AN INTRODUCTORY ORIENTATION 5 
hangs threateningly over the organic world. The attainment of 
any degree of complexity or perfection of organization is no 
guaranty against deterioration. There is not the slightest ground 
for believing that man himself is in any degree shielded from its 
insidious influence. In fact, it is not improbable that many 
existing peoples have descended from ancestors who were more 
favored with natural gifts, and we should bear in mind the possi- 
bility that our own civilization may become one with Nineveh 
and Tyre. 
If human progress involves the successive exhaustion of the 
best blood of those nations which gain the ascendency in the 
development of culture, it can scarcely lead to any other result 
than a general deterioration of the human species. If there have 
always been races of superior inheritance, such as those of Nordic 
stock, which have remained upon a relatively low cultural level, 
and which were capable of acquiring the civilization of the 
decadent nations which they supplanted, it by no means follows 
that the human species will always be so favorably situated. Mr. 
Seth Humphrey has recently drawn attention to the ‘‘exhaustion 
of reserves”? which are at present available for carrying on the 
work of civilization. Of all our national resources the most 
important is our supply of men of superior stock. And we are 
approaching a period in which the problem of the conservation of 
this resource is becoming more and more pressing. 
The biological situation of our race is at present in many 
respects unique. In the earlier stages of man’s evolution develop- 
ment was mainly along divergent lines. The spread of mankind 
over the continents and islands of the globe brought about the 
formation of more or less completely isolated stocks, subjected to 
different conditions of environment. This resulted in breaking up 
the human species into a great multitude of divergent groups, in a 
manner which closely parallels the diversification of species of 
plants and animals subjected to the combined influence of isola- 
tion and varied surroundings. Few species of organisms present so 
great a variety of hereditarily diverse strains as our own. And 
even if we divide Homo sapiens into several distinct species, 
