western Asia.
What happened to those who remained in America we shall possibly never
know. Some surmise that a fly not unlike the tsetse-fly of Africa
killed them out. Perhaps the members of the cat family, which are
steadily growing larger and fiercer, fed on their young if not upon
the older ones, and exterminated them. Perhaps the Glacial period
which followed was too cold for them. But, whatever may have been the
cause these horses died out not only in North but also in South
America, to which country they had spread.

The old world horse was the companion of man. The skeletons of those
found with early man in the caves of Europe look as if the horse had
been a creature to draw man's burdens and to serve him for food,
rather than to bear him upon its back. Its roasted bones are often
found about the old tribal fires. Upon the discovery of the new world
the Spaniards brought with them to Mexico and to the Mississippi
Valley the horses which carried them in their battles against the
Indians. In the course of these frays many riders were killed and
their horses roamed wild. Slowly they made their way to the western
plains; gradually they became tougher and more wiry; their diminished
hoofs learned to catch more carefully in the rocks of their mountain
home; and the mustang and bronco of more recent years are the
descendants of the little dawn horse, whose dainty skeleton is found
in the rocks over which his later descendants, after a long stretch of
perhaps four million years, are now running.

CHAPTER IX

EVOLUTIONARY THEORIES SINCE DARWIN

In considering the value of Charles Darwin's work and its permanent
effect upon the thought of mankind, we must be careful to distinguish
between two phases of his effort. It was his aim to prove two
propositions: first, that there is such a process as evolution;
second, that he had discovered the method by which evolution is
accomplished. Before his time there was no general agreement as to the
fact of evolution. People generally thought the idea absurd, as well
as irreligious. All previous efforts on the part of advanced thinkers
to persuade mankind of the truth of evolution had been nearly without
effect. Among the early philosophers the whole idea was purely
speculative. They made no attempt to prove it, and the conception was
without influence upon the thinking of the ordinary man. This remains
true until the time of Lamarck. This French genius succeeded in
pers