More important than any of these statements is the following testimony concerning the Karens of Burma, for which I am indebted to the Rev. Dr. Alonzo Bunker, who has been a resident among that people during more than twenty years. He says that, in some of their villages, exogamy prevails, in others endogamy, but marriages between parents and children, brothers and sisters, are prohibited everywhere, and even first cousins very seldom marry, though there is no law against such connections. There is a striking difference with regard to stature, health, strength and fecundity, between the inhabitants of the exogamous and those of the endogamous villages, the latter being much inferior in all these respects. Dr. Bunker has no doubt that this inferiority is owing to the intermarriage of kinsfolk, and he asserts that even the natives themselves ascribe it to this cause, though they obstinately keep up the old custom, regarding marriages out of their own village as highly unbecoming. In cases in which missionaries have been able to persuade young men to choose wives from another village, Dr. Bunker assures me that the good effects of a cross appeared at once.[2045]
There are some other peoples who ascribe evil results to close intermarriage. Mr. Cousins informs me that the Cis-Natalian Kafirs believe “that their offspring would be of a more sickly nature if such were allowed”; and Mr. Eyles writes that the Zulus, on the border of Pondoland, regard sterility and deformity as consequences of consanguineous unions. The Australian Dieyerie, according to Mr. Gason, have a tradition that, after the creation, fathers, mothers, sisters, brothers, and others of the closest kin intermarried promiscuously, until the bad effects of these marriages became manifest. A council of the chiefs was then assembled to consider in what way the evil might be averted, and the result of their deliberations was a petition to the Muramura, or Good Spirit. In answer to this he ordered that the tribe should be divided into branches, and distinguished one from the other by different names, after objects animate and inanimate, such as dogs, mice, emu, rain, and so forth, and that the members of any such branch should be forbidden to marry other members of the same branch.[2046] Again, touching the Kenai, in the north-western part of North America, Richardson states, “It was the custom that the men of one stock should choose their wives from another, and the offspring belonged to the race of the mother. This custom has fallen into disuse, and marriages in the same tribe occur; but the old people say that mortality among the Kenai has arisen from the neglect of the ancient usage.”[2047]
In a Greenland Eskimo tale, the father of Kakamak, finding that all his grandchildren have died before reaching the age of puberty, suggests to his son-in-law, “Perhaps we are too near akin.”[2048] Two Mohammedan travellers of the ninth century tell us that the Hindus never married a relation, because they thought alliances between unrelated persons improved the offspring.[2049] In Hadîth, the collection of Mohammedan traditions, it is said, “Marry among strangers; thus you will not have feeble posterity.” “This view,” says Goldziher, “coincides with the opinion of the ancient Arabs that the children of endogamous marriages are weakly and lean. To this class also belongs the proverb of Al-Meydânî, ‘ ... Marry the distant, marry not the near’ (in relationship).” A poet, praising a hero, says, “He is a hero, not borne by the cousin (of his father), he is not weakly; for the seed of relations brings forth feeble fruit.”[2050]
In opposition to the view that these opinions are the results of experience, it may be urged that any infraction of the customs or laws of ancestors is commonly thought to call down divine vengeance. Father Veniaminof tells us that, among the early Aleuts, incest, which was considered the gravest crime, was believed to be always followed by the birth of monsters with walrus-tusks, beard, and other disfiguration;[2051] and among the Kafirs, according to Mr. Fynn, it is a general belief that the offspring of an incestuous union will be a monster—“a punishment inflicted by the ancestral spirit.”[2052] But whatever may be said of the other cases referred to, no such explanation can possibly hold good for the Arabs. Among them, marriage with a near relation involved no infringement of their marriage regulations. On the contrary, in spite of the opinions in favour of exogamy, the preference for marriage with a cousin was dominant among them, and a man had even a right to the hand of his “bint ‘amm,” the daughter of a paternal uncle.[2053]
Taking all these facts into consideration, I cannot but believe that consanguineous marriages, in some way or other, are more or less detrimental to the species. And here, I think, we may find a quite sufficient explanation of the horror of incest; not because man at an early stage recognized the injurious influence of close intermarriage, but because the law of natural selection must inevitably have operated. Among the ancestors of man, as among other animals, there was no doubt a time when blood-relationship was no bar to sexual intercourse. But variations, here as elsewhere, would naturally present themselves; and those of our ancestors who avoided in-and-in breeding would survive, while the others would gradually decay and ultimately perish. Thus an instinct would be developed which would be powerful enough, as a rule, to prevent injurious unions. Of course it would display itself simply as an aversion on the part of individuals to union with others with whom they lived; but these, as a matter of fact, would be blood-relations, so that the result would be the survival of the fittest.
Whether man inherited the feeling from the predecessors from whom he sprang, or whether it was developed after the evolution of distinctly human qualities, we do not know. It must necessarily have arisen at a stage when family ties became comparatively strong, and children remained with their parents until the age of puberty, or even longer. Exogamy, as a natural extension of this instinct, would arise when single families united in small hordes. It could not but grow up if the idea of union between persons intimately associated with one another was an object of innate repugnance. There is no real reason why we should assume, as so many anthropologists have done,[2054] that primitive men lived in small endogamous communities, practising incest in every degree. The theory does not accord with what is known of the customs of existing savages; and it accounts for no facts which may not be otherwise far more satisfactorily explained.
The objection will perhaps be made that the aversion to sexual intercourse between persons living very closely together from early youth is too complicated a mental phenomenon to be a true instinct, acquired through spontaneous variations intensified by natural selection. But there are instincts just as complicated as this feeling, which, in fact, only implies that disgust is associated with the idea of sexual intercourse between persons who have lived in a long-continued, intimate relationship from a period of life at which the action of desire is naturally out of the question. This association is no matter of course, and certainly cannot be explained by the mere liking for novelty. It has all the characteristics of a real, powerful instinct, and bears evidently a close resemblance to the aversion to sexual intercourse with individuals belonging to another species.
Besides the horror of incest, there is another feeling to which reference may here be made. “L’amour,” says Bernardin de Saint-Pierre, “ ... ne résulte que des contrastes; et plus ils sont grands, plus il a d’énergie. C’est ce que je pourrois prouver par mille traits d’histoire.... L’influence des contrastes en amour est si certaine, qu’en voyant l’amant on peut faire le portrait de l’objet aimé sans l’avoir vu, pourvu qu’on sache seulement qu’il est affecté d’une forte passion.”[2055] Schopenhauer likewise observes that every person requires from the individual of the opposite sex a one-sidedness which is the opposite of his or her own. The most manly man will seek the most womanly woman, and vice versa. Weak or little men have a decided inclination for strong or big women, and strong or big women for weak or little men. Blondes prefer dark persons, or brunettes; snub-nosed persons, hook-nosed; persons with excessively slim, long bodies and limbs, those who are stumpy and short; and so on.[2056] A similar view is held by M. Prosper Lucas, Mr. Alexander Walker, Professor Mantegazza, Mr. Grant Allen, and other writers.[2057] “In the love of the sexes,” says Professor Bain, “the charm of disparity goes beyond the standing differences of sex; as in contrasts of complexion, and of stature.”[2058]
Some writers have suggested that love thus excited by differences is favourable to fecundity, those marriages in which it exists being more prolific than others.[2059] Thus Mr. Andrew Knight, a most experienced breeder, remarks, “I am disposed to think that the most powerful human minds will be found offspring of parents of different hereditary constitutions. I prefer a male of a different colour from the breed of the female, where that can be obtained, and I think that I have seen fine children produced in more than one instance, where one family has been dark and the other fair. I am sure that I have witnessed the bad effects of marriages between two individuals very similar to each other in character and colour, and springing from ancestry of similar character. Such have appeared to me to be like marriages between brothers and sisters.”[2060]