The most striking institution of this kind is however undoubtedly Especially from Exogamy that of Exogamy. There is as yet no complete consensus of opinion as to the causes that have led to the origin and development of exogamy, but the majority of the eminent investigators who have devoted themselves to the subject agree that the avoidance of incest is the principal factor that has led to the creation of the system. The various stages of exogamic development, as seen in Australia, appear to constitute so many fresh encroachments upon the liberty of incest[230], the later and more complex four class system prohibiting certain unions between relatives that the earlier and simpler two class system has permitted, while the eight class system in turn prevents those that are not excluded under the four class system, though the actual relationships prohibited differ somewhat according to whether descent is traced in the male or female line.
There is a considerable amount of evidence to show that Exogamy was probably preceded by Endogamy exogamy, where now in force, was preceded by a period in which the unions prohibited under its rule were freely indulged in, though the marriage tie was at the same time broader and less binding. Thus of the Central Australians Spencer and Gillen[231] say that tradition "seems to point back to a time when a man always married a woman of his own totem. The reference to men and woman of one totem always living together in groups would appear to be too frequent to admit of any other satisfactory explanation. We never meet in tradition with an instance of a man living with a woman who was not of his own totem." The same conclusion as to the former universal prevalence of endogamy emerges from a study of the actually observed condition of the Australian natives, the rude and uncultivated tribes of the interior being still to some extent endogamic, while there is a gradual increase in the frequency and strictness of exogamy, as we proceed from these to the more advanced communities of the north[232]. Among the Kacharis of Assam we have an example of what is probably the still more primitive process of a compulsory endogamy giving place to freedom to marry outside the totem group, endogamy being here thus not only permitted but enjoined[233]. Other indications of the co-existence of endogamy with a totemic system are found in Madagascar[234] and in N.W. America[235].
Frazer supposes that exogamy in its beginning arose originally as a restriction upon complete promiscuity, though he admits that such promiscuity need not have been characteristic of absolutely primitive man[236]. As a matter of fact the most primitive races that we know seem to be usually Really primitive races mostly monogamous and endogamous monogamous and endogamous. This is for instance to a greater or less extent the case with the Veddahs[237], the Andamanese[238], the lowest forest tribes of Brazil[239], the inhabitants of the interior of Borneo[240], the Semangs and Senoi of the Malay Peninsula[241], and the Negritos of the Philippines[242] and Central Africa[243].
In these primitive peoples and in those who, as we must The family is therefore their principal social unit suppose, formerly resembled them, the family would appear to be a more closely knit and socially a more important unit than in the later age of totemism and exogamy; there being in this respect a resemblance between the primitive condition and that of the post-totemic patriarchal period. There is reason to believe however that in the case of really primitive man (in distinction from the later patriarchal period) the family is often the only permanent and stable unit; such approximation to tribal organisation as exists being mostly of a temporary or Incest a natural consequence of such conditions fluctuating character. With such peoples the low state of culture will often necessitate a relatively scattered population, and in these circumstances endogamy and incest may be a natural—indeed possibly sometimes an inevitable—consequence; for where families live in relative isolation for long periods together, opportunities for marriage outside the family may be few, and abstention from sexual activities during these periods would imply a greater power of continence than would seem as a rule to be possessed by primitive peoples. Incest would naturally follow too under these conditions from the early ripening of the sexual instinct which is generally found in primitive man[244]. The very early cohabitation of the sexes which results therefrom would, in relatively isolated families, almost necessarily occur in an incestuous form.
If these influences have made incest a common practice How do past incestuous practices produce present tendencies to incest? at one period of man's history, in what ways has this practice contributed to the tendency to incest found at a later date and at the present day? In view of the widespread (we are probably justified in saying universal) occurrence of this tendency, of the relative uniformity of its ultimate nature in spite of manifold differences of culture, training, and environment, of the great strength which it possesses even after ages of repression, there is not unnaturally a temptation to regard it as an innate factor in man's mental constitution, i. e., to assert that there is in man an hereditary tendency to direct his love and sexual The influence of heredity and of tradition inclination to those who are of his own blood or at any rate to those with whom he has been brought up and has been familiar since his infancy[245]. Possibly in the long ages in which man or his pre-human ancestors lived in relatively isolated families, this tendency was of advantage in the struggle for existence, in so much as it may have contributed both to more rapid multiplication and to the greater consolidation, and therefore greater safety and stability, of the family, as the most important social unit. The tendency to incest may thus be due ultimately to the action of natural selection; the long period during which incest was regularly practised may have established and ingrained it as a normal feature of the race and its persistence to-day may be due to the continuance of the hereditary disposition thus formed and thus consolidated.
Apart from the direct influence of this hereditary factor however, a long period during which incest was habitual may have affected the tendency to incest at a later time through custom, law and tradition. These change but slowly in a primitive society, and, through their inertia, would tend to reinforce or maintain the hereditary factor, even when, owing to the action of other causes, incest may have been abandoned in the main in favour of exogamy. These influences may have kept alive the remembrance of, and desire for, incest, which would otherwise possibly have succumbed to the forces working to bring about its suppression.