POSSIBILITY OF MULTIPLE BIOGENESIS 



129 



lines within the phylum from different, but nearly related, lines of 

 mammal-like reptiles. Perhaps I allow the ideas of the practical 

 historian in geology to prevail too much over pure philosophical 

 reason. But to my mind we shall never be able to prove whether 

 biogenesis occurred only once or was multiple. As long as the results 

 are comparable, and as long as they are brought about by a com- 

 parable history, the use of the word 'related' is justified. 



POSSIBILITY OF MULTIPLE BIOGENESIS 



It follows that assumption 2, that biogenesis occurred only once, is 

 unnecessary. Moreover, we can make a case against it, and assume 

 that it was multiple. We have found that geologic history works with 

 extremely long periods, during which cumulation of small effects may 

 eventually lead to large consequences. We have noted the probability 

 of a very long period in the early history of life during which there 

 was coexistence of the inorganic photosynthetic reactions leading to the 

 'organic' materials of the 'thin soup', of proto-life and of early life. 



1 billion 



2 billion 



(A 

 X 



O 



3 billion 



4«,lllon 



(20 H NS Ca P Na K C 



morphological complexity end chemicol 

 uniformity 



actuolistic life 



the rirst fossils 



first evidence 

 of life 



eobionts. 



morphological 



evolution 



Origin of conventional life 



Establishment of biochemical 

 uniformity the'unity of life" 



Ascendancy of Systems based on 

 proteins and phosphote esters 



Al As B Ba Br C Co CI Co Cr Cu F Fe Go Ge H I K Mg Mn " 

 Mo N Na Ni O P S Se Si Sr Th Ti V Zn etc. 

 Chemical diversity and Structurol 

 simplicity 



chemical 

 evolution 



Fig. 34. Simplified presentation of the origin and the development of 

 life on earth. The Pirie drawing (compare Fig. 14) redrawn according 

 to the geological aspects of the origin of life on earth. 



