8 



LIFE S BEGINNING ON THE EARTH 



From the age of rocks in which petrified remains of life 

 are demonstrable we may infer the age of the earliest begin- 

 nings of life. Owing to the indistinctness of the earliest 

 remains, such estimates are very vague, but it is likely that 

 the earliest beginnings of life date back to about one billion 

 years. The base of a petrified tree from the Devonian period 

 is known to be 350,000,000 years old. This specimen is on 





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* 





Fig. 2. Petrified Trunk of Tree 350,000,000 Years Old 



The petrified remains of this tree may teach us how long life has existed 

 on the earth, even though it is by no means the oldest living thing. This 

 specimen is put up on the campus of the Oklahoma State Teachers College 

 as a memorial to the late Dr. David White, geologist of the United States 

 Geological Survey. (Courtesy of Science Service.) 



permanent exhibition on the campus of the Oklahoma 

 State Teachers College at Ada, Okla. (Fig. 2). Although 

 it may be one of the oldest petrifications of its kind, yet that 

 tree was certainly not the oldest living plant. Life had to 

 develop many hundreds of millions of years to produce such 

 a tree. 



Considering that only 5000 years sufficed to change do- 

 mesticated pigeons as described how much more must have 



