IMPLICATIONS OF UNIFORMITARIANISM 19 



UNIFORMITARIANISM AND ITS IMPLICATIONS FOR THE ORIGIN OF LIFE 



Hence, for all practical purposes, and leaving out philosophical con- 

 siderations, we may define actualism or uniformitarianism as the 

 tendency in geology to interpret facts of the history of the earth by 

 the same processes as we know or assume to be at work now on or 

 in the earth. It must, however, be explicitly stated that the intensity 

 of such processes may have varied over the time-span of geologic 

 history. 



The implications of uniformitarianism for our search into the 

 origin of life on earth are clear. We look for natural causes of the 

 same character as are in operation at present. We do not envisage 

 some sudden event, by which life appeared all at once as a fully 

 fledged phenomenon on every comer of the earth. The origin of life 

 will have covered an enormous time-span, if measured against human 

 standards. During this period development will have been slow, 

 almost beyond imagination. 



In its slowness, however, the origin of life may well have been 

 infinitely varied. For all we know, there may have been different 

 parallel series of development. Possibly only a small number of these, 

 or perhaps even only one single line of development, led to our 

 present life. 



In its slowness, moreover, the origin of life will have been subject 

 to the same physical and chemical laws as life is today. As we shall 

 see later, it is probable that our atmosphere, rivers and oceans are 

 quite different now from what they were in those years long past — 

 in those early years when the real "struggle for life", that for its 

 origin, took place. But even if the environment was quite different, 

 so different as to be unrecognizable by present-day standards, the 

 laws of nature were the same. This permits us to extrapolate the 

 findings of present-day microbiology and biochemistry into that 

 distant past, as indicative of the environment in which the origin of 

 life took place. 



In exploring the geological aspects of the origin of life, we have 

 now made an important stride. We have arrived at an understanding 

 of how geology works, how it arrives at its conclusions about events 

 long past. We found that the basic principle of uniformitarianism 

 underlies geologic studies, and what its implications are. In doing so 

 we became impressed by the enormous amount of time elapsed since 



