SELECTED PAPERS 



any similarity with some of the recent forms of life, first of all because 

 oxygen, indispensable for most of the latter, was lacking. But the ear- 

 lier mentioned anaerobic metabolic types cannot have existed either 

 because the entire environment was obviously in a greatly reduced 

 state. Although there was, therefore, certainly no dearth of hydrogen 

 donators, the equally necessary hydrogen acceptors cannot be found 

 in this environment. 



The principal argument against the notion that the first living 

 entities would primarily depend on some simple inorganic chemical 

 system is, however, the consideration that the conversion of its com- 

 ponents into organic matter, though in principle conceivable, assumes 

 nevertheless the presence of a primary living entity. And, in view of the 

 earlier demonstrated great complexity of even the smallest autotrophic 

 forms of life, a spontaneous appearance of a first living entity in this 

 primitive environment is entirely inconceivable. 



Haldane and Oparin have shown the way out of this dilemma by 

 introducing what, with the wisdom of hindsight, now appears so ob- 

 vious a notion, to wit that the origin of the first living organism must 

 have been preceded by an accumulation of organic matter. Hence the 

 question is whether there would be any reason for assuming that, 

 during the developmental stage of the earth we are now considering, 

 a strictly chemical formation and accumulation of organic matter may 

 have occurred. The above-mentioned scientists have answered this 

 question in the affirmative, and adduced strong arguments in its 

 favour. Bernal in particular has emphasized that during this period the 

 earth was subject to powerful ultraviolet solar irradiation of very small 

 wavelength; it has been established that such radiation can exert pro- 

 found chemical effects. At present we are protected from this strongly 

 biocidal radiation by the ozone layer in the stratosphere ; but on ac- 

 count of the absence of oxygen in the primitive atmosphere this screen 

 was initially lacking. 



Now it is entirely possible that this short-wavelength radiation, 

 acting on a system composed of methane, ammonia, hydrogen,, and 

 water, may have led to the formation of organic compounds. The 

 radiation would have caused a fission of water to hydrogen which 

 escapes, and hydroxyl which would have promoted a partial oxidation 

 of hydrogen donators, especially methane, and as a result of these 

 reactions organic hydrogen acceptors became available. In this con- 



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