Chemical Diversity and the Origins of Life 79 



labouring because very many people have w^ritten as if the problem of the origin 

 of life was the same as the problem of the spontaneous synthesis of proteins 

 and some, having realized that the latter involves difficulties, have concluded 

 that God or some similar agency must be involved. 



Proteins, so far as we know, are mainly useful to an organism because they 

 are enzymes that catalyse metabolic actions very efficiently. But there are in- 

 numerable non-protein catalysts of similar actions. Oxidations can be catalysed 

 by many metals and by thiourea, some of the rare earth elements are esterases 

 and so on. An organism using such systems might be sluggish but it would be 

 conceivable. If Corydum is indeed the fossil of an organism it was enigmatic in 

 more ways than the paleontologists have thought of and probably organized its 

 metabolism with the help of molecules that would not fit neatly into our systems 

 of classification. Proteins, built economically out of about twenty-five amino 

 acids, are probably a late development selected from a more chaotic group of 

 primitive chemical experiments. Evolution operates to give us morphological 

 structures that are relatively simple and efficient without being by any means 

 the only possible structures; it is only reasonable to conclude that it also operated 

 on chemical structure to make the efficient enzymes with which we are familiar. 



The evidence for evolution, and the Linnaean system of classification, both 

 make it appear that the number of species in existence at any time has been 

 getting larger. Projecting this principle back it seems reasonable to think that 

 all sprang from one or a few common ancestors [8]. This is logical enough but 

 it is illogical to think that this ancestor was the original organism. It seems much 

 more probable that this, the beginning of morphological complexity, was nearly 

 the limit of biochemical complexity. With this idea in mind we may consider 

 some aspects of biochemical complexity to see what hints they give us about 

 the mechanisms that may have been made use of initially, and about the manner 

 in which selection may have operated on them. 



The origins of life were probably local phenomena. It is an illusion to think 

 that rare events necessarily happen and prosper to an extent proportional to 

 the amount of material to which they could happen. Thus, although human 

 genius may arise unrecognized with a predictable frequency, it has flourished 

 and become effective most often in specialized and often small communities. 

 Similarly Vavilov showed that new plant species often arise in the isolated and 

 slightly adverse environments at the edge of the main areas of grovrth. I am 

 therefore perfectly willing to postulate an effective environment less extensive 

 rhan the whole probiotic hydrosphere. At different stages in Earth's history 

 either the whole environment of parts of it probably ranged from being alkaline 

 with NH3 to acid because of the oxidation of S and H2S. Two thousand million 

 years of leaching, precipitation and rearrangement have considerably diminished 

 the complexity of the mineral surfaces at which relevant actions may have gone 

 on so that, besides the elements commonly present in large bodies of water now, 

 it is reasonable to think about actions involving such elements as V, Ba, Cr, Se, 

 Ge etc. either in solution or, as Goldschmidt [9] suggested, at the reactive edges 

 of crystals. 



Oil and bitumen regularly contain vanadium; this suggests that it was once 



