EVOLUTION TRACED BIOCHEMICALLY 4 1 



scarcely conceivable that the high temperature of 120° to 

 300°c. developed on contact with the atmosphere would 

 leave unaffected the living complexes of these organisms, 

 and that the intense ultraviolet light from the sun, a great 

 portion of which does not penetrate the earth's atmosphere, 

 would not sterilize the organisms before they reached the 

 outer limit of the atmosphere. 



The theory of Arrhenius, furthermore, left unexplained 

 the origin of life. It merely postulated that hfe originated 

 somewhere else in the universe than on the earth and did not 

 attempt to explain how. If life originated elsewhere, what 

 were the conditions that promoted this origin, and in what 

 respect were they different from those which prevailed on the 

 earth at some time in Its history? 



One , must, accordingly, turn for intellectual satisfaction 

 to another theory which does not avoid the cardinal element 

 of the problem but predicates that life will originate any- 

 where in the universe where the conditions favoring its 

 origin obtain. It postulates also that such conditions obtained 

 on the earth during its earliest geological age, conditions 

 which, as Huxley expressed it, "it can no more see again 

 than a man can recall his infancy." Among those who have 

 been expositors of this theory during the last fifty years 

 may be named Pfliiger, Moore, Allen, Sharpey-Schafer, 

 and Osborn, and in 19 10 the author gave his unreserved 

 endorsement of it. 



This theory must not be confused with that of spontaneous 

 generation. The latter, discredited now, as already indicated, 

 implied that life could originate de novo today under the 

 conditions which ordinarily prevail on the earth's surface. 

 To prevent this confusion the theory now to be discussed 

 should be called the paleogenetic theory. 



The conditions necessary for this generation of living 

 forms must have prevailed on the earth's surface when the 

 temperature of its rock crust sank below ioo°c. At tem- 

 peratures above 350°c. all the water later forming the 

 oceans was then as water vapor in the atmosphere which 

 had a pressure more than two hundred times what it exercises 

 today. Countless condensations must have taken place 

 on the hot rock crust, and the water condensed must as 



