CHAPTER IV 
BIOLOGICAL EVOLUTION 
HAVING surveyed in outline the social theories of Comte and 
Spencer with special reference to their bearing on the doctrine of 
adaptation, and having reviewed the various methods in use in 
social science and social philosophy and considered their bearing 
on our subject, pointing out some of the dangers lurking in the 
use of the classifying, analogical and statistical methods, our next 
problem is to study the development of the doctrine of adapta- 
tion by those who have endeavored to explain evolution in terms 
of the influence of the environment on the organism or social 
group. 
The environment may affect the organism in three different 
ways: (1) by direct action, producing molecular, chemical or 
functional changes as in pigmentation and acclimatization; 
(2) by affording favorable opportunity for growth and functional 
variation, or the reverse, as in change of habitat resulting in 
increase or decrease of food, or (3) by furnishing conditions favor- 
able to struggle and selection. 
The first view, advocated by Buffon and Erasmus Darwin,! was 
eclipsed for a long time under the influence of the theory of nat- 
ural selection but has been upheld firmly by Viet, Scott Elliott, 
W.H. Dall and others, and still more recently by the advocates of 
the theory of geographical isolation as the most important factor 
in species formation.? 
The direct influence of environment on the organism is well 
illustrated by the words of Dall though in somewhat exaggerated 
terms: “ The environment stands in a relation to the individual 
such as the hammer and anvil bear to the blacksmith’s hot iron. 
The organism suffers during its entire existence a continuous 
1 Packard, Lamarck, pp. 203, 218. 
2 Kellogg, Darwinism To-day, ch. IX. 
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