128 ORIGIN OF LIFE AND EVOLUTION 



The first two assumptions quoted deal with the origin of life on 

 earth, the next five with its later evolution. Hence they are not 

 comparable in scope and they form the latest example to my know- 

 ledge, where origin and later evolution of life have been confused. 



Kerkut's last five assumptions consequently fall outside the scope 

 of this book. For the sake of completeness a few more remarks have, 

 however, to be added. 



The objections raised against these five assumptions have, I think, 

 been answered before in modem treatises on evolution. The reader 

 may be referred, for instance, to Simpson (1949). It must be pointed 

 out, however, that even within these five assumptions 3 to 6 are not 

 at all on the same footing as number 7. Perhaps one had better say 

 that some fish gave rise to amphibia, some reptiles to mammals and 

 birds, because on the one hand only some definite, narrowly defined, 

 structural groups within the earlier phyla led to the higher organiza- 

 tion, whilst on the other hand a polyphyletic origin of these higher 

 phyla remains quite possible. Stated in this way, however, assumption 

 7 is based on fact, i.e. on paleontological records, whereas assump- 

 tions 3 — 6 are theories based only on similarities within the present 

 flora and fauna, but without any support from the historical pale- 

 ontological record. 



But let us return to assumptions 1 and 2. The gist of what we 

 learned is that, according to a theory widely accepted by biologists, 

 organic material arose by inorganic processes and that non-living 

 matter subsequently developed into living. The facts gleaned from 

 geology make it probable that the environment postulated by that 

 theory, i.e. the anoxygenic atmosphere, has indeed been present. 

 This is not, of course, proof that biogenesis occurred. It only proves 

 the feasibility of that theory, and so it justifies the postulation of 

 assumption 1. 



Kerkut's second assumption, to my mind, does not do sufficient 

 justice to all the possibilities in biogenesis. Even if similar inorganic 

 photosynthetic reactions gave rise, say, at the same time but in 

 different localities, to similar organic material, whilst subsequently 

 non-living matter gave rise to living along some, or even along many, 

 parallel lines, we would, I think, still call such primitive life inter- 

 related. In the same way we call mammals interrelated, although 

 there is a possibility of polyphyletic origin of different evolutionary 



