CHAPTER V 



A THEORY OF RETROGRESSION 



The different parts of the higher animals were evolved at different 

 though overlapping periods of a long extending past — Evolu- 

 tion is due to stringent selection which affects only a few 

 parts at a time — Cessation of selection results in degeneration 

 — Difficult to observe in wild animals — Easy to observe in 

 tame animals and cultivated plants — Degeneration due to 

 atavism — In the absence of selection every species tends to 

 revert to ancestral type. 



We are now in position to make a fresh departure. 

 We have dealt with evolution ; it is time to glance 

 at the complementary doctrine of reversion.-' Un- 

 fortunately, it is difficult to place the doctrine clearly 

 and convincingly before the non-biological reader. 

 The data on which it is founded are very abstruse 

 — hardly to be expressed except in technical terms. 

 Some attempt must be made however. We have 

 seen that evolution results from a stringent selection 

 of the fit. Stringent selection implies stringent 

 elimination. Unless selection be stringent, no 



' Vide Appendix E ; also " The Present Evolution of Man," pp. 

 18-30, 46-8. 



