The Social Direction of Evolution: An Outline of the Science of Eugenics

by William E. Kellicott

The Galton Laboratory for Eugenics is already doing much in this direction and is publishing in the "Treasury of Human Inheritance" scores of human pedigrees. An agency is already in operation in this country. The American Breeders Association has appointed a Committee and Sub-Committees under highly competent leaders for the collection of exact data of human heredity upon a large scale. There is opportunity for everyone to help in this work in connection with the Eugenics Record Office already referred to.

The second great element in the eugenic program is Research. It is not enough to collect the known facts; new facts must be forthcoming. We cannot, perhaps, undertake definite experiments upon human evolution, but we can and must take advantage of the wealth of experiment which Nature is carrying out around us and before our eyes could we but learn to read her results. We need to know more about the process of differential fertility, of human variability, of the effects of Nurture as well as of the conditions of Nature.

We do know pretty well the effects, upon the individual, of training, education, good and ill housing conditions and conditions of labor, of disease, alcoholism, underfeeding. We need now to know, not to guess at, the effects of these things upon the race, upon human stock. A mere beginning has been made here in the way of a scientific treatment of this question, although many persons have their minds already made up, firmly and fully, as to the "effects of the environment." But all that we have guessed here may be wrong.

The discussion of this subject is filled with pitfalls. The common form of the query as to which is of the greater importance, "heredity or environment," in determining individual characteristics betrays a completely erroneous view of what heredity is, and of the organism's relation to its environment. The living organism reacts to its environment at every stage of its existence, whether as an egg, an embryo, or an adult. In this reaction both factors are essential, the environment as essential as the organism. The result of this continued reaction is the development on the part of the organism of certain physiological processes and structural conditions or characteristics. The nature of these resulting states, depending upon the two factors—organism and environment—can be changed by altering either factor. In general, organisms develop under pretty much the same conditions as their parents and general ancestry did, and their germinal substances are directly continuous, and therefore very similar. Consequently, primary organic structure and environing conditions of development being alike through successive generations, the results of their interaction are alike. This alikeness is heredity—the fact of similarity between parent and offspring. The usually indefinite question as to the effect of the environment ordinarily has a real meaning however, and this is, or should be, whether the alteration of particular elements of the environment, the presence of special, unusual factors which cannot be said to be "normally" present—whether these produce any effect upon the organism which is truly heritable.

This is in reality the old question of the "inheritance of acquired characteristics," or, in a word, of modifications—a question which has been debated heatedly and at length. And as in many similar instances the number of essays and the length and heat of the debate have been inversely as the number and clearness of the pertinent facts. The large majority of biologists have long felt that the great bulk of the evidence was on one side, namely, that acquired traits were not heritable. At the same time they have recognized the difficulty of explaining certain apparently demonstrated contradictory facts. Some recent experimental work has largely cleared away the theoretical difficulties in this field, and the present status of the old and really fundamental question may be stated as follows: External conditions—climate, temperature, moisture, nutritional conditions, results of unusual activity, and the like—incidences of the environment, undoubtedly produce effects upon the structure and behavior of the organism, but these effects must be clearly grouped into two distinct classes.

In the first place the effect of "external" conditions may be to bring about a reaction between the bodily parts affected and the environing conditions. Here the body alone is modified and not the germinal substance for the next generation within this body. Such responses to environing conditions do not affect nor involve the structure of the germ, and are therefore unrepresented in that series of reactions that result in the production of an individual of the next generation. In this class are found most of the instances of "functional modification" or acquired characteristics. In this category belong most of the stock illustrations—from the blacksmith's arm and the pianist's fingers, to the giraffe's neck and the fox's cunning. Here also belong the results of training and education; we can train and educate brain cells but not germ cells.

It is characteristic of most of these bodily reactions to external conditions that they are adaptive; that is, when a body reacts to such a condition it does so by undergoing a change which makes the organism better fitted to the new condition—better able to exist. The increased keenness of vision, the strengthened muscle, the thickened fur—all such changes meet new or unusual demands in such a way that the organism has better chances of survival than it would have had unmodified.

But in the second place there are certain environmental circumstances which do affect the structure of the germinal substance within the body of an organism. An unusually high temperature acting at a certain period in the life-history may bring about a change in the color of insects which is heritable—i. e., racial; but such a change results from the action of temperature upon the germ directly and not alone upon the body, which then itself affects the germ. It is essential to recognize that in all such cases it is not the structural change in the body that affects the germ, but it is the external condition itself that affects the germ directly. This is not the half of a hair; it is an extremely important and significant difference. The effects of this kind of action are not visible until the generation following that acted upon. They become expressed in the bodies of the organisms developed from the affected germs.

It is characteristic of such changes as these that they may not, usually do not, have an adaptive relation to the condition bringing about the change. There is no correspondence between the bodily and the germinal modifications resulting from the action of the same condition. Furthermore, there seems to be no adaptive relation between the general character of the germinal disturbance and the environmental disturbance. Rarely some of the organismal characters resulting from such germinal modification may be in the direction of greater adaptedness; usually they are neutral or in the direction of utter unfitness.

But such effects are heritable, whatever their nature with respect to adaptedness, and it becomes therefore very important to find out what are the conditions that may thus disturb the normal structure of the germ. Little more than a beginning has been made here and practically nothing can be said definitely with reference to the human organism in this respect. Enough is known, however, to make it clear that it is only rarely indeed that external conditions can thus affect the germinal structure. In most cases the effects of the incidence of environment are purely bodily. A most fruitful field for eugenic investigation is open here.