THE PHYSICAL CONDITIONS AT THE 

 BEGINNING OF LIFE 



By CARL SNYDER 



When we endeavour to conceive the conditions obtaining at 

 the earliest appearance of life on the earth, or at least life as we 

 know it, we are forced to the conclusion that those conditions 

 were probably not immeasurably different from such as obtain 

 now. 1 This is the unmistakable trend of present-day inves- 

 tigation, and is true whether we still cling to the classic idea 

 of an igneous earth cooling down, as in the nebular theory,, 

 or give adherence to the idea of a little earth growing up, as 

 in the meteoritic hypothesis as remodelled by Chamberlin and 

 Moulton. 



The temperature may have been somewhat higher, but it is 

 fairly certain that it could not have been much above 75 C, and 

 probably was considerably less. Whatever else life may be, 

 physically it is a reaction of colloids in solution, and these 

 colloids begin to coagulate at even moderately high temperatures 

 (6o° C). 



There may have been no continental land 2 ; but, as we shall 

 see, unless we accept the cosmozoic theory of germs brought 

 from elsewhere in space, 3 terrestrial life could scarcely have 

 begun in the sea. Unquestionably, however, the chief stages 

 in the evolution of living beings were passed in the sea-water, 

 and there is reason to believe that the salt constituents of the 

 ocean then were somewhat different from now. For example, 

 it seems possible that the early ocean was relatively limeless. 4 

 But in the light of our new knowledge as to the probable 

 chlorination of the sea by volcanic action, 5 there seems little 



1 A. C. Lane, "Early Surroundings of Life," Science. 26, 129, 1907. 



* Ratzel (Raum und Zeit, 1908) doubted if there was ever a landless earth. 



3 Cf. Arrhenius, Werden d. Welten, p. 191. 



4 Macallum, " Paleochemistry of the Ocean," Univ. of Toronto Studies, No. 5, 

 1904 ; R. A. Daly, " The Limeless Ocean of pre-Cambrian Time," Am. Journ. of 

 Science, 23, 93, 1907. 



5 Brun, Arch. d. Sciences de Geneve, 19, 439, 1905 ; 22, 425, 1906. 



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