THE ORIGIN OF LIFE HAS BEEN A SUB- 

 ject lor serious scientific consideration for only 

 little more than a century. The popular view 

 until comparatively recent times was that life continuously and 

 spontaneously appeared. The damp earth presumably formed 

 worms, bread brought forth molds, and decomposing matter 

 spawned insects, rodents, and snakes. The conclusion that life 

 inevitably and spontaneously appeared under proper conditions 

 was not easily changed. Although Francisco Redi had proved 

 in the seventeenth century that white maggots are simply the 

 larvae of flies by showing that no maggots appeared on meat 

 kept beneath a fine cloth and Spallanzani in 1765 had shown 

 that heated and protected cultures did not grow molds, the 

 matter was still not considered settled. Less than 100 years ago, 

 in 1802, the French Academy of Sciences offered a prize to 

 whoever, by means of convincing and accurate arguments, should 

 illuminate the subject of the primary origin of living creatures. 

 This prize was awarded to Louis Pasteur. Since his brilliant 

 work, it has been almost universally accepted that all organisms 

 now living descended from pre-existing organisms, and that no 

 instance of spontaneous generation has occurred in modern 

 times. The question we now ask is simply, can life ever arise 

 spontaneously? Do the conclusions of Redi, Spallanzani, and 

 Pasteur, which overthrew medieval notions based on poor and 

 inaccurate observations, apply to all times and all places? 



The first problem that confronts us in attempting to discuss 

 the origin of life is the lack of an adequate definition of life. 

 For the purposes of the present discussion we may adopt Bernal's 

 suggestion (1951) that life is the embodiment of self-maintaining 

 chemical processes within a certain volume. But no definition 

 can hide the fact that living systems include a multiplicity of 

 mechanisms that are only partly understood (Madison, 1953). 

 We cannot expect to postulate in detail the origin of things we 

 do not understand. 



