CHAPTER VII 



REGRESSION 



Summary The function of regression in evolution Development in 

 ancient environments Development in new environments The 

 evolution of man's higher faculties The "inadequacy of Natural 

 Selection" The unknown factor Theories of regression Germinal 

 selection. 



147. THE last three chapters are so important for a right 

 understanding of what I conceive to be the true principles of 

 heredity that it will be well to sum up and emphasize their 

 main contentions briefly. Since every individual follows 

 (with variations) in the developmental footsteps of his prede- 

 cessors, the recapitulation (with inaccuracies corresponding to 

 ancestral variations) of the life-history of his race is inevitable 

 in his own development unless indeed he happens to be an 

 extraordinary and incredible sort of monster. No such 

 monsters can have occurred in his ancestry, for monsters, 

 lacking adaptation to the environment, invariably perish. 

 While it is obviously impossible for any individual to so vary 

 from his immediate predecessors as to recapitulate the later 

 stages of development without first substantially recapitulat- 

 ing the earlier stages, it is of course quite possible for the 

 converse to happen. Thus a human being cannot become an 

 adult without first passing through the embryonic and foetal 

 stages ; but it is quite possible for him to cease developing 

 at any point. When this happens, when there is an omission 

 of the later stages, we have an instance of reversion, of 

 regression. It is customary to regard reversion as due to the 

 sudden activity of hitherto "latent ancestral units," but it is 

 infinitely more probable that it is due to incomplete recapitu- 

 lation. Since organisms vary in all possible directions, there 

 is no conceivable reason why they should not vary in this 

 particular direction. Indeed they are more likely to vary in 

 this direction than in any other ; for every variation must be 



86 



