In spite of these presumptions which the biologist would, to say the least, consider worthy of careful investigation, the world is full of well-intentioned people who are anxious to improve the race, and who in their attempts to do so, wholly ignore the germ-plasm. They see only the body-plasm. They are devoted to the dogma that if they can change the body (and what is here said of the body applies equally to the mind) in the direction they wish, this change will in some unascertainable way be reproduced in the next generation. They rarely stop to think that man is an animal, or that the science of biology might conceivably have something to say about the means by which his species can be improved; but if they do, they commonly take refuge, deliberately or unconsciously, in the biology of half a century ago, which still believed that these changes of the body could be so impressed on the germ-plasm as to be continued in the following generation.
Such an a.s.sumption is made to-day by few who have thoroughly studied the subject. Even those who still believed in what is conventionally called "the inheritance of acquired characteristics" would be quick to repudiate any such application of the doctrine as is commonly made by most of the philanthropists and social workers who are proceeding without seeking the light of biology. But the idea that these modifications are inherited is so widespread among all who have not studied biology, and is so much a part of the tradition of society, that the question must be here examined, before we can proceed confidently with our program of eugenics.
The problem is first to be defined.
It is evident that all characters which make up a man or woman, or any other organism, must be either germinal or acquired. It is impossible to conceive of any other category. But it is frequently hard to say in which cla.s.s a given character falls. Worse still, many persons do not even distinguish the two categories accurately--a confusion made easier by the quibble that _all_ characters must be acquired, since the organism starts from a single cell, which possesses practically none of the traits of the adult.
What we mean by an inborn character is one whose expression is due to something which is present in the germ-plasm; one which is inherent and due to heredity. An acquired character is simply a modification, due to some cause external to the germ-plasm acting on an inborn character. In looking at an individual, one can not always say with certainty which characters are which; but with a little trouble, one can usually reach a reliable decision. It is possible to measure the variation in a given character in a group of parents and their children, in a number of different environments; if the degree of resemblance between parent and offspring is about the same in each case, regardless of the different surroundings in which the children may have been brought up, the character may properly be called germinal. This is the biometric method of investigation. In practice, one can often reach a decision by much simpler means: if the character is one that appears at birth, e.g., skin color, it is usually safe to a.s.sume that it is a germinal character, unless there is some evident reason for deciding otherwise, as in the case of a child born with some disease from which the mother had been suffering for the previous few months. In general, it is more difficult to decide whether a mental trait is germinal, than whether a physical one is; and great care should be used in cla.s.sification.
To make the distinction, one ought to be familiar with an individual from birth, and to have some knowledge of the conditions to which he was exposed, in the period between conception and birth,--for of course a modification which takes place during that time is as truly an acquired character as one that takes place after parturition. Blindness, for example, may be an inborn defect. The child from conception may have lacked the requisites for the development of sight. On the other hand, it may be an acquired character, due to an ill-advised display of patriotism on July 4, at some time during childhood; or even to infection at the moment of birth. Similarly small size may be an inborn character, due to a small-sized ancestry; but if the child comes of a normal ancestry and is stunted merely because of lack of proper care and food, the smallness is an acquired character. Deafness may be congenital and inborn, or it may be acquired as the result, say, of scarlet fever during childhood.
Now the inborn characters (excepting modifications _in utero_) are admittedly heritable, for inborn characters must exist potentially in the germ-plasm. The belief that acquired characters are also inherited, therefore, involves belief that in some way the trait acquired by the parent is incorporated in the germ-plasm of the parent, to be handed on to the child and reappear in the course of the child"s development. The impress on the parental _body_ must in some way be transferred to the parental _germ-plasm_; and not as a general influence, but as a specific one which can be reproduced by the germ-plasm.
This idea was held almost without question by the biologists of the past, from Aristotle on. Questionings indeed arose from time to time, but they were vague and carried no weight, until a generation ago several able men elaborated them. For many years, it was the question of chief dispute in the study of heredity. The last word has not yet been said on it. It has theoretical bearings of immense importance; for our conception of the process of evolution will be shaped according to the belief that acquired characters are or are not inherited. Herbert Spencer went so far as to say, "Close contemplation of the facts impresses me more strongly than ever with two alternatives--either that there has been inheritance of acquired characters, or there has been no evolution." But its practical bearings are no less momentous. Again to quote Spencer: "Considering the width and depth of the effects which the acceptance or non-acceptance of one or the other of these hypotheses must have on our views of life, the question, Which of them is true?
demands beyond all other questions whatever the attention of scientific men. A grave responsibility rests on biologists in respect of the general question, since wrong answers lead, among other effects, to wrong belief about social affairs and to disastrous social actions."
Biologists certainly have not shirked this "grave responsibility" during the last 30 years, and they have, in our opinion, satisfactorily answered the general question. The answer they give is not the answer Herbert Spencer gave.
But the popular mind frequently lags a generation behind, in its grasp of the work of science, and it must be said that in this case the popular mind is still largely under the influence of Herbert Spencer and his school. _Whether they know it or not_, most people who have not made a particular study of the question still tacitly a.s.sume that the acquirements of one generation form part of the inborn heritage of the next, and the present social and educational systems are founded in large part on this false foundation. Most philanthropy starts out unquestioningly with the a.s.sumption that by modifying the individual for the better, it will thereby improve the germinal quality of the race.
Even a self-styled eugenist asks, "Can prospective parents who have thoroughly and systematically disciplined themselves, physically, mentally and morally, transmit to their offspring the traits or tendencies which they have developed?" and answers the question with the astounding statement, "It seems reasonable to suppose that they have this power, it being simply a phase of heredity, the tendency of like to beget like."
The right understanding of this famous problem is therefore fraught with the most important consequences to eugenics. The huge ma.s.s of experimental evidence that has been acc.u.mulated during the last quarter of a century has, necessarily, been almost wholly based on work with plants and lower animals. Even though we can not attempt to present a general review of this evidence, for which the reader must consult one of the standard works on biology or genetics, we shall point out some of the considerations underlying the problem and its solution.
In the first place, it must be definitely understood that we are dealing only with specific, as distinguished from general, transmission. As the germ-cells derive their nourishment from the body, it is obvious that any cause profoundly affecting the latter might in that way exercise an influence on the germ-cells; that if the parent was starved, the germ-cells might be ill-nourished and the resulting offspring might be weak and puny. There is experimental evidence that this is the case; but that is not the inheritance of an acquired character. If, however, a white man tanned by long exposure to the tropical sun should have children who were brunettes, when the family stock was all blond; or if men whose legs were deformed through falls in childhood should have children whose legs, at birth, appeared deformed in the same manner; then there would be a distinct case of the transmission of an acquired characteristic. "The precise question," as Professor Thomson words it, "is this: Can a structural change in the body, induced by some change in use or disuse, or by a change in surrounding influence, affect the germ-cells in such a _specific_ or representative way that the offspring will through its inheritance exhibit, even in a slight degree, the modification which the parent acquired?" He then lists a number of current misunderstandings, which are so widespread that they deserve to be considered here.
(1) It is frequently argued (as Herbert Spencer himself suggested) that unless modifications are inherited, there could be no such thing as evolution. Such pessimism is unwarranted. There _is_ abundant explanation of evolution, in the abundant supply of germinal variations which every individual presents.
(2) It is common to advance an _interpretation_ of some observation, in support of the Lamarckian doctrine, as if it were a _fact_.
Interpretations are not facts. What is wanted are the facts; each student has a right to interpret them as he sees fit, but not to represent his interpretation as a fact. It is easy to find structural features in Nature which _may be interpreted_ as resulting from the inheritance of acquired characters; but this is not the same as to say and to prove that they _have resulted_ from such inheritance.
(3) It is common to beg the question by pointing to the transmission of some character that is not proved to be a modification. Herbert Spencer cited the prevalence of short-sightedness among the "notoriously studious" Germans as a defect due to the inheritance of an acquired character. But he offered no evidence that this is an acquirement rather than a germinal character. As a fact, there is reason to believe that weakness of the eyes is one of the characteristics of that race, and existed long before the Germans ever became studious--even at a time when most of them could neither read nor write.
(4) The reappearance of a modification may be mistaken for the transmission of a modification. Thus a blond European family moves to the tropics, and the parents become tanned. The children who grow up under the tropical sun are tanned from infancy; and after the grandchildren or great-grandchildren appear, brown from childhood, some one points to the case as an instance of permanent modification of skin-color. But of course the children at the time of birth are as white as their distant cousins in Europe, and if taken back to the North to be brought up, would be no darker than their kinsmen who had never been in the tropics. Such "evidence" has often been brought forward by careless observers, but can deceive no one who inquires carefully into the facts.
(5) In the case of diseases, re-infection is often mistaken for transmission. The father had pneumonia; the son later developed it; ergo, he must have inherited it. What evidence is there that the son in this case did not get it from an entirely different source? Medical literature is heavily burdened with such spurious evidence.
(6) Changes in the germ-cells _along with_ changes in the body are not relevant to this discussion. The mother"s body, for example, is poisoned with alcohol, which is present in large quant.i.ties in the blood and therefore might affect the germ-cells directly. If the children subsequently born are consistently defective it is not an inheritance of a body character but the result of a direct modification of the germ-plasm. The inheritance of an acquired modification of the body can only be proved if some particular change made in the parent is inherited as such by the child.
(7) There is often a failure to distinguish between the possible inheritance of a particular modification, and the possible inheritance of indirect results of that modification, or of changes correlated with it. This is a nice but crucial point on which most popular writers are confused. Let us examine it through a hypothetical case. A woman, not herself strong, bears a child that is weak. The woman then goes in for athletics, in order better to fit herself for motherhood; she specializes on tennis. After a few years she bears another child, which is much stronger and better developed than the first. "Look," some one will say, "how the mother has transmitted her acquirement to her offspring." We grant that her improved general health will probably result in a child that is better nourished than the first; but that is a very different thing from heredity. If, however, the mother had played tennis until her right arm was over-developed, and her spine bent; if these characteristics were nowhere present in the ancestry and not seen in the first child; but if the second child were born with a bent spine and a right arm of exaggerated musculature, we would be willing to consider the case on the basis of the inheritance of an acquired character. We are not likely to have such a case presented to us.
To put the matter more generally, it is not enough to show that _some_ modification in the parent results in _some_ modification in the child.
For the purposes of this argument there must be a similar modification.
(8) Finally, data are frequently presented, which cover only two generations--parent and child. Indeed, almost all the data alleged to show the inheritance of acquired characteristics are of this kind. They are of little or no value as evidence. Cases covering a number of generations, where a _c.u.mulative_ change was visible, would be of weight, but on the rare occasions when they are forthcoming, they can be explained in some other way more satisfactorily than by an appeal to the theory of Lamarck.[13]
If the evidence currently offered to support a belief in the inheritance of acquired characters is tested by the application of these "misunderstandings," it will at once be found that most of it disappears; that it can be thrown out of court without further formality. The Lamarckian doctrine is now held mainly by persons who have either lacked training in the evaluation of evidence, or have never examined critically the a.s.sumptions on which they proceed. Medical men and breeders of plants or animals are to a large extent believers in Lamarckism, but the evidence (if any) on which they rely is always susceptible of explanation in a more reasonable way. It must not be forgotten that some of the ablest intellects in the world have been a.s.sidously engaged in getting at the truth in the case, during the last half-century; and it is certainly worthy of consideration that not in a single case has the transmission of an acquired body character ever been proved beyond dispute. Those who still hold a belief in it (and it is fair to say that some men of real ability are among that number) too often do so, it is to be feared, because it is necessary for the support of some theoretical doctrine which they have formulated. Certainly there are few men who can say that they have carefully examined the evidence in the case, and accept Lamarckism because the evidence forces them to do so. It will be interesting to review the various cla.s.ses of alleged evidence, though we can cite only a few cases from the great number available (most of them, however, dealing with plants or lower animals).
Nearly all the evidence adduced can be put in one of these four cla.s.ses:
(1) Mutilations.
(2) Diseases.
(3) Results of use or disuse.
(4) Physico-chemical effects of environment.
The case in regard to mutilations is particularly clear cut and leaves little room for doubt. The noses and ears of oriental women have been pierced for generations without number, yet girls are still born with these parts entire. Circ.u.mcision offers another test case. The evidence of laboratory experiments (amputation of tails) shows no inheritance. It may be said without hesitation that mutilations are not heritable, no matter how many generations undergo them.
(2) The transmissibility of acquired diseases is a question involved in more of a haze of ignorance and loose thinking. It is particularly frequent to see cases of uterine infection offered as cases of the inheritance of acquired characters. To use the word "heredity" in such a case is unjustified. Uterine infection has no bearing whatever on the question.
Taking an historical view, it seems fairly evident that if diseases were really inherited, the race would have been extinct long ago. Of course there are const.i.tutional defects or abnormalities that are in the germ-plasm and are heritable: such is the peculiar inability of the blood to coagulate, which marks "bleeders" (sufferers from hemophilia, a highly hereditary disease). And in many cases it is difficult to distinguish between a real germinal condition of this sort, and an acquired disease.
The inheritance of an acquired disease is not only inconceivable, in the light of what is known about the germ-plasm, but there is no evidence to support it. While there is most decidedly such a thing as the inheritance of a tendency to or lack of resistance to a disease, it is not the result of incidence of the disease on the parent. It is possible to inherit a tendency to headaches or to chronic alcoholism; and it is possible to inherit a lack of resistance to common diseases such as malaria, small-pox or measles; but actually to inherit a zymotic disease as an inherent genetic trait, is impossible,--is, in fact, a contradiction of terms.
(3) When we come to the effects of use and disuse, we reach a much debated ground, and one complicated by the injection of a great deal of biological theorizing, as well as the presence of the usual large amount of faulty observation and inference.
It will be admitted by every one that a part of the body which is much used tends to increase in size, or strength, and similarly that a part which is not used tends to atrophy. It is further found that such changes are progressive in the race, in many cases. Man"s brain has steadily increased in size, as he used it more and more; on the other hand, his canine teeth have grown smaller. Can this be regarded as the inheritance of a long continued process of use and disuse? Such a view is often taken, but the Lamarckian doctrine seems to us just as mystical here as anywhere else, and no more necessary. Progressive changes can be satisfactorily accounted for by natural selection; retrogressive changes are susceptible of explanation along similar lines. When an organ is no longer necessary, as the hind legs of a whale, for instance, natural selection no longer keeps it at the point of perfection. Variation, however, continues to occur in it. Since the organ is now useless, natural selection will no longer restrain variation in such an organ, and degeneracy will naturally follow, for of all the variations that occur in the organ, those tending to loss are more numerous than those tending to addition. If the embryonic development of a whale"s hind leg be compared to some complicated mechanical process, such as the manufacture of a typewriter, it will be easier to realize that a trivial variation which affected one of the first stages of the process would alter all succeeding stages and ruin the final perfection of the machine. It appears, then, that progressive degeneration of an organ can be adequately explained by variation with the removal of natural selection, and that it is not necessary or desirable to appeal to any Lamarckian factor of an unexplainable and undemonstrable nature.
The situation remains the same, when purely mental processes, such as instincts, are considered. Habit often repeated becomes instinctive, it is said; and then the instinct thus formed by the individual is pa.s.sed on to his descendants and becomes in the end a racial instinct. Most psychologists have now abandoned this view, which receives no support from investigation. Such prevalence as it still retains seems to be largely due to a confusion of thought brought about by the use of the word "instinctive" in two different senses,--first literally and then figuratively.
A persistent attempt has been made in America during recent years, by C. L. Redfield, a Chicago engineer, to rehabilitate the theory of the inheritance of the effects of use and disuse. He has presented it in a way that, to one ignorant of biology, appears very exact and plausible; but his evidence is defective and his interpretation of his evidence fallacious. Because of the widespread publicity, Mr. Redfield"s work has received, we discuss it further in Appendix B.
Since the importance of hormones (internal secretions) in the body became known, it has often been suggested that their action may furnish the clue to some sort of an inheritance of modifications. The hormone might conceivably modify the germ-plasm but if so, it would more likely be in some wholly different way.
In general, we may confidently say that there is neither theoretical necessity nor adequate experimental proof for belief that the results of use and disuse are inherited.
(4) When we come to consider whether the effects of the environment are inherited, we attack a stronghold of sociologists and historians.
Herbert Spencer thought one of the strongest pieces of evidence in this category was to be found in the a.s.similation of foreigners in the United States. "The descendants of the immigrant Irish," he pointed out, "lose their Celtic aspect and become Americanised.... To say that "spontaneous variation," increased by natural selection, can have produced this effect, is going too far." Unfortunately for Mr. Spencer, he was basing his conclusions on guesswork. It is only within the last few months that the first trustworthy evidence on the point has appeared, in the careful measurements of Hrdlicka who has demonstrated that Spencer was quite wrong in his statement. As a fact, the original traits persist with almost incredible fidelity. (Appendix C.)
In 1911, Franz Boas of Columbia University published measurements of the head form of children of immigrants[14] which purported to show that American conditions caused in some mysterious manner a change in the shape of the head. This conclusion in itself would have been striking enough, but was made more startling when he announced that the change worked both ways: "The East European Hebrew, who has a very round head, becomes more long-headed; the south Italian, who in Italy has an exceedingly long head, becomes more short-headed"; and moreover this potent influence was alleged to be a subtle one "which does not affect the young child born abroad and growing up in American environment, but which makes itself felt among the children born in America, even a short time after the arrival of the parents in this country." Boas" work was naturally pleasing to sociologists who believe in the reality of the "melting-pot," and has obtained widespread acceptance in popular literature. It has obtained little acceptance among his fellow-anthropologists, some of whom allege that it is unsound because of the faulty methods by which the measurements were made and the incorrect standards used for comparison.
The many instances quoted by historians, where races have changed after immigration, are to be explained in most cases by natural selection under new conditions, or by interbreeding with the natives, and not as the direct result of climate. Ellsworth Huntington, the most recent and careful student of the effect of climate on man,[15] finds that climate has a great deal of influence on man"s energy, but as far as inherited traits in general are concerned, he is constantly led to remark how little heredity is capable of being changed.
Most members of the white race have little toes that are partly atrophied, and considerably deformed. In many cases one of the joints has undergone ankylosis--that is, the bones have coalesced. It is confidently alleged that this is due to the inheritance of the effects of wearing tight shoes through many centuries. When it is found that the prehistoric Egyptians, who knew not tight shoes, suffered from the same defect in a similar degree, one"s confidence in this kind of evidence is much diminished.
The retrogression of the little toe in man is probably to be explained like the degeneration of the hind leg of the whale, as a result of the excess of deteriorating variations which, when not eliminated by natural selection, lead to atrophy. Since man began to limit the use of his feet to walking on the ground, the little toe has had much less value to him.
The feet of Chinese women offer another ill.u.s.tration along this line.
Although they have been tightly bound for many generations, no deformity is apparent in the feet of girl babies.
Breeders are generally of the opinion that good care and feed bestowed on their stock produce results in succeeding generations. This is in a way true, but it is due merely to the fact that the offspring get better nourishment and therefore a better start in life. The changes in breeds, the increase in milk yield, and similar facts, often explained as due to inheritance of acquired characters, are better explained as the results of selection, sometimes conscious, sometimes quite unconscious.
[Ill.u.s.tration: BOUND FOOT OF A CHINESE WOMAN
FIG. 5.--For centuries the feet of upper cla.s.s women, and many lower cla.s.s women, in China have been distorted in this manner; but their daughters have perfect feet when born.]
[Ill.u.s.tration: DEFECTIVE LITTLE TOE OF A PREHISTORIC EGYPTIAN
FIG. 6.--The above ill.u.s.tration shows the foot of a prehistoric Egyptian who is estimated to have lived about 8000 B. C. The last joint of the little toe had entirely disappeared, and careful dissection leaves no doubt that it was a germinal abnormality, such as is occasionally seen to-day, and not the result of disease. It is, therefore, evident that the degeneration of man"s little toe must be ascribed to some more natural cause than the wearing of shoes for many generations. Photograph from Dr. Gorgy Sobhy, School of Medicine, Cairo.]