Being Well-Born.
by Michael F. Guyer.
INTRODUCTION
The writer recalls that when he was a young boy, he heard the grown-up people in the community earnestly and incessantly debating the question: Does heredity play a greater part in shaping one"s mind and body than does his environment? From that day to this he has listened to men and women in every walk of life discussing the relation of heredity to environment in determining human traits. Teachers and parents are constantly asking: "Are such and such characteristics in my children due to their inheritance or to the way they have been trained?" Students of juvenile delinquency and of mental defect and deficiency are searching everywhere for light on this matter. It is not to be wondered at that practically all people are peculiarly interested in this problem, since it concerns intimately one"s personal traits, and it constantly confronts any one who is responsible for the care and culture of the young.
It is suggestive to note how people differ in their views regarding the extent to which a child"s physical and mental qualities and capacities are fixed definitely by his inheritance. The writer has often heard students in university cla.s.ses discuss the subject; and their handling of the problem has shown how superficially and even superst.i.tiously most persons regard the mechanism and functions of heredity. It is significant also to observe what extreme views many people hold regarding the possibility of affecting a child"s traits and abilities by subjecting him to specific influences during his prenatal life. In any group of one hundred persons chosen at random, probably seventy-five will believe in specific prenatal influence. Many of them will believe in birthmarks due to peculiar experiences of the mother. A popular book recently published a.s.serts among other things that if a mother will look upon beautiful pictures and listen to good music during the prenatal period of her child, the latter will possess esthetic traits and interests in high degree. On the other hand, people generally do not seem to think that degenerate parents beget only degenerate children. Alcoholics, feeble-minded persons and the like are permitted to bring children into the world.
Very few people have any precise knowledge of the mechanism of heredity.
The whole thing is inscrutable to them, and is shrouded in mystery.
Superst.i.tion flourishes among even intelligent persons in respect to heredity, and errors due to education, and tragedies resulting from vicious social organization are all alike ascribed to its uncontrollable forces. Most people are none the wiser because they do not know to what extent the physical and mental defects and deviations of individuals are due to inheritance or to the malign influences of the individual"s environment and training.
Professor Guyer, who has studied the whole problem in a thoroughgoing, scientific way, has prepared this book with a view to illuminating some of the mysteries that surround the subject of heredity, and to dispelling the illusions that persist regarding it. He shows the method which nature follows in the development of the individual. He presents the laws which have become established respecting the extent to which and the manner in which immediate and remote ancestors contribute to the child"s physical and mental organism. He answers many questions which those who are engaged in social work or in education in the home or the school are asking to-day. He discusses subjects upon which every serious-minded person wishes to be informed. He has thus made a book which is both of theoretical and of practical interest.
He has written in a style which should make his book attractive to the parent and the teacher as well as to the student of the complicated mechanism of inheritance. Only a few special terms are used, and these should not give any reader trouble, because the treatment throughout is so concrete that the meaning of the terms will be easily grasped. Further, the book is ill.u.s.trated, with many attractive and instructive ill.u.s.trations which will show at a glance the working of the principles of inheritance which are developed in the text.
This book may be heartily commended to all who are interested in questions of human nature, education and social reform. It should enable the parent, the teacher and the legislator to understand more clearly than most of them now do in how far children"s traits and possibilities are or can be fixed by inheritance as contrasted with environmental conditions and nurture in home, school, church and inst.i.tutional life.
M. V. O"SHEA.
Madison, Wisconsin.
PREFACE
One of the most significant processes at work in society to-day is the awakening of the civilized world to the rights of the child; and it is coming to be realized that its right of rights is that of being well-born.
Any series of publications, therefore, dealing primarily with the problems of child nature may very fittingly be initiated by a discussion of the factor of well-nigh supreme importance in determining this nature, heredity.
No principles have more direct bearing on the welfare of man than those of heredity, and yet on scarcely any subject does as wide-spread ignorance prevail. This is due in part to the complexity of the subject, but more to the fact that in the past no clear-cut methods of attacking the manifold problems involved had been devised. Happily this difficulty has at least in part been overcome.
It is no exaggeration to say that during the last fifteen years we have made more progress in measuring the extent of inheritance and in determining its elemental factors than in all previous time. Instead of dealing wholly now with vague general impressions and speculations, certain definite principles of genetic transmission have been disclosed.
And since it is becoming more and more apparent that these hold for man as well as for plants and animals in general, we can no longer ignore the social responsibilities which the new facts thrust upon us.
Since what a child becomes is determined so largely by its inborn capacities it is of the greatest importance that teachers and parents realize something of the nature of such apt.i.tudes before they begin to awaken them. For education consists in large measure in applying the stimuli necessary to set going these potentialities and of affording opportunity for their expression. Of the good propensities, some will require merely the start, others will need to be fostered and coaxed into permanence through the stereotyping effects of proper habits; of the dangerous or bad, some must be kept dormant by preventing improper stimulation, others repressed by the cultivation of inhibitive tendencies, and yet others smothered or excluded by filling their place with desirable traits before they themselves come into expression.
We must see clearly, furthermore, that even the best of pedagogy and parental training has obvious limits. Once grasp the truth that a child"s fate in life is frequently decided long before birth, and that no amount of food or hospital service or culture or tears will ever wholly make good the deficiencies of bad "blood," or in the language of the biologist, a faulty germ-plasm, and the conviction must surely be borne home to the intelligent members of society that one thing of superlative importance in life is the making of a wise choice of a marriage mate on the one hand, and the prevention of parenthood to the obviously unfit on the other.
In the present volume it is intended to examine into the natural endowment of the child. And since full comprehension of it requires some understanding of the nature of the physical mechanism by which hereditary traits are handed on from generation to generation, a small amount of s.p.a.ce is given to this phase. Then, that the reader may appreciate to their fullest extent the facts gathered concerning man, a review of the more significant principles of genetics as revealed through experiments in breeding plants and animals has been undertaken. The main applications of these principles to man is pointed out in a general discussion of human heredity. Finally, inasmuch as all available data indicate that the fate of our very civilization hangs on the issue, the work concludes with an account of the new science of eugenics which is striving for the betterment of the race by determining and promulgating the laws of human inheritance so that mankind may intelligently go about conserving good and repressing bad human stocks.
In order to eliminate as many errors as possible and to avoid oversights I have submitted various chapters to certain of my colleagues and friends who are authorities in the special field treated therein. While these gentlemen are in no way responsible for the material of any chapter they have added greatly to the value of the whole by their suggestions and comments. Thus I am indebted to Professor Leon J. Cole for reading the entire ma.n.u.script; to Professors A. S. Pea.r.s.e and F. C. Sharp for reading Chapter VII; to Professor C. R. Bardeen for reading special parts; to Doctor J. S. Evans for reading Chapter VI and part of V; to Doctor W. F.
Lorenz, of the Mendota Hospital, for reading Chapter VIII; to Judge E. Ray Stevens for reading Chapter IX, and to Helen M. Guyer for several readings of the entire ma.n.u.script.
Grateful acknowledgment is made to all of these readers, to various publishers and periodicals for the use of certain of the ill.u.s.trations, to the authors of the numerous books and papers from which much of the material in such a work as this must necessarily be selected, and to my artist, Miss H. J. Wakeman, for her painstaking endeavors to make her work conform to my ideas of what each diagram should show.
M. F. G.
CHAPTER I
HEREDITY
It is a commonplace fact that offspring tend to resemble their parents. So commonplace, indeed, that few stop to wonder at it. No one misunderstands us when we say that such and such a young man is "a chip off the old block," for that is simply an emphatic way of stating that he resembles one or the other of his parents. The same is true of such familiar expressions as "what"s bred in the bone," "blood will tell," and kindred catch phrases. All are but recognitions of the same common fact that offspring exhibit various characteristics similar to those of their progenitors.
=Blood Heritage.--=To this phenomenon of resemblance in successive generations based on ancestry the term heredity is applied. In man, for instance, there is a marked tendency toward the reappearance in offspring of structures, habits, features, and even personal mannerisms, minute physical defects, and intimate mental peculiarities like those possessed by their parents or more remote forebears. These personal characteristics based on descent from a common source are what we may call the blood heritage of the child to discriminate it from a wholly different kind of inheritance, namely, the pa.s.sing on from one generation to the next of such material things as personal property or real estate.
=Kind Determined by Origin.--=It is inheritance in the sense of community of origin that determines whether a given living creature shall be man, beast, bird, fish, or what not. A given individual is human because his ancestors were human. In addition to this stock supply of human qualities he has certain well-marked features which we recognize as characteristics of race. That is, if he is of Anglo-Saxon or Italian or Mongolian parentage, naturally his various qualities will be Anglo-Saxon, Italian, or Mongolian. Still further, he has many distinctive features of mind and body that we recognize as family traits and lastly, his personal characteristics such as designate him to us as Tom, Harry, or James must be added. The latter would include such minutiae as size and shape of ears, nose or hands; complexion; perhaps even certain defects; voice; color of eyes; and a thousand other particulars. Although we designate these manifold items as individual, they are in reality largely more or less duplicates of similar features that occur in one or the other of his progenitors, features which he would not have in their existing form but for the hereditary relation between him and them.
"O Damsel Dorothy! Dorothy Q.!
Strange is the gift that I owe to you;
What if a hundred years ago Those close-shut lips had answered "No,"
Should I be I, or would it be One-tenth another, to nine-tenths me?"
"Soft is the breath of a maiden"s yes; Not the light gossamer stirs with less; But never a cable that holds so fast Through all the battles of wave and blast, And never an echo of speech or song That lives in the babbling air so long!
There were tones in the voice that whispered then You may hear to-day in a hundred men."
When life steps into the world of matter there comes with it a sort of physical immortality, so to speak; not of the individual, it is true, but of the race. But the important thing to note is that the race is made up, not of a succession of wholly unrelated forms, but a continuation of the same kind of living organisms, and this sameness is due to the actual physical descent of each new individual from a predecessor. In other words, any living organism is the kind of organism it is in virtue of its hereditary relation to its ancestors.
It is part of the biologist"s task to seek a material basis, a continuity of actual substance, for this continuity of life and form between an organism and its offspring. Moreover, inasmuch as the offspring is never precisely similar to its progenitors he must determine also what qualities are susceptible of transmission and in what measure.
=Ancestry a Network.--=From the fact that each child has all of the ancestors of its mother as well as of its father, arises the great complications which are met with in determining the lineage of an individual. A person has two parents, four grandparents, eight great grandparents, and thus following out pedigree it is plain to be seen that through this process of doubling in each generation, in the course of a few centuries one"s ancestry is apparently enormous. By actual computation, according to Professor D. S. Jordan, if we count thirty generations back to the Norman invasion of England in 1066, at this ratio of duplication, the child of to-day would have had at that time an ancestry of 8,598,094,592 persons. But we know that the total number of inhabitants in England during the time of William the Conqueror was but a small fraction of this enormous aggregate. This means that we shall have to modify our inference that a child has twice as many ancestors as its parents; a condition which at first sight seems evident, but which is not literally true. The fact is that the parents of the child, in all probability, have many ancestors in common--a state of affairs which is brought about through the intermarriage of relatives, and this is especially frequent among remoter descendants of common progenitors. Time after time in genealogy strains of blood have crossed and recrossed until it is not improbable that a man of to-day who is of English origin has the blood in his veins from every inhabitant of England who lived during the time of William the Conqueror and left fruitful descendants. Instead of conceiving of ancestry as an ever branching and widening tree-like system as it recedes into the past, it is more accurate, therefore, to regard it in the light of an elaborate meshwork. The "family tree" in reality becomes the family net.
=Ancestry in Royalty.--=The pedigrees of royal families have proved to be of much importance in the study of human inheritance, not that royal traits are any more heritable than any other, but simply because the records have been carefully kept so that they are the most comprehensive and easily followed pedigrees available. The netlike weave of ancestry is particularly well exemplified in some of these families because of much close intermarriage. Their heritage typifies on an intensified scale the heritage of the ma.s.s of mankind. For example, if we go six generations back in the ancestry of Frederick the Great instead of the expected sixty-four individual ancestors we find only forty; or in a still more closely woven stock, in the Spanish royal line of Don Carlos we find in six generations instead of sixty-four individual ancestors, only twenty-eight. While the present German emperor might have had four thousand ninety-six ancestors in the twelfth generation back, it is estimated that owing to intermarriage he probably had only five hundred thirty-three.
=Offspring Derived from One Parent Only.--=So far in our reckoning of heredity we have counted elements from both father and mother, and the complications which arise from such a double ancestry are manifestly very perplexing ones. If we could do away with the elements of s.e.x and find offspring that are derived from one parent only, it would seemingly simplify our problem very much for we should thus have a direct line of descent, free from intermingling. This, in fact, occurs to a greater or less extent among lower animals in a number of instances. There may be only female forms for a number of generations and the eggs which they produce develop directly into new individuals. Moreover, many of the simpler organisms have the power of dividing their bodies into two and thus giving rise to two new forms, each of which resembles the parent.
This shows plainly that we may have inheritance without the appearance of any male ancestor at all, hence s.e.x is not always a necessary factor in reproduction or heredity. The development of eggs as.e.xually, that is, without uniting first with a male cognate, is termed _parthenogenesis_.
The ordinary plant louse or aphid which is frequently found upon geraniums is a familiar example of an animal which reproduces largely in this way.
During the summer only the females exist and they are so astonishingly fertile that one such aphid and her progeny, supposing none dies, will produce one hundred million in the course of five generations. In the last broods of the fall, males and females appear and fertile eggs are produced which lie dormant through the winter to start the cycle of the next year.
Again, the eggs of some kinds of animals which normally have to unite with a male germ before they develop, can be made to develop by merely treating them with chemical solutions. The difference between an offspring derived in such a manner, and one which has developed from an egg fertilized by the male is that it is made up of characteristics from only one source, the maternal.
=Dual Ancestry an Aid in Studying Heredity.--=Although we have the factors of heredity in a more simplified form in the case of as.e.xual transmission, as a matter of fact most of our insight into the problems of heredity has been attained from a study of s.e.xually reproducing forms, because the very existence of two sets of more or less parallel features offers a kind of checking up system by which we can follow a given characteristic.
=Reversion.--=Occasionally, however, plants and animals do not develop the complete individuality we might expect, but stop short at or re-attain some ancestral stage along the line of descent, and thus come to resemble some progenitor perhaps many generations back of their own time. Thus it is well known that as regards one or more characteristics a child may resemble a grandparent or often some remote ancestor much more closely than it does its immediate parent. The reappearance of such ancestral traits the student of heredity designates as _Reversion_ or _Atavism_.
Reversion may occur apparently in any cla.s.s of plants or animals. It is especially p.r.o.nounced among domesticated forms, which through man"s selection have been produced under more or less artificial conditions. For example, among fancy breeds of pigeons, there may be an occasional return to the old slaty blue color of the ancestral rock-pigeon, with two dark cross-bars on the wings, from which all modern breeds have been derived.