problem_. An unsolved factor in all race problems is the biological
influence of racial heredity, and this factor we must seek to understand
and estimate at the very outset of any scientific study of the negro
problem.

Racial Heredity as a Factor in Social Evolution.--We have already seen
that racial heredity is the most important and at the same time the
least known factor in the problem of immigration. While there is still
much disagreement among scientific men as to the importance of racial
heredity in social problems, it can be said that the weight of opinion
inclines to the view that racial heredity is a very real factor, and one
which cannot be left altogether out of account in studying social
problems. The view of Buckle that racial heredity counted for nothing in
explaining the social life of various peoples is not upheld by modern
biologists. On the contrary the biological view would emphasize the
importance of species and racial heredity in all problems connected with
life; thus no one denies that between different species of animals
heredity counts for everything in explaining their life activities, and,
as between the different breeds or races of a single species, no other
position is possible from the biological point of view. Nevertheless it
may be admitted that man no longer lives a purely animal life and that
racial heredity as a factor in his social life may be easily
exaggerated. On the whole, it is a safe rule to follow that racial
heredity should not be invoked to explain the social condition of a
people until practically all other factors have been exhausted.
Nevertheless as between the different races or great varieties of
mankind there must be a great difference in racial heredity. It could
not, indeed, be otherwise, since these different races were developed in
different geographical environments or "areas of characterization."
Natural selection has developed in each race of mankind an innate