The child's heredity

Front matter

ej it Saige n wee i ae ns gepsiere

% a; z A rece ef is 0) th es Tee nav vay Ad pride FSD

Sh Se os

Preface

This is a guide-book for parents. Their interests and practical needs have determined the selection, the arrangement, and the treatment of the material. This should be borne in mind by readers whose concern with the subject is less professional.

Racial differences are mentioned only incidentally, a more systematic treatment of them being left for Applied Eugenics.

For criticisms and suggestions, I am much indebted to Dr. Sewall Wright, associate professor of zodlogy, University of Chicago; Dr. Charles H. Danforth, associate professor of anatomy, Stanford University; and Dr. Karl M. Bowman, chief medical officer, Boston Psychopathic Hospital.

I am also under great obligations to Mr. E. S. Gosney of Pasadena, in association with whom I have been making a study of the workings of the California eugenic sterilization law during the past three years. Material gathered in the course of this study has been used freely in the present book.

PAUL POPENOE.

Pasadena, January 24, 1929, esl ee val a

Contents

CHAPTER XIII DISEASES OF THE Bopy 3 231 e eee saan) ae 120 CHAPTER XIV INTELLIGENCE. .....05.> | di a a LOM shee hare Dy ten ae nae Ee RMT RL ect tS OCT Rea 134 CHAPTER XV DIFFERENT KINDS OF INTELLIGENCE Ne ii eats ec aera scree nue non 146 CHAPTER XVI DIFFERENT LEVELS) OF INTELLECT aoe ois ee eerie ere talatete 153 CHAPTER XVII LO ame TAT ADs ie alsa (ipa h ole oi tig ava oru leds ee te menttal male ete enlaUacais tis 169 CHAPTER XVIII Bopy AND MIND oe eae eter ia ve i So tee 9 Se area eg aN ncn a 178 CHAPTER XIX CONSTITUTION oo CaP ase cine tag te Tele Cat ned eats Ca ean EC nn aR 190 CHAPTER XX TPEMPBERBAMENT 2p y)5's cho Als: Wiuiblalle tac Uisteieee cteteeck ciety sy te tT ORI LP Leay ont acum lean 197

DISEASES OF THE MIND) oye eee ete, an 217 CHAPTER XXTII

TEE ARTS iii oi5 (idinic la siete Se atn aon a ee aie ata ete edie ene agi ae ear 240 CHAPTER XXIV

Chapter I

A new-born baby lies wrapped in warm blankets in a basket near his mother, from whom he has emerged a few moments before. Red and wrinkled, he is not wholly an object of beauty, even to his doting parents. Yet there are three things about him that particularly endear him to those parents:

1. He is alive.

2. He is their baby.

3. He is different from every other baby ever born.

And those three facts, properly interpreted, tell the whole story of heredity.

Being alive, he is active; for life and activity go together. When the father lifts a corner of the blanket he sees his son in continuous, though slight, motion. These early activities of the infant did not require any practice—they were literally born in him, and indeed are not subject to his control.

More prolonged observations, such as relatives will enjoy through the window of the hospital nursery during the next few days, reveal a number of responses which baby makes to various stimuli, internal or external.

Any part of the body may move: hands and feet, arms and legs, trunk, head, eyes, mouth. None of these responses is more interesting than the power of grasping, which the infant possesses as soon as he is born, though he has certainly never had occasion to grasp anything in his lifetime. Many babies can support the full weight of the body with either hand for a period of time varying from a fraction of a second to almost a minute; even though they have not strength to hold up the head unaided. Often they refuse to perform unless angered by having the head held firmly for a moment; and they lose the ability in a few weeks or months, not - to regain it for a year or two.

Sneezing and hiccoughing can both be done to perfection by even the youngest infant; indeed, he sometimes practices the latter while still in the uterus, though naturally not the former, because his lungs are collapsed until after he gets his head outside the maternal birth canal and fills them with air at the time of his first cry, which is often the first sign of life that he gives.

Defecation, voiding of urine, and erection of the penis all occur immediately after birth, sometimes before.

But the movements on which most interest is centered, both by the infant and by the onlookers, are those of the mouth. This organ is, indeed, for some months the central feature of the babe’s existence, from one point of view.

It is in motion much of the time, and within a few days it assumes shapes that are interpreted by the relatives as smiles. The child does not smile deliberately, as a response to the antics of his kinfolk, for a month or two yet.

From the moment of birth, the mouth is capable of the sucking reflexes, which are adapted perfectly to draw milk from the maternal fount. Although many an infant has not (as lower animals have) sense enough to seek the breast for himself, but would starve to death lying with his face against it, he knows what to do immediately the nipple is placed in his mouth.

These movements connected with nursing form a complex series which is worth considering for a moment as an illustration of the way the unlearned responses take place. Reduced to simplest terms, the performance is something like this:

1. The baby gets the nipple between his lips.

2. He forms a vacuum in his mouth, largely by movements of the tongue and cheeks. The pressure of the atmosphere on the mother’s breast, at the rate of 14 pounds to the square inch of skin surface, then forces the milk out of the breast.

3. The contact of the milk with the infant’s mouth excites tongue and cheek movements which push the fluid back to the throat. ‘This is a specific response to a warm fluid tasting like milk. It would not be excited by warm coffee or cold lemonade.

wn,

Fic. 1. HoLDING ON FoR DEAR LIFE

This Negro baby, not yet two weeks old, can support the entire weight of his body by hisarms. Such an ability (which most babies have) is of no use to him now, but it was a matter of life and death to his ancestors who lived in trees millions of years ago. Hence the capacity became so thoroughly established in his germ plasm that it persists to this day. Photograph from the Journal of Heredity.

4, The arrival of the milk near the opening of the throat excites the muscles here, which push it on down, shutting off the windpipe and opening the esophagus at the same time.

And so on, in a long series of almost incredibly complicated nature, involving the most remote activities of nerves, muscles, body fluids, and in fact the whole baby.

It is an endless chain of reflexes. Nerve impulses or currents started in the mouth, by milk and nipple contacts, traverse paths through the nervous system that are laid out and established in working order even before the child is born. They are ancestral patterns: they are inherited. |

No one denies this. I rehearse it here because the same sort of inherited mechanism, that is, the same system of open paths and easy transfers through the nervous system, also explains the inheritance of innumerable other traits that appear later.

The baby then is born with an equipment of abilities which, if not unlimited, is at least more or less adequate to his needs; and it is an equipment which grows as he grows, so that as he meets each new problem in the future, he finds himself more or less prepared to grapple with it.

No two babies are alike in these respects any more than they are in appearance. The differences of both kinds—peculiarities of appearance and capacities that depend on the nervous system— go back far into the fetal life.

Racial differences appear distinctly as early as the third month after conception, and individual differences make their appearance at the same time. The human body is just as variable in the

uterus as it is in adult life. In other words, individuality is just as

definite a few months after conception, and long before the effects of surroundings, of training, and of teaching, have had a chance to exert whatever influence they can, as after the body has been exposed to them for a lifetime (336).

1 Numbers in parentheses refer to the list of references on page 280. These references refer either to original investigations, to critical reviews of such investigations, or to more extended popular articles on the same subject. No

When marked differences between babies thus appear six months before they are born, it is a fair assumption that these differences are much more the result of differences in the material of which these babies are made, than they are of the effects of climate, or exercise, or will power: that is, that they are inborn and little influenced from outside, in comparison with differences in language for instance—the ability to speak at all depends on the inheritance of certain capacities, but whether one speaks English or American depends wholly on surroundings, ambition, and training.

It is a fair assumption, I say, that such differences are part of the child’s original nature. But it is merely an assumption, to be tested in each case by the facts. Not everything that is evident at birth—not everything congenital, in a word—is inherited. The baby might be born with smallpox, but no one would call this inheritance. His mother had smallpox, and he was infected in the uterus, just as he might have been 10 years later by contact with an infected person.

Most cases are not so simple. Thus every baby is born with short legs, in proportion to the length of trunk and arms. His parents may have notably long legs. The short legs, though congenital, may not be inherited. They are, in general, due partly to the fact that the legs are not so well nourished in the uterus as is the rest of the body. Part of the blood supply goes through other portions of the body first, reaching the legs last after some of the nourishment it contains has presumably been removed by head and trunk. ‘The force of gravity may also play a part in the result: the child is standing on his head and it is easier for the blood to circulate through the lower part of the body than through the upper extremities. The short legs also seem to be a reminiscence of some ancestral period through which the child has to pass in attempt has been made to give a complete bibliography, since this book is not intended for the specialist (one of those persons who “knows more and more about less and less’). But on controversial subjects I have tried to give enough references to point the way to further knowledge for any interested reader.

covering, during a few years, the space that the race has covered in millions. The short-legged baby has somewhat the proportions of many of the higher apes; and some human races have retained these proportions, while others have become specialized in the opposite direction. ‘There are, then, a great many different factors that contribute to these short and weak baby legs. The poorer growth of the legs is not due to lack of exercise, for they have had more than any other part of the baby’s body, as any pregnant woman will testify when the little heels are beating a tattoo inside her abdomen.

To determine whether or not the short legs are inherited in the ordinary sense, one must give them a chance to grow to their full potentiality. If the child has plenty of good food and a wholesome, hygienic life until he is past adolescence, and if his legs are still short, it is a good guess that he inherited short legs. But if, under those conditions, he grows into the usual rangy and longlegged boy, it is more than a guess that the short legs with which he was born were merely a stage in development.

This, like scores of other familiar facts that might be recalled, illustrates the real nature of inheritance. The child does not inherit any definite thing; he inherits merely a potentiality of developing to a certain degree under normal conditions. He can never exceed the limits of this potentiality, but he may, and often does, fall short of them; he does not get the most out of his heredity because the conditions are not favorable to the development of his possibilities. ‘This is fortunate if the possibility is an injurious one, unfortunate if the possibility is a useful or desirable one. The ’ whole of education consists merely in trying to make conditions as favorable as possible for the good potentialities and as unfavorable as possible for the bad ones,—‘“‘goodness”’ and “badness” being determined by the needs of civilization.

If many undeniably inherited traits are represented in the newborn baby only in an early stage of development; if his eyes and hair may change color, his legs change their proportions, his nose change its shape, his teeth appear out of smooth gums, and so on;

it is equally true that many undeniably inherited traits are not evident at all in the new-born. Thus a child may inherit the peculiarity of having gray hair at an unusually early age; but there is nothing in his appearance at birth to prove it.

It is, therefore, absurd to say that every child (or any child) is born healthy, and that all the parents and the doctors have to do is to keep him healthy,—an argument often used to support “infant mortality campaigns.” Such an idea belongs to the philosophers of the eighteenth century,—not to go back to Confucius. Thus Jean Jacques Rousseau began his Emile, a treatise on education (1762), with the words, “Everything is good as it comes from the hand of the Creator; everything degenerates in the hands of man.” .

One might as well say that, because a child is born without gray hair or wisdom teeth, all the parents need to do is to give him plenty of spinach, sunshine, and certified milk, and he need never have gray hair or wisdom teeth. One would not expect a child to be born with scarlet fever, rickets, pneumonia, convulsions, and the other enemies of childhood. But it is none the less true, as I shall show later, that he is born with some definite relations to these diseases.

It is, then, not possible to get a clear idea of heredity so long as one looks only at the adult, still less at the infant. Such an attempt to view the subject from the outside leads only to confusion and question-begging.

But if, following the method of modern science, one feck at the subject from the inside, it becomes relatively simple. Attention is then focussed on the germ-plasm, on the individual germ-cells which give the baby his start.

The ancient Athenians, and perhaps many earlier generations, exercised themselves over the question which came first, the owl or the egg? Such a question is no longer put, for it is now well understood that owls do not produce eggs. The egg produced the owl, and also produced the other eggs. The eggs go on in an unbroken stream, which started with the first appearance of life on

Fics. 2,3. ANOTHER ECHO OF THE PAST

This healthy Portuguese girl was born with a tail 51 mm. long, 10 mm. in diameter at the base. It contains no bone. Every human embryo has a tail at an early stage of its life in the uterus, but it is not often that the tail persists as in this case. Photographs from Dr. J. A. Pires de Lima, director of the Institute of Anatomy, Faculty of Medicine, Porto, Portugal.

the world. The egg is everything, the owl a by-product. Every egg comes from some other egg; the owl is merely a package in which it is delivered.

Here are half a dozen eggs in a saucer. Even an expert, looking at them, would not venture to say what they will become. Given the appropriate kinds of food to grow on—and nothing else—one will become a whale, one a baby, one a cauliflower, one a starfish, one an earthworm, and one a cockroach.

It is plain enough that each egg has its own particular constitution, which causes it to develop into something different from the product of any other egg in the world: for though the products of whale egg and cockroach egg are widely different, yet the products of two successive eggs from one woman are not exactly the same, even if they have grown alongside each other into children born only a few minutes apart as twins. One of them may be a brown-eyed, mild-tempered, patrician girl, a ‘‘violet-crowned, pure, sweetly-smiling Sappho” such as Anacreon celebrated; the other a blue-eyed, pug-nosed boy with the disposition of a mustang,—‘‘half horse, half eracnen like Andrew Jackson’s soldiers at New Orleans.

The constitution of the germ-cells, then, determines not merely whether the fertilized egg will develop into a cauliflower or a cockroach or the Hope of the White Race; but it determines, in the first instance, the ways in which that particular cauliflower, or cockroach, or Hope, will differ from every other cauliflower, or cockroach, or Hope.

The most striking thing about the constitution of the cells is that it continues from generation to generation with so little change. A cauliflower always produces another cauliflower—it never produces a cockroach. ‘There are slow changes, spread over millions of years—these make up evolution. There are slighter changes almost incessantly—these make up variation. But the real changes are much less frequent than is sometimes supposed, for nearly all the differences between children and their parents are due not to any actual alteration in the germ-plasm, but merely to recombinations of the characters of the two parents.

This germ-plasm (which is merely a general name for the stream of germ-cells) has been going on from generation to generation, in an unbroken stream, since the beginning of life.

It is the oldest thing in existence.

It is the least changeable thing that lives.

It is the only immortal thing alive.

But it is time for the new-born baby, who was left in his basket _a few moments ago, to be given his first bath and moved to his nursery.

1. He is still very much alive, because he is the product of this germ-plasm—he is a part of the life-stuff of the world.

2. He is justifiably regarded by the parents as their baby, because he is the product of the union of the two strains of germ-plasm of which they, respectively, are the temporary custodians.

3. He is different from every other baby ever born because, owing to the mechanism which I will describe in the following chapters, no two germ-cells can ever be identical,—even though they are fundamentally alike through their similarity of constitution.

The germ-plasm consists merely of germ-cells. ‘They are dividing all the time: one becomes two; the two become four; the four multiply to eight, and so on in what appears to be an infinite series. Nearly all of them die. Perhaps one in many billions finds the opportunity to survive and perpetuate the chain of life.

Yet despite this endless series of cell divisions, the thread is never broken. Whatever it is that the cell contains, this content is passed on virtually unaltered, so that after an almost uncountable number of generations the latest cell is ready to produce, from the same old pattern, another model. If it is a cauliflower, it will be recognized at once as a cousin of the cauliflower that was produced from the same series a million cell-generations ago. If it is an antiseptic baby, whom five white-clad attendants wrap in the sterilized blankets of a modern hospital, it will be recognized at once as a cousin of the baby whom the cavewoman delivered unaided and laid among the fleas of a wolf skin on the floor beside her sooty fireplace.

The offspring is, broadly speaking, true to type. It is the product of heredity.

Heredity, then, may be defined as the persistence of certain constituents in the germ-cells, through an endless number of cell divisions.

Chapter II

Since every child, in addition to having two parents, also possesses four grandparents, eight great-grandparents, 16 great-great-grandparents, and so on back forever, the number of ancestors doubling in each generation; it is not necessary to count through many centuries to get an overwhelming number of forebears.

Thus if William the Conqueror is separated from the present by 24 generations, it would appear that any infant of British extraction must have had 16,000,000 ancestors at the time of the battle of Hastings. Yet there were not as many inhabitants as that in all Britain and France put together!

If one goes back to the days of Jesus, the number of calculated ancestors becomes some 18,000,000,000, although the Roman empire at the time of its greatest extension, under Trajan, had not over 100,000,000 inhabitants. And yet that period was only a few minutes ago, in the whole history of life on the globe.

Moreover, many of the ancients have no descendants in the present generation. Some of them died unmarried, others married but were childless; and the effect of these eliminations, carried through several generations, is to cut off lines of descent rapidly. Once gone, such a line is gone forever. The consequence is that after a few centuries the population becomes more and more predominantly made up of the representatives of certain stocks that are fecund. |

Obviously, if these self-perpetuating families differ in some way from those that die out (and they always do differ in many important ways), the whole character of the population will undergo a slow but steady change. That forms the problem of eugenics. Here I am concerned only to point out that lines of descent are disappearing all the time: so that if one could trace his ancestry back to Charlemagne, he would not find his patrimony spread out.

evenly among all the inhabitants of Europe in the ninth century A.D., but would discover the lines gathering together into bundles and ending in relatively few of the people who then possessed the earth.

It is clear enough that even though every child be “heir of all the ages,” he is not the descendant of all the people who lived in those ages, but perhaps of a minority. A few progenitors must be repeated, over and over and over again, in the pedigree.

Just as ancestors multiply rapidly when one counts back, so descendants multiply with equal rapidity when one counts forward. Thus William the Conqueror ought to have some 16,000,000 living descendants, a fact which deprives the claim to descent from him of any great value,—although it is rarely enough that anyone possesses the necessary documents to show the actual line of descent unbroken in all the generations intervening.

In the same way it can be computed easily that the little band of Pilgrims who came in the Mayflower to Plymouth Rock in 1620 must have literally millions of descendants in the existing population of the United States, even though only 33 of the original number founded families.

From the fact that a man six generations ago may now have 12,000 or more living descendants, it follows that the posterity of Jonathan Edwards on the one side, of Max Juke on the other, should not ascribe much of their importance to their eponyms, even if there has been a deal of consanguineous marriage since. What their pedigrees really show is the tendency of traits to run in families and social classes, not in a given line of descent.

When two persons who can trace back to a common ancestor, no matter how remote, marry each other, they are marrying their cousins. C. B. Davenport calcu’ated that virtually all the old Americans are related to each other not more distantly than thirtieth cousin, and most of them at least as close as fifteenth cousin. As one gets into other races, the relationship becomes more distant, but it is still a relationship. Adam or no Adam, the human species is distinctly one big family.

Thus it is easy enough to see why people are, in essentials, all alike. They all have legs, lungs, livers, and lips for the same reason that their ancestors all had legs, lungs, livers, and lips. The foundations for these things, and the other fundamental features that go to make up every man, or indeed every animal, are deep in the germ plasm—so deep that they can not now be got out.

Fic. 4. Tot HumMAN CHROMOSOMES

Each of these little rods consists of a string of genes. They are, therefore, the carriers of the heredity; they may be caJled the germ plasm. Among the 48 chromosomes in this cell (taken from the testicle of a white man), the X chromosome is visible, at the upper left-hand corner of the letter ‘“Y” that has been inserted; to the left just below itis the small round Y chromosome. If the cell had been taken from the body of a woman, the Y would be absent, a second X taking its place. Illustration from Dr. Theophilus S. Painter, professor of zodlogy, University of Texas.

In fact, these things are so much a matter of course that they are not even thought of as being part of the child’s heredity. No one remarks that John has two legs, just as his father has, or that Jane resembles her mother in having an ear on each side of her head. But John may be said to have unusually long legs, like his father, or Jane to have particularly small and beautiful ears, like her mother. In popular usage, heredity deals not so much with fundamentals as with superficials, and not so much with resemblances as with differences.

Studying the subject systematically, one can proceed in no other way than by studying the differences. When one has said that both John Sr. and John Jr. have livers, one has very nearly exhausted the liver as a subject for small talk, if one is confined to a consideration of likenesses. But if one begins to note the ways in which these livers differ from each other, and in which the two of them agree to differ from outsiders, then the conversation may be kept going until the party rises from the dinner table.

The practical study of heredity is therefore reduced to a study of individual differences and their correlations. This is one of the reasons why the old definition of heredity as resemblance from one generation to another (“like begets like”) is inadequate.

The idea of the continuity of germ plasm explains without any further discussion why people are people and equally why ‘“‘pigs is pigs.’ To understand why people differ from each other, and why one pig has red hair, another white, one must go more deeply into the constitution of the germ plasm. Studied from this point of view, each germ cell is found to be composed of two parts.

The bulk of it consists of a quantity of protoplasm which is complicated enough in its structure, but which serves mainly as a background and vehicle for the second part, and may therefore be disregarded in the present discussion. The second part is a central nucleus.

Properly stained and studied, this nucleus is found to contain some material that, at certain stages in the life history of the cell, is gathered into threads or rods that are easily visible. These rods are called the chromosomes, and so far as is known they are the actual carriers of the heredity. They are, therefore, essentially the germ-plasm, which is handed on from generation to generation, unchanged and yet continually changing; incessantly destroyed yet potentially immortal.

The rest of the cell has important parts to play in the development of the individual, but the chromosomes cast the deciding vote at every stage of the proceedings, and little error will be involved in centering this discussion on them.

The number of chromosomes in a cell differs with various species, ranging from one to 200 or more, but is normally the same for all members of the species. Thus the little fly, Drosophila, which is commonly found on decaying fruit, has eight chromosomes (or four pairs), the frog 24 (12 pairs), the human baby 48 (24 pairs),—a relatively high number which may represent a doubling of a smaller number at some time in history. As chromosomes are small and continually getting tangled, it is much easier to follow the evolutions of eight under the lens than to watch 48. For this reason, among others, Drosophila has made much greater contributions to the knowledge of heredity than has even the smartest baby.

In every animal or plant that reproduces sexually, the new embryo originates in the union of a germ-cell from each of the parents. This would double the number of chromosomes at every union. ‘Thus if a baby started from the union of an ovum and a spermatozoén, each containing 48 chromosomes, he would be made up of cells each containing 48-+-48=96 chromosomes; his children would contain 192, his great-grandchildren 568, and soon. Inno time at all, babies would be stuffed so full of chromosomes that they would burst before they were born.