The first move away from brother and sister marriages came about under the plural-wife mores because the sister-wife would arrogantly dominate the other wife or wives. Some tribal mores forbade marriage to a dead brother's widow but required the living brother to beget children for his departed brother. There is no biologic instinct against any degree of in-marriage; such restrictions are wholly a matter of taboo.

Outmarriage finally dominated because it was favored by the man; to get a wife from the outside insured greater freedom from in-laws. Familiarity breeds contempt; so, as the element of individual choice began to dominate mating, it became the custom to choose partners from outside the tribe.

Many tribes finally forbade marriages within the clan; others limited mating to certain castes. The taboo against marriage with a woman of one's own totem gave impetus to the custom of stealing women from neighboring tribes. Later on, marriages were regulated more in accordance with territorial residence than with kinship. There were many steps in the evolution of in-marriage into the modern practice of outmarriage. Even after the taboo rested upon in-marriages for the common people, chiefs and kings were permitted to marry those of close kin in order to keep the royal blood concentrated and pure. The mores have usually permitted sovereign rulers certain licenses in sex matters.

The presence of the later Andite peoples had much to do with increasing the desire of the Sangik races to mate outside their own tribes. But it was not possible for outmating to become prevalent until neighboring groups had learned to live together in relative peace.

Outmarriage itself was a peace promoter; marriages between the tribes lessened hostilities. Outmarriage led to tribal co-ordination and to military alliances; it became dominant because it provided increased strength; it was a nation builder. Outmarriage was also greatly favored by increasing trade contacts; adventure and exploration contributed to the extension of the mating bounds and greatly facilitated the cross-fertilization of racial cultures.

The otherwise inexplicable inconsistencies of the racial marriage mores are largely due to this outmarriage custom with its accompanying wife stealing and buying from foreign tribes, all of which resulted in a compounding of the separate tribal mores. That these taboos respecting in-marriage were sociologic, not biologic, is well illustrated by the taboos on kinship marriages, which embraced many degrees of in-law relationships, cases representing no blood relation whatsoever.

There are no pure races in the world today. The early and original evolutionary peoples of color have only two representative races persisting in the world, the yellow man and the black man; and even these two races are much admixed with the extinct colored peoples. While the so-called white race is predominantly descended from the ancient blue man, it is admixed more or less with all other races much as is the red man of the Americas.

Of the six colored Sangik races, three were primary and three were secondary. Though the primary races—blue, red, and yellow—were in many respects superior to the three secondary peoples, it should be remembered that these secondary races had many desirable traits which would have considerably enhanced the primary peoples if their better strains could have been absorbed.