In these primitive peoples and in those who, as we must 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 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. [Sidenote: How do past incestuous practices produce present tendencies to incest?] [Sidenote: The influence of heredity and of tradition]