Popular Science Monthly/Volume 46/February 1895/Brain Development as Related to Evolution
|BRAIN DEVELOPMENT AS RELATED TO EVOLUTION.|
NO subject in recent times has received so much attention, or been so carefully investigated, as the question of the origin and age of man. Even that large class of scholars who long since came to regard the development of man from lower forms as a closed question have persistently held that it would be extremely desirable to ascertain the full extent to which visible and indisputable evidences could be discovered and authenticated, bearing upon this particular issue of the antiquity of man in the developed form we now call a human being. And it is safe to add that no investigations have ever been carried forward with more circumspection on the one side, or under the fire of a more searching and severe criticism on the other. For this question, involving the origin, and age of man as such, constitutes the very pith and animus of the captious contention still going on as to the soundness of what is commonly called, in a broader sense, the doctrine of evolution.
If the theory of the gradual unfolding of all other organic life could possibly have been accepted without disturbing the belief in the recent and exceptional origin of man, it doubtless would have long since received the approval of all intelligent minds.
It is because man, the head and consummation of all animate existence on the globe, is drawn into the restless current of all common and lower life, although in the van yet as part and parcel, kith and kin of it, that the whole theory of evolution is at first thought and to many minds fearful and shocking. Therefore the arguments and the objections constantly hurled against the broad conception of evolutionary descent involving man are legion, and this theory could never have held its ground against such an assault but for the one controlling fact that, fortunately or unfortunately, it is true. It is so true that, like a principle in morals, or the philosophy and spirit of Christianity, or a logical sequence, or a theorem in mathematics, when once understood, it compels belief.
Its critics, therefore, from whose ranks nearly all converts to the theory have been made, regarding the antiquity and origin of man as its most objectionable feature, have very naturally and from the first attempted to discredit all evidences of his prehistoric existence.
For instance, the reality and authenticity of the "human remains and works found in the Danish shell mounds and peat mosses, in the lake dwellings, in the coral reefs of Florida, in the cromlechs, barrows, and kistvaens, and in the rock shelters," were at first disputed, and when fully established by repeated discoveries it was then claimed that they all fell within the historic period. This contention was, however, quickly overshadowed and swept away by the more recent and numerous discoveries of stone implements, carvings, and human remains found in England, France, Belgium, Sicily, and America.
"Many of these discoveries were made in the valley of the Somme, the caves of the Dordogne, the valley of the Ouse, the basin of the Seine, the valley of the Thames; in the clay of the Hoxne, in the gravel of Icklingham, in the caves of Engis, Engihoul, and Neanderthal; in the cavern of Wells, in the caves of Gower in Glamorganshire, in the Grotto di Maccaquone in Sicily"; in the aqua-glacial deposits of the Delaware, of southern Ohio, of Mississippi, in Minnesota, and also in the old river bed under Table Mountain in California, and in many other localities, carrying back, in some instances, the age of man as a human being probably to the first or great Glacial period, and certainly to the beginning of the Quaternary, "for many of these remains are found intermingled with the bones of that large class of extinct animals which passed away with the telluric conditions to which these animals were organically related."
Now, since the almost immeasurable antiquity of man, as such, has been thus shown and placed beyond reasonable doubt, a new and popular objection has come to the front which brings us face to face with the subject in hand.
It is claimed by an immense number of people who-are but slightly acquainted with the subject in its broadest significance, that the cranial capacity of these early men is found to be nearly equal to that of modern savages; that the cranial capacity of the modern savage is nearly equal to that of the average routine laborer among the civilized of to-day; and that these facts are inconsistent with the alleged progressive and developing character of man structurally and organically. And it is also urged that these discoveries really show affirmatively that man, as a human being, has always been mentally, structurally, and organically just what he is now, at least as far back as we have been able, with all our research, to trace him.
Now, these objections merged in one are, as-we have stated, based upon an alleged comparative uniformity, or nearly equal cranial capacity, at present and during all the past ages, whenever and wherever man has been revealed.
This objection is what it appears to be, a random shot, or a convenient expedient, resorted to by that large class of persons who have made no exhaustive examination of the subject; but, baseless as it is in fact, it has about it a certain degree of plausibility not common with its predecessors. Moreover, as it is probably the last objection possible in the premises, it is better to deal with it patiently and set it aside carefully and becomingly.
It is not quite true that the cranial capacity of these ancient and primitive men has been shown to be nearly equal to that of modern savages, but, not to split hairs, let it pass that it is so, for a comparison of the cranial capacity of the savage and civilized races now existing, and an explanation of their relations in this respect, can be more accurately made, and it may be assumed that no one will be found to deny that a great change of some sort has taken place which is synonymous with what is commonly called the rise from savage to civilized life, even though the cranial capacity of the two classes should be held to be nearly equal—which, however, is not, as a rule, the case; at any rate, the two questions thus presented are as exactly alike as are two equilateral triangles, and so the former is fully answered by making a satisfactory disposition of the latter.
If we first consider, then, the difference in cranial capacity between the lowest savages and the highest civilized men, we shall at least know that all other cases will fall within the limits of this comparison. For this purpose perhaps no better or more reliable information can be found than that furnished by the exhaustive and well-known investigation made by John R. Marshall, F. R. S., Surgeon to University College, London, and reported in the Transactions of the Royal Society as early as 1864, and thus before the question we are examining became important. The entire report is very lengthy, extending to the minutest details.
The subject was an average Bushwoman, selected and sent him on request from southern Africa. She was about fifty years of age and five feet in height. Her brain weighed thirty-one ounces, while that of an average European woman of the same age and height would weigh forty ounces. The ratio of the Bushwoman's brain weight to her entire weight was as one to forty-five, while that of an average European woman of the same age and height would be as one to thirty-seven. Let us now look at the extremes. The cranial capacity of the Bushwoman was sixty-one cubic inches, while the largest cranial capacity known in America is that reported by Morton, of Philadelphia, as being one hundred and fourteen cubic inches, and the largest in Europe is that reported by Wagner, of Germany, as one hundred and fifteen cubic inches. Still, this Bushwoman had a generous cranial capacity considering her race, for the average negro has but from sixty-one to sixty-nine cubic inches—the former being her exact capacity. The Malay, although much higher in intelligence, has a still less cranial capacity, being only from fifty-seven to sixty-two, thus showing at the largest but one cubic inch in excess of that of the Bushwoman, and at the lowest, four cubic inches below hers. The Hottentots, but a shade if any higher in intelligence, have the large comparative average of seventy-five, or fourteen cubic inches more than the Bushwoman; while the Hindu, with all his arts and sciences, his literature, castes, complex government, and great book religions dating back to the very dawn of the historic period, has a less cranial capacity than the Malay, the negro, or the Hottentot, and it has been found in some normal instances as low as forty-six cubic inches. Is it not clear, then, that cranial capacity alone is not an infallible index of mental capacity or intelligence?
But Mr. Marshall found other and more important conditions in which the Bushwoman was exceedingly low down, notwithstanding her comparatively ample cranial capacity.
Let us quote his own words: "The convolutions are remarkably simple. The extreme curved convolution forming the outer border of the frontal lobe consists of three short, simple, curved branches, very like those found in the ape, instead of the tortuous sulci seen in the European brain. The forms of the surrounding orbital convolutions themselves, including the supra-orbital, are so broad and simple that the subordinate divisions which are so complex in the European brain can hardly be said to exist. All four of the primary convolutions are present, but all are characteristically short, narrow, and simple, instead of being complex and occupying a large space, but the arrangement is normal. They are evidences of structural inferiority, and show an infantile or even fœtal leaning." Having regard to the sum of its convolutional characters, judged by their presence or absence, their individual and relative size and position, their comparative simplicity or complexity, and the symmetry or asymmetry of particular fissures and convolutions, there is after all, Mr. Marshall concludes, a greater difference between the Bushwoman's brain and that of the highest apes yet described than between it and the European brain, but not so great a difference as exists between the brain of the orang and that of the chimpanzee, or between the brains of many other species of quadrumana.
Here we have two very interesting and important facts disclosed, which have been substantiated by many other similar investigations, of which this recital is but an example. First, that cranial capacity is not the main factor in determining intellectual and emotional development, but that increased brain surface, or the extent, number, variety, and depth of convolutions by which the brain surface is increased, do furnish a better index. Second, that this physical co-ordination with increased mental and emotional activity, this physical manifestation of developing mind, has already taken place in the brains of apes, and is foreshadowed in the lower species of quadrumana. Furthermore, from an intelligent standpoint this is precisely what might have been expected.
Let us bear in mind that out of all the innumerable, almost infinite number of variations, eccentricities, and oddities, however slight, found by examining each individual microscopically (if such a thing were possible), those minute changes and peculiarities, and those only, will be preserved in the long run, and after many generations, which are of such a character as to secure for their possessors more vigor and longevity than those without them can possibly have, simply because vigor and longevity vastly increase the opportunities of heredity.
Now the size and weight of the brain in proportion to the size and weight of the body is just one of those important proportions of parts which would make for or against the vigor and long life of the individual in a marked degree. One other concurrent condition, however, would perhaps be of even greater importance, and it is this: that the height, size, form, and weight of the whole body should have the fittest adaptation to its circumstances and to the work required of it, in order to secure the greatest vigor and longest life, and so at last to become the characteristic of every member of the species. So it is plain that the brain as to size and weight must stand two tests. It must not only bear the best possible proportion to the body, but that body must be of the fittest size and weight to meet successfully, and for the longest period, all that it is compelled to encounter, and thus to succeed above all other less fortunate individuals in finally making this double due proportion the property and the universal characteristic of the species. Within these limitations and conditions, but not otherwise, the size and weight of the brain and consequent cranial capacity are doubtless subject to the amount of mental instinctive, receptive and emotional activity demanded of it, and carried on within it. In shorter phrase, the brain may grow with increased exercise and larger and more frequent demands upon it like any other organ up to the point of becoming out of due proportion to the body, but still, the individuals possessing brains which exceed this limit would necessarily labor under such a disadvantage, as entire organisms, that they would in time be eliminated from the species. Now these are not simple deductive conclusions, as we shall soon see.
We have now cleared the ground for a statement of the actual sequential physical development accompanying increased mental activity after the head has attained such size that the cranial capacity can not be further enlarged without serious disadvantage to the individual. It is well known that the exterior surfaces of the brains of the lower vertebrates have, as a rule, comparatively smoother surfaces where they come in contact with the cranium, showing that the capacity of such heads as are in best proportion to their bodies is quite sufficient (without any such convolutional development as we find in the case of man) for all the mental and emotional activity and brain work demanded in the lives they lead.
But there are other animals that have thumbs opposed to four fingers like our own, and they can use these hands as we use ours, they can pick up stones and sticks, fruits, seeds, and nuts, catch insects, break branches and throw them down; they can pick and pull things in pieces, examine, inspect, and experiment with them, and reach conclusions (such as they are) about almost everything with which they come in contact. They can also unite their strength and their ingenuity, and can thus render services to each other. All this naturally multiplies their needs, and much more their desires, renders the exigencies of their daily experience more frequent and important, and their lives more diversified and complex. Thus the mental and emotional activities of all the quadrumana are so much increased by the use of a thumb and fingers that a head which is in due proportion to a body such as would be best adapted to springing, climbing, jumping, swinging, and other arboreal habits requiring great activity and expertness, has not sufficient cranial capacity for a brain with so much mental and emotional work to do. Here, then, we find for the first time a variation which characterizes more or less the whole family of quadrumana according to the degrees of intelligence of the several species. It consists of slight corrugations on the exterior of the brain, thus increasing the superficial area for the gray matter, without enlarging the head, the brain weight, or the cranial capacity to their disadvantage in other respects.
In the case of anthropoid apes, and proportioned to their greater intelligence, these corrugations or convolutions are increased in number. In the case of the lowest savage there is still another increase in number, variety, and depth, as we have seen in the case of the Bushwoman. And thus these convolutions go on pari passu with increasing manual dexterity and intelligence, multiplying, assuming more varied and complex forms and greater depth, until we reach the most thoughtful and learned members of the highest civilized communities, where the brain surface if smoothed out would measure, on an average, about four square feet.
What immediately concerns us, however, in this connection, is the fact that not only the savage and the primitive man, but the ape and even certain quadrumana, have already found more contriving, thinking, remembering, and other kinds of brain work to do than a head and cranial capacity in due proportion to their bodies will admit of. And thus each and all are preserving and perpetuating by natural selection and heredity all the variations of increased cerebral surface resulting from more numerous, varied, and deeper convolutions.
Is it inconsistent, then, with the theory of evolutionary descent for the savage to have the largest possible cranial capacity and head not out of due and advantageous proportion to his body and the demands of his mode of life? This question is completely answered by the fact, which has now been fully set forth, that the further growth of head and consequent cranial capacity in his case has been already arrested, as in the case of the ape and the quadrumana, at the point of becoming too large for his body and mode of life, while his still increasing and developing mental and emotional powers and activities have already found a substitute for further cranial capacity, or head growth, in more numerous, complex, and deeper convolutions, thus increasing the brain surface.
It is surprising that this objection has not been earlier demurred to on the specific ground of inadequacy. It now appears that as well might the cranial capacity of an ape as that of a savage or a primitive man be made the basis of this objection, since in all three cases further head growth has been checked at the point of undue proportion to the body, and thereafter increasing mental activity has found a physical substitute for further head or brain growth in the preservation, as a fitter adaptation, of every fortuitous variation in the direction of these increased convolutions, first foreshadowed in the quadrumana, reaching the highest complexity in civilized man, and co-ordinated to advancing intelligence at every intermediate step.
Thus we see that this popular objection crumbles at the first touch of a few simple and well-known facts.
We have now reached a position where we may compare with more interest than before the mental activities of the savage with those of the routine laborer in civilized life, and thus show inductively that the conclusions adopted are sustained by an applied and practical test.
We are all equally well qualified probably to form an estimate of the degree of emotional intensity and mental strain exercised in making again and again for a lifetime the same one single thing—for instance, a pair of shoes or trousers or a coat; in doing mason, painting, or plumbing work; in constructing furniture, shoeing horses, or setting type; in putting bobbins into and taking them from a machine in a factory, or in running the machine itself by switching on and off the belt; or in running the engine which propels the machine, or even in running a lathe which carves out over and over again the same part of some machine or implement; or in planting, harvesting, mowing, or chopping, or any other kind of routine work which is learned by imitation and thereafter performed automatically. Of course, the case was different when the same man, as formerly, had to perform nearly all the above kinds of labor for himself.
It is safe to say, however, since the recent extreme division of labor, that a month of any one kind of such work would not give rise to as many exciting incidents or unexpected exigencies stirring the emotions and requiring sagacity, mental alertness, quick perceptions, rapid decisions, and skillful execution, as would be encountered in a successful attempt to catch a squirrel, kill a deer, or fight a wild cat with savage appliances.
Flippant and superficial as such a comparison may seem, at first blush, in a serious paper, it is, however, quite necessary to illuminate, as no other method of presentation would do, the almost immeasurable difference between all the vocations of the savage and those of the routine laborer in our civilized life. To get a living, the hunting savage of the stone age is obliged to go through these wildly exciting experiences and vicissitudes, no two of which are exactly alike, nearly every day of his life, and frequently several times a day. It is, moreover, the exciting nature of primitive pursuits which makes this everyday labor of the savage a lively and interesting recreation for the most cultured and intellectually advanced classes among the civilized.
Now this wide and extreme dissimilarity arising from the very nature of savage pursuits, when compared with those of the routine laborer, uncovers to our view a far-reaching cause in development of which careful note should be taken.
The savage, as we might even now imagine, and a little later on shall more fully see, has a brain which is insufficient for his mode of life, and it is therefore constantly overtaxed by the amount of mental and emotional activity required of it. This, too, is the one antecedent condition and primal cause underlying, lifting, and advancing not only his but all human brain development, and probably all brain development.
Here we must leave for a time the savage and consider the present condition of the routine laborer.
He, on the other hand, has more cranial capacity, and convolutional development than he needs or knows what to do with. Two great changes have recently come over the whole civilized world, and among many other far-reaching effects these two changes have left him in this unfortunate condition. In the first place, machinery has taken the place of implements, and the latent energy of lifeless matter has been transformed into kinetic force and has taken the place of muscular power. The greater and constantly increasing part of his food is sown by machinery, cultivated by machinery, harvested, thrashed, transported, ground, cooked, and brought to his door by machinery. He is clothed, sheltered, and shod by machinery. His house, except the putting of it together, is made by machinery. The water of a distant lake or stream is brought through pipes to his very lips by machinery. His furniture, utensils, and tools are all made by machinery. His distant communications are conveyed by machinery. . He himself is transported about from place to place by machinery. His cradle and his coffin are made by machinery, and from the time he leaves the one till he enters the other he is lucky if he finds any more soul-stirring or intellectual employment than feeding, watering, shining up, waiting upon, and serving a machine.
The second great change is of a social character, but it has been greatly hastened and extended as a result of the first. At any rate, the two, each supplementing the other, have left his inherited cerebral outfit almost wholly unemployed, as compared with its busy activity at a time not very remote, even in the age of our grandfathers, when, like the savage, the worker cared for himself and his family and did nearly everything for himself, instead of doing possibly, as at present, some one thing for himself, and having all else done for him.
His children now receive a rudimentary education in public institutions, their moral and religious instruction is received in the free Sunday school; hospitals, dispensaries, and doctors take care of him when ill, and charitable societies take charge of him when he comes to want; savings banks receive his money and manage his investments; insurance companies relieve him from the calamities of fire and flood, accidents, illness, and death; public health officers sniff through his dwelling and order its sanitary conditions; public overseers of buildings supervise its construction, and are required to serve notice on him when it is likely to tumble down and hurt him; the police protect his person and his property, and the courts settle his disputes; he is examined, vaccinated, and protected from contagious diseases at public expense; the overseers of the poor help him in unexpected exigencies; public baths are provided for his use, and public soup houses are opened for him in time of general depression; temperance societies try to help him control his appetite; salvation armies endeavor to restrain his vices and improve his habits; trades unions tell him when he may and may not work, what work he may do and who he may work with, how much he may do in one day when he does work, within how many hours of that day he will be permitted to do it, and who he may or may not work for, and the least price he will be permitted to receive for his labor; the churches all assist him in his spiritual and religious life, and the largest and oldest of them all will engage, for a small weekly pittance and a few formal observances on his part, to safely deliver in paradise at last what little soul a man may have left after such a life as this. Thus all the complex cerebral and convolutional development in his case, which it has taken perhaps some hundreds of centuries to build up, is rendered comparatively superfluous and, to the same extent like all unexercised and useless organs or parts of organs positively detrimental and so to be modified or got rid of, and all brought about by these two great changes, we brag of (and with good reason from other points of view), both of which changes have taken place within the last two centuries, chiefly within the last hundred years, and the most important features of each within our own lifetime.
It is possible, of course, that some unforeseen change may occur, and it may bring with it some new and unexpected field for the exercise of his former mental activity, but at present it is neither apparent nor probable. Thus the routine laborers, constituting a large proportion of the inhabitants in many civilized countries, most of whom have, or recently had, sufficient cerebral capacity for great mental activity, are left with little more need of, or exercise for a complex organ of thought in the performance of their actual work than a caged squirrel has in rotating his wheel, and outside of their actual work society in one form or another has taken almost complete charge of them and of all which formerly interested them. It is certain that with this continuing condition—despite all social and educational efforts to the contrary—the routine laborer must fall back through atrophy and degeneration to some plane where the equilibrium between his inherited cerebral capacity and the actual demand for mental activity shall be restored.
We have now only time left us to review briefly two or three of the many peculiarities of savage life which stimulate increasing mental activity and its physical manifestation in convolutional development, and which peculiarities do not to the same extent, if at all, affect civilized men, and especially the routine laborers among them. To do this exhaustively would require a volume, and we can therefore only glance at the matter in the most cursory manner.
It is an open question as to the extent that the use to which learning is to be put constitutes a factor in determining the value of the mental development received in acquiring such learning. To whichever school of thought one may incline, it can hardly be denied by either side that in the acquisition of the same knowledge by two persons, the one for one purpose and the other for an entirely different but equally important object, the strengthening and developing effect, other things being equal, would be the same. Now the common hunting savage of the neolithic age takes up one branch of the study of natural history and pursues it until he is able to teach an Agassiz, an Audubon, or a Darwin. Not one of these learned men knew, after a life of study and observation, as much about this one thing, the habits of the wild beasts, birds, and fishes, as does the average savage hunter. To him such knowledge means food and life, and the lack of it hunger and starvation. He must know their color, size, and movements; when, where, and how they get their food and water; where and how they make their nests or lairs or homes; when they rest and when they go forth, and where; all their cries and sounds, and the meaning of them; and he must be able to imitate them so exactly that they shall think these sounds made by one of their own kind; he must know when and where they are moved about by winter and summer, by drought and flood; when and where they breed their young, and in each case whether the young are protected by hiding, defense, or flight. He must know what animals have leaders or sentinels, and how to distinguish them, and how to interpret their sounds of alarm, and distinguish them from the sounds of safety, and he must be able to perfectly produce both; he must know their strength, alertness, and acuteness of sense, speed, and endurance as related to the species and to the age and sex of the individual; he must be familiar with their dispositions, their courage, cunning, intelligence, and timidity, and be able to determine in advance what they would probably do under all conceivable conditions. Then it is not less necessary that he should know all the relations of each species to each and all of the others. To acquire this knowledge he must roam far and wide, and to do this with safety he must learn the physical geography and topography of the country; he must know the trend of the coast, the course of the rivers, the valleys, and the mountains, and the extent of the different water-sheds; he must discover the location and character of all the varieties of vegetation upon which animals feed; he must learn all their methods of capture and escape in all cases where they feed upon each other; he must become an expert in the study of all their tracks and the traces of their movements. The broken twig, the cropped grass, the grazed log, the pressed or upturned leaf must each reveal to him a whole series of facts in which a determination of the lapse of time is always most difficult; he must study the movements of the sun and moon and planets, and the position of the stars; he must learn to determine direction by the growth of mosses, the leaning of trees and the appearance of the foliage, and many other things equally important.
It is true that some part of this vast amount and variety of information may be communicated and so handed down from one generation to another, but the larger part must be acquired in the field and by each individual for himself. Much of it to be of practical use must be accompanied by the most wonderful skill and adroitness in its application. A practiced eye, an acute sense of hearing, deftness in movement, promptness in decision, coolness in execution are indispensable, and can not be taught orally or communicated. No civilized man could equal a savage hunter in this whole department of knowledge.
But comparisons of this sort are unsatisfactory to the last degree, because the probability of deriving a reasonable and fair conclusion from them depends more upon the ability of the mind to grasp and value details, to weigh justly many considerations, and to deal fairly and wisely with the facts, than it does upon the facts themselves. One thing is certain, however, that the savage would exercise the same amount of mental activity in obtaining all this knowledge for the purpose of getting a living by it, that a student of natural history would exercise in obtaining it for the purposes of a scientific classification. Moreover, the strength of motive, depth of desire, and intensity of emotion of the savage in his work would be as much greater than that of the student as it is more important to sustain life than it is to make a scientific classification; for the student, admitting that he works for bread or for fame or for gratification, may find many other ways if he fails in this to obtain either, while the savage must succeed in this one way or die in the attempt. Lastly, the savage obtains and applies his knowledge by the Baconian method of experience and experiment, while the student obtains his largely from books, and the balance by observation, but the routine laborer does not rise to either method, relying on oral instruction and imitation for the little he needs or learns.
Let us now glance at another peculiarity of savage life. In all civilized communities, and under every form of government, the protection of the person, of life, and of property devolves upon a few members of society who from time to time are appointed or elected for that especial purpose. This, except in rare exigencies, relieves the individual from taking any direct measures for the defense of his rights. Indeed, he is forbidden as a rule to do so, but is required in case of assault or trespass to call to his aid those officers who have been selected to defend him. Neither may he make reclamation, obtain redress, or inflict punishment directly in his own behalf. The savage, on the other hand, contrives and maintains all of his own safeguards. All these things he invariably does for himself in obedience to the quickest and strongest of his instincts—that of self-preservation. Thus the civilized man is guarded, policed, and protected by others, while the savage is his own patrolman, judge, jury, and executioner., All the protective devices he needs, at any rate all he can have, he must contrive and enforce for himself. He is his own defender, detective, and avenger. This whole broad field of activity, therefore, which we call domestic police regulation, including also many other departments of the general government, the savage concentrates in himself and brings within the scope of his own mental, emotional, and physical activity.
It would be a mistake to conclude, however, from what has been said, that the savage enjoys a wider freedom by reason thereof than the man who lives on the avenue and pays taxes, or strolls in the park and reads the notice, "Keep off the grass." The savage has a government and laws in abundance, all founded on traditions, maxims, customs, signs, omens, religious superstitions, quasi canon law, and crude ecclesiastical usages, and the notions and whims of a despotic chief, which reach to every detail of life, but they are all mandatory and restrictive rather than protective in their purpose and character.
When we couple all this with the amount they must learn, the ingenuity they must exercise, and the exigencies they must encounter in wrenching even the most precarious livelihood from unreclaimed Nature, is it at all strange that their immature brains are overtaxed, and that every variation in convolutional development is preserved and perpetuated, especially after head growth and cranial capacity have been checked at the point of undue and disadvantageous proportion to the body?
Thus it appears, in view of all the facts which modern investigation has disclosed, the merest outlines of which have been here given, that the comparatively equal head growth of all known men is no evidence whatever against the theory of their evolutionary descent, while the closely related fact that man shares with certain lower species of animals built like himself a brain development peculiar to him and them, and which has succeeded to an arrested head growth in his and their case alike, is more than an indication, it is very good proof so far as it goes that he and they had a similar if not the same origin and are members of the same family. And it is also evident, in the case of man at least, that this convolutional brain development is continuous from the lowest savages up to the age of machinery and the extreme division of labor, the accompanying institution of voluntary benevolent associations, and the modern forms of parental government, when it thus meets for the first time with a threatened reversal in the case of the routine laborer. He finds himself as a result of these changes in this predicament, he is still in possession, by inheritance, of the full brain development of the civilized, but with less use for, or need of it than has the hunting savage of the neolithic period.
In taking leave of this subject, one question not quite pertinent to the issue can not be repressed. Since all civilizations thus far have encountered a brood of incidental evils peculiarly their own, and, if not of their own creation, still consequent upon them, who can say that the one just exposed may not be the primal cause of the world-wide unrest of the present laboring classes, finding expression in all sorts of disorder from strikes to anarchy—the first fruits of atrophy—the vain attempt to employ an otherwise idle and already degenerating organ of thought, and, like all readjustments to a lower plane, resulting in vicious and reactionary conduct? If this result had been foreseen, could the cause have been suppressed? Is social growth, to any greater extent than individual, modified by desire and volition?
- Read before the Fortnightly Club for the Study of Anthropology, of Yonkers, N. Y., February 16, 1893, by G. Hilton Scribner, president.
- Functions of the Brain, by David Terrier, M. D., F. R. S., Professor of Forensic Medicine, King's College, London, published by Smith, Elder & Co., 51 Waterloo Place, London, p. 297: "The brain of man is constructed on the same type as that of the monkey, and essentially the same primary fissures and convolutions are recognizable in both, the chief differences consisting in the greater complexity of the convolutional arrangement of the human brain, caused by the development of the numerous secondary and tertiary gyri, which tend to obscure the simple type of the simian brain. These differences are more marked in the adult and highly developed brain, but are less pronounced in the fœtal human brain." See, also, Ecker on the Convolutions of the Human Brain, translated by Gallon, etc.