THE PROGRESSION OF LIFE ON EARTH 



Beginning by living to eat, the series soon advances toward 

 eating to live. Then comes the reign of flesh, with just 

 enough nerve to make the muscles effective for moving and 

 grasping. Finally, the brain end of the nerve begins to pre- 

 ponderate, so that the animal no longer responds listlessly to 

 its surroundings but improves first in instinct, then in reason, 

 and eventually attains supreme intellectual control. 



The question therefore arises whether this regular advance 

 has any meaning. If all animals and Man came into existence 

 at one and the same time in their present forms science might 

 find the meaning of the world of life beyond its ken. The 

 fossilised remains of animals embedded in rocks afford, how- 

 ever, direct evidence that the different kinds appeared on the 

 earth not suddenly, at one time, but in orderly succession, the 

 lower first, the higher later. Existing animals are seen to be 

 merely the scattered and more or less altered survivors of 

 various groups that have had their day one after another 

 during the march of the ages. There seems to have been a 

 slow evolution of life from the lowest to the highest, one 

 group after another flourishing in turn and then dying down, 

 leaving only a few remnants as their posterity. The earth 

 thus records its own history within itself; it writes in imper- 

 ishable rocks the story of advancing life, and the writing may 

 be as clearly seen and deciphered as the writing on the 

 Rosetta stone, although it is only half a century since Man 

 has systematically attempted to read the story told by the 

 rocks. 



The succession of rocks containing fossils was, however, 

 made out in part long before naturalists in general had 

 framed any theories as to the evolution of one group of ani- 

 mals from another, and they therefore were not subject to 

 bias in dealing with the evidence. Indeed, most of the pio- 

 neers in geology were firmly convinced that the progenitors 



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