It is not wholly fair to attribute these profound conclusions to the geneticist, however; the farmer discovered the facts years ago, while the geneticist was floundering in a sea of philosophic doubts. Do not, I beg of you, ask a farmer whether he can turn a hackney colt into a thoroughbred by giving it special food and training, if you wish to retain a reputation for intelligence. Do not ask him what changes can be made in a Concord grape or a Winesap apple or an Elberta peach by an altered soil or a diverse climate. He knows well enough that every plant of each of these asexually propagated varieties has the same genetic constitution as all the others, and that, for this reason, they are recognizable members of their respective groups wherever they are grown.

The facts being what they are, therefore, one should not ask whether heredity or environment is the more powerful. It is a silly question. Both are essential. They are collaborating artists, their finished product the individual, yet with different roles to play as moulders of destiny. The gene pattern received by the fertilized egg definitely delimits the end result. One does not gather figs from thistles. Nevertheless, environments can differ to some extent without preventing development; and these diverse factors may have a recognizable effect upon the final product. Ordinarily such effects are restricted to such quantitative changes as we are familiar with under conditions of good hygiene and bad hygiene. And the alterations to be expected in man by environmental diversity are probably less than for any other organism, owing to the delicacy of his organization and the mechanisms that have been produced to keep his environment constant.

I know of no better analogy to use in comparing the respective functions of heredity and environment than one borrowed from photography. The gene plan of the fertilized egg makes it like an exposed plate. The potentiality of a picture is there, waiting to be developed. The environment is the developer. It can make or mar the picture, but that picture will have the same general character in any event. Translating these matters into the terms of sociology, one may say: Give the growing child the best conditions possible; it is highly desirable; but do not expect to change the character of his features or the quality of his brains.

If it has not been made perfectly clear before, the last sentence will serve to indicate that man cannot be excluded from the aggregation of organisms ruled by genetic law. Well, why should he be excluded? Man is simply a higher mammal, with a structure and a set of physiological processes very similar to those of other mammals high in the evolutionary series. From these facts one might assume that the method by which his heritage is passed on would be essentially the same as that which is common to all the remaining members of the animal and vegetable kingdoms which reproduce sexually. But no such abstract deduction is necessary. The observations of competent cytologists have shown conclusively that human body cells contain forty-eight chromosomes, and that, at the maturation of the germ cells, these chromosomes undergo the special type of reduction division required for the distribution of the genes by the Chromosome Theory of Heredity. In addition, analyses of voluminous genealogical records have demonstrated that numerous character differences, affecting each of the various organ systems, are inherited as we should expect them to be inherited if they are due to one or more genes carried by the chromosomes and distributed by the normal mechanism for such distribution. Sex is even fixed by the possession of a particular type of chromosome carried by all of the eggs but by only one-half of the sperms. And it has been proved that hemophilia (loss of the blood-clotting mechanism) and color-blindness (diminished sensitivity of the cones of the eye) are carried in this same chromosome, just as sex-linked characters in other organisms are due to genes carried in this so-called X-chromo-some which has the most direct influence over sex. Other more complex characters follow the same scheme. The details of gene interaction are more difficult to determine in such cases, as, for instance, skin color in negro-white crosses; yet it is significant that where complex character differences are under consideration, the genealogical records and the records from the genetics laboratories are virtually identical in character. Mathematical analysis of controlled experiments brings out certain conditions which ought to be satisfied in the genealogical records if the heredity mechanisms are comparable in the two cases; and these conditions are satisfied. Geneticists are convinced, therefore, that inheritance in man is the same as in melons, or mosquitoes, or monkeys.

Certain critics who accept this genetic generalization for physical characteristics question whether it holds for mental characteristics. And, unfortunately, the less they have studied the subject, the more positive they are in their assertions. Dr. John B. Watson, the extremist leader, completely oblivious to genetic facts, even boasts that he can make a fool or a genius of any normal child if he begins his instruction at a sufficiently early period. Since man is chiefly interested in man, it may be well to develop the genetic beliefs on this point in a little more detail. The argument will give a better orientation for the remarks on the applicability of genetic philosophy to sociology, to which the concluding pages of the chapter are devoted.

The convictions of the radical behaviorists are wholly emotional in character. For some unknown reason, they wish to believe in the innate intellectual parity of all members of the human race. Their minds are firmly conditioned in this respect, to use one of their own terms; hence, a knowledge of the genetic facts, if one grants such enlightenment, has little influence. Their sole argument, stripped of all verbiage, is an example of a paradox in logic that would have given William de Morgan great pleasure. They grant that the human race exhibits heritable differences in all sorts of external features, and in various parts of the skeletal, muscular, circulatory, digestive, and secretory systems. They admit that the central nervous system is the physical basis of mental capacity and that heritable defects in it may cause feeble-mindedness. And despite these admissions, they stolidly maintain that the normal central nervous system does not vary. At least their arguments are all reducible to this simple and obvious fallacy.