In social heredity the transmission is not determined by consanguinity, and therefore extends to members of alien races when they are incorporated in the social organization.
While the transmission of biological inheritance to each offspring is inevitable and complete, that of social inheritance is largely voluntary. It is also more or less complete, according to the knowledge, purpose, and effort of the individuals concerned. The transmission of acquired social and psychic characteristics even from parents to offspring depends on their association, and the imposition on their offspring by parents of their own modes of life. Sharing with parents their bodily activities, their language and their environment, both social and psychical, the offspring necessarily develop psychic and social characteristics similar to those of the parents.
Evolution takes place through the transformation of inheritance. The evolution of innate physiological, anatomical, and psychical characters takes place through the transformation of biological inheritance; and the evolution of society and of acquired characters chiefly through the transformation of social inheritance.
Nearly all biologists admit that change in the form of natural selection is one of the principles transforming biological inheritance; but whether the acquired characters of parents are even in the least degree inherited by the offspring, thus becoming innate characters, is one of the important biological problems of recent years. Into this problem we have not entered, though we recognize that it must have important bearings on sociological science. Briefly stated, it is this: Do social and psychic characteristics, acquired by individuals or by groups of individuals, affect the intrinsic inherited and transmissible psychic nature in such ways that offspring, by the mere fact of being offspring, necessarily manifest those characteristics, regardless of the particular social environment in which they may be reared? Into this problem, thus broadly stated, we do not enter. Limiting our view to those advanced races which manifest practically equal physiological development, we ask whether or not their differentiating psychic characteristics are due to modifications of their inherited and intrinsic psychic nature, such that those characteristics are necessarily transmitted to offspring through intrinsic biological heredity. Current popular and scientific sociology seems to give an affirmative answer to this question. The reply of this work emphasizes the negative. Although it is not maintained that there is absolutely no difference whatever in the psychic nature of the different races, or that the psychic differences distinguishing the races are entirely transmitted by social heredity, it is maintained that this is very largely the case—far more largely than is usually perceived or admitted. Such inherent differences, if they exist, are so vague and intangible as practically to defy discovery and clear statement, and may be practically ignored.
The only adequate disproof of the position here maintained would be about as follows. Let a Japanese infant be reared in an American home from infancy, not only fed and clothed as an American, but loved as a member of the family and trained as carefully and affectionately as one's own child. The full conditions require that not only the child himself, but everyone else, be ignorant of his parentage and race in order that he be thought to be, and be treated as though he were, a genuine member of his adopting home and people. What would be the psychic characteristics of that child when grown to manhood? If he should manifest psychic traits like those of his Japanese parents, if he should think in the Japanese order, if he should have a tendency to use prepositions as postpositions, if he should drop pronouns and should use honorific words in their place, if he should be markedly suspicious and inferential, if he should bow in making his salutations rather than shake hands, if he should show marked preference for sitting on the floor rather than on chairs, and for chopsticks to knives and forks, and if developing powers as an artist he should naturally paint Japanese pictures, Japanese landscapes, and Japanese faces, finding himself unable to draw according to the canons of Western art, if on developing poetic tastes he should find special pleasure in seventeen syllable or thirty-one syllable exclamatory poems, finding little interest in Longfellow or Shakespeare, if, in short, he should develop a predilection for any distinctive Japanese custom, habit of thought, method of speech, emotion or volition, it would evidently be due to his intrinsic heredity. If in all these matters, however, he should prove to be like an American, acquiring an American education like any American boy, and if on being brought to Japan, at, say, thirty years of age, still supposing himself to be an American, he should have equal difficulty with any American in mastering the language and adapting himself to and understanding the Japanese people, then it would follow that his psychic characteristics have been inherited socially and he is what he is, nationally, because of his social heritage. Such a result would show that the psychic traits differentiating races are social and not intrinsic.
We have limited our discussion to the advanced races because the problem is then relatively simple, the material abundant, and the issue clear. Much discussion in theology, psychology, and sociology is futile because it concerns that practically mythical being, the aboriginal man, about whose social and psychic life no one knows anything, and any theorizer can say what he chooses without fear of shipwreck on incontrovertible facts. Whether the lowest races known to-day are differentiated from the highest only by acquired social and psychic characteristics, or also by differences of psychic nature, may perhaps be an open question. However this may be, the case is fairly clear in regard to the higher races inhabiting the earth. Their differentiating psychic characteristics are, for the most part, not due to diverse psychic nature, but to diverse social orders, while the transmission of these characteristics takes place, as a matter of observation, through social heredity.
The discussions of this work are exclusively concerned with the evolution of society and of psychic characteristics. But even in this limited field we have not attempted to cover the whole ground. We have given our chief attention to the interdependence of social phenomena and psychic characteristics. The causes of evolution in the social order have not been the main subject under discussion.
Segregation is the essential condition on which divergent evolution is dependent. Many forms of segregation may be specified, under each of which evolution proceeds on a different principle. In brief, it may be said that biological segregation prevents the swamping of incipient organic divergences, by preventing the intermarriage of those possessing such divergences, while social segregation prevents the swamping of incipient social divergences and their corresponding incipient psychic characteristics by preventing the inter-association of those having such tendencies.
Biologically segregated groups undergo divergent biological evolution through segregated marriage, producing distinct physiological unities or racial types. These racial types are now relatively fixed and can be appreciably modified only by the intermarriage of different races.
Socially segregated groups undergo divergent social evolution through the segregated social intercourse of the members of each group, producing distinct civilizational and psychic unities. The differences between these social or psychic groups are relatively plastic and are the subject of constant variation. The modification of the social and psychic characteristics of a group takes place through a change in the physical or social environment of the group, or through the rise of strong personalities within the group.