ON THE ORIGIN OF LIFE 



the vessel, using a high-frequency arc or a silent discharge. The 

 results were surprising indeed (Miller, 1955). 



Using partial pressures of 10 cm Hg for H 2 , 20 cm Hg for 

 CH 4 , and 30 cm Hg for NH 3 , Miller found that glycine, alanine, 

 sarcosine, /^-alanine, y-aminobutyric acid, aspartic acid, and glu- 

 tamic acid were formed. We have repeated Miller's experi- 

 ments and found as many as 14 ninhydrin-positive compounds. 

 In addition, a series of compounds that are almost universal 

 metabolic intermediates, such as acetic, propionic, lactic, and 

 succinic acids and urea, were identified. These are most un- 

 usual results. Fifteen per cent of the carbon placed in the ap- 

 paratus was found in the compounds listed. The mechanism 

 of building up amino acids seems to be via the Strecker synthesis. 



2. The Global Reaction System 



Consider, then, an atmosphere that for ages receives intense 

 ultraviolet irradiation from the sun, producing in the atmos- 

 phere large quantities of organic compounds that fall with the 

 rain into the sea. Now a solution covered by an atmosphere 

 containing NH :1 will be somewhat alkaline. Organic acids, 

 unlike amines, will not evaporate from alkaline solutions. The 

 result is the accumulation of organic acids and the recycling of 

 tb/e short-chain amines into the atmosphere. In fact, they will 

 be recycled until one of two things happens. Either they be- 

 come converted into amino acids, which are not volatile under 

 these conditions, or they will be converted into polyamines, 

 which are only very slightly volatile. Therefore, the lower 

 amines, which are almost universally toxic, would not have been 

 stockpiled in the sea. The primeval earth was one gigantic 

 reaction system beautifully adapted to produce vast quantities 

 of both amino acids and other organic acids that animals, plants, 

 and bacteria still utilize as metabolic intermediates. Ultra- 

 violet radiation is not the only, or necessarily the chief, source 

 of these compounds. Hasselstrom, Henry, and Murr (1957) 

 have shown that glycine and aspartic acid were formed when 

 ammonium acetate was exposed to /? radiation, while Paschke 

 (1957) demonstrated the formation of formate, glycine, and 

 possibly alanine from ammonium carbonate irradiated by Co 60 

 gamma rays. Present interest is no longer in whether amino 



