18 



1950 by Calvin and his associates. The availability of radiocarbon 14 

 and the Berkeley cyclotron provided the ideal tools for such an 

 experiment. A mixture of carbon dioxide, water, and hydrogen was 

 exposed to 40 MeV helium ions from the 60-in. cyclotron at 

 Berkeley. (Unfortunately no nitrogen was added to the mixture of 

 gases irradiated.) A curious fact about this experiment was that 

 although they referred to Oparin's idea of a reducing atmosphere, 

 they used an oxidized source of carbon. Among the products identi- 

 fied were formaldehyde and formic acid. 



Soon after the results of this experiment were reported in 

 Science in 1951, there appeared a detailed paper by Harold Urey on 

 the early chemical history of the Earth's atmosphere. In this paper 

 Urey clearly defined the conditions under which a primitive atmo- 

 sphere may have arisen and argued from the abundance of hydrogen 

 in the universe, the rate of escape of the lighter elements, and equi- 

 librium constants that the early atmosphere must indeed have been 

 reducing. This paper was soon followed by the now-celebrated 

 experiment by Urey's graduate student, Stanley Miller, in which 

 methane, ammonia, and water were exposed to electric discharges 

 (fig. II-2). Among the compounds formed and identified were four of 

 the amino acids commonly found in protein: glycine, alanine, 

 aspartic and glutamic acid. 



Over the years, although new evidence on atmospheric outgas- 

 sing and the geological conditions of the early Earth has led us to 

 reconsider our thinking on the true nature of the Earth's primitive 

 atmosphere, Urey and Miller had set the pattern for most of the 

 synthetic experimental work in chemical evolution. 



THE SPACE AGE 



The scientific inquiry into the origin of life soon began to 

 receive worldwide attention. In 1957, under the sponsorship of the 

 International Union of Biochemistry and the leadership of Oparin, 

 who was at that time its vice president, an international conference 

 on the subject was convened at Moscow. At this meeting a number of 

 biochemists were gathered who reported on their theoretical or 



