The Problem of Stages in Biopoesis 31 



application to the origin of life, it is to search in the inorganic world for the origin 

 of the processes, as well as the materials, of the organic world. This implies 

 more than the condition that the process of the organic world must not be 

 contrary to chemical laws or Henderson's principle of the fitness of the environ- 

 ment. It requires, in addition, that just as the elements used in building up 

 living structures are a selection from those found in the inorganic atmosphere, 

 hydrosphere, and lithosphere, so also are the basic reactions of oxidation- 

 reduction, hydrolysis-condensation likely to have an unbroken continuity with 

 those occurring on the surface of the Earth. It is, indeed, a fact of observation 

 that some soluble simple ions like those of potassium and magnesium and the 

 labile atoms of sulphur, phosphorus and iron, which undergo the greatest 

 transformations in the mineral world, have a key importance in biochemistry, 

 while the stable atoms, such as silicon, aluminium, or sodium, which constitute 

 a far larger part of the Earth's crust, are either absent or play a subsidiary role. 



The one limitation to our study oi biopoesis or Ufe-making is that it is a special 

 and not a general problem. We are limited, and necessarily so in the first place, 

 to the origin of the one form of Ufe that we can observe now on this Earth. There 

 may have been other radically incompatible forms on this Earth at earUer times 

 and these or others we succeed in making artificially. Where Ufe exists on other 

 planets it is most likely that it will be radically incompatible with ours, though 

 we may suspect that it will show striking parallels, biochemically as well as 

 structurally. However, pending the advent of practical biopoesis or trips in 

 space to acquire the basis of comparative biopoesis, we must restrict ourselves to 

 tracing the genealogical tree of life as we know it right back to its origin or 

 origins, for they may be multiple, in the inorganic world. The biochemical 

 genealogy of the terrestrial life, though uniquely determined working backwards, 

 is by no means unique working forwards. This is what makes the biochemical 

 approach to biopoesis more hkely to give results than the purely geochemical, 

 except at the very outset. Starting from any initial inorganic origins there are 

 too many possible lines to be followed up. At a number of occasions in biopoesis 

 there must have been alternative arrangements with httle to choose between 

 them — even trivial ones such as right- or left-hand configurations of molecules. 

 There may well be potential biochemical cycles that would have solved the 

 problems of the formation of life and reproduction of organism as well as, and 

 even better than, those actually evolved. But biochemical evolution differs from 

 that of organisms in that variant forms, if not actually incorporated in the com- 

 mon biochemical pattern, became absolutely extinct. There is only one dominant 

 chemical pattern of life. If more than one exist the others must be obscure, 

 as are some of the red algae, and unnecessary to the survival of the dominant. 

 It is as if in the subsequent evolution of species only man and a few of his pets 

 were to survive. 



One of the major reasons for assuming that, in tracing the origin of life on 

 this planet, we are deahng with a very particular form and have not exhausted 

 the biochemical potentialities of life, is the extreme chemical and structural 

 conservatism or inertia of once estabhshed patterns of structure or activities. 

 At and above the level of the protozoa there is no essential change in structure 



