CHAPTER IX 



THE EFFECTS OF CHANGED CONDITIONS: ADAPTATION 



In the attempt to conceive a process by which Evolution 

 may have come about, the first phenomenon to be recognized 

 and accounted for is specific difference. With that recognition 

 the outline of the problem is defined. The second prerogative 

 fact is adaptation. Forms of life are on the whole divided into 

 species, and these species on the whole are adapted and fit the 

 places in which they live. To many students of Evolution, 

 adaptation has proved so much more interesting and impressive 

 than specific diversity that they have preferred it to the first 

 place in their considerations. 



Whether this is, as I believe, an inversion of the logical order 

 or not, there is one most serious practical objection to such 

 preference, that whereas specific diversity is a subject which 

 can be investigated both by the study of variation and by the 

 analytical apparatus which modern genetic science has developed, 

 we have no very effectual means of directly attacking the problems 

 of Adaptation. 



The absence of any definite progress in genetics in the last 

 century was in great measure due to the exclusive prominence 

 given to the problem of Adaptation. Almost all debates on 

 heredity centered in that part of the subject. No one disputes 

 that the adaptation of organisms to their surroundings is one 

 of the great problems of nature, but it is not the primary problem 

 of descent. Moreover, until the normal and undisturbed course 

 of descent under uniform conditions is ascertained with some 

 exactness, it is useless to attempt a survey of the consequences 

 of external interference; nor as a rule can it be even possible to 

 decide with much confidence whether such interferences have or 

 have not definite consequences. Those, for example, who de- 

 bated with enthusiasm whether acquired characters are or are 

 not transmitted were constantly engaged in discussing occur- 



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