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Most experiments that model events on the primitive Earth 

 focus on one or two steps in the process of chemical evolution. With 

 the advent of sensitive analytical techniques it is now feasible to set 

 up long term experiments where reactants are gradually added and 

 removed from a flask over a long period of time in a situation which 

 mimics the formation and reaction of biomolecules on the early 

 Earth. The effect of changing the temperature, the exposure to light, 

 and the reactants can be followed over periods of weeks and months 

 by analysis. This experimental approach provides a more accurate 

 model of the flux of chemicals through the primitive oceans and 

 hence should provide useful information concerning the rates at 

 which specific biomolecules were formed. This approach would also 

 be ideal for the investigation of reactions taking place using mixtures 

 of several reactants. For example, the reaction of carbon dioxide, 

 hydrogen cyanide, formaldehyde, and UV light could be investigated 

 in one such system. 



As has been pointed out, much clearly remains to be learned 

 about monomers. If, however, we assume for the purpose of the fol- 

 lowing discussion that, in principle, the problem of monomer pro- 

 duction is solved, the next step requires condensation of amino acids 

 into polypeptides and of bases, sugars, and phosphate into mono- 

 and poly-nucleotides. This problem is still unsolved, despite the fact 

 that many successful condensations have been carried out utilizing, 

 as reagents, products of the electric-discharge reaction. The reason 

 this problem remains unsolved is that, for ease of experimentation, 

 only a limited number of organic molecules are used in most of these 

 condensation studies. For example, amino acids (used in experiments 

 to produce peptides) are only a fraction of the total organic com- 

 pounds produced in the spark discharge, and amino acids would be 

 expected to react with non-amino acids most of the time if the com- 

 plex mixture were heated. The same criticism can be made of most 

 of the "prebiotic" dehydration condensations that have been 

 published. 



Unless some experiment using complex mixtures of monomers 

 actually yields polymers of interest, it would appear that a process of 

 fractionation must have intervened between the formation of the 

 original prebiotic pool of organic compounds and their condensation 

 into biologically useful polymers. Some related questions include 

 whether amino acids and nucleic acids can polymerize in the same 



