The Descent of Man

certain the precise causes and their manner of
action, it ought not to be so to our reason, as
long as we keep steadily in mind that the increase
of each species and each race is constantly
checked in various ways; so that if any new
check, even a slight one, be superadded, the
race will surely decrease in number; and decreasing
numbers will sooner or later lead to
extinction; the end, in most cases, being promptly
determined by the inroads of conquering
tribes.
ON THE FORMATION OF THE RACES OF
MAN.
In some cases the crossing of distinct races has
led to the formation of a new race. The singular
fact that the Europeans and Hindoos, who belong
to the same Aryan stock, and speak a language
fundamentally the same, differ widely in
appearance, whilst Europeans differ but little
from Jews, who belong to the Semitic stock, and