In primitive society there is no such mental cleavage to render the idea of fusion abhorrent to the superior race; the bar is religious, and while it places the inferior race in a despised and abject position, there is no prohibition of illicit unions nor any such moral feeling or principle as would tend to restrict them.

The ideas of the responsibilities and duties of parentage in connection with heredity, or the science of eugenics, are entirely modern, and have no place at all in ancient society.

As racial and religious distinctions fade away, and social progress takes place, a fresh set of divisions by wealth and occupation grows up.

But though this happened also in the Greek and Italian cities, the old religious divisions were not transferred to the new occupational groups, but fell slowly into abeyance, and the latter assumed the simply social character which they have in modern communities.

The main reason for the obliteration of religious barriers, as already stated, was the growth of the idea of nationality and the public interest.