The orang-outang comes next in this series. It inhabits the islands of Borneo and Sumatra, where we find two distinct species. It is a reddish colored animal standing about four feet four inches high, with rather long hair. It is bulky, slow and deliberate in action, and when it walks in a semi-erect position it rests its knuckles upon the ground, swinging its long arms as crutch-like supports. Like the gibbon, it does not walk upon all four feet in the way that the monkeys and baboons do, and we find in the still further development of the brain and the higher arch of the cranium the reasons for its semi-erectness. It cannot remain with its hands and feet upon the ground and bend back its head so as to direct its vision forward.
The chimpanzee of intertropical Africa brings us to a still less monkey-like and more manlike stage. This creature attains the height of five feet, which is more than that of some of the lower races of man. It possesses large ears and heavy overarching brows; its thumb and great toe are more like those of man, though its foot is still practically a hand. Its lower limb curves like those of the other apes, and its soles are turned toward one another; in brief, it is naturally bow-legged, a character that adapts it for a tree-climbing life. This animal also is nearly, though not quite, erect. It shows a most marked advance in the matter of the brain, for the cerebrum is richly folded or convoluted, and with this higher degree of physical complexity is correlated its superior intelligence; it is well known that chimpanzees can be taught to wear clothing and to use a cup and spoon and bowl like a human child. Indeed, in mental respects, the chimpanzee surpasses all of the other mammalia, with the sole exception of man. An eminent psychologist has stated that it is about the equal, in mental ability, of a nine months' old human infant.
The last form among the apes, the gorilla, is one that brings us to a realization of our own human physical degeneracy. The animal lives in West Equatorial Africa, and it is a veritable giant in bulk, though its height may not exceed five feet six inches. The heavy ridges over the eyes, the upturned nostrils and triangular nose, place it near to the orang-outang, but it is superior to that form in its relatively greater brain-box, and in the fact that its heavy lower jaws do not protrude so greatly. It, too, is semi-erect, so that the line of the vertebral axis makes an angle with the plane of the ground of about seventy degrees. Its anterior limbs, or arms, are again very long and bulky; and like the chimpanzee, it rests its knuckles upon the ground in walking.
It is a short step further to the human organism, whose brain has become larger and more complex, with a corresponding advance in the functional powers of reason and the like that owe their existence to the improved structural basis. After what has been said earlier regarding the relation between the erect attitude in walking and the increased size of the cranial part of the skull as compared with the face, it will not be difficult to see how inevitably the former is the result of the latter. Should we get upon the ground upon our hands and knees in the position of a tailed monkey, the eyes look straight into the ground, for the bulging cranium has pushed out over the jaws and face so that they lie under the brain-case instead of in front. A person in this position can bend back the head so as to look ahead, but the strain is too great for comfort. Rising to the knees, and lifting the hands from the ground, a feeling of ease at once succeeds that of tension. In the course of evolution accomplished primarily by the increase of the higher portions of the brain, the erect position has been assumed gradually and naturally, and to maintain it has necessitated many other changes in skeleton and muscles; for example, the pelvis has broadened to support the intestines, which bear downwards instead of upon the abdominal walls; a double curve has arisen in the axis of the vertebral column, giving an easier balance to the upper part of the body and the head. Countless structures of the human frame testify to an originally four-footed position and to a rotation of the longer axis through an angle of ninety degrees, as evolution has produced the human type.
The conclusion that the human brain has made mankind is thus established as one of fundamental importance. Proceeding further, we learn that this organ proves to be essentially the same as the brain of lower primates; it does not gain its greater size and efficiency by the origination of wholly new and unique parts, but solely by the further elaboration of the ones present in lower forms. In a word, it is only a difference in degree and not in essential kind that separates man from the apes and other primates. Human nature is animal nature, and human structure is animal structure, for nowhere can final and absolute differences be found. This does not mean that no differences appear, for it would be absurd to contend that man and the apes are identical in every respect; but it does mean that the resemblances are fundamental and comprehensive, and any details of dissimilarity are in the degree of complexity only. The supreme place in nature attained by man is therefore due to progressive evolution in the nervous system. The other systems have degenerated to a greater or less degree, but such regressive changes are more than compensated for by the superior control exerted by the improved brain. In purely physical and mechanical respects, the human body is a degenerate as compared with a gorilla; the arm of the latter is more powerful than the lower limb of the former, while the gorilla's chest is more than twice as broad as the human, and more than four times as capacious. It is not through superior physique, but by superior ability to direct the activities of his body, that man excels in the struggle for existence with the lower animals.
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Moreover, the human body is a veritable museum of rare and interesting relics of antiquity. This characterization is justified by those vestigial and rudimentary structures that represent organs of value to human relatives among the lower animals, though they play a less active part at the present time in human economy. There is scarcely a single system that does not exhibit many or fewer of these rudimentary structures, but only a few need be specified. As compared with those of the apes, the human wisdom teeth are degenerate; in the gorilla they are cut at the same time as the other molars; and in the lower human races they come through the gums in early youth, while in the more advanced Caucasic races they are cut only in later life or not at all. The reduced vermiform appendix of man, a source of much ill health, is another structure that is a counterpart of a relatively larger and useful part of the digestive tract in the lower primates and other animals. Furthermore, the human tail is a reality, not a fiction. Now and then an individual is born with a tail that may reach a length in later life of eight or ten inches; such structures are, of course, abnormal. But in every normal human being there is a series of little bones at the lower end of the vertebral column, constituting the coccyx, and this is just where the abbreviated tail of the ape and the still longer prehensile tail of the monkey arises from the body. Unless the coccyx is a tail, what can it be? And if it does not represent a reduced counterpart of the tails of other mammals, what does it represent?
Many of the vestigial structures of man appear more clearly in infancy and in embryonic development. The human embryo possesses a complete coat of hair, called the lanugo, which usually disappears before birth. This hair cannot be regarded as any less significant than the coat of hair which the infant whale possesses; it means a completely haired ancestor. The elements of this coat are arranged precisely as they are in the apes; upon the arm, for example, they point from shoulder to elbow and from wrist to elbow. Unless the anterior limb of the hairy human ancestor was held in the position of the climbing ape's, this arrangement would be disadvantageous, for the hair as a rain-shedding thatch would be effective only upon the upper arm, while the hairs upon the forearm would catch the rain. In a word, this vestigial coat indicates in the clearest possible manner that the ancestor of the human species was not only hairy, but also arboreal in its mode of life.
Every human infant is bow-legged at birth, and the natural position of its curved limbs is like that of the gorilla's, for the soles of the feet are turned toward one another. Again, the so-called great toe is at first shorter than the others, and for a time it retains the power of free movement that indicates a handlike character of the lower limb in the ancestor. Many savage human races, however, whose feet remain unshod, make use of the primitive grasping power of the foot which the higher races lose completely. An Australian and Polynesian can pick up small objects with the foot very much as we may with the hand.
Among the wonderful reminiscent characters displayed by the human infant is the firm clasping power of the hand, which it possesses for a time after birth and which enables it to hang suspended for several minutes from a stick placed in its grasp. The muscles which enable the infant to do this gradually dwindle, so that the two-year-old child can hang suspended for only a few seconds. This grasping muscle is a heritage from the ape, where there is an obvious necessity for the newborn individual to have a firm hold upon the hairy coat of its tree-climbing mother. When the newborn child hangs in this way, it bends its curved lower limbs so that the soles of the feet are turned toward one another, thus increasing its resemblance to the ape.
Let us realize that these curious relics found in so many places in the framework of man are not unique, and that they are reduced counterparts of larger and more valuable structures in the ape. Unless evolution is true, they have absolutely no sensible reasons for existence. Science prefers the evolutionary explanation of their occurrence because this explanation is more in harmony with the facts known about other organisms, and it is more reasonable than any other.
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When we dealt with the general doctrine of natural transformation, it appeared that the evidence of embryology was in many respects more cogent and conclusive than that derived from the comparative study of animal structures. In the case of man, as before, no one could demand any surer or more convincing proof that an organic mechanism with one structure can change into an organic mechanism with a different structure, than the obvious facts of development. The embryo, which is not an infant or an adult, becomes an infant which must work its way onward by the gradual accumulation of slight changes here and there and everywhere in its anatomy, until it becomes mature. Each and every one of us has actually undergone the process of organic change in becoming what we are, and we cannot deny the reality of such a process without challenging the evidence of our senses.
When the full import of this history is realized, and when we look further into the nature of these preliminary conditions through which the human organism passes in development, we are forcibly impressed by other facts than the one to which I have directed your attention, for not only do we find natural transformation, as in the other mammals, but the embryonic stages are marvelously similar to the earlier conditions in other mammals. Not very long before birth the human embryo is strikingly similar to the embryo of the ape; still earlier, it presents an appearance very like that of the embryos of other mammals lower in the scale, like the cat and the rabbit,—forms which comparative anatomy independently holds to be more remote relatives of the human species. Indeed, as we trace back the still earlier history, more and more characters are found which are the common properties of wider and wider arrays of organisms, for at one time the embryo exhibits gill-slits in the sides of its throat which in all essential respects are just like those of the embryos of birds and reptiles and amphibia, as well as of other embryo mammals and these gill-slits are furthermore like those of the fishes which use them throughout life. All the other organic systems exhibit everywhere the common characteristics in which the embryos of the so-called higher animals agree with one another and with the adult forms among lower creatures; the human embryo possesses a fishlike heart and brain and primitive backbone, fishlike muscles and alimentary tract. Can we reasonably regard these resemblances as indications of anything else but a community of ancestry of the forms that exhibit them?
Yet a still more wonderful fact is revealed by the study of the very earliest stages of individual development. The human embryo begins its very existence as a single cell,—nothing more and nothing less; in general structure the human egg, like the eggs of all other many-celled organisms, is just one of the unitary building blocks of the entire organic world. And yet the egg may ultimately become the adult man. Does this mean that man and all the other higher forms have evolved from protozoa in the course of long ages? Science asks if it can mean anything else. When the comparative anatomist bids us look upon the wide and varied series of adult animals lower than man as his relatives, because they display similar structural plans beneath their minor differences, it may be difficult at first to obey him. But in the brief time necessary for the human egg to develop into an adult, the entire range is compassed from the single cell to the highest adult we know. There are no breaks in the series of embryonic stages like those between the diverse adult animals of the comparative array. I do not think we could ask nature for more complete proof that human beings have evolved from one-cell ancestors as simple as modern protozoa beyond the obvious facts of human transformation during development. They at least are real and not the logical deductions of reason; yet their very reality and familiarity render us blind to the deeper meaning revealed to us only when science places the facts in intelligible order.
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And now, in the third place, we may look to nature for fossil evidence regarding the ancestry of our species. Much is known about the remains of many kinds of men who lived in prehistoric times, but we need consider here only one form which lived long before the glacial period in the so-called Tertiary times. In 1894 a scientist named Dubois discovered in Java some of the remains of an animal which was partly ape and partly man. So well did these remains exhibit the characters of Haeckel's hypothetical ape-man, Pithecanthropus, that the name fitted the creature like a glove. Specifically, the cranium presents an arch which is intermediate between that of the average ape and of the lowest human beings. It possessed protruding brows like those of the gorilla. The estimated brain capacity was about one thousand cubic centimeters, four hundred more than that of any known ape, and much less than the average of the lower human races. Even without other characters, these would indicate that the animal was actually a "missing link" in the scientific sense,—that is, a form which is near the common progenitors of the modern species of apes and of man. We would not expect to find a missing link that was actually intermediate in all respects between modern apes and modern men, any more than we should look for actual connecting bands of tissue between any two leaves upon a tree. A missing link, in the true sense, is like a bud of earlier years which stood near the point from which two twigs of the present day now diverge. So Pithecanthropus is a part of the chain leading to man, not far from the place where the human line sprang from a lower primate ancestor.
Of the fossil remains of true prehistoric men, little need be said. We cannot know whether the races now living in the regions where these remains are found are really the descendants of the older types, and so a direct comparison cannot be made. It is true that the brain capacities of the man of Spy, of the Neanderthal, and of the English caverns are lower than those of modern civilized races, but the differences are not so striking and not so clearly indicative of the apelike ancestor of man as in the case of the previous comparison of Pithecanthropus with apes and men.
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The foregoing facts illustrate the conclusive evidence brought forward by science that human evolution in physical respects is true. Even if we wished to do so, we cannot do away with the facts of structure and development and fossil history, nor is there any other explanation more reasonable than evolution for these facts. If now we should inquire into the causes of this process, we would find again that the present study of man and men reveals their subjection to the laws of nature which accomplish evolution elsewhere in the organic world.
The fact of human variation requires no elucidation; it is as real for men as for insects and trees. Indeed, some of the most significant facts of variation have been first made out in the case of the human species. The struggle for existence can be seen in everyday life. We cannot doubt its reality when scores perish annually because of their failure to withstand the extreme degrees of temperature during midwinter and midsummer; when starvation causes so many deaths, and when the incessant combat with bacterial enemies alone brings the list of casualties on the human side in our own country to more than two hundred and fifty thousand a year. As in nature at large, the more unfit are eliminated as a result of this struggle, while the more adapted succeed. In the long run, that particular applicant for a clerkship or any other work who may be the more fitted is the one who gets it. While the severity of competition may be somewhat mitigated as the result of social organization, and while our altruistic charitable institutions enable many to prolong a more or less efficient existence, the struggle for existence cannot be entirely done away with. Heredity also is a real human process, and it follows the same course as in animals at large; as in the case of variation, some of the fundamental laws of its operation have been first worked out in the case of human phenomena, and have been found subsequently to be of general application.
Reverting to the specific question as to the earliest divergence of man from the apes, we can readily see how the superior development of the ape-man's brain gave him a great advantage over his nearest competitors, and how truly human ingenuity enabled the earliest men to employ weapons and crude instruments instead of brute force. Thus the gap between men and apes widened more and more, as reasoning power increased through successive generations. This is another aspect of the statement that the supreme position of man has been gained, not by superior organization in physical respects outside of the nervous system, but by the superior control of human organization by the higher organs of this system.
The unity of nature and of its processes is established more and more surely as the naturalist classifies the facts of structure, development, fossil history, and evolutionary method. Our own species is not unique; it takes its high place among other organic forms whose lives are controlled in every way by the uniform consistent laws of the world.
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The physical evolution of human races is the next major division of the large subject before us. Heretofore the obvious differences displayed by various races have been disregarded and the species has been treated as a unit, in order that its evolution from pre-human ancestors might be made clear. Knowing now how the facts of structure show that the supreme position of our kind has been attained mainly as the result of the progressive elaboration of the higher portions of the brain, and not because new and unique structures have been developed, we are prepared to turn our attention to the diverse characteristics of human races; and during this inquiry anatomical matters will still be the only ones to be reviewed. The intellectual and social characters of numerous races belong to the category of physiological or functional phenomena, which are to receive due consideration at a later time. It is the meaning of the facts of racial diversity for which we are now to look.
For many reasons this subject is more difficult to describe in a concise outline than those taken up before. It is true that every one is familiar with different types of human beings, such as the Negro and Japanese and Chinese, while furthermore the obvious differences between such races as the Norwegian and Italian are sufficiently marked to strike the attention of any one who looks about at his fellow-passengers in a crowded street car. But few indeed have a comprehensive knowledge of the wider range of racial variation in which these familiar examples find their place. Anthropology, or the science of mankind, is a large and well-organized department of knowledge, dealing with the entire array of structural and physiological characters of all men. One of its subdivisions, anthropometry, is almost an independent discipline with methods of its own; it describes the characteristics of human races as these are determined by statistical methods of a somewhat technical nature. There is still another science, ethnology, which deals more particularly with institutions, customs, beliefs, and languages rather than with physical matters, although it is clear that ethnology and anthropology cannot be sharply separated, and that each must employ the results of the other for its own particular purposes.
Because men have always been interested in the study of themselves, the subject of racial evolution is literally enormous, and the attempt to give anything like a complete description of what is known would obviously be futile. But it is possible to obtain a clear conception of certain of the fundamental principles that fall into line with the other parts of the doctrine of organic evolution with which we have now become acquainted. The main questions, therefore, may be stated in simple terms. The first deals with the evidences as to the reality of evolution during the historical and prehistoric development of the various types of man from earlier common ancestors; the second asks whether the lines of racial evolution are further continuations of the line leading from ape-like ancestors to the human species as a type. In order to give the proper perspective, it will be well to state at the present juncture, first, that the various kinds of men do not vary from each other in a chance manner so as to show all possible types and varieties, but that they fall into natural groups or families distinguished by certain common characteristics, just as do all other kinds of species of animals; in the second place, it appears that some of the differences between the races denoted higher on structural accounts and the lowest forms of man are of the same nature as those observed in the review of the various species of primates from the lemurs to man.
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It is best to look at the whole question in a very simple and common-sense way before undertaking an extended examination of the details of human diversity. The most casual survey of the peoples that we know best because of our own individual nearness to them enables us to realize that the races now upon the earth have not existed forever and ever, or even for the age of 6000 years as contended by Archbishop Ussher. They have all come into existence as such, and they differ from their known antecedents; so that at the very outset common-sense leads us to accept evolution as true, if we admit that human races have changed during the course of recent centuries. We know, for example, that the so-called Mexicans of to-day are a people produced by a fusion of Spanish conquerors and Indian aborigines the Mexican is neither Spaniard nor Indian, though he may resemble both in certain respects; he is a product of natural evolution, accomplished in this case by an amalgamation of two contrasted types. When we speak of the American people, we must realize that it too has come into existence as such, and even, indeed, that it is in the actual process of evolution at the present time. The various foreign elements that have been added during the last few decades by the hundreds of thousands are becoming merged with the people who preceded them, just as the Dutch and the French and the English coalesced during the days of early settlement to form the young American nation. Perhaps most of us call ourselves Anglo-Saxon, but we are in reality somewhat different even in physical respects from the Englishmen of Queen Elizabeth's time, who alone deserved the name Anglo-Saxon. This very term indicates an evolution of a type that differs from both the Angles and the early Saxons of King Alfred's age. These are simple examples which illustrate many features of the universal history of human races wherever they are to be found. Even in the comparatively peaceful times of our modern era the history of any race is a veritable turmoil of constant changes; conquerors impress their characters upon the vanquished, while the victors often adopt some of the features of the conquered. Colonies split off from the mother nation to follow out their destinies under other conditions. Nowhere does the naturalist find evidence of long-established permanence, or an unentwined course of an uninterrupted and unmodified line of racial descent.
It is the task of the student of human evolution to unravel the tangled threads of human histories. The task is relatively simple when it is concerned with recent times where the aid of written history may be summoned but when the events of remote and prehistoric ages are to be placed in order, the difficulties seem well-nigh insuperable. All is not known, nor can it ever be known; but wherever facts can be established, science can deal with them. By a study of the present races of mankind, much of their earlier history can be worked out, for their genetic relations may be determined by employing the principle that likeness means consanguinity. Let us suppose an alien visitor to reach our planet from somewhere else; if he were endowed with only ordinary human common-sense, he would very soon ascertain the common origin of the English-speaking people in Canada, the United States, Australia and New Zealand, South Africa, and many other places. Even if he could not understand a word of the English language, he would be justified in regarding them all as the descendants of common ancestors because they agree in so many physical qualities. The anthropologist works according to the same common-sense principle, obtaining results that find no explanation other than evolution when the varying characters that are used to determine social relationship are properly classified and related. It is to these characters that we must now give some attention.
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The average stature of adults varies in different races from four feet one inch in certain blacks to nearly six feet and seven inches, as among the Patagonians. These are the extreme values for normal averages, although dwarfs only fifteen inches high have been known, while "giants" sometimes occur with a height of nine feet and five inches. Such individuals are of course rare and abnormal, and are not to be taken into account in establishing the average stature of a race for use in comparison with that of another group.
The color of the skin is another criterion of racial relationship, though it is more variable in races of common descent than we are wont to assume. We are familiar with the fair and florid skin of the northern European, the fair and pale skin in middle and southern Europe, the coppery red of the American Indian, the brown of the Malay, of the Polynesian and of the Moor, the yellowish cast of the Chinese and Japanese, and the deeper velvety black of the Zulu; but it has been found that many of the close relatives of the black are lighter in skin color than some of our Caucasian relatives, so that this character cannot be taken by itself as a single criterion of racial affinity.
Perhaps the most conservative and most reliable character that serves for the broad classification of the human races is the shape of the individual hairs of the head. We are familiar with the straight lank hair of the Mongolian peoples and of the various tribes of American Indians, in whom the hair possesses these peculiarities because each element grows as a nearly perfect cylinder from the cells of the skin at the bottom of a tiny pit or hair-follicle. The familiar wavy hair of white men owes its character to the fact that the individual elements are formed by the skin, not as pencil-like rods, but as flattened cylinders. They are oval or elliptical in cross-section, and when they emerge from the skin they grow into a long spiral. If, now, the hair is formed as a very much flattened rod about one-half as wide in one diameter as in the other, it curls into a very tight close spiral and gives the frizzly or woolly head-covering of the Papuan and of the Negro.
In the next place, the shape of the cranium is a character of much value. This is determined as the proportion between the transverse diameter of the skull above the ears to the long diameter, namely, the line that runs from the middle of the brow to the most posterior point of the skull. In the so-called "long-headed" or dolichocephalic races, the proportion is seventy-five to one hundred, while in those forms that have more rounded or brachycephalic heads, like the Polynesian and the black pygmy, the relation is eighty-three to one hundred. The cranial capacity again varies considerably, from nine hundred cubic centimeters to twenty-two hundred cubic centimeters. Many striking variations are also found in the projection of the jaws. A line drawn from the lower end of the nose to the chin makes a certain angle with the line drawn from the chin to the posterior end of the lower jaw; if the jaw projects very greatly, this angle will be much less than when they do not. In most of the Caucasian peoples, the lines meet at an angle of eighty-nine degrees, or very nearly a right angle, but in some of the lower races the figure may be only fifty-one degrees. Additional characters of the teeth and of the palate are also taken into account, and have proved their utility. Finally, the nose exhibits a wide range of variation from the small delicate feature of the Chinaman to the large, well-arched nose of the Indian. It may be hollowed out at the bridge instead of arched; again, it may be nearly an equilateral triangle in outline, as in the Veddahs, and the nostrils may open somewhat forward instead of downward. As many as fifteen distinct varieties of the human nose have been catalogued by Bertillon.
These are the principal bodily characters which the anthropologist uses to distinguish races and by their means to determine the more immediate or remote community of origin of comparable types. Many of these characteristics, as indeed we may already see, are decidedly important in connection with the second problem specified above, for in the case of the flat triangular nose and projecting jaws of a low negroid we may discern clear resemblances to certain features of the apes.
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Long before the doctrine of evolution was understood and adopted, students of the human races had been deeply impressed by their natural resemblances. As early as 1672 Bernier divided human beings according to certain of these fundamental similarities into four groups; namely, the white European, the black African, the yellow Asiatic, and the Laplander. Linnaeus, in the eighteenth century, included Homo sapiens in his list of species, recognizing four subspecies in the European, Asiatic, African, and Indian of America. Blumenbach in 1775 added the Malay, thus giving the five types that most of us learned in our school days. But the different varieties of men recognized by these observers were believed to be created in their modern forms and with their present-day characteristics; the common character of skin color exhibited by any group of peoples of a single continent was to them only a convenient label for purposes of description and classification. It was not until years later that fundamental resemblances were recognized as indicating an actual blood relationship of the races displaying them, and therefore of evolution. Since the doctrine of human descent and of the divergence of human races in later evolution has been accepted, those who have attempted to work out fully the complete ancestry of different peoples have found that no single character can be taken by itself, while the various criteria themselves differ in reliability; the color of the skin is not so sure a guide as the character of the hair and skull, wherefore the classifications of recent times, notably those of Huxley and Haeckel, have been based largely upon the latter. The latest systems have been more rigidly scientific and more in accord with the most modern conceptions of organic relationships in general, as evidenced by the thoroughgoing methods of Duckworth in his recent treatise on human classification.
It now remains to present the salient facts regarding the genetic relationships of typical human races, although it is obviously impossible to go into all of the details of the subject. But these are not essential for the main purpose, which is to show that the evolutionary explanation is the only one that is reasonable and self-consistent. Opinions are sometimes widely at variance regarding countless minor points, but no anthropologist of to-day can be anything but an evolutionist, because the main principles upon which the specialists agree fall directly into line with those established elsewhere in zooelogy. It seems best to state these principles without reverting to controversial matters which find their place in the monographs of the experts. Any comprehensive account such as that of Keane, even if it may not give the final word, will be entirely sufficient to demonstrate how fruitful are the methods of evolution when they are employed for the study of human races, and indeed how impossible it is to discuss human histories without finding conclusive evidences of their evolutionary nature.
The facts that are available indicate that the first members of our species evolved in an equatorial continent which is now submerged, and which occupied a position between the present continents of Asia and Africa. From this center hordes of primitive men migrated to distant centers where they differentiated into three primary and distinct groups. The first of these was gradually resolved into the darker-skinned peoples most of whom now live in the continent of Africa, although many dwell also in the islands of the western Pacific Ocean. The second branch divided almost immediately to produce, on the one hand, the Indians of the new world and, on the other, the yellow-skinned inhabitants of Asia and other places. The third branch developed as such in the neighborhood of the Mediterranean Sea, and produced the series of so-called Caucasian peoples, which are by far the most familiar to us and to which most of us belong. But so early did the second branch divide that there are virtually four main divisions of the human species that are to be examined in serial order.
It is best to begin with our own division, because its greater familiarity makes it easier to become acquainted with the methods and results of anthropology, on the basis of facts that we already know. Three subordinate types exist, located primarily in northern, central, and southern Europe respectively, but many other races dwell elsewhere that are assignable to one or another of these subdivisions. In northeastern Europe we find people such as the Norwegians, Swedes, Danes, and north Germans, that average five feet eight inches in height. They have the long, wavy, and soft hair which is a general characteristic of the whole Caucasian group, although its light flaxen color is distinctive. The blue eye and florid complexion accompany the light color of the hair. The skull is of the longer type, the jaws and forehead are straight and square, the nose is large and long without a distinct arch, and the teeth are relatively small. It is not so well known that the Scandinavian type is so closely copied by many people of Asia, such as the western Persians, Afghans, and certain of the Hindus, living in a continent that we are inclined to assign to the Mongol only. In the possession of these characters the Northern Europeans and other races specified display evidences of their common ancestry and evolution quite as conclusively as in the case of the cats discussed in an earlier chapter where the meaning of essential likeness was first demonstrated.
A broad zone may be drawn from Wales, across Europe and Asia, and even to the eastern islands of the South Seas, in which we find peoples that are obviously of Caucasian descent, but they differ from the members of the first group in some details of structure. On the average they are about five feet five or six inches in height, the hair is dark and wavy, but it is not the pencil-like structure of the Mongol. The complexion is pale, the skull is rounder, and the eyes are usually brown in color. These peoples agree also in their volatile temperament and vivacious manner and are thus markedly different from the more stolid northerners. To this minor branch of the Caucasian stock belong the Welsh, most of the French, South Germans and Swiss, Russians and Poles, Armenians, eastern Persians, and finally some of the inhabitants of Polynesia. The last, it is true, form a well-marked group of darker-skinned and taller races, but in spite of the admixture of these and other unusual features, we can still discern the bodily characters that supplement their traditions, telling of an Asian origin, in demonstrating their common ancestry with round-headed Persians and middle Europeans. Below the zone of middle Europe and Asia is another broad region inhabited by the "Mediterranean" type of Caucasian. The Spaniard, Italian, Greek, and Arab are sufficiently familiar to illustrate the distinctive qualities of this subdivision. These people have the smaller stature, dark hair, dark eyes, and paler skin of the middle Europeans, but the skull is of the long instead of the rounded type. A well-marked subordinate group is formed by the so-called Semitic peoples, such as the Arabs and their Hebrew relatives. The Berbers and other North African races possess a darker skin probably because of the admixture of Ethiopian stock, and they, too, are so well characterized that they form a clearly marked outlying group as the so-called Hamites. Passing over into Asia we find relatives of the Mediterranean man in the Dravidas and Todas of India, possibly in the degenerate Veddahs of Ceylon, and finally in the Ainus or "hairy men" of some of the Japanese islands. The last-named people certainly possess some Mongolian features, but these seem to have been added to a more fundamental form of body that is distinctly Caucasian.
All of the races we have mentioned, together with their relatives, may be compared to the leaves borne upon three branches that take their origin from a single limb of the widespread human part of the tree. They cannot be classified in any mode on the basis of their primary and secondary resemblances without employing the treelike plan of arrangement, which to the man of science is a sure indication of their evolutionary relationships.
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The people of the second or Mongolian group agree in certain well-marked characteristics in such a way as to be well separated from the other divisions of mankind; these characteristics we may speak of as constituting a second "theme," of which the various peoples of the group are so many variations. To visualize them we need only to recall the appearance of the Chinaman, perhaps the most familiar example of the entire series. Here the hair is coarse and black, and straight because of its round transverse section; the mustache and beard of the Caucasians are seldom found except in later life; the skin is a fleshy yellow in color; the skull is round, indeed, it is one of the roundest that we know; the jaws are not so straight as in the Caucasian, for the angle at the point of the chin is about sixty-eight degrees. The cheek bones project laterally, with greater or less prominence; the nose is very small, tilted up slightly at the end, and is usually hollowed instead of arched. The eyes are small and black in color, set somewhat obliquely, and the upper lid is drawn down over the eye at its inner corner so as to make the obliquity still more marked. The teeth are larger than those of the Caucasian. Finally, the Mongol is below the average of all men as regards height, being usually about five feet four inches tall.
The original Mongolians probably developed the characteristic features we have just noted in a Central Asiatic region, and then almost immediately they divided into two great groups. Each of these evolved along certain lines of its own, one sweeping northward to develop into what are now called the Northern Mongols, the other working its way eastward and southward to produce the peoples of China proper, Indo-China, and many parts of Malaysia. Considering first the peoples of the Northern Mongolian division, we find in the typical Manchurian what is perhaps the nearest among modern people to the original race. Spreading northward and westward from the middle Asiatic plains, this great wave has produced the nomadic tribes of Siberia, like the Chukchi, the Buryats, and the Yukaghir. The present inhabitants of Turkestan connect those forms which have remained near the original home with the races of Mongolian origin that live farther to the westward, like the Turks of Asia. But the Mongolian tide originally swept much farther to the west, although it was driven back later by conquering Caucasian peoples; and it has left behind such remnants as the Finlander and the Laplander, the Bulgar, and the Magyar. It is evident that these western branches of the Mongol stock are not at all pure in their racial characteristics, for they clearly show the effects of a mixture with alien European peoples. To assign them to the Northern Mongol division means only that their dominant characteristics are mainly those of Mongolian nature. We have referred the Russians to the middle Caucasian division even though the Slav or Tartar infusion is very great, but it does not dominate over the Caucasian peculiarities as it does in the case of the peoples we have mentioned. As regards the remaining types we must add to this brief list the Koreans and the Japanese, the former being far purer in Mongolian nature than the latter people, which has apparently been affected by a Malay influence from the south.
Turning now to the southern Mongol, we find that from their cradle in the Tibetan plateau they too have spread widely, and their descendants have also come to differ in certain respects as they have established themselves in other lands. Most of the present people of Tibet belong to this section; the Gurkhas of Hindustan, the people of Burma proper, of Annam, and Cochin China are close relatives of one another and of the more characteristic Mongolians of China proper who make up the vast bulk of the population. From this stock we may also derive the Malays of Sumatra and Java, of Borneo and Celebes, and the Tagals and Bisayans of the Philippine Islands. Even the Hovars and other tribes of Madagascar may be referred to this division, for although in them the skin has become somewhat darker, we may still discern the characteristics which indicate their common ancestry with the Oceanic Mongols.
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The American Indians taken collectively constitute a group that is well set off from the rest of mankind by such characters as taller stature, small, straight, and black eyes, a large nose that is usually bridged or aquiline, a skull of medium roundness, and the yellow copper color of the skin. The common origin with the Mongols is demonstrated by the straight and long, coarse, black hair and by the absence of a beard; the mustache also is almost always absent.
All of us have seen Indians belonging to the tribes of the plains, which serve as excellent examples of this grand division. Many have also visited the homes of the Pueblo Indians, and have learned how uniform is the physical appearance of the tribes living in various parts of the United States. Indeed throughout all of North America the basic characteristics of Indians prove to be strikingly conservative, although in the Eskimo there are some departures which seem to indicate a closer connection of these peoples with the Mongols, probably as the result of some more recent influx from the neighboring and not very distant region of northeastern Siberia. Extending our survey southward through Central America, the Aztecs and Mayas are found to possess many of the same characters, though in some respects they are transitional to the Caribs of the northern edge of South America and to the Indians of South America. Traveling still farther southward, we meet the very tall Patagonian, still an Indian in essential respects, and finally, the Yahgan and Alacaluf of the Fuegian region, the most degenerate members of the race. The last-mentioned people are dull and brutish and most degraded in all respects, and stand at the lowest end of the red Indian series as regards intellectual ability and cultural attainment.
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We now come to the last of the four great divisions of the human species which includes the races usually spoken of as Africans or Ethiopians. But these races are by no means restricted to the continent of Africa, for quite as typical black types are found in far-distant lands such as Australia and many islands of the Pacific Ocean. The races assigned to this division group themselves about two subordinate types,—the tall negro proper and the shorter or dwarf negrito,—and each of these has representatives both in Africa and in the oceanic territory.
The black slaves of America were all descended from typical negros brought from the western part of Africa, and they provide us with adequate illustrations of Ethiopians as a group. In them the stature is above the average of men in general, specifically about five feet ten inches. The short jet-black hair is strikingly different from the head covering of the other great groups of human races; each individual hair is so flat in cross-section that it curls into a very tight close spiral, and this brings about a frizzly appearance of the whole head covering. There is little or no beard, the skin is soft and velvety and of various shades approaching black in color. The skull is long, the cheek bones are small, but the most distinctive characteristics of the head are found in the apelike ridges over the eyes and in the very broad flat nose which projects only slightly and turns up so that the nostrils open forward to a marked degree, while in the jaws there is an astonishing divergence from the Caucasian condition in the great protrusion which causes the angle at the chin to be about sixty degrees.
The warlike Zulus and other peoples of Southern and Central Africa are perhaps the most characteristic races in this division. Their relatives are found to the northward as far as the Sahara desert, along the southern borders of which they have spread out to the eastward and westward. Fusion with other races has taken place along this border so that many of these northern tribes are much lighter than the Zulus in the color of the skin. But many relatives of the taller African negro are found in other parts of the world, namely in Australia, and in New Hebrides and New Caledonia—islands to the north and east of this continent. The Papuan of New Guinea is a typical negro in all true respects, with strongly marked Ethiopian characteristics, though there are some differences which are transitional to the more aberrant natives of Melanesia, which includes many archipelagos like the Fiji, Bismarck, Marshall, and Solomon islands. Undoubtedly the most degenerate member of the tall negro division is the Australian native, the so-called "blackfellow." The bulbous nose and the well-grown beard mark him off from the typical stock, but his obvious relationship to this is indicated by the low brain capacity, the prominent ridges over the eyes, and the heavy projecting jaws.
Taking up the other division of the so-called Ethiopian race, constituting the Negrito section, we may begin with its Oceanic members. The natives of the Andaman Islands, the Kalangs and the Sakais of Java and neighboring regions, and the Aetas of the Philippine Islands agree in a dwarfed stature of four feet or a little over, in their yellowish brown skin color, a round head, and woolly reddish-brown hair. They, too, possess large ridges over the eyes and extremely prominent jaws, and in these latter characteristics particularly we see evidences of their relationship to the negro. But perhaps the most characteristic pygmies are found in Africa. The little Bushmen and Hottentots are low types of the Negrito stock, and they lead us to the lowest men of all, the Akkas of the West Congo region. It is difficult for us to realize how utterly degenerate and apelike these pygmies are. The jaws are disproportionately large as compared with the cranium or brain-case, and project to a degree which brings the skull very close to that of the higher apes; while in mental respects, in the absence of dwellings, and in many other ways they prove to be the lowest of all mankind,—veritable brutes in form and mode of life.
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Without a full series of photographs before us the foregoing sketch of the various races of men cannot make us fully acquainted with all the strange varieties of the human body, but it will suffice to establish two fundamental results. While all men agree in the possession of certain features which set them apart from other members of the primate order, they differ among themselves in such a way as to fall into four well-marked subdivisions branching out from a common starting-point. Furthermore, in each of these primary groups the subordinate types arrange themselves also in the manner of branches arising from a common limb. This is the relation that we have earlier found to be a universal one throughout the animal kingdom, and science believes that it indicates everywhere an evolutionary history—an actual development along different lines of descent of forms which have a common starting-point and ancestry.
The second principle is perhaps even more significant: when we review the many races from the Caucasian to the dwarf Negrito, we traverse a downward path which will bring us inevitably to the higher apes. In our survey of human races, we have passed from the Caucasian, with the largest brain and cranium and with straight jaws well underneath the brain-case, to the pygmy with a relatively small brain, with huge projecting jaws and with prominent ridges over the eyes; one step more along that path would bring us to the gorilla or the chimpanzee. The array of lower primates, from the lemur to the gorilla, gives a series of forms exhibiting a progressive advance in respect to the size of the brain and cranium, and a gradual retreat of the jaws to a position underneath the cranium; and one step further brings us to man. In a word, these two lines join—in fact, they are directly continuous. There is a far smaller difference between the lowest man and the highest ape than we have been accustomed to suppose.
Thus in general terms, it can justly be said that process of evolution which developed the first man from its ape-man progenitor seems to have continued during subsequent ages. Spreading out in diverging lines of evolutionary descent no less clearly than they have in geographical respects, certain races have far surpassed their fellows of a lower order, which, like the brute pygmy, remain nearer the common structural form from which all men have sprung.
THE MENTAL EVOLUTION OF MAN
The problems dealing with the make-up of the human mind and with the evidences of mental evolution bring the student to matters of more vivid human interest. Mental phenomena are so complex and intricate that it is well-nigh impossible to analyze their history without a knowledge of the principles derived from the broad study of evolution as a general doctrine, where human prejudice is not so large a factor and where his perspective is less affected by the proximity of the observer to his facts. For these and other reasons the foregoing treatment of human evolution has been confined to the purely structural characteristics of man as a species and of human races as so many varieties of this type. When the broad comparative methods of biological science are employed for the elucidation of human anatomical facts, the result in this special case, like that established through the study of the characteristics of living things in general, is the proof that evolution gives the most rational and natural explanation of the observed data. This being true, the naturalist who turns from purely structural matters to human intellect and its history, finds well-tried methods of inquiry already available, and he approaches his further studies with a conviction that evolution, having proved to be universal so far, in all probability will be found equally true in the case of psychological phenomena. This expectation is indeed realized, and the scope of the doctrine is extended over a new field, when the facts of human psychology are treated as materials for impersonal comparative study; and this result is not only useful and valuable in and by itself, but it also provides in the principles of mental evolution the transition to the field of social relations and ethical ideas and ideals which are apparently the unique possessions of men as individuals and as associated groups.
The field of comparative psychology might seem at first sight to be a foreign territory to the average well-informed layman in science, but the contrary is really the case. Every one has thought at one time or another about his own mental make-up, and about the minds of others. No one can watch a child at play with his toys or at work with his schoolbooks without being struck by many evidences of marked differences between the immature and the experienced types of mind. Every one knows also that the mental "scheme of things" is by no means the same for all nations or races of mankind existing to-day, while furthermore the fact is entirely familiar that the intellectual heritage of a present race has changed in the course of previous ages. Therefore in this field as before we need only to amplify our knowledge of such representative psychological facts as these by drawing upon the full stores of the special investigator, in order to learn that human thought, like the human frame, has undergone a natural history of transformation to become what it is and what it was not.
Many who would be ready to accept the evolution of physical characteristics find it impossible to treat the history of human mentality as a subject for dispassionate consideration, because above all else the intellectual powers of mankind seem to be truly distinctive. It is only after constant use of the methods of science that we can bring ourselves to see how closely we resemble lower forms in physical make-up; still greater reluctance must be overcome before we can view our mental processes as counterparts of those of inferior animals, so essential to our very humanity do they seem. But our duty to undertake the task is plain, and its discharge will be greatly facilitated by a clear realization that mental evolution is but a part of human transformation in times past, as the latter is only a small fraction of the universal process of organic evolution in general. While our own nature and inquisitiveness give us so intense an interest in the teachings of science that relate to the constitution and history of human faculty, wherefore these matters gain an undue prominence in perspective, it must never be forgotten that these teachings do not stand by themselves, for they are built upon the sure foundations already laid in physical evolution; and these foundations cannot be disturbed by our failure to use them as a basis when we construct our own conceptions of human intellect and its history.
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Before passing to the systematic review of the facts and principles of comparative psychology which demonstrate evolution, there are certain general aspects of the subject to be considered so as to clear the ground, as it were, for further progress. When the several organic systems of the human body were compared with those of the apes and of lower animals, their evolution was proved as far as the purely physical and material characteristics were concerned. But we know that there is no part of any one of these systems which has not its own particular function, even though this may be a relatively passive one; while furthermore, science does not know of any physiological activity without some organ or tissue or cell as its material basis. Therefore the evolution of an organic system in material respects involves its functional or dynamic evolution as an inseparable correlate; the two proceed in unity, and they cannot be regarded as entirely distinct without violating common-sense.
The fin of a fish is used as an organ of locomotion in water; from some such organ have evolved the walking limbs of amphibia and reptiles, constructed for progression upon land. Among the mammalia the fore limbs have become structurally adapted so as to be such diverse organs of locomotion as the stilt-like leg of a horse, the flipper of a seal, the whale's paddle, and the bat's wing, while among the birds the wing may change into a flipper like that of the penguin, or become reduced to a vestige as in Apteryx. We may focus our attention upon the material likenesses and differences in such a series of locomotory organs, but an inevitable accompaniment of their physical changes in the transformation of species has been an evolution in the functional matter of locomotion. The most complex and differentiated tracts of even the highest animals have evolved from a simple sac like that of a polyp or jellyfish, as we know from the independent testimony of comparative anatomy and embryology; in this case also the evolution of alimentary functions is no less inseparable from the transformations in structural respects. And again, we cannot understand the historical development of vision without taking into account the eyes of various types belonging to lower and higher animals.
So it is with the nervous systems of man and other animals, and with their functions. The nervous system of the human organism comprises identical organs with the same arrangements that are found in other primates and in lower vertebrates as well; the differences in structure are differences in the degree of the complexity of certain parts, notably of the cerebrum. Therefore the evolution of human mentality, which depends upon a human type of brain as a physical basis, is already demonstrated with the proof that the human brain and nervous system have evolved. It is true that an invariable and necessary connection between mind and matter is implied in the foregoing statement, and this is something which demands further consideration at a later point. But just how the human mind is produced by or depends upon the brain, is of far less importance for us at this time than the obvious fact that mental performance requires active nervous tissues. So far investigation has been unable to discover a valid reason for a belief in the existence of mental phenomena, as such, apart from some kind of material basis. And while we may prefer to restrict the use of the word mind to the series of nervous processes going on in the human organ of thought, in so far as these processes are carried on by the peculiar tissues of the nervous system they cannot be finally distinguished from the functional products or accompaniments of the same kind of active tissues and organs in lower creatures. Thus the subject of mental evolution becomes much clarified at the outset by understanding that nervous processes and nervous systems evolve together.
In the direct treatment of the facts and principles of mental evolution we can use exactly the same classification and subdivisions of the materials of study as heretofore, because psychological data are the correlates of material organic systems, and also because the former, being natural phenomena, are subject to the methods of analysis which can be employed for any series of objects that have undergone evolution. Separating the matter of fact from the question as to the method, and recalling the main bodies of evidence as to the reality of evolution, we may establish four sections of the subject before us: these are (1) the anatomy, (2) the embryology, and (3) "palaeontology" of mind, and (4) an inquiry into the way nature deals with the psychical characteristics of organisms in accomplishing their evolution. To specify more particularly, it is possible in the first place to compare the activities belonging to the category of mental and nervous operations, displayed by man and other organisms, and the results form the subject of comparative descriptive psychology; the second division, namely, developmental or genetic psychology, deals with the sequence of events in the life of a single individual by which the infantile and adolescent types of mind become adult intellectuality; in the third place, in speaking of the palaeontology of mind, the phrase is used to refer to the varied and changing mental abilities of human races in historic and prehistoric times as they may be demonstrated and determined by the evidences of the culture of such earlier epochs. In considering the matter of method, the questions are whether variation, inheritance, and selection are as real in the world of mental phenomena as they are in the material world, and whether the laws are the same or similar in the two cases. We shall learn how the results of such studies prove with convincing clearness, first, that the contents of the individual mind and of the minds of various human races are truly the products of natural evolution, and second, that the human mind differs only in degree from that of lower organisms, and not in kind or fundamental nature.
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When the operations of human mental life are examined, they include what are called processes of reason as apparently distinctive elements. The lower mammalia exhibit a simpler order of "mentality" denoted intelligence, while the nervous processes of still simpler forms are called instinctive and reflex activities. These are the terms of the comparative array of psychology which are to be separately examined and classified, and to be brought into an evolutionary sequence if common-sense directs us to do so.
Let us begin our comparative study with an example of the simplest animals that consist of only a single cell, such as the little protozoon Amoeba. We have become familiar with this organism as one that carries on all of the vital functions within the limits of a single structural unit; it is a mass of protoplasm enclosing a nucleus, and as a biological individual it must perform all of the eight tasks that are essential for life. It does not possess a digestive tract, but it does digest; it does not have breathing organs, but it does respire; and it is particularly noteworthy that it must coordinate the different activities of its parts, and maintain definite relations with the environment, even though its coordination and sensation are not accomplished by any special parts that would deserve the name of elementary nervous organs. Its many activities are simple responses to stimuli that reach it from without, and its reactions to such stimuli are called reflex processes. Should the light become too strong, it will slowly crawl to a shady place; should the water in which it lives become warmer, it responds by displaying greater activity. It exhibits, in a word, the property of irritability—that is, simply the power of receiving and reacting to stimuli; and being only a single cell this property is held in common by all of its parts.
We come next to a simple many-celled animal like the polyp Hydra, or a jellyfish. In such an animal the body is composed of numerous cells which are not all alike either in their make-up or in their functions. Some of them are concerned primarily with digestion, others with protection, while still others are exempt from these tasks and as sense-cells they devote all their energies to the reception of stimuli from without, or, beneath the outer sheet of cells of the two-layered body, they conduct impulses from one part of the animal to another, and thus serve as coordinating members of the community. For the first time, then, a nervous system as such is set apart and specialized to devote itself to the two tasks of sensation and coordination that are performed by nervous systems throughout the entire range of organisms higher in the scale. But the activities of Hydra, like those of Amoeba, are reflex and mechanical,—that is to say, given similar stimuli and similar physiological states of the animal, the reactions will be the same. A little water-crustacean like Daphnia may swim against the tentacles of Hydra; it is stung to death by the minute cell-batteries which the animal possesses, and then in a mechanical way the tentacles transport the food to the mouth, through which it is passed inward to the digestive cavity. There is nothing that can be called "mentality" throughout these processes, but the series of activities is much more complex than in Amoeba because the whole organism is constructed more elaborately, and because the special and peculiar mechanism directing the activities has advanced to a far higher condition.
Passing to the jointed animals like worms and insects, we find nervous mechanisms that are still more intricate, and with their advance in structural respects there is a corresponding and correlated progress in their functions. Because the whole organism has developed more highly differentiated groups of organs to perform the several biological tasks, such as eating and respiring and moving, it is necessary for the nervous structures concerned with the direction of these actions to become more efficient. An earthworm avoids the light of day and digs its burrow and seeks its food by wonderfully cooerdinated activities of its muscles and other parts, which are controlled by a double chain of ganglia along its ventral side, connected with a similar pair of grouped nerve-cells above the anterior part of the digestive tract. The ganglia of each segment exercise immediate supervision over the structures of their respective territory, while they pass on impulses to other ganglia so that movements involving many segments can be properly adjusted. Everything an earthworm does is controlled by the cells grouped in these ganglia, or scattered along the intervening connecting cords. We speak of its acts as instinctive, employing a term which seems to indicate a different kind of operation carried on by the nervous system, but a moment's thought will show that an instinctive act is simply a complex group of reflex acts. The physical basis and ultimate unit is a cell, and the functional unit is likewise a cell act; therefore the seeming difference proves to be one merely of degree and not of kind. The greater complexity of the worm's nervous system as compared with that of Hydra gives to the whole mechanism a plasticity that diverts the attention from the mechanical nature of the entire instinctive act and of its basic cell elements.
The instinct, like the elementary reflex, is determined by heredity. Because a certain configuration of the cells and fibers making up a nervous system is inherited as well as the characters of the constituent elements themselves, a worm or an insect is enabled to act as it does. A butterfly does not have to learn how to fly, for it flies instinctively. When it emerges from its chrysalis with its complete adult series of wings and muscles, it has also the nervous mechanism by which these parts are mechanically controlled. A ground-wasp deposits its eggs in a small burrow in which it places also a caterpillar or a grasshopper paralyzed by stinging, so that when the larva is hatched from an egg it finds an ample supply of fresh food provided by a complex series of its mother's acts that seem to be directed by conscious maternal solicitude. When the larva passes through the later stages of development and makes its way to the open air as a fully formed adult, it in its turn may go through the same course of action as its parent, but it is clear that it cannot have any remembrance of its mother's work or any personal knowledge of the value of burying its own eggs in a chamber with a living prisoner to serve as food. It was an egg when its parent did these things; as a parent itself it does not remain on watch to see how beneficial or fruitless its acts may be. A mechanism produced by nature's methods, the ground-wasp behaves as it is capable of working with its inherited structure and its inherited instinctive powers of cooerdination and sensation.
The complex lives of communal insects like ants and bees bring us to the level of mentality where an understanding of causes and effects seems to be the guide for conduct. Nevertheless the facts do not warrant the assumption that reason and intelligence play any part in the mental life of these creatures, as they do in the lives of man and the apes. Because we ourselves can see the utility of the definite and peculiar behavior of the queen and the worker, there is no logical necessity for assuming an identical form of knowledge as a possession of these insects. Many investigators have dealt with these fascinating subjects, and they are almost unanimous in the conclusion that the instinct of an insect is a mechanical and hereditary synthesis of combined reflex acts.
The lower orders of psychological processes play a far larger part in the lives of the higher animals than we are wont to believe. A pointer and sheep dog possess different qualifications in the way of instincts that make them useful to man in different ways. A bulldog or a game-cock does not reason out its course of action during a contest, but like a mechanism when the spring is released, it acts promptly and with effect. A ball flashing past the human eye causes the lids to close unconsciously, and it is not always possible to inhibit this instinctive mechanical act by the exercise of the will. An examination of the workings of the human body reveals manifold activities of an even lower or reflex nature, like the movements of the viscera and the adjustments in respect to the amount of supplies of blood sent to different parts of the body as local needs arise. Directed always by specific portions of the nervous system, such reflex actions play their part in human life without any effort on the part of reason and so-called will, and without coming into consciousness except indirectly and subsequently.
Passing by many interesting members of the psychological series of intergrading forms, we reach the familiar animals like the cat and dog and horse which display what is called intelligence. This is the power to learn by experience, and to improve the quality and promptitude of reactions to stimuli. In certain respects intelligence seems to differ from instinct, inasmuch as it involves a response to stimuli that may be altered and quickened by repeated experience, but in ultimate analysis the two forms of psychological processes are fundamentally alike. A single example chosen from Thorndike's extensive investigation will serve to bring out the primary characteristics of intelligence. A cat was placed in a latticed cage provided with a door that could be opened from within when a catch was pressed down, and meat was put in a dish outside the door where the cat could see it. At first, the animal escaped from the cage by freeing the door during its aimless scrambling about the catch, but as trial after trial was made, the time necessary for the cat to make its way out was shortened, until after seventy-five or one hundred trials, the animal immediately opened the door and seized the food. In mechanical terms, the connection between "scrambling about the door" and "freedom to get the meat" became established by numerous repetitions until the originally disconnected elements were physiologically associated and made inseparable. When animals like horses and seals and dogs are trained for the circus, it is by exactly the same method, for training consists merely in the establishment of a psychological sequence so that the performance of one series of acts leads mechanically to others. Thus we learn that the psychological property called intelligence is the ability to establish wide relations between numerous activities which are themselves of a more or less complex nature; and we find also that because these elements are ultimately nerve-cell and sense-cell reflexes, an intelligent response is quite as machine-like as any and all of its elements. A difference in degree of complexity and extent is the only thing that places intelligence apart from instinct and reflex action, for the units are the same in all cases,—so far as science knows.
The apes are of the greatest value in providing the transition from the grade of intelligence to the human level where reason is found. Whether or not a chimpanzee can reason at all is less important than the fact that its total "mental" powers are lower than those of man, and higher than those of inferior mammalia. Apes are far more susceptible to training than cats and dogs, because their improved nervous mechanism enables them to establish a psychological sequence with greater facility. If we are to judge by the facts at hand, these creatures possess a low order of mentality, like, but by no means equivalent to, that of man.
At the end of the comparative scale, we reach the human mind which is characterized by its ability to perceive and recognize far wider relations than those which are involved in intelligence. Human consciousness is the stream of thoughts and feelings which constitute the immediate contents of mind. In our own case, we know both the activities we perform and some of the internal phenomena with which such activities are connected. Then we are impelled to compare the objective phenomena of action with the behavior of other men and of lower organisms, and if their behavior does not coincide with our own we are justified in believing that its direction lacks some of the elements we know about in our own case. This is the method of comparative psychology, which establishes the conclusion that reason is the more complex term of a series to which reflex action, instinct, and intelligence directly lead.
Were we to study in detail the psychology of adult human beings, we would find only more truly that instinct and intelligence play a large part in our everyday mental life, and more certainly that even the highest reasoning powers we possess are only more complex in nature than the nervous processes of lower mammals and invertebrates. Just as the nervous systems advance in physical or structural respects, so must their activities become more and more complex until the result is human faculty.
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We must now briefly consider what may be called the "comparative anthropology" of mind which deals with the various degrees of mental ability displayed by different human races; this subject follows inevitably upon the comparison of the human mind viewed as a single type with the psychological processes of lower animals. When we reviewed the diverse characteristics of human races—the protrusion of the jaws, greater or lesser stature, and the like—it appeared that so-called "lower" races could be distinguished which differed from the "higher" races in the direction of the apes; the question immediately arises whether similar distinctions and relations are discoverable on the basis of mental traits. But in the present case there are not so many well-substantiated differentia at the disposal of the student, and it does not appear so clearly that the "higher" races are furthest from the lower primates and lower mammalia as regards their mental processes. What facts there are, however, prove to be highly significant, and they materially amplify our conception of human faculty as a product of evolution. The essential point is that the intellectual attainments of various races are by no means the same. The calculus is a mental product of the white race only; gunpowder and printing from movable type were independently invented by the Caucasian and Mongolian races; but the American Indian and the Negro never originated them. Human faculty, to employ the most general term for all that distinguishes man from the brutes, proves to be a very varied thing when we draw comparisons between and among races with independent lines of ancestry and heredity occupying widely separated areas. Should we analyze it, we find it to be composed of three constituents; namely, the physical elements of the brain, the degree to which the observational or perceptual and higher elements cooperate in building up the conceptions peculiar to the type, and the materials with which the physical mechanism deals, in the way of environmental, educational, and social "grist for the mental mill." Many anthropologists accord too great an importance to the third constituent of human faculty, I believe, and they are therefore led to deny that races differ in mental respects to so large a degree as the thoroughgoing evolutionist would contend. They hold that differences in such things as powers of observation are due to training: that, for example, an American Indian or a South Sea Islander sees certain things in his environment more quickly than a white man only because these are the things which the experiences of his earlier life have accustomed him to look for and to find. This may be granted, and it may also be admitted that children of so-called "lower" races can be educated side by side with the youth of white races without noticeably falling behind, up to a certain point when, at the age of adolescence, in the classic case of the Australian natives, other factors prove to be obstacles to further progress. We must also recognize that the character of the environment of a race determines to a large extent the mode of life of the people; a forest-dwelling Indian of the interior is a hunter as well as a warrior, while a South Sea Islander is a navigator and a fisherman.
But the fact remains that the inhabitants of similar countries have reached markedly different grades of intellectual and cultural life. Anglo-Saxon dominance must be referred ultimately to Anglo-Saxon heredity and not to the peculiarities of the land. Although adaptation is no less necessary for men as individuals and as social groups than it is for all other living things, I believe that it is to diversity in constitutional endowments, however these may have arisen, that we must attribute the superiority of some races over others. The question is not whether a savage race can or cannot adopt the higher conceptions of a civilized people; the fact is that they have not actually become civilized by themselves. Thus, while evolution in mental respects has not resulted in the loss of plasticity in the case of the brain and the nervous system as a whole, wherefore the activities of these organs still remain capable of individual and racial modifications that are impossible in the case of the skeleton and in the color and shape of the eye, it remains true that races do differ intellectually, and that their differences are marks of a mental evolution quite as definite as their physical natural histories of change.
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In my own view the strongest and most impressive evidence bearing upon the great problem before us is provided by the series of transformations by which the human intellect develops during an individual life. Mind has an embryology no less significant than that of the skull or of any other element of the body; and its investigation leads to the evolutionary interpretation quite as surely as the study of the various grades of adult psychology constituting the anatomical sequence, which we have reviewed previously. When in the earlier part of the book we dealt with embryology in general, we learned how the changes which take place when an organism develops from an egg demonstrate the actuality of true organic transformation without the necessity of concluding or inferring that this process might occur. It is not superfluous to insist again that the essential fact in evolution is the alteration of one organic characteristic into another type; must we not recognize at the very outset that mental transformation is as real as physical development?
In the first instance we might concern ourselves with the physical basis of mind and its history. In the earliest stages of human embryology no nervous system whatsoever is present, and it is unreasonable to suppose that there is anything going on which corresponds to human thought. A little later a cellular tube is established as a primitive nerve axis, which at first is nearly uniform throughout its entire length and displays no differentiation into brain and spinal cord. Before long an enlargement of the anterior end expands and develops into a primitive three-parted brain. It is not yet a real brain, however, and it is entirely incapable of functioning in such a way as to justify the use of the word mental for the results of its operations. We know that it is only in the cerebral hemisphere of the adult brain that the processes of true human consciousness go on. But it is not until long after the three-parted stage that the cerebral hemispheres make their appearance therefore we cannot speak of mind as present when the cell and tissue basis of mind is not present. When, now, the cerebral hemispheres do appear, they are small bean-shaped structures no larger relatively than those of a fish. Later they enlarge so as to attain the relative size of the cerebral hemispheres of an amphibian, and still later they are like those of a reptilian brain. Continuing to enlarge, they begin to fold so that the total surface is increased without very much addition to their bulk. At this time the cerebral hemispheres of the brain of the human embryo are like those of an adult cat or dog. The process of general enlargement and of progressive convolution are continued, and stages are reached and passed which correspond with the monkey and ape conditions.