46 The Nature of Biological Diversity 



held in Moscow (Oparin, 1957) with distinguished scientific contrib- 

 utors from all over the world. 



H. C. Urey, among others, has written at length about the origin of 

 the earth and of its early atmosphere, and has concluded that this was 

 originally a reducing rather than the oxidizing medium it is today 

 (Urey, 1959) . It has been pointed out that ultraviolet and other forms 

 of radiation, acting upon this primitive atmosphere, must probably 

 have led to the synthesis of large quantities of small-molecular or- 

 ganic compounds and the production of what has been called a "pri- 

 mordial soup." 



Miller (1957) has shown — and his observations have been repeat- 

 edly confirmed — that among the products of irradiation of gaseous 

 mixtures approximating in composition to that of the earth's primitive 

 atmosphere glycine, formic, acetic, and succinic acids appear in high 

 yields, together with a remarkably assorted collection of other organic 

 materials (Table 1). It can hardly be without significance that even 

 today these are still the starting materials for the biosynthesis of many 

 elaborate compounds — acetate for the synthesis of fatty acids, sterols, 

 and steroids, and glycine and succinate for that of porphyrins. 



The gap between this stage in chemical evolution and the eventual 

 emergence of the first organized, self-replicating system is a difficult 

 one to bridge in the present state of knowledge. It has been said that, 

 given enough monkeys, enough typewriters, and enough time, one of 

 the animals would eventually produce a typescript of all Shake- 

 speare's sonnets. There seems to be no reason why this should not be 

 true. Equally, given a large enough number of small molecules as 

 letters of a biochemical alphabet and a few billion years to do it in, 

 there seems to be little reason why random permutations and com- 

 binations should not eventually lead to the production of some primi- 

 tive kind of organized system possessing potentialities for self-replica- 

 tion, survival, and eventual evolution. 



No doubt the monkeys would have produced some other interesting 

 documents in the course of their efforts, documents corresponding to 

 other kinds of organized systems; systems that failed to stand up 

 to alterations in a constantly changing external environment, and 

 which subsequently died out and left no trace. 



Possibly these random processes were less random than the aimless 

 and totally undirected performance of the monkeys because, as Cal- 

 vin (1957) has pointed out, autocatalysis and catalysis by simple in- 

 organic compounds or heavy metals may have played a large part, 

 not only in the synthesis of new and more elaborate molecules, but 

 also as a selective and therefore directive agent. There may well have 



