MAN AND THE APES
Objections to Zoölogical Discussion of Man's Place—Owen's Prudence—Huxley's Determination to Speak out—Account of his Treatment of Man's Place in Nature—Additions Made by More Recent Work.
Even before the publication of The Origin of Species there was a considerable nervousness in the minds of the more orthodox as to discussions on the position of the human species in zoölogical classification. Men of the broadest minds, such as Lyell, who himself had suffered considerably from outside interference with the scientific right to publish scientific conclusions, was strongly opposed to anything that seemed to tend towards breaking down the barrier between man and the lower creatures. Sir William Lawrence, a very distinguished and able man, had been criticised with the greatest severity, and had been nearly ostracised, for a very mild little book On Man; and Huxley tells us that the electors to the Chair of a Scotch University had refused to invite a distinguished man, to whom the post would have been acceptable, because he had advocated the view that there were several species of man. The court political leaders, and society generally, resented strongly anything that seemed at all likely to disturb the somewhat narrow orthodoxy prevalent in those times; and, as there were comparatively few posts open to scientific men, and comparatively greater chances of posts being made for men of talent and ability who adhered to the respectable traditions, those who tampered with so serious a question as the place of man were likely to burn their fingers severely. However, the difficulties of discussing these problems were much greater immediately after 1859. One of the most surprising things in the history of this century is the sudden intensity of the opposition of the public, particularly the respectable and religious public, to zoölogical writing upon man, immediately after the publication of the Origin. Before that time anatomists did not necessarily hesitate to point out the close resemblance between the anatomy of man and that of the higher apes, and the difficulties anatomists had in making anatomical distinction of value between them. Thus Professor Owen, who, as a writer, was rather unusually nervous about expressing facts to which any objection might be raised by those outside the strictly scientific world, had written the following paragraph in the course of an essay on the characters of the class Mammalia, published, in 1857, in the Journal of the Proceedings of the Linnæan Society:
"Not being able to appreciate or conceive of the distinction between the psychical phenomena of a chimpanzee and of a Boschisman or of an Aztec, with arrested brain-growth, as being of a nature so essential as to preclude a comparison between them, or as being other than a difference of degree, I cannot shut my eyes to the significance of that all-pervading similitude of structure—every tooth, every bone, strictly homologous—which makes the determination of the difference between Homo and Pithecus the anatomist's difficulty."
It is true, he went on to explain his belief in the existence of certain characters in the brain which seemed to him to justify the separation of man in a different group from that in which the apes were placed; but it is certain that he regretted having said anything which seemed to support the Darwinian view; and, two years later, when the opposition to Darwin was in its acutest stage, Owen withdrew his words. His "Reade Lecture," delivered in the University of Cambridge, was in all respects a reprint of the essay from which we have just quoted, but the apparently dangerous words were omitted. More than that, the points insisted on in the essay as being sufficient for the purpose of separating man in zoölogical classification were elevated into a reason against descent. Although Huxley, in several addresses and publications, disproved the existence of the alleged differences, and although Sir William Flower gave an actual demonstration shewing the essential identity of the brain of man and of the apes in the matter in question, Owen never admitted his error.
CHARLES DARWIN
From the painting by Hon. John Collier in the National Portrait Gallery
It is not surprising that, if an anatomist so distinguished and acute as was Owen allowed his judgment to be completely overborne by the storm of prejudice against Darwinism, those who were not anatomists should have held up to ridicule all idea of comparison between man and the apes. In The Origin of Species itself, no elaborate attempt had been made to set forth the anatomical arguments in favour of or against a community of descent for man and the apes. But it was made sufficiently plain, and the public laid hold of the point eagerly, that the doctrine of descent was not meant to exclude man from the field of its operation. Huxley, in the course of his ordinary work as Professor of Biology, had, among many other subjects, naturally turned his attention to the anatomy and classification of the higher animals. When Owen's essay appeared, he found that he was unable to agree with many of the conclusions contained in it, and had set about a renewed investigation of the matter. Thus it happened that, when the question became prominent, in 1860, Huxley was ready with material contributions to it. He believed, moreover, that, as Darwin was not specially acquainted with the anatomy and development of vertebrates, there was an opportunity for doing a real service to the cause of evolution. Accordingly, in 1860, he took for the subject of a series of lectures to workingmen the "Relation of Man to the Lower Animals," and, in 1862, expanded the lectures into a volume called Man's Place in Nature. When it was ready, he was prepared to say with a good conscience that his conclusions "had not been formed hastily or enunciated crudely."
"I thought," he wrote in the preface to the 1894 edition, "I had earned the right to publish them, and even fancied I might be thanked, rather than reproved, for so doing. However, in my anxiety to promulgate nothing erroneous, I asked a highly competent anatomist and very good friend of mine to look through my proofs, and, if he could, point out any errors of fact. I was well pleased when he returned them without any criticism on that score; but my satisfaction was speedily dashed by the very earnest warning, as to the consequences of publication, which my friend's interest in my welfare led him to give; but, as I have confessed elsewhere, when I was a young man there was just a little—a mere soupçon—in my composition of that tenacity of purpose which has another name, and I felt sure that all the evil things prophesied would not be so painful to me as the giving up of that which I had resolved to do, upon grounds which I conceived to be right. So the book came out, and I must do my friend the justice to say that his forecast was completely justified. The Boreas of criticism blew his hardest blasts of misrepresentation and ridicule for some years; and I was even as one of the wicked. Indeed, it surprises me, at times, to think how anyone who had sunk so low could have emerged into, at any rate, relative respectability."
Further, in the same preface, Huxley strongly advises others to imitate his action in this matter. There are now, and no doubt there always will be, truths "plainly obvious and generally denied." Whoever attacks the current ideas is certain, unless human nature changes greatly, to encounter a bitter opposition, and there will always be those among his friends who recommend him to temper truth by prudence. Huxley's advice is different:
"If there is a young man of the present generation who has taken as much trouble as I did to assure himself that they are truths, let him come out with them, without troubling his head about the barking of the dogs of St. Ernulphus. Veritas prævalebit—some day; and, even if she does not prevail in his time, he himself will be all the better and wiser for having tried to help her. And let him recollect that such great reward is full payment for all his labour and pains."
Although they were written so long ago, the lectures on "Man's Place in Nature" are still the best existing treatise on the subject, and we shall give an outline of them, mentioning the chief points in which further work has been done. Information concerning the man-like apes was scattered in very different places, in the grave records of scientific societies, in the letters of travellers and missionaries, in the reports of the zoölogical societies which had been in possession of living specimens. The facts had to be sifted out from a great mass of verbiage and unfounded statement. With a characteristic desire for historical accuracy, more usual in a man of letters than in an anatomist, Huxley began with a study of classical and mediæval legends of the existence of pigmies and man-like creatures; but, while recognising that legends of satyrs and fauns were presages of the discovery of man-like apes, he was unable to find any actual record earlier than that contained in Pigafetta's Description of the Kingdom of Congo, drawn up from the notes of a Portuguese sailor and published in 1598. The descriptions and figures in this work apparently referred to chimpanzees. From this date onwards he traces the literature of the animals in question, and then proceeds to give an account of them.
There are four distinct kinds of man-like apes: in Eastern Asia the Orangs and the Gibbons (although some later writers differ from Huxley in removing the Gibbons from the group of anthropoids); in Western Africa, the Chimpanzees and the Gorillas. All these have certain characters in common. They are inhabitants of the old world; they all have the same number of teeth as man, possessing four incisors, two canines, four premolars, and six true molars in each jaw, in the adult condition, while the milk dentition, as in man, consists of twenty teeth,—four incisors, two canines, and four molars in each jaw. Since Huxley wrote, a large bulk of additional work upon teeth has been published, and we now know that man and the anthropoid apes display the same kind of degenerative specialisation in their jaws. Simpler and older forms of mammals had a much larger number of teeth, and these differed among themselves more than the teeth of the higher forms. In the Anthropoids and Man, the jaws are proportionately shorter and less heavy than in simpler forms, and, in correspondence with this, the number of the teeth has become reduced, while the teeth themselves tend to form a more even row. The canine or eye-teeth are relatively smaller in the gorilla than in primitive mammals; they are still smaller in the lower races of man; while in ordinary civilised man they do not project above the others. The shortening of the jaw is still proceeding, and, although in lower races of man the last molar or wisdom tooth is almost as large as the molars in front of it, in the higher races the wisdom tooth is much smaller and frequently does not develop at all, or begins to decay very soon after its appearance. If the process of extinction of lower races were to proceed much further, so that civilised white races became the only human inhabitants of the earth, then the gap between the Anthropoids and Man would be wider than it now is; man would be characterised by the presence of one tooth less than the anthropoids, just as the anthropoids and some lower monkeys are characterised by having one tooth less than monkeys still lower.
In all, the nostrils have a narrow partition and look downwards as in man. The arms are always longer than the legs, the difference being greatest in the orang and least in the chimpanzee. We know now that in the lower races of man, the arms are proportionately longer than in higher races, and it has recently been shewn that, although there is a general proportion between the length of the long bones and the height of the whole body in man, so that the height may be calculated with an average error from these bones, yet the probable error is greater when the calculation is made from the arms than when it is made from the legs. In fact, the length of arm as compared to the length of leg and to whole height is a more variable feature in man than the length of leg.
In all the anthropoids, the forelimbs end in hands with longer or shorter thumbs, and the great toe, always smaller than in man, is far more movable and can be opposed like a thumb to the other toes. Since Huxley wrote, a considerable amount of evidence has been collected shewing that partial opposability of the toe in man is not uncommon, and that there is evidence as to a tendency to increase of length of the great toe within historical times. None of the great apes have tails, and none of them have the cheek pouches common among lower monkeys.
Huxley then gives an account of the natural history of these animals, an account which still remains the best in literature. He sums up the habits of the Asiatic forms as follows:
- They may readily move along the ground in the erect, or semi-erect position, and without direct support from the arms.
- They may possess an extremely loud voice, so loud as to be readily heard one or two miles.
- They may be capable of great viciousness and violence when irritated; and this is especially true of adult males.
- They may build a nest to sleep in.
He finds the same general characters in the case of the gorilla and chimpanzee, but in their case there was not quite so reliable evidence upon which to go.
Although, since Huxley wrote, there has been much greater opportunity of studying anthropoid apes, both in confinement and in their native haunts, there is not much to add to his account. Some little time ago, the world was interested by the assertion of a clever American that he had discovered a kind of language used by the higher apes, and that he was able to communicate with them. Mr. Garnier, the person in question, declared his intention of going out to tropical Africa and establishing himself in a strong cage in the forests inhabited by gorillas and chimpanzees, in the hope that, impelled by curiosity, they would look upon him as we look on monkeys in a zoölogical garden, and that he would thus be able to make his knowledge and records of monkey language more perfect. As a matter of fact he went to Africa, and on his return published a volume which aroused the indignation of naturalists. There was internal evidence that he had gone no further than the garden of a coast station, and his pretended account of the habits of monkeys as they lived in their native haunts contained nothing that was not already known. There is no doubt but that the anthropoid apes, like many other animals, use modulations of their voice to express emotional states; that, in fact, they have love-cries and cries of warning, of alarm, and of pleasure; but there is not the smallest evidence to suppose that in the case of the anthropoids these cries approach more nearly to speech than the cries of any other of the higher mammals.
Since Huxley's volume was published, a large amount of information has been published by Darwin, Romanes, and others upon the mental capacities of anthropoids kept in confinement, and the result of this has been to prove that the anthropoids, in especial the chimpanzees, possess mental powers more akin to those of man than are to be found in the most intelligent of the quadrupeds. We may cite some instances of these higher powers. Vosmaern had a tame female orang-outang that was able to untie the most intricate knot with fingers or teeth, and took such pleasure in doing it that she regularly untied the shoes of those who came near her. The female chimpanzee called Sally, that lived for many years in the Zoölogical Society's Gardens in London, was taught by its keeper and by Romanes an interesting variety of "tricks" involving at least the rudiments of what may be called human intelligence. Among other feats, it would pick up from the floor and present to the keeper or to a visitor, a stated number of straws up to five. Many monkeys seem nearly purely destructive in their dealings with objects within their reach; but Leutemann tells of an orang-outang which "tried to put to its proper use whatever was given to him. To my great surprise he attempted to put on a pair of gloves. He supported himself on a light walking cane and, when it bent under him, made ridiculous motions to right it again." Brehm tells of a chimpanzee:
"After eating, he at once begins to clean up. He holds a stick of wood in front of him, or puts his hands in his master's slippers, and slides about the room, then takes a cloth and scrubs the floor. Scouring, sweeping, and dusting are his favourite occupations; and, when he once gets hold of the cloth, he never wants to give it up."
Falkenstein has given a detailed description of a gorilla which was remarkable for his delicacy in eating.
"He would take a cup or glass with the greatest care, using both hands to carry it to his mouth, and setting it down so carefully that I do not remember having lost a single piece of crockery through him, though we had never tried to teach him the use of such vessels, wishing to bring him to Europe as nearly in his natural condition as possible."
These and a multitude of similar observations which have been made since Huxley wrote are typical of the increase of our knowledge on the habits and capacities of the anthropoid apes. They all serve to show that in them the instinct for experimental investigation of everything with which they are surrounded, and their imitative faculties are peculiarly great. The importance of this, from the point of view of Huxley's argument, is great. The difference between the instincts of the lower animals and the intelligence of man is that instincts are to a large extent fixed and mechanical. The proper performance of an instinct demands the presence of exactly the right external conditions for its accomplishment. In the absence of these conditions, the call to perform the instinctive action is equally great, and results in useless performances. In many of the higher animals these elaborate instincts are more general in their character, and are supplemented by a considerable but varying aptitude for modification of instinctive action to suit varieties of surrounding circumstances. As this intelligence becomes more and more developed, the blind, mechanical instinct becomes weaker. A large number of instances might be given of such instincts modified by dawning intelligence. The chief factors in producing the change are, as has been shewn by Professor Groos, the possession of a general instinct to imitate and to experiment, and the existence of a period of youth in which the young creature may practise these instincts, and so prepare itself for the more serious purposes of adult life. The anthropoid apes seem to possess these experimental instincts to an extent much greater than that observed in any other class of animals, and, as they have a long period of youth, they have the opportunity of putting them into practice to the fullest possible extent.
From the natural history of the anthropoid apes, Huxley passed to consideration of their relation to man, prefacing his observations with a passage defending the utility of the enquiry, a passage necessary enough in these days of prejudice, but now chiefly with historical interest:
"It will be admitted that some knowledge of man's position in the animate world is an indispensable preliminary to the proper understanding of his relations to the universe; and this again resolves itself in the long run into an enquiry into the nature and the closeness of the ties which connect him with those singular creatures whose history has been sketched in the preceding pages.
"The importance of such an enquiry is, indeed, intuitively manifest. Brought face to face with these blurred copies of himself, the least thoughtful of men is conscious of a certain shock; due perhaps not so much to disgust at the aspect of what looks like an insulting caricature, as to the awakening of a sudden and profound mistrust of time-honoured theories and strongly rooted prejudices regarding his own position in nature, and his relations to the underworld of life; while that which remains a dim suspicion for the unthinking, becomes a vast argument, fraught with the deepest consequences, for all who are acquainted with the recent progress of the anatomical and physiological sciences."
Huxley then proceeded to elaborate the argument from development for the essential identity of man and the apes. This argument has now become more or less familiar to us all, as it has gained additional support from recent extension of embryological knowledge, and as it has been used in every work on evolution since Huxley first laid stress on it. The adult forms of animals are much more complex than their embryonic stages, and the series of changes passed through in attaining the adult condition make up the embryological history of the animal. Huxley took the embryology of the dog as an example of the process in the higher animals generally, and as it had been worked out in detail by a set of investigators. The dog, like all vertebrate animals, begins its existence as an egg; and this body is just as much an egg as that of a fowl, although, in the case of the dog, there is not the accumulation of nutritive material which bloats the egg of the hen into its enormous size. Since Huxley wrote, it has been shewn clearly that among the mammalian animals there has been a gradual reduction in the size of the egg. The ancestors of the mammals laid large eggs, like those of birds or reptiles; and there still exist two strange mammalian creatures, the Ornithorhynchus and Echidna of Australia, which lay large, reptilian-like eggs. The ancestors of most living mammalia acquired the habit of retaining the eggs within the body until they were hatched; and, as a result of this, certain structures which grow out from the embryo while it is still within the egg and become applied to the inner wall of the porous shell for the purpose of obtaining air, got their supply of oxygen, not from the outer air, but from the blood-vessels of the maternal tissues. When this connection (called the placenta) between embryo and mother through the egg-shell became more perfect, not only oxygen but food-material was obtained from the blood-vessels of the mother; and, in consequence, it became unnecessary for the eggs to be provided with a large supply of food-yolk. Among existing marsupial animals, which, on the whole, represent a lower type of mammalian structure than ordinary mammals, there is more food-yolk than in ordinary mammals, and less food-yolk than in the two egg-laying mammals. In the ordinary mammals, such as the rabbit, dog, monkey, and man, there is practically no yolk whatever deposited in the egg; the egg is of minute size, and the embryo obtains most of its food from the maternal blood.
The small egg of the mammal divides into a number of cells, which form a hollow sphere; on the upper surface of this the development of organs begins with the formation of a depression which indicates the future middle line of the animal, and is, in fact, the beginning of the nervous system. Under this is formed a straight rod of gelatinous material, the foundation of the vertebral column, and the body of the embryo is gradually pinched off from the surface of the hollow sphere. After tracing the details of this process, Huxley proceeded as follows:
"The history of the development of any other vertebrate animal, lizard, snake, frog or fish, tells the same story. There is always, to begin with, an egg, having the same essential structure as that of the dog; the yolk of that egg always undergoes division, or segmentation, as it is often called; the ultimate products of that segmentation constitute the building materials for the body of the young animal; and this is built up round a primitive groove, in the floor of which a notochord is developed. Furthermore, there is a period in which the young of all these animals resemble one another, not merely in outward form, but in all essentials of structure, so closely, that the differences between them are inconsiderable, while in their subsequent course they diverge more and more widely from one another. And it is a general law, that, the more closely any animals resemble one another in adult structure, the longer and the more intimately do their embryos resemble one another; so that, for example, the embryos of a snake and of a lizard remain like one another longer than do those of a snake and of a bird; and the embryos of a dog and of a cat remain like one another for a far longer period than do those of a dog and a bird; or of a dog and an opossum; or even than those of a dog and a monkey."
This general rule, that the longer the paths of embryonic development of two animals keep identical the more nearly the two animals are related, when Huxley wrote, was founded on a much smaller number of facts than now are known. Since 1860 an enormous bulk of embryological investigation has been published, and the total result has been to confirm Huxley's position in the fullest possible way. A certain number of exceptions have been found, but these exceptions are so obviously special adaptations to special circumstances that their existence only makes the general truth of the proposition more clear. The most common kind of exception occurs when two closely related animals live under very different conditions. For instance, many marine animals have close allies that in comparatively recent times have taken to live in fresh water. The conditions of life in fresh water are very different, especially for delicate creatures susceptible to rapid changes of temperature, or unable to withstand strong currents. Thus most of the allies of the fresh-water crayfish, which live in the sea, lay eggs from which there are soon hatched minute, almost transparent larvæ, exceedingly unlike the adult. In the comparatively equable temperature of sea-water, and in the usual absence of strong currents, these small larvæ, as Huxley shewed later in his volume on the Crayfish, live a free life, obtaining their own food, and by a series of slow transformations gradually acquire the adult form. In fresh water, however, the delicate larvæ would be unable to live, and the mode of development is different. The series of slow transformations is condensed, and takes place almost entirely inside the egg-shell; so that, when hatching occurs, the young crayfish is exceedingly like the adult. Apart from such special cases, it is true that the study of development affords a clear test of closeness of structural affinity.
Huxley then proceeds to discuss the development of man.
"Is he something apart? Does he originate in a totally different way from dog, bird, frog, and fish, thus justifying those who assert him to have no place in nature, and no real affinity with the lower world of animal life? Or does he originate in a similar germ, pass through the same slow and gradually progressive modifications, depend on the same contrivances for protection and nutrition, and finally enter the world by the help of the same mechanism? The reply is not doubtful for a moment, and has not been doubtful any time these thirty years. Without question, the mode of origin, and the early stages of the development of man are identical with those of animals immediately below him in the scale; without doubt, in these respects, he is far nearer the apes than the apes are to the dog."
Then, on lines with which, by continuous repetition and expansion by authors subsequent to him, we have now become familiar, Huxley compared, stage by stage, the development of man with that of other animals, and shewed, first, its essential similarity, and then that in every case where it departed from the development of the dog it resembled more closely the development of the ape. He went on to review the anatomy of man:
"Thus, identical in the physical processes by which he originates,—identical, in the early stages of his formation—identical in the mode of his nutrition before and after birth, with the animals which lie immediately below him in the scale,—Man, if his adult and perfect structure be compared with theirs exhibits, as might be expected, a marvellous likeness of organisation. He resembles them as they resemble one another—he differs from, them as they differ from one another. And, though these differences cannot be weighed and measured, their value may be readily estimated; the scale or standard of judgment, touching that value, being afforded and expressed by the system of classification of animals now current among zoölogists."
Having explained the general system of zoölogical classification, he tried to dispel preliminary prejudice by inducing his readers or bearers to take an outside view of themselves.
"Let us endeavour for a moment to disconnect our thinking selves from the mask of humanity; let us imagine ourselves scientific Saturnians, if you will, fairly acquainted with such animals as now inhabit the earth, and employed in discussing the relations they bear to a new and singular 'erect and featherless biped,' which some enterprising traveller, overcoming the difficulties of space and gravitation, has brought from that distant planet for our inspection, well preserved, may be, in a cask of rum. We should all, at once, agree upon placing him among the mammalian vertebrates; and his lower jaw, his molars, and his brain, would leave no room for doubting the systematic position of the new genus among those mammals whose young are nourished during gestation by means of a placenta, or what are called the placental mammals.
"Further, the most superficial study would at once convince us that, among the orders of placental mammals, neither the whales, nor the hoofed creatures, nor the sloths and ant-eaters, nor the carnivorous cats, dogs, and bears, still less the rodent rats and rabbits, or the insectivorous moles and hedgehogs, or the bats, could claim our Homo as one of themselves.
"There would remain, then, but one order for comparison, that of the apes (using that word in its broadest sense), and the question for discussion would narrow itself to this—Is Man so different from any of these apes that he must form an order by himself? Or does he differ less from them than they differ from one another,—and hence must take his place in the same order with them?
"Being happily free from all real or imaginary personal interest in the results of the enquiry thus set afoot, we should proceed to weigh the arguments on one side and on the other, with as much judicial calmness as if the question related to a new opossum. We should endeavour to ascertain, without seeking either to magnify or diminish them, all the characters by which our new mammal differed from the apes; and if we found that these were of less structural value than those which distinguish certain members of the ape order from others universally admitted to be of the same order, we should undoubtedly place the newly discovered tellurian genus with them."
In pursuit of this method, and taking the gorilla as the type for immediate comparison with man, he passed in review the various anatomical structures, shewing that in every case man did not differ more from the gorilla than that differed from other anthropoids. We shall take a few examples of his method and results, reminding our readers, however, that Huxley carried his comparisons into every important part of the anatomical structure.
There is no part of the skeleton so characteristically human as the bones which form the pelvis, or bony girdle of the hips. The expanded haunch-bones form a basin-like structure which affords support to the soft internal viscera during the habitually upright position, and gives space for the attachment of the very large muscles which help man to assume and support that attitude. In the gorilla this region differs considerably from that in man. The haunch-bones are narrower and much shallower, so that they do not form so convenient a supporting basin; they have much less surface for the attachment of muscles. The gibbon, however, differs more vastly from the gorilla than that differs from man. The haunch-bones are flat and narrow, and totally devoid of any basin-like formation; the passage through the pelvis is long and narrow, and the ischia have outwardly curved prominences, which, in life, are coated by callosities on which the animal habitually rests, and which are coarse, corn-like patches of skin wholly absent in the gorilla, in the chimpanzee, in the orang, and in man.
In the characters of the hands, the feet, and the brain, certain real or supposed structural distinctions between man and the apes had been relied upon.
"Man has been defined as the only animal possessed of two hands terminating his fore-limbs, and of two feet terminating his hind-limbs, while it has been said that all the apes possess four hands; and he has been affirmed to differ fundamentally from all the apes in the characters of his brain, which alone, it has been strangely asserted and reasserted, exhibits the structures known to anatomists as the posterior lobe, the posterior cornu of the lateral ventricle, and the hippocampus minor.
"That the former proposition should have gained general acceptance is not surprising—indeed, at first sight, appearances are much in its favour; but, as for the second, one can only admire the surpassing courage of its enunciator, seeing that it is an innovation which is not only opposed to generally and justly accepted doctrines, but which is directly negatived by the testimony of all original enquirers who have specially investigated the matter; and that it has neither been, nor can be, supported by a single anatomical preparation. It would, in fact, be unworthy of serious refutation except for the general and natural belief that deliberate and reiterated assertions must have some foundation."
The last remarks referred, of course, to the statements of Owen, which had made a great impression at the time and the result of which still lingers in some of the worse-informed treatises attacking evolution. Huxley gave a lucid account of the general structure and arrangement of the brain in the vertebrate series, explaining the well-known fact that from fish up to man the general ground-plan of the brain is identical, but that there is a progressive increase in the complexity and in the size of some parts compared with others. Next, he showed that, so far from its being possible to erect any barrier in the structure of the brain between man and the apes, there exists among the mammals an almost complete series of gradations from brains a little higher than that of the rabbit to brains a little lower than that of man. He laid great stress on
"the remarkable circumstance that though, so far as our present knowledge extends, there is one structural break in the series of forms of simian brains, this hiatus does not lie between man and the man-like apes, but between the lower and the lowest simians; or, in other words, between the old-and new-world apes and monkeys, and the lemurs. Every lemur which has yet been examined, in fact, has its cerebellum partially visible from above, and its posterior lobe, with the contained posterior cornu and hippocampus minor, more or less rudimentary. Every marmoset, American monkey, old-world monkey, baboon, or man-like ape, on the contrary, has its cerebellum entirely hidden, posteriorly, by the cerebral lobes, and possesses a large posterior cornu, with a well-developed hippocampus minor." ... "So far from the posterior lobe, the posterior cornu, and the hippocampus minor being structures peculiar to, and characteristic of man, as they have over and over again been asserted to be, even after the publication of the clearest demonstration of the reverse, it is precisely these structures which are the most marked cerebral characters common to man with the apes. They are among the most distinctly simian peculiarities which the human organism exhibits." ... "Man differs from the chimpanzee or the orang, so far as cerebral structure goes, less than these do from the monkeys, and the difference between the brains of the chimpanzee and of man is almost insignificant, when compared with that between the chimpanzee brain and that of a lemur."
Although Huxley found no structural differences between the brains of man and of anthropoid apes, he was careful to lay great stress on the important difference in size and weight. A full-grown gorilla is nearly twice as heavy as a European woman, and yet the heaviest known gorilla brain probably does not exceed twenty ounces in weight, while healthy adult human brains probably never weigh less than thirty-one or thirty-two ounces. This difference is not of systematic importance; for cranial capacities shew that relatively and absolutely there is a greater difference in brain-weight between the lowest and highest human beings than there is between the highest ape and the lowest human being.
In dealing with the suggestion that man differs from the apes in being bimanous, while the apes are quadrumanous, Huxley first explained and discussed what the exact differences between hands and feet are. He shewed that in man the foot is absolutely distinguished from the hand by three structural points, although the two organs are similar in general ground-plan. These structural points are:
- The arrangement of the tarsal bones.
- The possession of a short flexor and short extensor muscle of the digits.
- The possession of a muscle named peronæus longus.
Then he described the foot of the gorilla, and shewed that although it was superficially hand-like, it possessed all the structural characters that distinguish a foot from a hand. Tracing the structure of the foot downwards through the series of anthropoids and monkeys, he established clearly that, while important differences existed in nearly every single creature, the differences between the gorilla and man were not greater than those between the gorilla and other anthropoids, and less than between the gorilla and lower monkeys.
This wonderful series of lectures ranks very high among the important works of Huxley. It is true that a considerable proportion of the work was not absolutely original, but it had all been specially verified by him. It was a task undertaken with the greatest courage, and with a care equal to the courage; and it settled conclusively for all time the impossibility of making between man and the anthropoids any anatomical barriers greater than those which exist between the different although closely related members of any of the other family groups in the animal kingdom. The advance of knowledge has only added to the details of Huxley's argument; it has not made any reconstruction of it necessary. A writer on the same subject to-day would to all certainty make use of the same general methods. The chief differences, perhaps, that would be made are two: First, greater stress would be laid on the distinction, first made by Huxley himself, between intermediate and linear types. (See p. 87). To use the popular phrase, a great deal of water has passed under the bridges since the separation of man from the ape-like progenitors common to him and to the existing anthropoids. It has already been pointed out that the gradual extinction of lower races of man is widening the apparent gap between existing man and existing apes; and evidence accumulates that many still more primitive and more ape-like races of man than the lowest existing savages have disappeared from the surface of the earth. Moreover, we know that existing anthropoids are the degenerate and scattered remnants of what was once a much more widely spread and more important group. We have some reason for believing the contrary, and no reason for believing that the surviving anthropoids represent the most man-like apes that have lived.
The second great point in which a modern writer would amend Huxley's statement of the case is more purely anatomical. One result of Darwin's work has been that anatomists attend much more closely to the slight variations of anatomical structure to be found among individuals of the same species. A comparison between an individual human body and the body of an individual gorilla is not now considered sufficient. The comparison must be made between the results of dissection of a very large number of men and of a very large number of gorillas. The anatomy of a type is not the anatomy of an individual; it is a kind of central point around which there oscillate the variations presented by the individuals belonging to the type. So far as this newer method has been applied, it has been found that the variations of the gorilla type frequently, in the case of individual organs, overlap the variations of the human type, and that the structure of man differs from the structure of any anthropoid type only in that the abstract central point of its variations is slightly different from the abstract central point of the variations presented by individual orangs, gorillas, and chimpanzees.
