Chapter IX 



MISCELLANEOUS GEOLOGICAL 

 CONSIDERATIONS 



GENERAL 



Apart from fossils and other indications of early life on earth, and 

 apart from the character of the environment which can be deduced 

 from contemporary exogenic geologic processes, there are several 

 other considerations which also have a bearing on the study of the 

 origin of life on earth. Fossils and biogenic deposits, and also the 

 environment, were studied in the two preceding chapters. This 

 chapter is reserved for those additional, miscellaneous topics. 



First, the importance of clays and quartz for a selective growth of 

 some of the 'organic' compounds during those earliest days of in- 

 organic photosynthesis. Another topic is to enquire whether there 

 possibly has ever been enough carbon dioxide in the early atmos- 

 phere for organic photosynthesis to be able to produce our present 

 amount of free oxygen: or conversely, where all the carbon is which 

 has been produced by organic photosynthesis over the last billion 

 years at least. We will have to inquire if geochemistry can answer 

 these questions by drawing up quantitative global estimates of certain 

 elements. Then follows a discussion on the apparent stability of the 

 temperature of the earth over the last couple of billion years. During 

 that time it was never so hot or so cold all over the earth that the 

 protein-based life which had formed earlier was extinguished. At the 

 end of this chapter a few remarks have been added, not on geology 

 itself, but on the danger of a certain type of scientific reasoning 

 which now crops up. That is a form of comparative biochemistry 

 that tries to determine which is 'oldest' or more primitive. Geologists 

 well remember the comparative anatomy which was the fashion 

 during the first half of this century, and which used much the same 

 line of reasoning as comparative biochemistry tends to do now. 

 Paleontological evidence has shown how easily even the most obvious 



