cause it throws light on the path along
which I want to lead you. Why did the racial barrier between Iberian and
Indian break down? Was it because the Iberian did not possess--was not
influenced by--a sense of race-caste such as we have seen to dominate
the Nordic colonist? I believe that race-caste or race-prejudice is and
has been a more potent force in the Nordic than in the Iberian stock.
The Iberian people are near neighbours of the African races; in physique
they are differentiated from the African stocks in a somewhat less
degree than the Nordic stocks which represent the utmost point in the
physical specialization of all European peoples. If the Iberian pioneer
carried with him to America a lesser degree of race-caste, the process
of hybridization would begin the more easily. The great north and south
experiments differed, however, in another important circumstance. The
Nordic encountered a scattered, nomadic, proud race; the Iberian a
settled people living in dense communities. The Iberian was thus exposed
to conditions in which a racial barrier was harder to maintain.

STRUGGLE BETWEEN RACE AND SEX IMPULSES

But neither of these two circumstances--a lesser developed sense of
race-caste in the Iberian, nor the massing of the southern Indians in
settled communities--explain the disappearance of a racial frontier. The
true explanation lies in the fact that Nature has grafted in the human
mind instinctive impulses which are far stronger than those designated
as race-prejudice. Nature has spent her most painstaking efforts in
establishing within the human organization a mechanism to ensure, above
all other ends, that the individual shall continue. The instinct to
propagate is the strongest of the instinctive impulses with which
mankind has been fitted. It dominates and conquers the race instinct on
all occasions save one. Sex impulse is the battery which breaks down
race-barriers. Race instinct becomes the master of sexual impulse only
when a pure stock has established itself as a complete and growing
community in a new country. Sexual impulses are the endowments of
individual men and women; they dominate and are manifested by
individuals, whereas race antipathies are manifestations not of the
individual, but of the mass. Race instinct comes into play only when
men, women, and children of the same stock are organized into
communities. Until such a community is organized sex instinct traffics
freely across racial