The origin and development of the moral ideas

In a previous work I have endeavoured to show that in all probability there has been no stage in the social history of mankind where marriage has not existed, human marriage apparently being an inheritance from some ape-like progenitor.1 I then defined marriage as a more or less durable connection between male and female, lasting beyond the mere act of propagation till after the birth of the offspring. This is marriage in the natural history sense of the term. As a social institution, on the other hand, it has a somewhat different meaning: it is a union regulated by custom or law.2 Society lays down rules relating to the selection of partners, to the mode of contracting marriage, to its form, and to its duration. These rules are essentially expressions of moral feelings.

There is, first, a circle of persons within which marriage is prohibited. It seems that the horror of incest is well-nigh universal in the human race, and that the few cases in which this feeling is said to be absent can only be regarded as abnormalities. But the degrees of kinship within which marriage is forbidden are by no means the same everywhere. It is most, and almost universally, abominated between parents and children. It is also held in general abhorrence between brothers and sisters who are children of the same mother as well as of the same father. Most of the exceptions to this rule refer to royal persons, for whom it is considered improper to contract marriage with individuals of less exalted birth; but among a few peoples incestuous unions are practised on a larger scale on account of extreme isolation or as a result of vitiated instincts.3 It seems, however, that habitual marriages between brothers and sisters have been imputed to certain peoples without sufficient reason.4 This is obviously true of the Veddahs of Ceylon, who have long been supposed to regard the marriage of a man with his younger sister as the proper marriage.5 “Such incest,” says Mr. Nevill, “never was allowed, and never could be, while the Vaedda customs lingered. Incest is regarded as worse than murder. So positive is this feeling, that the Tamils have based a legend upon the instant murder of his sister by a Vaedda to whom she had made undue advances. The mistake arose from gross ignorance of Vaedda usages.

The title of a cousin with whom marriage ought to be contracted, that is, mother’s brother’s daughter, or father’s sister’s daughter, is nagâ or nangî. This, in Sinhalese, is applied to a younger sister. Hence if you ask a Vaedda, ‘Do you marry your sisters?’ the Sinhalese interpreter is apt to say, ‘Do you marry your nagâ?’ The reply is (I have often tested it), ‘Yes—we always did formerly, but now it is not always observed.’ You say then, ‘What? marry your own-sister-nagâ?’ and the reply is an angry and insulted denial, the very question appearing a gross insult.” The same writer adds:—“In no case did a person marry one of the same family, even though the relationship was lost in remote antiquity. Such a marriage is incest. The penalty for incest was death.”6

As a rule, the prohibited degrees are more numerous among peoples unaffected by modern civilisation than they are in more advanced communities, the prohibitions in a great many cases referring even to all the members of the tribe or clan; and the violation of these rules is regarded as a most heinous crime.7

Not less intense is the horror of incest among nations that have passed beyond savagery and barbarism. Among the Chinese incest with a grand-uncle, a father’s first cousin, a brother, or a nephew, is punishable by death, and a man who marries his mother’s sister is strangled; nay, punishment is inflicted even on him who marries a person with the same surname as his own, sixty blows being the penalty.20 So also incest was held in the utmost horror by the so-called Aryan peoples in ancient times.21 In the ‘Institutes of Vishnu’ it is said that sexual intercourse with one’s mother or daughter or daughter-in-law is a crime of the highest degree, for which there is no other atonement than to proceed into the flames.22

Various theories have been set forth to account for the prohibition of marriage between near kin. I criticised some of them in my book on the ‘History of Human Marriage,’ and ventured at the same time on an explanation of my own.23 I pointed out that there is an innate aversion to sexual intercourse between persons living very closely together from early youth, and that, as such persons are in most cases related by blood, this feeling would naturally display itself in custom and law as a horror of intercourse between near kin. Indeed, an abundance of ethnographical facts seem to indicate that it is not in the first place by the degree of consanguinity, but by the close living together, that prohibitory laws against intermarriage are determined. Thus many peoples have a rule of “exogamy” which does not depend on kinship at all, but on purely local considerations, all the members of a horde or village, though not related by blood, being forbidden to intermarry.24 The prohibited degrees are very differently defined in the customs or laws of different nations, and it appears that the extent to which relatives are prohibited from intermarrying is nearly connected with their close living together. Very often the prohibitions against incest are more or less one-sided, applying more extensively either to the relatives on the father’s side or to those on the mother’s, according as descent is reckoned through men or women.

Now, since the line of descent is largely connected with local relationships, we may reasonably infer that the same local relationships exercise a considerable influence on the table of prohibited degrees. However, in a large number of cases prohibitions of intermarriage are only indirectly influenced by the close living together.25 Aversion to the intermarriage of persons who live in intimate connection with one another has called forth prohibitions of the intermarriage of relations; and, as kinship is traced by means of a system of names, the name comes to be considered identical with relationship. This system is necessarily one-sided. Though it will keep up the record of descent either on the male or female side, it cannot do both at once;26 and the line which has not been kept up by such means of record, even where it is recognised as a line of relationship, is naturally more or less neglected and soon forgotten. Hence the prohibited degrees frequently extend very far on the one side—to the whole clan—but not on the other. It should also be remembered that, according to primitive ideas, the name itself constitutes a mystic link between those who have it in common. “In Greenland, as everywhere else,” says Dr. Nansen, “the name is of great importance; it is believed that there is a spiritual affinity between two people of the same name.”27 Generally speaking, the feeling that two persons are intimately connected in some way or other may, through an association of ideas, give rise to the notion that marriage or sexual intercourse between them is incestuous.

The question arises:—How has this instinctive aversion to marriage and sexual intercourse in general between persons living closely together from early youth originated? I have suggested that it may be the result of natural selection. Darwin’s careful studies of the effects of cross- and self-fertilisation in the vegetable kingdom, the consensus of opinion among eminent breeders, and experiments made with rats, rabbits, and other animals, seem to have proved that self-fertilisation of plants and close inter-breeding of animals are more or less injurious to the species; and it is probable that the evil chiefly results from the fact that the uniting sexual elements were not sufficiently differentiated. Now it is impossible to believe that a physiological law which holds good of the rest of the animal kingdom, as also of plants, would not apply to man as well. But it is difficult to adduce direct evidence for the evil effects of consanguineous marriages. We cannot expect very conspicuous results from other alliances than those between the nearest relatives—between brothers and sisters, parents and children,—and the injurious results even of such unions would not necessarily appear at once. The closest kind of intermarriage which we have opportunities of studying is that between first cousins. Unfortunately, the observations hitherto made on the subject are far from decisive.