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 preponderate, 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, however, 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 imperishable 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 animals from another, and they therefore were not subject to bias in dealing with the evidence. Indeed, most of the pioneers in geology were firmly convinced that the progenitors
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