heritable differences of much importance,
which are given too little recognition--namely, the differences of
disease resistance. Here one can speak unhesitatingly of a real
inferiority in respect to the environment of North America.

As was pointed out in the chapter on Natural Selection, the Negro has
been subjected to lethal selection for centuries by the Negro diseases,
the diseases of tropical Africa, of which malaria and yellow fever are
the most conspicuous examples. The Negro is strongly resistant to these
and can live where the white man dies. The white man, on the other hand,
has his own diseases, of which tuberculosis is an excellent example.
Compared with the Negro, he is relatively resistant to phthisis and will
survive where the Negro dies.

When the two races are living side by side, it is obvious that each is
proving a menace to the other, by acting as a disseminator of
infection. The white man kills the Negro with tuberculosis and typhoid
fever. In North America the Negro can not kill the white man with
malaria or yellow fever, to any great extent, because these diseases do
not flourish here. But the Negro has brought some other diseases here
and given them to the white race; elephantiasis is one example, but the
most conspicuous is hookworm, the extent and seriousness of which have
only recently been realized.

In the New England states the average expectation of life, at birth, is
50.6 years for native white males, 34.1 years for Negro males. For
native white females it is 54.2 years and for Negro females 37.7 years,
according to the Bureau of the Census (1916). These very considerable
differences can not be wholly explained away by the fact that the Negro
is crowded into parts of the cities where the sanitation is worst. They
indicate that the Negro is out of his environment. In tropical Africa,
to which the Negro is adapted by many centuries of natural selection,
his expectation of life might be much longer than that of the white man.
In the United States he is much less "fit," in the Darwinian sense.

In rural districts of the South, according to C. W. Stiles, the annual
typhoid death rate per 100,000 population is:

_Whites_ _Negroes_
Males 37.4 75.3
Females 27.4 56.3

These figures again show, not alone the greater intelligence of the
white in matters of hygiene, but probably also the greater inherent
resistance of the white to a diseas