Nothing in human development is more impressive than the origin of the cerebrum and its development by passing through successive stages which are counterparts in the main of the adult brains of other and lower animals. The alteration of a tissue-mechanism constructed in one way into a tissue-mechanism of a more complex nature, provides the most conclusive evidence of the reality of brain evolution, because the process of transformation actually takes place.

But in the present connection we are more interested in the dynamic or functional aspects of mental evolution, which it must be remembered are inseparably bound up with the physical structures and their modifications. After a human infant is born its activities are reflex and mechanical like those of the adult members of lower groups. As it grows it performs instinctive acts because its inherited nervous system operates in the purely mechanical manner of a lower mammal's nervous system. For these reasons an eminent psychologist has said that the mental ability of an infant six months old is about that of a well-bred fox terrier. The same infant at nine months displays an intelligence of a higher order equal to that of a well-trained chimpanzee; it has become what it was not, and in so far it has truly evolved in mental respects. At two years of age the child is incapable of solving problems of the calculus, for its reasoning powers are elementary and restricted, but these same powers change and intensify so as to render the older mind quite capable of grasping the highest of human conceptions and ideas. In my judgment the unbroken transformation of a child's mind that exhibits only instinct and intelligence into an adult's mind with its power of reasoning, is far more conclusive as proof of mental evolution than the inference drawn from the comparisons we have made above of the adult psychological phenomena of man, ape, cat, and fish. It is surely natural for such mental transformations to take place, for they do take place in the vast majority of human beings; when they do not, in cases where the brain fails to mature, we speak of unnatural or diseased minds.

The third division of our evidence relating to mental evolution constitutes what we have called the palaeontology of mind. By this term we mean the study of human minds of the past as we may know them through the many varied relics and documents which indicate their characters. It is only too obvious to every one that human knowledge has advanced in the course of time and that every department of human thought and mental activity has participated in this progress. No one would have the temerity to assert that we know nothing more than our ancestors of 5000 or even 1000 years ago. Our common-sense teaches us even before the man of science produces the full body of evidence at his disposal that human faculties have evolved. With regard to reasoning powers, which form one of the four distinguishing characteristics of the human species as contrasted with other animals, the case has already been reviewed, and we now turn to speech and language and other departments of human mentality. When we compare the attainments of present day men with the abilities and ideas of their ancestors we will do for mental phenomena precisely what was done when we compared the skeletons of modern animals with those of creatures belonging to bygone geological ages; in this reason is found the justification for the phrase employed in the present connection.

Written history furnishes a wealth of material for interpreting the mental conditions of ancient peoples, but beside documentary evidence the anthropologist learns to use inscriptions of prehistoric times, the primitive graphic representations on tombs and monuments, and even the characteristics of crude implements like axes and arrow-heads. The layman finds it difficult at first to regard such relics as indications of the mental stature of the people who made and possessed them; but a little thought will show that a man who used a rough stone ax in the time of the ancient Celts could not possibly have had a mind which included the conception of a finished iron tool or modern mechanism. So in all departments of human culture, the evolution of material objects may be justly employed in interpreting and estimating the mental abilities of ancient peoples.

Language is undoubtedly the most important single intellectual possession of mankind, for it constitutes, as it were, the very framework of social organization. Without a ready means of communication the myriad human units who perform the varied tasks necessary for the economic well-being of a body-politic would be unable to coordinate their manifold activities with success, and the structure of civilized societies at least would collapse. It needs no legend of a Tower of Babel to make this plain. So fundamental is this truth that although we may not have recognized it explicitly, we unconsciously form the belief that speech and language are exclusive properties of the human species, and even more characteristic of man alone than the power of reason itself. While organized language is clearly something that as such we do not share with the lower animals, nevertheless we cannot regard the communication of ideas or states of feeling by sound as an exclusive property of mankind. All are familiar with the difference between the whine and the bark of a dog and with the widely different feelings that are expressed by these contrasted sounds. And we know too that dogs can understand what many of their master's words signify, as when a shepherd gives directions to his collie. We could even go further down in the scale and find in the shrill chirping of the katydid at the mating season a still more elementary combination of significant instinctive sound elements. To the comparative student the speech of man differs from these lower modes of communication only in its greater complexity, and in its employment of more numerous and varied sounds,—in a word, only in the higher degree of its evolution. And it is even more evident that the diverse forms of speech employed by various races have gradually grown to be what they now are.

At the outset it is well to distinguish between writing, as the conventional mode of symbolizing words, and spoken language itself; the two have been more independent in their evolution than we may be wont to believe. Speech came first in historical development, just as a child now learns to talk before it can understand and use printed or written letters. Furthermore, many races still exist who have a well-developed form of language without any concrete way of recording it. It is true, of course, that back of the conventions of speech and writing are the ideas themselves that find expression in the one way or the other, or even by the still more primitive use of signs and gestures. But it is not with these ultimate elements of thought that we are now concerned; our task is to learn, first, what evidences are discoverable which show that the property of human language in general has originated by evolution, and then, in the second place, to perceive how this development proves an evolution of one group of ultimate ideas, namely, human concepts of the modal value of words and symbols as expressions of ideas themselves.

A simple common-sense treatment of obvious facts will greatly facilitate our progress. We know very well that the English we speak to-day differs in many ways from the language of Elizabethan times, and that the former is a direct descendant of the other. The latter, in turn, was a product of Norman French and Anglo-Saxon,—a combination of certain elements of both, but identical with neither of its immediate parents. The Saxon tongue itself has a history that leads back to King Alfred's time and earlier. Thus we are already aware of the fact that our speech has truly evolved, like the physical structure of the men who employ it; and we know, too, how readily new words are adopted into current English, like tabu from Polynesia, or garage from the French, showing that language is even now in process of evolution.

The sounds that make up spoken words can be resolved into a single element with its modifications; this basic element is the brute-like call or shout made with the mouth and throat opened wide—a sound we may have heard uttered by men under the stress of pain or terror. All of the various vowels are simply modifications of this element by altering the shape of the mouth cavity and orifice, while the consonants are produced by interrupting the sound-waves with the palate or lips or tongue. Like the cell as a unit of structure throughout the organic world, this elemental utterance proves to be the basic unit of all human languages, which vary so widely among races of to-day no less than they have in the history of any single people.

One of the first steps in the making of spoken words was taken by human beings when they imitated the calls or other sounds produced by living things, and tacitly agreed to recognize the imitation as a symbol of the creature making it. Thus the names for the cuckoo and the crow in many languages besides our own are simply copies of the calls uttered by these birds; a Tahitian calls a cat mimi; the name for a snake almost invariably includes the hissing attributed to that creature. After a time words which were at first simply imitations and which referred only to the things that made these sounds came to refer to certain qualities of the things imitated, so that the naming of other than natural objects, such as qualities, began, leading ultimately to the use of words for qualities belonging to many and different objects in the way of abstractions.

Much light upon the evolution of language is obtained when we treat the speech of various races as we did the skeletal structures of cats and seals and whales. When we compare the Italian, Spanish, Portuguese, and French languages, they reveal the same general structure in thousands of their words,—a common basis which in these cases is due to their derivation from the same ancestor, the Latin tongue. The Latin word for star is stella, and the Italian word of to-day is an identical and unchanged descendant, like a persistent type of shark which lives now in practically the same form as did its ancestor in the coal ages. The Spanish word is estrella, a modified derivative, but still one that bears in its structure the marks of its Latin origin; the French word etoile is a still more altered product of word evolution. Even in the German stern, Norse stjern, Danish starn, and English star we may recognize mutual affinities and common ancestral structure. Choosing illustrations from a different group, the Hebrew salutation "Peace be with you," Shalom lachem, proves to be a blood cousin of the Arabic Salaam alaikum, indicating the common ancestry of these diverse languages. Among Polynesian peoples the Tahitian calls a house a fare, the Maori of New Zealand uses whare, while the Hawaiian employs the word hale, and the Samoan, fale. Whenever we classify and compare human languages, we find similar consistent anatomical evidences of their relationships and evolution. We can even discern counterparts of the vestigial structures like the rudimentary limbs of whales. In the English word night certain letters do not function vocally, though in the German counterpart Nacht their correspondents still play a part. In the word dough as correctly pronounced the final letters are similarly vestigial, although in the phonetic relative tough they are still sounded.

The evolution of the art of writing appears with equal clearness when we compare the texts of modern peoples with inscriptions found on ancient temples and monuments and tablets. Even races of the present day employ methods of communicating ideas by writing symbols that are counterparts of the earliest stages in the historic development of writing. An Eskimo describes the events of a journey by a series of little pictures representing himself in the act of doing various things. A simple outline of a man with one arm pointing to the body and the other pointing away indicates "I go." A circle denotes the island to which he goes. He sleeps there one night, and he tells this by drawing a figure with one hand over the eyes, indicating sleep, while the other hand has one finger upraised to specify a single night. The next day he goes further and he employs the first figure again. A second island is indicated, in this case with a dot in the center of the circle to show a house in which he sleeps two nights, as his figure with closed eyes and two fingers uplifted shows. He hunts the walrus, an outline of which is given alongside of his figure waving a spear in one hand; likewise he hunts with a bow and arrow, which is demonstrated by the same method. A rude drawing representing a boat with two upright lines for himself and another man with paddles in their hands gives a further account of his journey, and the final figure is the circle denoting the original island to which he returns.

Pictography, as this method of communicating ideas is called, is often highly developed among the American Indians. For example, a petition from a tribe of Chippewa Indians to the President of the United States asking for the possession of certain lakes near their reservation is a series of pictures of the sacred animals or "totems" which represent the several subtribes. Lines run from the hearts of the totem animals to the heart of the chief totem, while similar lines run from the eyes of the subsidiary totems to the eyes of the chief, and these indicate that all of the subtribes feel the same way about the matter and view it alike,—the sentiment is unanimous. From the chief totem run out two lines, one going to the picture of the desired object, while the other goes to the President, conveying the petition. Thus pictography, a method of writing that belongs to the childhood of races, may be made to communicate ideas of a strikingly complex nature.

The ancient and modern inscriptions of Asia, from the Red Sea to China, present many significant stages in the development of picture-writing. In earliest ages the men of Asia made actual drawings of particular objects, such as the sun, trees, and human figures; subsequently these became conventionalized to a certain degree, but even as late as 3000 B.C. the Akkadian script was still largely pictographic. From it originated the knife-point writing of Babylonian and Chaldean clay tablets, while among the peoples of Eastern Asia, who continued to draw their symbols, the transition to conventionalized pictures such as those made by the Chinaman was slower and less drastic.

In another line of evolution, the hieroglyphics of Egyptian tombs and monuments illustrate a most interesting intermediate condition of development. These inscriptions have been deciphered only since the discovery of the famous Rosetta stone-fragment, which bears portions of three identical texts written in hieroglyphics, in Greek, and in another series of symbols. The Egyptian used more or less formalized characters to represent certain sounds, while in addition to the group of such characters combined to make a word, the scribe drew a supplementary picture of the thing or act signified. For instance, xeftu means enemies, but the Egyptian graver added a picture of a kneeling bowman to avoid any possible misapprehension as to his meaning. The symbols denoting "to walk" are followed by a pair of legs; the setting sun is described not only by a word but also by its outline as it lies on the horizon. Here again one is struck by the similarity between a stage in the historic development of racial characteristics and a method employed at the present time to teach the immature minds of children that certain letters represent a particular object; in a kindergarten primer the sentence "see the rat and the cat" is accompanied by pictures of the animals specified, in true hieroglyphic simplicity.

Just as the child's mind develops so that the aid of the picture can be dispensed with, and the symbolic characters can be used in increasingly complex ways, in like manner the minds of men living in successive centuries have evolved. While an evolution of human conceptual processes in general is not necessarily implied by the evolution of the forms of written language, the former process is in part demonstrated by the latter in so far as the change from the writing of pictures to the use of conventional symbols involves an advance in human ideas of the interpretation and value of the symbols in question. A man of ancient times drew a tree to represent his conception of this object; in the writing of English we now use four letters to stand for the same object, and none of these symbols is in any way a replica of the tree. It is certainly obvious that some change in the mental association of symbol and object has been brought about, and to this extent there has been mental evolution.

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Passing now to other departments of human culture, we must deal in the next place with the basic "arts of life"; that is, the modes of conducting the necessary activities of every day. All men of all times, be they civilized or savage, are impelled like the brutes by their biological nature to seek food and to repel their foes. The rough stone club and ax were fashioned by the first savage men, when diminishing physical prowess placed them at a disadvantage in the competition with stronger animals. Smoother and more efficient weapons were made by the hordes of their more advanced descendants, some of whom remained in the mental and cultural condition of the stone age like the Fuegian, until the white travelers of recent centuries brought them newer ideas and implements. In Europe and elsewhere the period of stone gave place to the bronze and iron ages, and throughout the changing years human inventiveness improved the missile and weapon to become the bow and arrow of medieval civilization and recent African savagery. The artillery and shells of modern warfare are their still more highly evolved descendants.

So it is with the dwellings of men, and the significance of the changes displayed by such things. The cave was a natural shelter for primitive man as well as for the wolf, and it is still used by men to-day. Where it did not exist, a leafy screen of branches served in its stead; even now there are human beings, like the African pygmy and the Indian of Brazil, who are little beyond the orang-outang as regards the character of the shelter they construct out of vegetation. From such crude beginnings, on a par with the lairs and nests of lower animals, have evolved the grass huts of the Zulu, the bamboo dwelling of the Malay, the igloo of the Arctic tribes, and the mud house of the desert Indians. The modern palace and apartment are merely more complex and more elaborate in material and architectural plan, when compared with their primitive antecedents.

Baskets, clay vessels, and other household articles testify in the same way to an evolution of the mental views of the people making them. The means of transportation are even more demonstrative. The wagon of the early Briton was like a rough ox-cart of the present day, evolved from the simple sledge as a beginning. In its turn it has served as a prototype for all the conveyances on wheels such as the stage-coach and the modern Pullman. The history of locomotives, employed in the first chapter to develop a clear conception of what evolution means, takes its place here as a demonstration of the way human ideas about traction have themselves evolved so as to render the construction of such mechanisms possible.

The primitive savage swimming in the sea found that a floating log supported his weight as he rested from his efforts. By the strokes of his arms or of a club in his hand, he could propel this log in a desired direction; thus the dugout canoe arose, to be steadied by the outrigger as the savage enlarged his experience. A cloth held aloft aided his progress down or across the wind, and it became an integral element of the sailing craft, which evolved through the stages of the galley and caravel to the schooner and frigate of modern times. When the steam-engine was invented and incorporated in the boat, a new line of evolution was initiated, leading from the "Clermont" to the "Lusitania" and the battleship.

The history of clothing begins with the employment of an animal's hide or a branch of leaves to protect the body from the sun's heat or the cold winds. Other early beginnings of the more elaborate decorative clothing are discerned by anthropologists in the scars made upon the arms and breast as in the case of the Australian black man, and in the figured patterns of tattooing, so remarkably developed by the natives in the islands of the South Pacific Ocean. A visit to a gallery of ancient and medieval paintings clearly shows that the conventional modes of clothing the human body have changed from century to century, while it is equally plain that they alter even from year to year of the present time, according to the vagaries of fashion.

A brief review of the "arts of pleasure," including music and sculpture and painting, demonstrates their evolution also. The earliest cavemen of Europe left crude drawings of reindeer and bears and wild oxen scratched upon bits of ivory or upon the stone walls of their shelters; the painting and sculpture of early historic Europe were more advanced, but they were far from being what Greece and Rome produced in later centuries. Indeed, the evolution of Greek sculpture carried this higher art to a point that is generally conceded to be far beyond that attained by even our modern sculptors, just as flying reptiles of the Chalk Age developed wings and learned to fly long before birds and bats came into existence.

In the field of music, the earliest stages can be surmised only by a study of the actual songs and instruments of primitive peoples now living in wild places. No doubt the song began as a recitation by a savage of the events of a battle or a journey in which he had participated. In giving such a description he lives his battles again, and his simulated moods and passions alter his voice so that the spoken history becomes a chant. From this to the choral and oratorio is not very far.

Musical instruments seem to have had a multiple origin. The ram's horn of the early Briton and the perforated conch-shell of the South Sea Islander are natural trumpets; when they were copied in brass and other metals they evolved rapidly to become the varied wind instruments typified to-day by the cornet and the tuba. In the same way the reed of the Greek shepherd is the ancestor of the flute and clarionet. Stringed instruments like the guitar, zither, and violin form another class which begins with the bow and its twanging string. The power of the note was intensified by holding a gourd against the bow to serve as a resonance-chamber. When the musician of early times enlarged this chamber, moved it to the end of the bow, and multiplied the strings, he constructed the cithara of antiquity,—the ancestor of a host of modern types, from the harp to the bass-viol and mandolin.

The dance and the drama find their beginnings in the simple reenactment of an actual series of events. Among Polynesians of to-day the dances still retain the rhythmic beat of the war-tread measure, and many of the motions of the arms are more or less conventionalized imitations of the act of striking with a club, or hurling a spear, and other acts. To such elements many other things have been added, but the fact remains that our own formal dances, as well as the sun-dance of the Indian and the mad whirl of the Dervish, are modern products which have truly evolved.

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When we turn to science and philosophy and other intellectual attainments of modern civilized peoples, it is easier to see how evolution has been accomplished, because we possess a wealth of written literature which explains the way that human ideas have changed from century to century. In these cases there can be no question that such evidences provide accurate instruments for estimating the mental abilities of the writers who produced them. We shall take up the higher conceptions of mankind at a later juncture, so at this point we need only to note that even these mental possessions, like household culture and even the physical structures of a human body, have changed and differentiated to become the widely different interpretations of the world and supernature that are held by the civilized, barbarous, and savage races of to-day.

As we look back over the facts that have been cited, and as we contemplate the large departments of knowledge about human psychology, mental development, and racial culture which these few details illustrate, we come to realize how securely founded is the doctrine that even the human mind with all its varied powers has grown to be what it is. Indeed, it is solely due to his mental prowess that man has attained a position above that of any lower animal. And yet every human organ and its function can be traced to something in the lower world; it is a difference only in degree and not in category that science discovers. The line connecting civilized man with the savage leads inevitably through the ape to the lower mammalia possessing intelligence, and on down to the reflex organic mechanisms which end with the Amoeba. It is a long distance from the mechanical activities of the protozooen to the processes of human thought; yet the physical basis of the latter is a cellular mechanism and nothing more, developed during a single human life in company with all other organs from a one-celled starting-point—the human egg.

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The method by which mental evolution has been accomplished is likewise demonstrable, because the factors are identical with those which bring about specific transformation in physical respects. This is to be expected, for the contention that the structures and the functions of the several organs constituting any system are inseparable has never been gainsaid.

Mental variation is real. It needs no scientist to tell us that human beings differ in intellectual qualifications and attainments, and that no two people are exactly similar even though they may be brothers or sisters. The struggle for existence or competition on the basis of mental ability is equally real, and every day we see the prize awarded to the more fit, while those who lose are crowded ever closer to the wall. As in all other fields of endeavor, the goal of success can be attained only by adaptation, which involves an adjustment to all of the conditions of existence—to social and ethical as well as to the more expressly material biological circumstances.

Heredity of mental qualities has also been demonstrated notably by Galton, Pearson, Woods, and Thorndike, who have also shown that the strength of inheritance in the case of mental traits is approximately the same as for physical characteristics like stature and eye-color. Just as a worker-bee inherits a specific form of nervous system which cooeperates with the other equally determined organic systems, wherefore the animal is forced to perform "instinctively" its peculiar specialized tasks, so the mental capacity of a human being is largely determined by congenital factors. Upon these primarily depends his success or failure. It is quite true that environment has a high degree of influence, so great indeed that some speak of a "social heredity"; they mean by this phrase that the mental equipment of an individual is determined by the things he finds about him, or learns from others without having to invent or originate them himself. Thus a Zulu boy acquires the habits of a warrior and a huntsman when he grows up in his native village, although he would undoubtedly develop quite different aptitudes if he should be taken as an infant to a city of white men. Nevertheless his mental machinery itself would be no less surely determined by heredity, even though the things with which it dealt would be provided by an alien environment.

Our present knowledge of the nature and history of human mentality enables us to learn many lessons that have a direct practical value, although it is impossible under the present limitations to give them the full discussion they deserve. Starting from the dictum that physical inheritance provides the mechanism of intellect, education and training of any kind prove to be effective as agents for developing hereditary qualities or for suppressing undesirable tendencies. Just as wind-strewn grains of wheat may fall upon rock and stony soil and loam, to grow well or poorly or not at all according to their environmental situations, so children with similar intellectual possibilities would have their growth fostered or hampered or prevented by the educational systems to which they were subjected. But the common-sense of science demonstrates that the mental qualities themselves could not be altered in nature by the circumstances controlling their development any more than the hereditary capability of the wheat grains to produce wheat would be altered by the character of the ground upon which they fell. Education and training thus find their sphere of usefulness is developing what it is worth while to bring out, and inhibiting the growth of what is harmful. That heredity in mental as well as in physical aspects provides the varying materials with which education must deal is a fundamental biological fact which is too often disregarded. It would be as futile for an instructor to attempt the task of forcing the children in a single schoolroom into the same mental mold, as it would be for a gymnasium master to expect that by a similar course of exercise he could make all of his students conform to the same identical stature, the same shape of the skull, or the same color of the eye and hair.

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Before leaving the subject of mental evolution we must return to the conception of inseparable mind and matter with which the present discussion began. The whole problem of human mental evolution is solved when we accept the conclusion that the nervous mechanism and the total series of its functional operations have evolved together in the production of the human brain and human faculty. The case regarding the physical organs rests solidly on the basis of the evidences outlined in a previous chapter; the special examination of purely mental phenomena has likewise been made in the foregoing sections. Just here we must pause to give further attention to the invariable relation between the human mind and the human brain.

The personality of human consciousness consists of the current of thoughts and feelings flowing continuously as one of them rises for a time to dominance only to fade when it leads to and is replaced by another dominant element of thought. This current is affected by the messages brought to the brain by nerves from the outer parts of the body where lie the eye and ear and other sense-organs. In like manner the various non-nervous parts of the body exert their influences upon consciousness, but the affective processes, as they are called, are not as well understood as the impressions passed inwards by the sense-organs along their nervous roadways to the central organ, the brain. But the brain is the place where the thinking individual resides; and this is one of the most important teachings of psychology, for not only does it help us to understand the evidence that human faculty has evolved, but it also inevitably brings us to consider certain vital questions of metaphysics, such as the immortality of the thinking individual after the material person with its brain ceases to exist. However, the latter question is something which does not concern us here; now it is most important to realize how completely mind is connected with the brain.

Many of the facts demonstrating this connection are matters of common knowledge. In deep and dreamless sleep the essential tissues of the brain are inactive, and in correspondence with the cessation of material events the thinking individual actually ceases to exist for a time. Any one who has ever fainted is subsequently aware of the break in the current of human consciousness when the blood does not fully supply the brain and this organ ceases to function properly; a severe blow upon the head likewise interrupts the normal physical processes, and at the same time the mind is correspondingly affected. Again, a progressive alteration of the brain as the result of diseased growth causes the mind to grow dim and incapable. Sometimes infants are born which are so deficient mentally as to be idiots, and an examination of the brain in such a case reveals certain correlated defects in physical organization. These and similar facts form the basis for the dictum that the development and evolution of the brain mean the growth and evolution of human intellect.

The further question as to the nature of the connection is interesting, but it relates to matters of far less consequence to the naturalist than the central fact of the invariable relation which does exist. Throughout the centuries many philosophers and naturalists of numerous peoples have endeavored to explain the connection in question in ways that have been largely determined by the changing states of knowledge of various periods, as well as by differences in individual temperament. Three general conceptions have been developed: first, that the material and mental phenomena interact; second, that they are parallel; and third, that they are one.

According to the first view, the individual thoughts and feelings forming elements in the chain of consecutive consciousness are affected by the events in the material physiology of the brain as a physical structure; the latter in turn react upon the psychical or mental elements. Thus there would be two complete series of phenomena, which are interdependent and interacting at all times, although each would be in itself a complete chain of elements.

The second interpretation is that the two series of events—namely, the physical processes of the brain and the elements of consciousness—are completely independent but entirely parallel. As one writer has put the case, it is as though we had two clocks whose machinery worked at the same rate and whose relationships were such that "one clock would give the proper number of strokes when the hands of the other pointed to the hour." But in my opinion this attempted explanation of the relation of mind to matter evades the whole question, as it does not account for the dependence of the former upon the latter, but merely assumes the existence of a more ultimate and unknown group of causes for a parallelism in the rates of operation of two series of things regarded as disconnected.

The third conception recommends itself to many on account of its greater simplicity. Formulated as the doctrine of monism, it states that the mind and its material basis are merely different aspects of one and the same thing, and that there is only one series of connected elements which are known to us directly as the current of our thoughts and indirectly as the physiological processes going on mainly in the cerebrum. Thus mind is purely subjective, the brain is only mediately objective. It is because the mental and the material are so intimately related that the monist believes them to be connected as are the lungs and respiration, the hand and grasping, or the eye and the reception of visual impressions from without.

But whichever one of these explanations we choose to adopt as our own, the basic fact of primary importance is that there is an invariable dependence of human thought upon a brain comprising a highly developed cerebrum, whatever may be the ultimate nature of the way mental processes are determined by physical processes, or vice versa. This fact stands unquestioned and unassailable; human faculty and the brain cannot be considered apart, even if they may not actually be different aspects of the same basic "mind-stuff," as Clifford calls the ultimate dual thing.

Like all of the other organs of lesser importance belonging to the nervous system, the brain is a complex of tissues which in the last analysis are groups of cell-bodies with their fibrous prolongations. When these cellular elements are in operation, mental processes go on; the unit of the mental process therefore is the functioning of a brain-cell. But we know that the substance of a brain-cell is the wonderful physical basis of life called protoplasm, that demanded our attention at the outset. The chemicals that go to make up protoplasm are everywhere carbon, hydrogen, oxygen, and other substances that are exactly the same outside the body as inside. It is the combination of these substances in a peculiar way which makes protoplasm, and it is the combination of their individual properties which in a real even though unknown manner gives the powers to protoplasm, even to that of a living brain-cell. Does science teach us, then, that the ultimate elements of human faculty are carbon-ness and hydrogen-ness, and oxygen-ness, which in themselves are not mind, but which when they are combined, and when such chemical atoms exist in protoplasm, constitute mental powers? Plain common-sense answers in the affirmative. We need not, indeed, we must not, attribute mind as such to rock salt or to the water of a stream, but we do know that salts and water and other dead substances may enter into the composition of the material brain which is the physical basis of mind.

In my opinion the individual argument renders the monistic conception of mind and matter unassailable. The food that we may eat and the water we may drink are dead, and as such they display absolutely no evidence of nervous or mental processes. When they enter our bodies, they with other foods replenish the various tissues, and among these the parts of the brain. In a material sense they become actual living protoplasm, replacing the worn-out substances destroyed during our previous thinking; and their properties are combined to make brain and thought, to play for a time their part in life, and to pass back into the world of dead, unthinking things. Every one of us knows that hunger reduces our ability to think clearly and fully, and every one knows also that mental vigor is renewed when fresh supplies of nourishment reach the brain. What can be the source of mentality, if it is not something brought in from the outer world along with the chemical substances which taken singly are devoid of mind? Scientific monism frankly replies that it is unable to find another origin.

We are thus brought to recognize, not only the continuity taught by organic evolution, but also the uniformity of the materials constituting the entire sensible world, inasmuch as the ultimate unit of all nervous phenomena is the reflex act of a protoplasmic mass, which itself is a synthesis of properties inhering in the chemical elements making up living matter. Among inorganic things the mind-stuff units are combined in relatively simple ways, and the "stuff" does not give any outward evidences of "mind" as such. Living things are almost infinitely complex as regards their chemical organization, and even in the very lowest of them we can discern a cell-reflex element which, combined with others like it, forms the unit of the compounds we call instinct, intelligence, and reason. Hence through an analysis of mental evolution we are enabled to form the larger conception of a continuous universe whose ultimate elements are the same everywhere.



VII

SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS

We now reach a critical juncture in our study of the foundations of evolutionary doctrine, for we must pass at this point to an inquiry into the nature and origin of human social relations. In undertaking this task we may seem to leave the field which is properly that of organic evolution, and many perhaps will be unwilling to view such aspects of human life as materials for purely biological analysis, arrangement, and explanation. But even before the reasons for doing so may be made apparent, every one must admit that the subject of mental evolution, which comprises so large a bulk of details expressly social in their character and value, virtually compels us to scrutinize the history of the economic and other interrelationships maintained by the human constituents of civilized, barbarous, and savage communities. Language has been treated as an individual mental product, and so have the arts of life and of pleasure; but all of these things find their greatest utility in their social usage,—in their value as bonds which hold together the few or many human beings composing groups of lower or higher grade. Without discovering any other reasons we would be impelled to take up social evolution, for this process is inextricably bound up with the origin and development of all departments of human thought and action.

If now this new field is actually to be included within the scope of the laws controlling the rest of nature's evolution, two general conclusions must be established. Although no formal order need be followed, it must at some time be shown that human social relations are biological relations, to be best explained only through their comparison with the far simpler modes of association found by the biologist among lower orders of beings; and in the second place it must be demonstrated that identical biological laws, uniform in their operation everywhere in the organic world, have controlled the origin and establishment of even the most complex societies of men. So far no reason has been discovered by science for believing that evolution has been discontinuous, holding true only for the merely physical characteristics of humanity as a whole; and furthermore, the impersonal student of nature finds ample positive evidences showing that the basic laws of associations of whatever grade are exactly the same. For these laws we are to seek.

Heretofore the doctrine of organic evolution has been discussed with reference to the single individual organism viewed as a natural object whose history and vital relations require elucidation. Both in the general arguments of the first few chapters and in the fifth and sixth chapters dealing with the single case of the human species, the proof has been given that all of the structural and physiological characters of any and every organic type fall within the scope of the principles of evolution, by which alone they can be reasonably interpreted. It has been unjust in a sense to ignore completely the importance of the organic relations of a social nature to which we are now to turn, because no individual can exist without having its life directly influenced, not only by other kinds of organisms, but even more intimately by other members of its own species. In a single day's activity we who are citizens of a great metropolis are forced into contact with almost countless other lives, glancing off from one and another after influencing them to some degree, and gaining ourselves some impetus and stimulus from our longer or shorter intercourse with each of them. Our varied social relations are so many and obvious that it is quite superfluous to specify them as essential things in human life. For the very reason that they are so obvious and constitute so large a part of our daily life, we are in danger of conceiving them to be exclusively human; we unconsciously regard them as different from anything to be found elsewhere and quite independent of the biological laws controlling the human unit.

On the contrary, as we trace the development of social organization from its earliest rudiments it becomes ever clearer that evolution has been continuous, and that during later ages there has been no suspension of the natural laws which earlier produced the human type of organism. The lessons we have learned are by no means to be ignored from this point forward; all of our conceptions of human biological history must be kept in mind, for anything new that we may learn is superadded to the rest,—it cannot disturb or alter the foundations already laid. It is even more important to realize that the same scientific method is to be employed which has been so fruitful heretofore. It has given us interesting facts; it has indicated the most profitable lines of attack upon one and another scientific problem; and it has demonstrated the practical value of accurate knowledge, even of information about the evolutionary process. As familiarity with the laws of human physiology enables one to lead a more hygienic and efficient life, and as the results of analyzing the evolution of mentality make it possible to advance intellectually with greater sureness, conserving our mental energies for effort along lines established by hereditary endowment, so now we are justified in expecting that a clear insight into the origin of our social situation and social obligations will have a higher usefulness beyond the value of the mere interest inhering in our new knowledge. Every one is necessarily concerned with social questions; never before has there been so much world-wide discussion of topics in this field. And while it is true that much good may be accomplished in utter ignorance of the past history of human institutions and of the underlying principles which control the varied types of organic associations, surely enlightened efforts will be more effective for good. Therefore every member of a community who is capable of thinking straight rests under an obligation imposed by nature to learn how he is related to his fellow-men; he must act in concert with them or else he forfeits his rights as a social unit. And it is his clear duty to search among the results of science for aid in ascertaining what he ought to do, and what reasons are given by evolution for the nature of his vital duties.

Despite the growing appreciation of the fundamental relation between biology and sociology, it is still far from universal. That the latter science is in a sense a division of the former is more often recognized by the biologist than by the average well-informed student of human social phenomena. The layman in sociology too often concerns himself solely with the complexities of the human problems, and he remains unaware of the manifold products in the way of communal organisms far lower in the scale of life firmly established as primitive biological associations ages before the first human beings so advanced in mental stature that tribal unions were found good. Among insects especially the biologist finds many types of organized living things, ranging widely from the solitary individual—a counterpart of something even more primitive than the most unsocial savage now existing—up to communities that rival human civilization, as regards the concerted effect of the diversified lives of the component units. The student of the whole of living nature is favored still more in that he learns how the make-up of such a simple organism as a jellyfish displays principles underlying the structure of the whole and the interplay of the parts that are identical with principles of organization everywhere else. And all of these things can be dealt with in a purely impersonal way which is impossible when attention is restricted to the human case alone. Thus it becomes the biologist's privilege and his duty as well to place his findings before those who wish to understand the constitution of human society in order that evils may be lessened and benefits may be extended. He does this so far as he may be able in full confidence that the elements and basic principles are discoverable in lower nature, just as they are in the case of the material make-up and mental constitution of the single human individual.

A more explicit preliminary statement must now be given of the grounds for the belief that social evolution is but a part of organic evolution in general. Some of these reasons are not far to seek, but their cogency can scarcely be appreciated until we have examined the concrete facts of the whole biological series. Any human society selected for examination—be it a tribe, a village community, or a nation—is in last analysis an aggregate of human units and nothing besides. Its life consists of the combined activities of such components—and nothing else. Could we subtract the members one by one, there would be no intangible residuum after all the people and their lives had been taken away. When these simple facts are recognized, it is clear at once that the concerted activities performed by biological units cannot be anything but organic in their ultimate basis and nature; the evolution of such activities thus takes its place as a part of organic evolution.

The task of tracing out the history of social organizations of whatever grade can now be defined in precise terms: in simple words, it is to learn how the activities of the component biological units making up any association really differ from the vital performances of biological units existing by themselves. What is it that distinguishes a savage of antiquity from an American of to-day? The modern example is just as much an animal as the earlier type, and his physiology is essentially the same. It is something added to the common biological qualities of all men, some relation which does not appear as such in the life of rude tribes, that makes the distinction. And it is just this superadded relation that requires explanation, as regards its exact biological value and its historic development as well.

In undertaking this difficult task, it seems best to begin with the very simplest organisms that biology knows, working upwards through the scale to man. By this course the most basic elements of organization can be discovered without having to look for them among the intricate details of our own vital situation, where secondary and adventitious elements stand out in undue prominence, and where the impersonal view is well-nigh impossible. Step by step we will then work up the scale of social morphology, approaching in the natural evolutionary order that part of the subject which interests us most deeply.

Just as the construction of an edifice must begin with the fashioning of the individual brick and bolt and girder, so the evolution of a biological association begins with the unitary organisms consisting of single cells, like Amoeba. We have had occasion to discuss this animal many times in our previous studies of one or another aspect of evolution, and once again we must return to it in order to reestablish certain points that are of fundamental importance for our present purposes. Within the limits of its simple body, Amoeba performs the several tasks which nature demands a living thing shall do; it feeds and respires and moves, continually utilizing matter and energy obtained from the environment for the reconstruction of its substance and replenishment of its vital powers; it cooerdinates the activities of its simple body, and by its reflex responses to environmental influences it maintains its adjustment to the external conditions of life. The animal does all of these things with a purely individual benefit, namely, the prolongation of its own life. While it is performing these individual tasks, it does not concern itself with anything else but its own welfare; the interests of other living things are not involved in any way, excepting in the case of other organisms that may serve the animal as food. Amoeba, like every other living thing, if it is to exist, must unconsciously obey the first great commandment of nature,—"Preserve thyself."

But its life is incomplete if it stops with the furtherance of aims that we may call purely selfish. Nature also demands that an Amoeba, again like every other living thing, shall perpetuate its kind. The mode by which it reproduces is ordinarily quite simple; the animal grows to a certain bulk and then it divides into two masses of protoplasm, each of which receives a portion of the mother nucleus. Sometimes by a peculiar process it breaks up into numerous small fragments called spores, which also receive portions of the parent nucleus. The most striking feature in both kinds of reproduction in Amoeba is the complete destruction of the individual parent that exists before the act and does not afterwards. It is quite true that every part of the mother animal passes over into one or another of its products, but it is equally true that no one of these products is by itself the original individual. So even the simplest animal we know performs a task that is not only useless to itself, but is completely destructive of itself, for nature's greater purpose of preserving the race. We can readily see why this must be so; there is no place in the world for a species whose members put individual well-being above the welfare of the race, for which the production of new generations is essential, even though the satisfaction of this demand should necessitate the sacrifice of the parent organism. We might hesitate to use the word "altruistic" in describing the self-destructive reproductive act of an Amoeba, because this word connotes some degree of consciousness of the existence of other than personal interests, and of the welfare of different individuals. There is no reason to believe that such conscious recognition of any natural duties is possible in the case of so low an organism. But the fact remains that the result worked out by nature is the same as though there were a definite understanding of real duties. Even this unitary organism, then, acts mechanically so as to fulfil two primal obligations, first to itself, through activities with individual benefit as the result, and to the race by the act of reproduction which closes its individual existence and inaugurates a new generation.

The life of this example, representing the whole series of one-celled organisms, is almost infinitely simpler than that of a member of a human community, yet it reveals the beginnings of certain characteristics of the latter. Here, it is true, the natural obligations in question are not like those which are ordinarily denoted social, but it is equally true that even in this most elementary instance a living thing does not live unto itself alone. It is easy to see the value to the species as a whole of obedience to the second great law—"Preserve thy kind." But a little further thought makes it plain that even the performance of acts in compliance with the first mandate—"preserve thyself"—are not purely selfish, although their immediate value is realized as individual benefit. Surely an organism that failed to live an efficient individual life would be ineffective in reproduction, so that from one point of view everything an animal does is tributary to the culminating act performed for the larger good of the life of the whole species. It is a nice balance that nature has worked out in Amoeba, as well as in all other cases, between the personal life of the individual, complete only when the final process of multiplication supervenes, and this process itself, which demands an efficient performance, even though this is destructive of the performer.

Before passing to the next members of the series, which reveal additional principles more truly social in the human sense, let us pause to note that already we have found certain natural criteria that belong in the department of ethics. Even in the case of the biological unit like Amoeba, which is entirely solitary and unrelated to other individuals of its kind excepting in so far as it is a link in the chain of successive generations, any vital activity can be called good or bad, right or wrong. Nature judges an act good and right if it tends to preserve the animal and the species; an act is wrong and evil if it is biologically destructive of the animal or if it interferes with the perpetuation of its kind. Again it must be pointed out that these terms are human words, employed for the complex conceptions that belong alone to retrospective and contemplative human consciousness to most of us they seem to imply the existence of some absolute standard or ideal by which a given act may be tested to see if it is right or the opposite.

If human ethics is truly unrelated to beginnings found in lower nature, something that has arisen by itself from supernature, then we must not use the terms in question except by way of analogy. If, however, nature has been continuous in the working out of every department of human life and human thought through evolution, then the criteria of the righteousness of the acts performed even by an Amoeba may be found to be basic and fundamental for ethical systems of whatever human race or time. This subject remains to be discussed in the final chapter, but it must be clear that we cannot survey the evolutionary process by which social systems have come into being without dealing at the same time with the origin and growth of ethical conduct as such.

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Without leaving the group of one-celled animals typified by Amoeba, we find colonies of the most elementary biological nature, where other natural obligations are added to the two of greatest importance. Some species of the bell-animalcule, Vorticella, provide characteristic examples of these primitive compound protozoa. Here the assemblage is made up of one-celled individuals essentially similar to one another in structure and in physiological activities; in the latter respect each one of them is like Amoeba as well. They may remain together for a longer or shorter period, or during their whole existence until the time of reproduction. Like the solitary protozooen, each member leads a complete life in and by itself, equivalent to that of every biological unit. It obeys the two great laws already laid down, but in addition it seems to be required to remain with the others for some mutual good. The biological value of the association which imposes this additional obligation may be found perhaps in the fact that a large group is not so readily eaten by an enemy as an individual cell; but it is clearer that the process of reproduction, which consists of the fusion of small "gametes," or nucleated fragments produced by diverse or similar parents, must be greatly facilitated by the occurrence of gamete-forming individuals in one and the same colony. "To remain together" is the new duty imposed by nature for the good of all and for the welfare of each member of the group. Some biological advantage accrues to the several components, just as the banding of wolves enables the pack to accomplish something which the single wolf is unable to do, although in the latter case it is not so much a reproductive alliance that is formed as an offensive and defensive union.

One step higher in the scale stands the plant-form called Volvox, near the border-line between the one-celled and the many-celled organisms. This aquatic type, about the size of the head of an ordinary pin, is a hollow spherical colony, with a wall composed of closely set cellular components. These elements are not all alike, as in the case of colonial protozoa like Vorticella, for they fall into two classes which are distinguished by certain structural and functional characteristics. Most of them are simple feeding individuals which absorb nourishment for themselves primarily, but they pass on their surplus supplies to less favored neighbors if occasion demands. The other members begin life like the first-named, but later they become specialized to serve as reproductive individuals solely. Every member of the colony must obey the first precept of nature, otherwise it would be unable to play its part in the life of the whole community. But the discharge of the second natural obligation, namely to preserve the race, is here assigned to some, and to some only, of the whole group of cell individuals. It follows therefore that the division of the tasks necessary for the maintenance of a complete biological individual, and the differentiation of the members of the group into two kinds, leads to the establishment of an individuality of a higher order than the cell. Neither the purely nutritive nor the reproducing member is complete in itself; the two kinds must be combined to make a perfect organism. The life of any member can be selfish no longer, for if it is to exist itself, it must help others for the mutual advantage of all. A clear social relation is thus established; and the reflex conduct of the units of a Volvox colony can be justly denoted altruistic, even though in this case, as before, there can be no conscious recognition of the reasons why mutual interests are best served by what is actually done.

One of the most interesting and significant aspects of the life-history of Volvox is the appearance for the first time of biological death. More elementary organisms are immortal potentially even if not actually, for every portion of the body is capable of passing over into an animal of a succeeding generation. But in Volvox a division of labor has been effected of such a nature that most of the components discharge the tasks of individual value, and with the performance of these they die. Only the reproductive members are immortal in the sense that Amoeba is, for they only have a place in the chain of consecutive generations of Volvox colonies. From the standpoint of the nutritive individual it is better to be relieved of the reproductive task in order that there may be no interruption of its specialized activities for the good of all, but the entailed mortality is certainly disadvantageous to it. It is the higher interest of the colony as a whole that supersedes the welfare of the parts taken singly, and this larger welfare is safeguarded by a differentiation worked out by natural evolution which results in the assignment of personal and racial duties to different individuals, at the cost ultimately of the lives of the former.

We now reach the realm of the true many-celled animals, or Metazoa, where the biological units are combined to form an organic association displaying many more resemblances to a human society. The freshwater polyp Hydra, like the foregoing illustrations, is one whose structure has already been discussed in the earlier chapters, but now we may use it for an analysis of another series of biological phenomena. Its sac-like body consists of two cell-layers; the outer one is concerned primarily with offense and defense, while the inner layer is made up of digesting or nutritive elements. The essential cells concerned solely with reproduction lie below the outer sheet. Comparing this animal with an association like Volvox, we discover the same differentiation into immortal germ-elements and mortal cells, concerned respectively with the Hydra's racial existence and with its individual life; but far-reaching changes have come about in the biological relationships of the second class of cells. In describing the new phenomena it is absolutely necessary to employ the terms of human social organization, because the Hydra's body is a true colony of diverse cells in exactly the same sense that a nation is a body of human beings with more or less dissimilar social functions.

To begin with the differentiation into ectoderm and endoderm, the organism is comparable to a human community made up of military and agricultural classes. The cells of the former group protect themselves and the feeding elements also, while the units of the second defenseless type devote themselves to the task of provisioning the whole community, giving supplies of food to the defenders in exchange for the protection they afford; each kind needs the other, and each performs some distinctive task for the other as well as for itself. But the parallel thus drawn need not stop here. In the case of the outer layer, the cells are mostly flat covering elements that are the first to be torn off and injured when the animal is attacked. Scattered about among them are sense-cells standing like sentinels with delicate upright processes which receive stimuli from without the sense-cells transmit impulses to the network of nerve-cells below, which is a counterpart of the signal corps of an army, keeping all parts of the whole organization in communication with one another. Most wonderful of all are the stinging-cells of the outer layer; these produce a flask-shaped, poisoned bomb which is discharged by the convulsive contraction of the cell itself so as to stun and injure the enemy or prey. The bomb-throwing cells die immediately after they have ejected their missiles; like soldiers participating in a forlorn hope, they sacrifice their lives in one supreme effort of service to the cell-community of which they are members.

These and similar facts prove conclusively that Hydra is a true community even in the human sense, and that the laws of biological association are established at a point far below the level of the insects. The individuality of the unit is still maintained, and each cell must guard its own interests to a certain degree, but the original independence of the unit has become so altered by differentiation and division of labor that a close interdependent relation has come about. The complete individual is now the whole aggregate; it is the entire Hydra itself which must obey the primary commands of nature to live efficiently and to perpetuate its kind. True it is that the life of the higher individual is the sum total of the activities performed by its constituent cells, but no one of the varied specialized elements is biologically perfect by itself or equivalent to the whole. And, as we have seen, the welfare of the complete animal takes precedence over that of any one of its parts, just as the existence of a nation may be preserved only by the death of soldiers warring for its honor and life.

If, now, we should pass on to the more complex organisms like worms and insects and vertebrates, and should disregard the communal relations of some of these animals, each individual proves to be like Hydra as regards the principles underlying its make-up and workings. A single bee, like a man, is a definitely constituted aggregate of cells, differing as a whole from Hydra only in the degree of differentiation exhibited by its constituent elements. Instead of a loose network of nerve-cells there is the far more complex nervous system whose evolution has been outlined in the sixth chapter. The blood-vascular and respiratory and excretory systems have become well organized, in response, so to speak, to the demands on the part of the nervous and alimentary organs that they may be relieved of the tasks of circulation and respiration and the discharge of ash-wastes. Therefore the cells which make up an insect and a man are more diverse, they have more varied interrelationships, and they are far more interdependent then in the case of the components of Hydra. Yet all the many-celled organisms that we are so accustomed to regard as individuals are really communities, demonstrating the existence and partial antithesis of the great laws of egoism and altruism, which are traceable even down to Amoeba and its like.

So much has been made of the lower kinds of cell-associations because the mind of the layman is unconsciously imbued with the idea that human society is a new thing,—an idea which we now see it is necessary to discard at the outset. Indeed, the cell-association of the Hydra and insect type is a more compact and a more stable kind of community than any group of human individuals worked out by nature toward the present end of the whole scheme of evolution. That is to say, the subordination of cell-interest to cell-group welfare, while it must not go so far as to render the unit incapable of doing its work, is sufficiently advanced to make uncontrolled individualism impossible. Let any class of Hydra's cells, such as the nerve or muscle network, assume to exercise a selfish preeminence or to conduct a "strike," the other classes, like the feeding cells, would not be properly served and they would be unable in consequence to work efficiently for the strikers. The immediate result would be suicidal, for the selfish nerve-class would inevitably suffer through the downfall of the whole social fabric. It is a nicely adjusted equilibrium that is established, where the "equal rights" of all the diverse cells consist in freedom to play a special part in the life of the group, serving other individuals in return for their service. The Golden Rule is a natural law as old as nature; for even in Hydra's life, unconscious discharge of duties to the race, and hence to others, is obligatory. And all these low types of organic associations evolved ages before the rules of human social order were vaguely recognized by the reflective self-consciousness of man, to be formulated as the science of ethics.

The evolution of the wonderfully varied societies found among insects begins with the solitary insect itself, just as this, viewed as a cell-community, originates from one-celled beginnings like Amoeba through progressive evolution in time. The similarity between social insects and human associations is clearer than in the case of a comparison between an example from either group and a cell-community, because the higher forms lack the organic contact of the components which is so prominent a feature in the lower instance. The social bonds are looser and they allow a freer play of the constituents; but nevertheless the same laws that control the activities of the cells making up what we now take as the individual element, command obedience on the part of the interrelated members of an insect community with equal strictness.

A butterfly or a moth is primarily egoistic and unsocial in the ordinary sense during its entire life-history, until the final reproductive act which has a value to the species. The caterpillar larva devotes all of its energies to feeding and growing, unconcerned with the final duties of the moth with which it is connected just as the indifferent unit of a young Volvox colony is related to a reproducing member of the full-grown organism. Now and then, it is true, species like the so-called tent caterpillar are met with where numerous larvae spin silken communal nests to which they retire at night and in which they remain to molt. The pupa, like the larva, is individualistic and employs its time in producing the final adult form. The mature individual, however, is constructed almost solely for the greater purpose of perpetuating the species. Indeed the larger silkworm moths do not and cannot feed, and their value is only that of a device for keeping the race established. Adult may-flies live only a few minutes, just long enough to provide for the fertilization and deposition of the eggs, although to prepare for these acts the young individuals must have toiled for months; the preparatory time may amount to many years in such a case as the seventeen-year locust. But nature is satisfied, as long as the organic mechanisms obey her double commandment, "Live and grow so as to multiply." Like an Amoeba, the solitary insect must be egoistic at first, in order to be altruistic in a racial sense in its last days.

Wasps, bees, and ants provide many familiar examples of colonial organizations that become all the more marvelous on closer acquaintance, on account of their resemblances to human associations on the one hand, and to cell-associations on the other. Their illustrative beauty is enhanced by their wide variety, for they grade from counterparts of highly civilized men down to a savage among insects, such as the strictly solitary digger-wasp, whose instincts served to exemplify the insect type of "mentality" in the discussions of the preceding chapter.

The true communities founded by wasps and hornets must be assigned to a low grade in the scale because they originate during a single season and break up at its end; for this very reason the wasp community is intensely interesting to the student of comparative social evolution. In the spring a solitary female emerges from the crevice where she has hibernated and resumes active life; she feeds for a time to renew her strength and then she constructs a simple nest of mud or masticated wood-pulp. In the first few cells of this nest she deposits her eggs, and when they hatch she herself provides the larvae with food, but still continues to enlarge the house and to produce more eggs. Thus during the first few weeks of the colony's existence this single individual performs a variety of tasks of racial as well as of purely egoistic value; but as time goes on, a profound change comes about in her activities and in the life of the whole community. The members of the first brood do not grow into counterparts of their mother; they are all sexless "workers" who progressively relieve their parent of the tasks of nest-building and foraging and nursing, so that their mother becomes a "queen" who devotes her entire time to the special reproductive task which she only can perform. We may justly compare the queen to the reproductive organ of Hydra, for the values to the life of the species are identical in the two cases, while the various classes of workers are counterparts of such units as the muscle and nerve and nutritive components of the Hydra or any other cell-community individual. Another resemblance between the two is found in the death of all the sexless individuals at the end of the season, when reproducing males and females are finally formed, of whom the fertile queens only survive in their winter hiding places; and again we can discover the cause for biological death in that division of labor which calls upon certain members of the whole community to perform tasks that have no value when once provision has been made for perpetuating the species. Finally the mode by which the colony grows and amplifies is in all respects like the embryonic development of an egg into a Hydra, so that we may add the phrase "social embryology" to our vocabulary. The original female is an undifferentiated master of all trades; the small tribe she first establishes is little better off than a horde of savages; but during its seasonal existence the community increases in numbers and complexity until it advances well toward the civilized condition, when each class performs its special task for the good of all.

The bees take us higher in the scale, although many solitary species occur, as well as social forms like the bumblebees where colonies are formed in a single season only to break up with the advent of cold weather. The honeybees, however, establish permanent communities from which swarms may set out during the warm months to become new colonies elsewhere. Many hundreds of bees make up a hive, and they belong to three classes or castes, which differ in structure and social function. The queen is a fertile female, the drones are males, and the workers are stunted and infertile females which take no part in reproduction. In this case the queen never discharges any menial duties, for these are attended to by the workers; she devotes her entire time to laying eggs, which are cared for by her subjects, who act as nurses and guards for the monarch as well. The young workers serve at first as doorkeepers, and only later do they take the field in the search for nectar and pollen, and work as house-builders. Each individual performs its special task for its own benefit and for the weal of all; each possesses an equal right to share in the prosperity of the whole community so long as it acts altruistically as well as egoistically. And just as the welfare of Hydra is superior to that of any one of its constituent cells, so the well-being of a hive of bees may be safeguarded only by the actual sacrifice of some of its members. Should food supplies be inadequate, the superfluous drones are stung to death,—the victims of legalized murder. But more marvelous still is the provision that is said to be made by certain individuals for their own destruction should this become desirable. As every one knows, a reigning queen may leave the hive with many of her subjects and "swarm" in a new locality. When she does this, during the warm months, the workers of the original hive feed some of the female larvae with richer food, and place these potential queens or princesses in special roomy cells apart from the ordinary brood chambers; one of them soon emerges to become a new sovereign. Let us note in passing how similar this is to the production of new egg-cells in a Hydra, when the mature germs of an earlier generation are prepared and discharged. When, now, the colder weather sets in, and the possibility of subsequent swarming is set aside, the reigning queen is allowed by her attendant guards to visit the royal cells, whose occupants she stings to death, thus destroying any possible claimant to her place. And when the royal princess constructs her part of the pupal case, she leaves an aperture so that if and when it should become necessary for the queen to kill her, the sovereign would not injure her sting and be unable to kill the other individuals who might become aspirants for the throne and so precipitate a civil war! As in the case of the self-destructive act on the part of a stinging cell in Hydra, altruistic subservience to the interests of the colony can go no farther.

The ants form stable colonies of still higher grades, where the workers are not all alike in general structure, but become more rigidly specialized for the performance of restricted tasks. As before, there is the fundamental differentiation into the sexual "queens" and males, and the sterile workers concerned with the immediate material life of the community. In some species the workers serve as herdsmen, caring for the ant-cattle or aphids, from which they receive minute drops of a sweet juice for food. The aphids are tended on the leaves of various plants during the summer, and are carefully reared and stabled and fed below ground during the winter months. In other species seeds are procured and stored in underground granaries. The leaf-cutters are forms which grow food supplies of fungi in subterranean mushroom gardens; the compost consists of cuttings brought from the leaves of bushes by myriads of workers, whose processions are guarded by larger-headed soldiers of several ranks. In the honey-ants of Colorado and tropical America certain individuals pass their time suspended from the roof of a large nest-chamber, where they receive the sweet juice brought in by the workers. They serve as animated preserve jars, distended sometimes to the size of a grape with the communal stores of food, which they return to the workers when external sources of food may fail. Finally there are the slaveholding species which conduct forays upon the nests of other forms, to procure the young of the latter, which grow up in their captors' nests and serve them as nurses and masons and foragers. So long has this custom been established that some slaveholders are entirely unable to feed themselves, and would die out if their slaves failed to support them.

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Let us pause at this point to summarize the results of the foregoing analysis, in order that we may approach the biological study of human associations with definite and clear conceptions of the fundamental laws controlling living communities of all grades.

We have dealt mainly with Amoeba, Hydra, and the ant-community which exemplify three somewhat distinct types of organic individuality. Some of the transitional forms have been specified to show how the second kind originates from the first, and how in its turn this grows in time into the third and most complex association; thus Vorticella and Volvox connect Amoeba with the cell-community individual like Hydra and a solitary wasp, while the annually established colonies of social wasps and of bumblebees lead to the permanent colony-individual. Restricting attention to the three primary examples, and remembering that the criterion of completeness is the ability to discharge satisfactorily all of the eight biological tasks, it is clear that the entire Hydra and the whole ant-community correspond physiologically with Amoeba, although the first-named is structurally a cell-community equivalent to many protozoa, and the insect colony is composed of many such cell-communities as elements. In the third type, neither a single queen nor a single worker is able to carry on all of the biological tasks any more than a muscle-cell or an unformed egg of Hydra can maintain itself capably in isolation. Therefore the ant-society as a whole and the Hydra in its entirety are organic individuals on the same physiological plane with Amoeba, and they are equally subject to the same great laws of nature demanding selfish maintenance and racial perpetuation.

But we must not lose sight of the fundamental value of the unit during the evolution of a higher from a lower type. The tissue-cell of Hydra must still obey the mandate to live an efficient personal life, because this is necessary for the welfare of other cells and of the whole complex. The original egoistic tasks are not abolished, but new duties are added to them in ways we have learned to distinguish. In Vorticella the products of fission do not separate, and certain advantages accrue from the organic continuity thus maintained. The success of Hydra in its ceaseless struggle to live depends wholly upon the cooperation of its differentiated cell-units, now no longer equivalent in function to the all-powerful Amoeba, although each one must be kept alive until its task is done, or the whole association would have no place in nature. Similarly in the higher insect community, the superadded duties to fellow-components are even clearer, for in the competition of colony with colony, involving terrific battles whose casualties may be numbered by thousands, the stronger wins; and strength depends upon the concerted efforts of all the members of the kingdom, that only collectively constitute a complete biological whole. Mere self-protection demands altruistic conduct: if the worker ceased to bring in food when its own hunger was satisfied, there would be no tribal stores for the stay-at-home queens and nurses; and if the soldier fled from the field of battle to save its own life, its act would be suicidal ultimately, for to the degree of one unit the defense of its non-military supporters would be weakened and they would be so much the less unprotected during their service for the soldiers and all others. Furthermore, we must admit the reality of natural criteria of ethical values, established far below mankind in the scale of life. In an ant-republic, laws are instinctively obeyed quite as implicitly as though they were intelligibly proclaimed to all of the emmet citizens. Right is might when community battles with community, for right is that which is biologically favorable. And what may be correct conduct on the part of the members of one species may be naturally wrong and evil in another case. To kill the princesses in order to obviate the possibility of civil war seems advantageous and therefore right when the queen remains in the persistent colony of honeybees, ready to do her part the following spring; but it might result in disaster and evil in the case of the social wasps, where the community dies as such in the fall, and the continuity of the species from one year to another requires the production of many queens lest the severe conditions of the winter's hibernation should kill all fertile females if only one or two were available. The standards of conduct are simple indeed; and whether or not it may seem best to separate the processes of social and ethical evolution culminating in human phenomena, the fact remains that these processes begin with elements discovered by the biologist among organisms of the lower levels in the scale.

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We come at length to the biological interpretation of human social evolution, in so far as this may be expounded in a simple and concise form. The comparative method must be employed in order to discover the fundamental attributes of savage, barbarous, and civilized communities which seem to differ so considerably in their complexity of social structure, and in order also to show that such basic elements are like those of communities formed by lower animals, and are equally the products of natural evolution. This whole subject seems to be exceedingly complex, because in our daily contact with others of our kind and in our occasional views of foreign races like our own, the smaller details occupy our attention, diverting it from the great basic principles according to which every society is organized and operates. But when once the major elements have been discovered in civilized and more primitive nations, the secondary and less essential phenomena fall into their proper relations, and a statement of the whole process of development becomes relatively simple. So much space has been devoted to lower types of communal organisms in order to learn what the fundamentals are, and not merely to provide analogies that may be useful hereafter. It now remains to arrange the evidences of social progress during the history of mankind itself, and to bring such human facts into relation with what has been discovered in lower nature. It is helpful to begin this part of the subject by asking ourselves what is already part of common knowledge about human history. Do we know of any civilized nation that is absolutely stable and unvarying in social structure, or one that has remained unchanged throughout historic time? The answer must be negative, for in no case does the past disclose an example of permanence in social or in any other respect; monarchies and republics are plastic like the human frame itself. The American Commonwealth is a relatively young social organism, and it is an easy task to trace its growth from beginnings in the diffuse and uncorrelated colonies of pre-Revolutionary years. Those colonies that were formed by English settlers were transplanted outgrowths from a civilized social parent which in its turn had clearly evolved from the state of King John's time and the still cruder form it had under King Alfred.