With regard to illnesses to which attention must especially be paid in connexion with sexual selection, we have here, in the first place, to consider the “three scourges” of humanity: alcoholism, syphilis, and tuberculosis.
Apart from the fact that alcoholism leads in the drinker himself to nervous weakness, to mental disturbances of all kinds (delirium tremens, imbecility, mania, peripheral neuritis, etc.), it also exercises a very serious influence upon the offspring, who are, unfortunately, in many cases very numerous,[748] as the study of “drinker families” shows (cf. Jörger, “The Family Zero,” published in the Archives for Racial Biology, 1905, vol. ii., pp. 494-559). Only a very small fraction of the offspring of such families are physically and mentally normal (about 7 to 17 %); the majority display a rapidly progressive degeneration, which manifests itself physically more especially by the tendency to tuberculosis and epilepsy, and mentally by the tendency to drunkenness, crime, and imbecility. Alcohol is a direct poison to the germ cells, so much so that, according to the degree of drunkenness, it is almost possible to estimate beforehand the degree of hereditary taint. Moreover, an otherwise healthy father, in a single severe acute alcoholic intoxication, may procreate a child either quite incompetent to live, or weakly, or completely degenerate. On the other hand, it has been observed that a person given to chronic alcoholism is competent, during a temporary diminution in his consumption of alcohol, to procreate a comparatively vigorous child. From this it follows that marriage, or sexual union in general for reproductive purposes, with a man or woman addicted to alcohol, and no less the act of procreation in a state of intoxication, are absolutely to be condemned.
The danger of alcoholism to the offspring is illustrated by the experience that about one-eighth of the surviving children of drunken parents become affected with epilepsy, and that more than one-half of idiotic children are born of drunken parents (Kraepelin, “The Psychiatric Duties of the State,” p. 3; Jena, 1900).
In an earlier chapter ([pp. 361]-[363]) attention was drawn to the fact that syphilis rivals alcohol in its potency as a cause of racial degeneration.[749] Thanks to the researches of Alfred Fournier and of Tarnowsky, the sinister influence of syphilis in this respect is now widely recognized. E. Heddaeus rightly[750] asserts that since at the present day the whole world is contaminated with congenital or acquired syphilis, the eradication of syphilis is the most important task of reproductive hygiene. The previously mentioned etiological and prophylactic-therapeutic researches, among which may be included the quite recent discovery of syphilitic antibodies in the system of those who have formerly suffered from syphilis,[751] open to us a prospect of the realization of this magnificent idea. The weakening and degeneration of the individual by acquired and inherited syphilis, is also shown by the recent researches into the influence of syphilis upon the duration of life, among which I may mention the works of A. Blaschko[752] and Hans Tilesius.[753] Regarding the disastrous influence of syphilis continued into the second and third generations, see the monograph of B. Tarnowsky, “La Famille Syphilitique et sa Descendence” [Clermont (Oise), 1904]. (See note [325] to [p. 363].)
The third disease leading to degeneration is tuberculosis, which may be inherited either by direct infection of the germ, or (more frequently) by the transmission of a predisposition to the offspring. This simple predisposition, recognized by the so-called “tubercular physique” (long, thin individuals, with a flattened chest, poorly developed muscles, and a pale countenance), does not offer any absolute ground for prohibiting reproductive activity, since the health of the other party to the marriage may diminish or entirely remove the danger of inheritance. But, on the other hand, manifest tuberculosis or scrofula is a contra-indication to marriage.
The same is true of actual mental disorders, of severe diatheses, such as gout, obesity, or diabetes; and of cancer and other malignant tumours; whereas the bulk of “nervous” affections and other bodily diseases only exclude marriage in certain special circumstances.[754]
Very unfavourable to the offspring is the atrophy of the female breasts, and the consequent incapacity for lactation, a matter to which Mensinga,[755] G. von Bunge,[756] G. Hirth,[757] Emil Abderhalden,[758] A. Hegar,[759] and others, have referred, and which exercises a very unfavourable influence upon the offspring, since natural lactation cannot be adequately replaced by artificial feeding. According to Bunge, alcoholism, tuberculosis, syphilis, and mental disorders of the ancestry are the principal causes of atrophy of the mammary glands. Whether atrophy of the mammary glands is really on the increase, and whether it is hereditary, are matters demanding, as Abderhalden insists, more careful critical investigation.
Marriage at an age too youthful (below twenty on the part of the woman, below twenty-four on the part of the man) and at too advanced an age (above forty on the part of the woman, above fifty on the part of the man) is also disadvantageous to the offspring, as manifested by higher mortality of the infants, by the more frequent occurrence of malformations, idiotcy, rickets, etc. Equally disadvantageous is too close relationship by blood,[760] since in this way any unfavourable tendencies are greatly strengthened. Upon a certain degree of inbreeding, or, rather, upon an approximation to inbreeding, depends the formation of every race. The “racial problem” in this sense is a kind of exaltation of the inbreeding principle, for the very idea of race implies a more or less close relationship between all the members of a definite stock. Thus the entire absence of fresh blood does not necessarily give rise to any degeneration; but it is certain that long-continued close in-and-in breeding on the part of near blood-relatives in the same family results in a progressive tendency to degeneration, because, among those who unite in marriage, the same morbid tendencies are present, and accumulate in consequence of the inbreeding. This is shown very clearly by some statistics collected by Morris (published by Gruber, op. cit., p. 32). Marriage between uncle and niece, or between aunt and nephew, and the, unfortunately, far too frequent marriages between first cousins, are therefore to be condemned.
The greatest value is to be placed, in love’s choice, upon intellectual qualities. Intelligent persons, and those full of character, are to be preferred. Precisely in relation to the breeding of talents, Nietzsche recommended (“Posthumous Works,” vol. xii., p. 188; Leipzig, 1901) polygamy for men or women of predominant intellectual capacity, so that they might have the opportunity of reproducing their kind in intercourse with several persons of the opposite sex, and in this way, since the later children of the same women are not so powerful nor of such striking capacity as the first-born, they might have the possibility of being the parents of several talented and distinguished individuals. In relation to the woman’s question, the breeding of women well endowed with talent is a matter of especial interest. Charles Darwin[761] writes:
“In order that woman should reach the same standard as man, she ought, when nearly adult, to be trained to energy and perseverance, and to have her reason and imagination exercised to the highest point; then she would probably transmit these qualities chiefly to her adult daughters. All women, however, could not be thus raised, unless during many generations those who excelled in the above robust virtues were married, and produced offspring in larger numbers than other women.”