EXOGAMY (Gr. ἔξω, outside; and γάμος, marriage), the term proposed by J. F. McLennan for the custom compelling marriage “out of the tribe” (or rather “out of the totem”); its converse is endogamy (q.v.). McLennan would find an explanation of exogamy in the prevalence of female infanticide, which, “rendering women scarce, led at once to polyandry within the tribe, and the capturing of women from without.” Infanticide of girls is, and no doubt ever has been, a very common practice among savages, and for obvious reasons. Among tribes in a primitive stage of social organization girl-children must always have been a hindrance and a source of weakness. They had to be fed and yet they could not take part in the hunt for food, and they offered a temptation to neighbouring tribes. Infanticide, however, is not proved to have been so universal as McLennan suggests, and it is more probable that the reason of exogamy is really to be found in that primitive social system which made the “captured” woman the only wife in the modern sense of the term. In the beginnings of human society children were related only to their mother; and the women of a tribe were common property. Thus no man might appropriate any female or attempt to maintain proprietary rights over her. With women of other tribes it would be different, and a warrior who captured a woman would doubtless pass unchallenged in his claim to possess her absolutely. Infanticide, the evil physical effects of “in-and-in” breeding, the natural strength of the impulse to possess on the man’s part, and the greater feeling of security and a tendency to family life and affections on the woman’s, would combine to make exogamy increase and marriages within the tribe decrease. A natural impulse would in a few generations tend to become a law or a custom, the violation of which would be looked on with horror. Physical capture, too, as soon as increasing civilization and tribal intercommunication removed the necessity for violence, became symbolic of the more permanent and individual relations of the sexes. An additional explanation of the prevalence of exogamy may be found in the natural tendency of exogamous tribes to increase in numbers and strength at the expense of those communities which moved towards decadence by in-breeding. Thus tradition would harden into a prejudice, strong as a principle of religion, and exogamy would become the inviolable custom it is found to be among many races. In Australia, Sir G. Grey writes: “One of the most remarkable facts connected with the natives is that they are divided into certain great families, all the members of which bear the same name . . . these family names are common over a great portion of the continent and a man cannot marry a woman of his own family name.” In eastern Africa, Sir R. Burton says: “The Somal will not marry one of the same, or even of a consanguineous family,” and the Bakalahari have the same rule. Paul B. du Chaillu found exogamy the rule and blood marriages regarded as an abomination throughout western Equatorial Africa. In India the Khasias, Juangs, Waralis, Otaons, Hos and other tribes are strictly exogamous. The Kalmucks are divided into hordes, and no man may marry a woman of the same horde. Circassians and Samoyedes have similar rules. The Ostiaks regard endogamy (marriage within the clan) as a crime, as do the Yakuts of Siberia. Among the Indians of America severe rules prescribing exogamy prevail. The Tsimsheean Indians of British Columbia are divided into tribes and totems, or “crests which are common to all the tribes,” says one writer. “The crests are the whale, the porpoise, the eagle, the coon, the wolf and the frog.... The relationship existing between persons of the same crest is nearer than that between members of the same tribe.... Members of the same tribe may marry, but those of the same crest are not allowed to under any circumstances; that is, a whale may not marry a whale, but a whale may marry a frog, &c.” The Thlinkeets, the Mayas of Yucatan and the Indians of Guiana are exogamous, observing a custom which is thus seen to exist throughout Africa, in Siberia, China, India, Polynesia and the Americas.

Authorities.—J. F. McLennan, Primitive Marriage (1865), and Studies in Anc. Hist. (1896); Lord Avebury, Origin of Civilization (1902); Westermarck, History of Human Marriage (1894); A. Lang, Social Origins (1903); L. H. Morgan, Ancient Society (1877); J. G. Frazer, Totemism and Exogamy (1910); see also Totem.