MICROBE AND LIFE 



In the first place, the human mind cannot be satisfied by the alter- 

 native of accepting innumerable de novo creations; numerous factual 

 observations can hardly be harmonized with this idea. Furthermore, 

 there is the unequivocal testimony of the fossil remains of forms of life 

 that have populated the earth during consecutive epochs; in numer- 

 ous instances these reflect an unmistakable relationship between the 

 inhabitants of successive geological periods. 



However, the concept of evolution receives its strongest support 

 from the results of modern genetics studies. It was in this very hall 

 that, in 1900, Hugo de Vries expounded his ideas concerning the 

 saltatory hereditary changes for which he coined the term mutations. 

 A month later, Beijerinck discussed in connexion herewith the vari- 

 ability of micro-organisms. In a footnote to the corresponding publi- 

 cation Beijerinck declared his acceptance of the principle of mutation; 

 some ten years later he furnished an impressive contribution to our 

 knowledge of mutational phenomena in microbes. But only during 

 recent years has the high frequency with which mutations occur in the 

 microbial world been clearly illustrated, and this has cast a bright 

 light on its significance as a general characteristic of life. Even though 

 anything but agreement has been reached with respect to the forces 

 that govern evolution, this situation makes it nonetheless understand- 

 able that many investigators proclaim the principle that reduces evo- 

 lution to a random mutation, coupled with selective action of the en- 

 vironment. 



We must keep in mind, however, that the fossil documentation of 

 pre-historic life is practically limited to the last 500 million years of 

 the earth's history. In a sense this is rather a short episode, at least if 

 one takes into account the fact that until recently the age of our planet 

 was estimated at more than 3,000 million years, while the most recent 

 conclusions indicate that it may even be 4-5,000 million years. 



If we accept the paleontologist's view that many of the phyla 

 distinguishable among the present-day animals have existed during 

 the above-mentioned span of 500 million years, i.e., during the era be- 

 ginning with what the geologists have termed the Cambrian, the evo- 

 lutionist cannot escape the inference that life must have originated in 

 still earlier times. The lack of fossils in the Pre-cambrian must then be 

 ascribed to the fact that the living organisms that then existed were 

 so small and fragile that, once enclosed in the sedimentary strata, they 



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