continually used. We can thus perhaps understand how it is, as Dr. Maudsley has truly remarked,27 that the sense of smell in man "is singularly effective in recalling vividly the ideas and images of forgotten scenes and places;" for we see in those animals, which have this sense highly developed, such as dogs and horses, that old recollections of persons and places are strongly associated with their odour.
Man differs conspicuously from all the other Primates in being almost naked. But a few short straggling hairs are found over the greater part of the body in the male sex, and fine down on that of the female sex. In individuals belonging to the same race these hairs are highly variable, not only in abundance, but like-wise in position: thus the shoulders in some Europeans are quite naked, whilst in others they bear thick tufts of hair.28 There can be little doubt that the hairs
27 'The Physiology and Pathology of Mind,' 2nd edit. 1868, p. 134.
28 Eschricht, Ueber die Richtung der Haare am menschlichen Körp er 'Müller's Archiv für Anat. und Phys.' 1837, s. 47. I shall often have to refer to this very curious paper.
thus scattered over the body are the rudiments of the uniform hairy coat of the lower animals. This view is rendered all the more probable, as it is known that fine, short, and pale-coloured hairs on the limbs and other parts of the body occasionally become developed into "thickset, long, and rather coarse dark hairs," when abnormally nourished near old-standing inflamed surfaces.29
I am informed by Mr. Paget that persons belonging to the same family often have a few hairs in their eyebrows much longer than the others; so that this slight peculiarity seems to be inherited. These hairs apparently represent the vibrissæ, which are used as organs of touch by many of the lower animals. In a young chimpanzee I observed that a few upright, rather long, hairs, projected above the eyes, where the true eyebrows, if present, would have stood.
The fine wool-like hair, or so-called lanugo, with which the human fœtus during the sixth month is thickly covered, offers a more curious case. It is first developed, during the fifth month, on the eyebrows and face, and especially round the mouth, where it is much longer than that on the head. A moustache of this kind was observed by Eschricht30 on a female fœtus; but this is not so surprising a circumstances as it may at first appear, for the two sexes generally resemble each other in all external characters during an early period of growth. The direction and arrangement of the hairs on all parts of the fœtal body are the same as in the adult, but are subject to much variability. The whole surface, including even the forehead and ears, is thus thickly clothed; but it is a significant fact that the palms of the hands and
29 Paget, 'Lectures on Surgical Pathology,' 1853, vol. i. p. 71.
30 Eschricht, ibid. s. 40, 47.
the soles of the feet are quite naked, like the inferior surfaces of all four extremities in most of the lower animals. As this can hardly be an accidental coincidence, we must consider the woolly covering of the fœtus to be the rudimental representative of the first permanent coat of hair in those mammals which are born hairy. This representation is much more complete, in accordance with the usual law of embryological development, than that afforded by the straggling hairs on the body of the adult.
It appears as if the posterior molar or wisdom-teeth were tending to become rudimentary in the more civilised races of man. These teeth are rather smaller than the other molars, as is likewise the case with the corresponding teeth in the chimpanzee and orang; and they have only two separate fangs. They do not cut through the gums till about the seventeenth year, and I am assured by dentists that they are much more liable to decay, and are earlier lost, than the other teeth. It is also remarkable that they are much more liable to vary both in structure and in the period of their development than the other teeth.31 In the Melanian races, on the other hand, the wisdom-teeth are usually furnished with three separate fangs, and are generally sound: they also differ from the other molars in size less than in the Caucasian races.32 Prof. Schaaffhausen accounts for this difference between the races by "the posterior dental portion of the jaw being always shortened" in those that are civilised,33 and this shortening may, I presume, be safely attributed to civi-
31 Dr. Webb, 'Teeth in Man and the Anthropoid Apes,' as quoted by Dr. C. Carter Blake in 'Anthropological Review,' July, 1867, p. 299.
32 Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 320, 321, and 325.
33 'On the Primitive Form of the Skull,' Eng. translat. in 'Anthropological Review,' Oct. 1868, p. 426.
lised men habitually feeding on soft, cooked food, and thus using their jaws less. I am informed by Mr. Brace that it is becoming quite a common practice in the United States to remove some of the molar teeth of children, as the jaw does not grow large enough for the perfect development of the normal number.
With respect to the alimentary canal I have met with an account of only a single rudiment, namely the vermiform appendage of the cæcum. The cæcum is a branch or diverticulum of the intestine, ending in a cul-de-sac, and it is extremely long in many of the lower vegetable-feeding mammals. In the marsupial kaola it is actually more than thrice as long as the whole body.34 It is sometimes produced into a long gradually-tapering point, and is sometimes constricted in parts. It appears as if, in consequence of changed diet or habits, the cæcum had become much shortened in various animals, the vermiform appendage being left as a rudiment of the shortened part. That this appendage is a rudiment, we may infer from its small size, and from the evidence which Prof. Canestrini35 has collected of its variability in man. It is occasionally quite absent, or again is largely developed. The passage is sometimes completely closed for half or two-thirds of its length, with the terminal part consisting of a flattened solid expansion. In the orang this appendage is long and convoluted: in man it arises from the end of the short cæcum, and is commonly from four to five inches in length, being only about the third of an inch in diameter. Not only is it useless, but it is sometimes the cause of death, of which fact I have lately heard two instances: this is due to small hard bodies,
34 Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 416, 434, 441.
35 'Annuario della Soc. d. Nat.' Modena, 1867, p. 94.
such as seeds, entering the passage and causing inflammation.36
In the Quadrumana and some other orders of mammals, especially in the Carnivora, there is a passage near the lower end of the humerus, called the supra-condyloid foramen, through which the great nerve of the fore limb passes, and often the great artery. Now in the humerus of man, as Dr. Struthers37 and others have shewn, there is generally a trace of this passage, and it is sometimes fairly well developed, being formed by a depending hook-like process of bone, completed by a band of ligament. When present the great nerve invariably passes through it, and this clearly indicates that it is the homologue and rudiment of the supra-condyloid foramen of the lower animals. Prof. Turner estimates, as he informs me, that it occurs in about one per cent. of recent skeletons; but during ancient times it appears to have been much more common. Mr. Busk38 has collected the following evidence on this head: Prof. Broca "noticed the perforation in four and a half per cent. of the arm-bones collected in the 'Cimetière du Sud' at Paris; and in the Grotto of Orrony, the contents of which are referred to the Bronze period, as many as eight humeri out of thirty-two were perforated; but this extraordinary proportion, he thinks, might be due to the cavern having been a sort of
36 M. C. Martins ("De l'Unité Organique," in 'Revue des Deux Mondes,' June 15, 1862, p. 16), and Häckel ('Generelle Morphologie,' B. ii. s. 278), have both remarked on the singular fact of this rudiment sometimes causing death.
37 'The Lancet,' Jan. 24, 1863, p. 83. Dr. Knox, 'Great Artists and Anatomists,' p. 63. See also an important memoir on this process by Dr. Grube, in the 'Bulletin de l'Acad. Imp. de St. Pétersbourg,' tom. xii. 1867, p. 448.
38 "On the Caves of Gibraltar," 'Transact. Internat. Congress of Prehist. Arch.' Third Session, 1869, p. 54.
'family vault.' Again, M. Dupont found 30 per cent. of perforated bones in the caves of the Valley of the Lesse, belonging to the Reindeer period; whilst M. Leguay, in a sort of dolmen at Argenteuil, observed twenty-five per cent. to be perforated; and M. Pruner-Bey found twenty-six per cent. in the same condition in bones from Vauréal. Nor should it be left unnoticed that M. Pruner-Bey states that this condition is common in Guanche skeletons." The fact that ancient races, in this and several other cases, more frequently present structures which resemble those of the lower animals than do the modern races, is interesting. One chief cause seems to be that ancient races stand somewhat nearer than modern races in the long line of descent to their remote animal-like progenitors.
The os coccyx in man, though functionless as a tail, plainly represents this part in other vertebrate animals. At an early embryonic period it is free, and, as we have seen, projects beyond the lower extremities. In certain rare and anomalous cases it has been known, according to Isidore Geoffroy St.-Hilaire and others,39 to form a small external rudiment of a tail. The os coccyx is short, usually including only four vertebræ: and these are in a rudimental condition, for they consist, with the exception of the basal one, of the centrum alone.40 They are furnished with some small muscles; one of which, as I am informed by Prof. Turner, has been expressly described by Theile as a rudimentary repetition of the extensor of the tail, which is so largely developed in many mammals.
The spinal cord in man extends only as far downwards as the last dorsal or first lumbar vertebra; but a
39 Quatrefages has lately collected the evidence on this subject. 'Revue des Cours Scientifiques,' 1867-1868, p. 625.
40 Owen, 'On the Nature of Limbs,' 1849, p. 114.
thread-like structure (the filum terminale) runs down the axis of the sacral part of the spinal canal, and even along the back of the coccygeal bones. The upper part of this filament, as Prof. Turner informs me, is undoubtedly homologous with the spinal cord; but the lower part apparently consists merely of the pia mater, or vascular investing membrane. Even in this case the os coccyx may be said to possess a vestige of so important a structure as the spinal cord, though no longer enclosed within a bony canal. The following fact, for which I am also indebted to Prof. Turner, shews how closely the os coccyx corresponds with the true tail in the lower animals: Luschka has recently discovered at the extremity of the coccygeal bones a very peculiar convoluted body, which is continuous with the middle sacral artery; and this discovery led Krause and Meyer to examine the tail of a monkey (Macacus) and of a cat, in both of which they found, though not at the extremity, a similarly convoluted body.
The reproductive system offers various rudimentary structures; but these differ in one important respect from the foregoing cases. We are not here concerned with a vestige of a part which does not belong to the species in an efficient state; but with a part which is always present and efficient in the one sex, being represented in the other by a mere rudiment. Nevertheless, the occurrence of such rudiments is as difficult to explain on the belief of the separate creation of each species, as in the foregoing cases. Hereafter I shall have to recur to these rudiments, and shall shew that their presence generally depends merely on inheritance; namely, on parts acquired by one sex having been partially transmitted to the other. Here I will only give some instances of such rudiments. It is well known that in the males of all mammals, in
cluding man, rudimentary mammæ exist. These in several instances have become well developed, and have yielded a copious supply of milk. Their essential identity in the two sexes is likewise shewn by their occasional sympathetic enlargement in both during an attack of the measles. The vesicula prostratica, which has been observed in many male mammals, is now universally acknowledged to be the homologue of the female uterus, together with the connected passage. It is impossible to read Leuckart's able description of this organ, and his reasoning, without admitting the justness of his conclusion. This is especially clear in the case of those mammals in which the true female uterus bifurcates, for in the males of these the vesicula likewise bifurcates.41 Some additional rudimentary structures belonging to the reproductive system might here have been adduced.42
The bearing of the three great classes of facts now given is unmistakeable. But it would be superfluous here fully to recapitulate the line of argument given in detail in my 'Origin of Species.' The homological construction of the whole frame in the members of the same class is intelligible, if we admit their descent from a common progenitor, together with their subsequent adaptation to diversified conditions. On any other view the similarity of pattern between the hand of a man or monkey, the foot of a horse, the flipper of a seal, the wing of a bat, &c., is utterly inexplicable. It is no scientific
41 Leuckart, in Todd's 'Cyclop. of Anat.' 1849-52, vol. iv. p. 1415. In man this organ is only from three to six lines in length, but, like so many other rudimentary parts, it is variable in development as well as in other characters.
42 See, on this subject, Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 675, 676, 706.
explanation to assert that they have all been formed on the same ideal plan. With respect to development, we can clearly understand, on the principle of variations supervening at a rather late embryonic period, and being inherited at a corresponding period, how it is that the embryos of wonderfully different forms should still retain, more or less perfectly, the structure of their common progenitor. No other explanation has ever been given of the marvellous fact that the embryo of a man, dog, seal, bat, reptile, &c., can at first hardly be distinguished from each other. In order to understand the existence of rudimentary organs, we have only to suppose that a former progenitor possessed the parts in question in a perfect state, and that under changed habits of life they became greatly reduced, either from simple disuse, or through the natural selection of those individuals which were least encumbered with a superfluous part, aided by the other means previously indicated.
Thus we can understand how it has come to pass that man and all other vertebrate animals have been constructed on the same general model, why they pass through the same early stages of development, and why they retain certain rudiments in common. Consequently we ought frankly to admit their community of descent: to take any other view, is to admit that our own structure and that of all the animals around us, is a mere snare laid to entrap our judgment. This conclusion is greatly strengthened, if we look to the members of the whole animal series, and consider the evidence derived from their affinities or classification, their geographical distribution and geological succession. It is only our natural prejudice, and that arrogance which made our forefathers declare that they were descended from demi-gods, which leads us to demur to
this conclusion. But the time will before long come when it will be thought wonderful, that naturalists, who were well acquainted with the comparative structure and development of man and other mammals, should have believed that each was the work of a separate act of creation.
VOL. I. D
COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS.
The difference in mental power between the highest ape and the lowest savage, immense — Certain instincts in common — The emotions — Curiosity — Imitation — Attention — Memory — Imagination — Reason — Progressive improvement — Tools and weapons used by animals — Language — Self-consciousness — Sense of beauty — Belief in God, spiritual agencies, superstitions.
WE have seen in the last chapter that man bears in his bodily structure clear traces of his descent from some lower form; but it may be urged that, as man differs so greatly in his mental power from all other animals, there must be some error in this conclusion. No doubt the difference in this respect is enormous, even if we compare the mind of one of the lowest savages, who has no words to express any number higher than four, and who uses no abstract terms for the commonest objects or affections,1 with that of the most highly organised ape. The difference would, no doubt, still remain immense, even if one of the higher apes had been improved or civilised as much as a dog has been in comparison with its parent-form, the wolf or jackal. The Fuegians rank amongst the lowest barbarians; but I was continually struck with surprise how closely the three natives on board H.M.S. "Beagle," who had lived some years in England and could talk a little English, resembled us in disposition and in most of our mental faculties. If no
1 See the evidence on these points, as given by Lubbock, 'Prehistoric Times,' p. 354, &c.
organic being excepting man had possessed any mental power, or if his powers had been of a wholly different nature from those of the lower animals, then we should never have been able to convince ourselves that our high faculties had been gradually developed. But it can be clearly shewn that there is no fundamental difference of this kind. We must also admit that there is a much wider interval in mental power between one of the lowest fishes, as a lamprey or lancelet, and one of the higher apes, than between an ape and man; yet this imense interval is filled up by numberless gradations.
Nor is the difference slight in moral disposition between a barbarian, such as the man described by the old navigator Byron, who dashed his child on the rocks for dropping a basket of sea-urchins, and a Howard or Clarkson; and in intellect, between a savage who does not use any abstract terms, and a Newton or Shakspeare. Differences of this kind between the highest men of the highest races and the lowest savages, are connected by the finest gradations. Therefore it is possible that they might pass and be developed into each other.
My object in this chapter is solely to shew that there is no fundamental difference between man and the higher mammals in their mental faculties. Each division of the subject might have been extended into a separate essay, but must here be treated briefly. As no classification of the mental powers has been universally accepted, I shall arrange my remarks in the order most convenient for my purpose; and will select those facts which have most struck me, with the hope that they may produce some effect on the reader.
With respect to animals very low in the scale, I shall have to give some additional facts under Sexual Selection, shewing that their mental powers are higher than
might have been expected. The variability of the faculties in the individuals of the same species is an important point for us, and some few illustrations will here be given. But it would be superfluous to enter into many details on this head, for I have found on frequent enquiry, that it is the unanimous opinion of all those who have long attended to animals of many kinds, including birds, that the individuals differ greatly in every mental characteristic. In what manner the mental powers were first developed in the lowest organisms, is as hopeless an enquiry as how life first originated. These are problems for the distant future, if they are ever to be solved by man.
As man possesses the same senses with the lower animals, his fundamental intuitions must be the same. Man has also some few instincts in common, as that of self-preservation, sexual love, the love of the mother for her new-born offspring, the power possessed by the latter of sucking, and so forth. But man, perhaps, has somewhat fewer instincts than those possessed by the animals which come next to him in the series. The orang in the Eastern islands, and the chimpanzee in Africa, build platforms on which they sleep; and, as both species follow the same habit, it might be argued that this was due to instinct, but we cannot feel sure that it is not the result of both animals having similar wants and possessing similar powers of reasoning. These apes, as we may assume, avoid the many poisonous fruits of the tropics, and man has no such knowledge; but as our domestic animals, when taken to foreign lands and when first turned out in the spring, often eat poisonous herbs, which they afterwards avoid, we cannot feel sure that the apes do not learn from their own experience or from that of their parents what fruits to select. It is however certain, as we shall presently see, that apes have
an instinctive dread of serpents, and probably of other dangerous animals.
The fewness and the comparative simplicity of the instincts in the higher animals are remarkable in contrast with those of the lower animals. Cuvier maintained that instinct and intelligence stand in an inverse ratio to each other; and some have thought that the intellectual faculties of the higher animals have been gradually developed from their instincts. But Pouchet, in an interesting essay,2 has shewn that no such inverse ratio really exists. Those insects which possess the most wonderful instincts are certainly the most intelligent. In the vertebrate series, the least intelligent members, namely fishes and amphibians, do not possess complex instincts; and amongst mammals the animal most remarkable for its instincts, namely the beaver, is highly intelligent, as will be admitted by every one who has read Mr. Morgan's excellent account of this animal.3
Although the first dawnings of intelligence, according to Mr. Herbert Spencer,4 have been developed through the multiplication and co-ordination of reflex actions, and although many of the simpler instincts graduate into actions of this kind and can hardly be distinguished from them, as in the case of young animals sucking, yet the more complex instincts seem to have originated independently of intelligence. I am, however, far from wishing to deny that instinctive actions may lose their fixed and untaught character, and be replaced by others performed by the aid of the free will. On the other hand, some intelligent actions—as when birds on oceanic islands first learn to avoid man—after
2 'L'Instinct chez les Insectes.' 'Revue des Deux Mondes,' Feb. 1870, p. 690.
3 'The American Beaver and his Works,' 1868.
4 'The Principles of Psychology,' 2nd edit. 1870, pp. 418-443
being performed during many generations, become converted into instincts and are inherited. They may then be said to be degraded in character, for they are no longer performed through reason or from experience. But the greater number of the more complex instincts appear to have been gained in a wholly different manner, through the natural selection of variations of simpler instinctive actions. Such variations appear to arise from the same unknown causes acting on the cerebral organisation, which induce slight variations or individual differences in other parts of the body; and these variations, owing to our ignorance, are often said to arise spontaneously. We can, I think, come to no other conclusion with respect to the origin of the more complex instincts, when we reflect on the marvellous instincts of sterile worker-ants and bees, which leave no offspring to inherit the effects of experience and of modified habits.
Although a high degree of intelligence is certainly compatible with the existence of complex instincts, as we see in the insects just named and in the beaver, it is not improbable that they may to a certain extent interfere with each other's development. Little is known about the functions of the brain, but we can perceive that as the intellectual powers become highly developed, the various parts of the brain must be connected by the most intricate channels of intercommunication; and as a consequence each separate part would perhaps tend to become less well fitted to answer in a definite and uniform, that is instinctive, manner to particular sensations or associations.
I have though this digression worth giving, because we may easily underrate the mental powers of the higher animals, and especially of man, when we compare their actions founded on the memory of past events, on foresight, reason, and imagination, with
exactly similar actions instinctively performed by the lower animals; in this latter case the capacity of performing such actions having been gained, step by step, through the variability of the mental organs and natural selection, without any conscious intelligence on the part of the animal during each successive generation. No doubt, as Mr. Wallace has argued,5 much of the intelligent work done by man is due to imitation and not to reason; but there is this great difference between his actions and many of those performed by the lower animals, namely, that man cannot, on his first trial, make, for instance, a stone hatchet or a canoe, through his power of imitation. He has to learn his work by practice; a beaver, on the other hand, can make its dam or canal, and a bird its nest, as well, or nearly as well, the first time it tries, as when old and experienced.
To return to our immediate subject: the lower animals, like man, manifestly feel pleasure and pain, happiness and misery. Happiness is never better exhibited than by young animals, such as puppies, kittens, lambs, &c., when playing together, like our own children. Even insects play together, as has been described by that excellent observer, P. Huber,6 who saw ants chasing and pretending to bite each other, like so many puppies.
The fact that the lower animals are excited by the same emotions as ourselves is so well established, that it will not be necessary to weary the reader by many details. Terror acts in the same manner on them as on us, causing the muscles to tremble, the heart to palpitate, the sphincters to be relaxed, and the hair to stand on end. Suspicion, the offspring of fear, is eminently characteristic of most wild animals. Courage
5 'Contributions to the Theory of Natural Selection,' 1870, p. 212.
6 'Recherches sur les Mœurs des Fourmis,' 1810, p. 173.
and timidity are extremely variable qualities in the individuals of the same species, as is plainly seen in our dogs. Some dogs and horses are ill-tempered and easily turn sulky; others are good-tempered; and these qualities are certainly inherited. Every one knows how liable animals are to furious rage, and how plainly they show it. Many anecdotes, probably true, have been published on the long-delayed and artful revenge of various animals. The accurate Rengger and Brehm7 state that the American and African monkeys which they kept tame, certainly revenged themselves. The love of a dog for his master is notorious; in the agony of death he has been known to caress his master, and every one has heard of the dog suffering under vivisection, who licked the hand of the operator; this man, unless he had a heart of stone, must have felt remorse to the last hour of his life. As Whewell8 has remarked, "who that reads the touching instances of maternal affection, related so often of the women of all nations, and of the females of all animals, can doubt that the principle of action is the same in the two cases?"
We see maternal affection exhibited in the most trifling details; thus Rengger observed an American monkey (a Cebus) carefully driving away the flies which plagued her infant; and Duvaucel saw a Hylobates washing the faces of her young ones in a stream. So intense is the grief of female monkeys for the loss of their young, that it invariably caused the death of certain kinds kept under confinement by Brehm in N.
7 All the following statements, given on the authority of these two naturalists, are taken from Rengger's 'Naturges. der Säugethiere von Paraguay,' 1830, s. 41-57, and from Brehm's 'Thierleben,' B. i. s. 10-87.
8 'Bridgewater Treatise,' p. 263.
Africa. Orphan-monkeys were always adopted and carefully guarded by the other monkeys, both males and females. One female baboon had so capacious a heart that she not only adopted young monkeys of other species, but stole young dogs and cats, which she continually carried about. Her kindness, however, did not go so far as to share her food with her adopted offspring, at which Brehm was surprised, as his monkeys always divided everything quite fairly with their own young ones. An adopted kitten scratched the above-mentioned affectionate baboon, who certainly had a fine intellect, for she was much astonished at being scratched, and immediately examined the kitten's feet, and without more ado bit off the claws. In the Zoological Gardens, I heard from the keeper that an old baboon (C. chacma) had adopted a Rhesus monkey; but when a young drill and mandrill were placed in the cage, she seemed to perceive that these monkeys, though distinct species, were her nearer relatives, for she at once rejected the Rhesus and adopted both of them. The young Rhesus, as I saw, was greatly discontented at being thus rejected, and it would, like a naughty child, annoy and attack the young drill and mandrill whenever it could do so with safety; this conduct exciting great indignation in the old baboon. Monkeys will also, according to Brehm, defend their master when attacked by any one, as well as dogs to whom they are attached, from the attacks of other dogs. But we here trench on the subject of sympathy, to which I shall recur. Some of Brehm's monkeys took much delight in teasing, in various ingenious ways, a certain old dog whom they disliked, as well as other animals.
Most of the more complex emotions are common to the higher animals and ourselves. Every one has seen
how jealous a dog is of his master's affection, if lavished on any other creature; and I have observed the same fact with monkeys. This shows that animals not only love, but have the desire to be loved. Animals manifestly feel emulation. They love approbation or praise; and a dog carrying a basket for his master exhibits in a high degree self-complacency or pride. There can, I think, be no doubt that a dog feels shame, as distinct from fear, and something very like modesty when begging too often for food. A great dog scorns the snarling of a little dog, and this may be called magnanimity. Several observers have stated that monkeys certainly dislike being laughed at; and they sometimes invent imaginary offences. In the Zoological Gardens I saw a baboon who always got into a furious rage when his keeper took out a letter or book and read it aloud to him; and his rage was so violent that, as I witnessed on one occasion, he bit his own leg till the blood flowed.
We will now turn to the more intellectual emotions and faculties, which are very important, as forming the basis for the development of the higher mental powers. Animals manifestly enjoy excitement and suffer from ennui, as may be seen with dogs, and, according to Rengger, with monkeys. All animals feel Wonder, and many exhibit Curiosity. They sometimes suffer from this latter quality, as when the hunter plays antics and thus attracts them; I have witnessed this with deer, and so it is with the wary chamois, and with some kinds of wild-ducks. Brehm gives a curious account of the instinctive dread which his monkeys exhibited towards snakes; but their curiosity was so great that they could not desist from occasionally satiating their horror in a most human fashion, by lifting up the lid of the box in which the snakes were kept. I was so much surprised at his account, that I took a stuffed and
coiled-up snake into the monkey-house at the Zoological Gardens, and the excitement thus caused was one of the most curious spectacles which I ever beheld. Three species of Cercopithecus were the most alarmed; they dashed about their cages and uttered sharp signal-cries of danger, which were understood by the other monkeys. A few young monkeys and one old Anubis baboon alone took no notice of the snake. I then placed the stuffed specimen on the ground in one of the larger compartments. After a time all the monkeys collected round it in a large circle, and staring intently, presented a most ludicrous appearance. They became extremely nervous; so that when a wooden ball, with which they were familiar as a plaything, was accidently moved in the straw, under which it was partly hidden, they all instantly started away. These monkeys behaved very differently when a dead fish, a mouse, and some other new objects were placed in their cages; for though at first frightened, they soon approached, handled and examined them. I then placed a live snake in a paper bag, with the mouth loosely closed, in one of the larger compartments. One of the monkeys immediately approached, cautiously opened the bag a little, peeped in, and instantly dashed away. Then I witnessed what Brehm has described, for monkey after monkey, with head raised high and turned on one side, could not resist taking momentary peeps into the upright bag, at the dreadful object lying quiet at the bottom. It would almost appear as if monkeys had some notion of zoological affinities, for those kept by Brehm exhibited a strange, though mistaken, instinctive dread of innocent lizards and frogs. An orang, also, has been known to be much alarmed at the first sight of a turtle.9
9 W. C. L. Martin, 'Nat. Hist. of Mammalia,' 1841, p. 405.
The principle of Imitation is strong in man, and especially in man in a barbarous state. Desor10 has remarked that no animal voluntarily imitates an action performed by man, until in the ascending scale we come to monkeys, which are well-known to be ridiculous mockers. Animals, however, sometimes imitate each others' actions: thus two species of wolves, which had been reared by dogs, learned to bark, as does sometimes the jackal,11 but whether this can be called voluntary imitation is another question. From one account which I have read, there is reason to believe that puppies nursed by cats sometimes learn to lick their feet and thus to clean their faces: it is at least certain, as I hear from a perfectly trustworthy friend, that some dogs behave in this manner. Birds imitate the songs of their parents, and sometimes those of other birds; and parrots are notorious imitators of any sound which they often hear.
Hardly any faculty is more important for the intellectual progress of man than the power of Attention. Animals clearly manifest this power, as when a cat watches by a hole and prepares to spring on its prey. Wild animals sometimes become so absorbed when thus engaged, that they may be easily approached. Mr. Bartlett has given me a curious proof how variable this faculty is in monkeys. A man who trains monkeys to act used to purchase common kinds from the Zoological Society at the price of five pounds for each; but he offered to give double the price, if he might keep three or four of them for a few days, in order to select one. When asked how he could possibly so soon learn whether
10 Quoted by Vogt, 'Mémoire sur les Microcéphales,' 1867, p. 168.
11 'The Variation of Animals and Plants under Domestication,' vol. i. p. 27.
a particular monkey would turn out a good actor, he answered that it all depended on their power of attention. If when he was talking and explaining anything to a monkey, its attention was easily distracted, as by a fly on the wall or other trifling object, the case was hopeless. If he tried by punishment to make an inattentive monkey act, it turned sulky. On the other hand, a monkey which carefully attended to him could always be trained.
It is almost superfluous to state that animals have excellent Memories for persons and places. A baboon at the Cape of Good Hope, as I have been informed by Sir Andrew Smith, recognised him with joy after an absence of nine months. I had a dog who was savage and averse to all strangers, and I purposely tried his memory after an absence of five years and two days. I went near the stable where he lived, and shouted to him in my old manner; he showed no joy, but instantly followed me out walking and obeyed me, exactly as if I had parted with him only half-an-hour before. A train of old associations, dormant during five years, had thus been instantaneously awakened in his mind. Even ants, as P. Huber12 has clearly shewn, recognised their fellow-ants belonging to the same community after a separation of four months. Animals can certainly by some means judge of the intervals of time between recurrent events.
The Imagination is one of the highest prerogatives of man. By this faculty he unites, independently of the will, former images and ideas, and thus creates brilliant and novel results. A poet, as Jean Paul Richter remarks,13 "who must reflect whether he shall make a
12 'Les Mœurs des Fourmis,' 1810, p. 150.
13 Quoted in Dr. Maudsley's 'Physiology and Pathology of Mind,' 1868, pp. 19, 220.
character say yes or no—to the devil with him; he is only a stupid corpse." Dreaming gives us the best notion of this power; as Jean Paul again says, "The dream is an involuntary art of poetry." The value of the products of our imagination depends of course on the number, accuracy, and clearness of our impressions; on our judgment and taste in selecting or rejecting the involuntary combinations, and to a certain extent on our power of voluntarily combining them. As dogs, cats, horses, and probably all the higher animals, even birds, as is stated on good authority,14 have vivid dreams, and this is shewn by their movements and voice, we must admit that they possess some power of imagination.
Of all the faculties of the human mind, it will, I presume, be admitted that Reason stands at the summit. Few persons any longer dispute that animals possess some power of reasoning. Animals may constantly be seen to pause, deliberate, and resolve. It is a significant fact, that the more the habits of any particular animal are studied by a naturalist, the more he attributes to reason and the less to unlearnt instincts.15 In future chapters we shall see that some animals extremely low in the scale apparently display a certain amount of reason. No doubt it is often difficult to distinguish between the power of reason and that of instinct. Thus Dr. Hayes, in his work on 'The Open Polar Sea,' repeatedly remarks that his dogs, instead of continuing to draw the sledges in a compact body, diverged and separated when they came to thin ice, so that their weight might be more evenly distributed. This was often the first warn-
14 Dr. Jerdon, 'Birds of India,' vol. i. 1862, p. xxi.
15 Mr. L. H. Morgan's work on 'The American Beaver,' 1868, offers a good illustration of this remark. I cannot, however, avoid thinking that he goes too far in underrating the power of Instinct.
ing and notice which the travellers received that the ice was becoming thin and dangerous. Now, did the dogs act thus from the experience of each individual, or from the example of the older and wiser dogs, or from an inherited habit, that is from an instinct? This instinct might possibly have arisen since the time, long ago, when dogs were first employed by the natives in drawing their sledges; or the Arctic wolves, the parent-stock of the Esquimaux dog, may have acquired this instinct, impelling them not to attack their prey in a close pack when on thin ice. Questions of this kind are most difficult to answer.
So many facts have been recorded in various works shewing that animals possess some degree of reason, that I will here give only two or three instances, authenticated by Rengger, and relating to American monkeys, which stand low in their order. He states that when he first gave eggs to his monkeys, they smashed them and thus lost much of their contents; afterwards they gently hit one end against some hard body, and picked off the bits of shell with their fingers. After cutting themselves only once with any sharp tool, they would not touch it again, or would handle it with the greatest care. Lumps of sugar were often given them wrapped up in paper; and Rengger sometimes put a live wasp in the paper, so that in hastily unfolding it they got stung; after this had once happened, they always first held the packet to their ears to detect any movement within. Any one who is not convinced by such facts as these, and by what he may observe with his own dogs, that animals can reason, would not be convinced by anything that I could add. Nevertheless I will give one case with respect to dogs, as it rests on two distinct observers, and can hardly depend on the modification of any instinct.
Mr. Colquhoun16 winged two wild-ducks, which fell on the opposite side of a stream; his retriever tried to bring over both at once, but could not succeed; she then, though never before known to ruffle a feather, deliberately killed one, brought over the other, and returned for the dead bird. Col. Hutchinson relates that two partridges were shot at once, one being killed, the other wounded; the latter ran away, and was caught by the retriever, who on her return came across the dead bird; "she stopped, evidently greatly puzzled, and after one or two trials, finding she could not take it up without permitting the escape of the winged bird, she considered a moment, then deliberately murdered it by giving it a severe crunch, and afterwards brought away both together. This was the only known instance of her ever having wilfully injured any game." Here we have reason, though not quite perfect, for the retriever might have brought the wounded bird first and then returned for the dead one, as in the case of the two wild-ducks.
The muleteers in S. America say, "I will not give you the mule whose step is easiest, but la mas racional,—the one that reasons best;" and Humboldt17 adds, "this popular expression, dictated by long experience, combats the system of animated machines, better perhaps than all the arguments of speculative philosophy."
It has, I think, now been shewn that man and the higher animals, especially the Primates, have some few instincts in common. All have the same senses, intuitions and sensations—similar passions, affections, and emotions, even the more complex ones; they feel
16 'The Moor and the Loch,' p. 45. Col. Hutchinson on 'Dog Breaking,' 1850, p. 46.
17 'Personal Narrative,' Eng. translat., vol. iii. p. 106.
wonder and curiosity; they possess the same faculties of imitation, attention, memory, imagination, and reason, though in very different degrees. Nevertheless many authors have insisted that man is separated through his mental faculties by an impassable barrier from all the lower animals. I formerly made a collection of above a score of such aphorisms, but they are not worth giving, as their wide difference and number prove the difficulty, if not the impossibility, of the attempt. It has been asserted that man alone is capable of progressive improvement; that he alone makes use of tools or fire, domesticates other animals, possesses property, or employs language; that no other animal is self-conscious, comprehends itself, has the power of abstraction, or possesses general ideas; that man alone has a sense of beauty, is liable to caprice, has the feeling of gratitude, mystery, &c.; believes in God, or is endowed with a conscience. I will hazard a few remarks on the more important and interesting of these points.
Archbishop Sumner formerly maintained18 that man alone is capable of progressive improvement. With animals, looking first to the individual, every one who has had any experience in setting traps knows that young animals can be caught much more easily than old ones; and they can be much more easily approached by an enemy. Even with respect to old animals, it is impossible to catch many in the same place and in the same kind of trap, or to destroy them by the same kind of poison; yet it is improbable that all should have partaken of the poison, and impossible that all should have been caught in the trap. They must learn caution by seeing their brethren caught or poisoned. In North America, where the fur-bearing animals have long been
18 Quoted by Sir C. Lyell, 'Antiquity of Man,' p. 497.
VOL. I. E
pursued, they exhibit, according to the unanimous testimony of all observers, an almost incredible amount of sagacity, caution, and cunning; but trapping has been there so long carried on that inheritance may have come into play.
If we look to successive generations, or to the race, there is no doubt that birds and other animals gradually both acquire and lose caution in relation to man or other enemies;19 and this caution is certainly in chief part an inherited habit or instinct, but in part the result of individual experience. A good observer, Leroy,20 states that in districts where foxes are much hunted, the young when they first leave their burrows are incontestably much more wary than the old ones in districts where they are not much disturbed.
Our domestic dogs are descended from wolves and jackals,21 and though they may not have gained in cunning, and may have lost in waryness and suspicion, yet they have progressed in certain moral qualities, such as in affection, trust-worthiness, temper, and probably in general intelligence. The common rat has conquered and beaten several other species throughout Europe, in parts of North America, New Zealand, and recently in Formosa, as well as on the mainland of China. Mr. Swinhoe,22 who describes these latter cases, attributes the victory of the common rat over the large Mus coninga to its superior cunning; and this latter quality may be attributed to the habitual exercise of all its faculties in avoiding extirpation by man, as well
19 'Journal of Researches during the Voyage of the "Beagle,"' 1845, p. 398. 'Origin of Species,' 5th edit. p. 260.
20 'Lettres Phil. sur l'Intelligence des Animaux,' nouvelle edit. 1802, p. 86.
21 See the evidence on this head in chap. i. vol. i. 'On the Variation of Animals and Plants under Domestication.'
22 'Proc. Zoolog. Soc.' 1864, p. 186.
as to nearly all the less cunning or weak-minded rats having been successively destroyed by him. To maintain, independently of any direct evidence, that no animal during the course of ages has progressed in intellect or other mental faculties, is to beg the question of the evolution of species. Hereafter we shall see that, according to Lartet, existing mammals belonging to several orders have larger brains than their ancient tertiary prototypes.
It has often been said that no animal uses any tool; but the chimpanzee in a state of nature cracks a native fruit, somewhat like a walnut, with a stone.23 Rengger24 easily taught an American monkey thus to break open hard palm-nuts, and afterwards of its own accord it used stones to open other kinds of nuts, as well as boxes. It thus also removed the soft rind of fruit that had a disagreeable flavour. Another monkey was taught to open the lid of a large box with a stick, and afterwards it used the stick as a lever to move heavy bodies; and I have myself seen a young orang put a stick into a crevice, slip his hand to the other end, and use it in the proper manner as a lever. In the cases just mentioned stones and sticks were employed as implements; but they are likewise used as weapons. Brehm25 states, on the authority of the well-known traveller Schimper, that in Abyssinia when the baboons belonging to one species (C. gelada