When we look at the evolution of life on a grand scale, nature seems to feel her way, like a blind man, groping, hesitating, trying this road and then that.  In some cases the line of evolution seems to end in a cul de sac beyond which no progress is possible.  The forms thus cornered soon become extinct.  The mystery, the unaccountable thing, is the appearance of new characters.  The slow modification or transformation of an existing character may often be traced; natural selection, or the struggle for existence, takes it in hand and adapts and perpetuates it, or else eliminates it.  But the origin of certain new parts or characters—­that is the secret of the evolutionary process.  Thus there was a time when no animal had horns; then horns appeared.  “In the great quadruped known as titanothere,” says Osborn, “rudiments of horns first arise independently at certain definite parts of the skull; they arise at first alike in both sexes, or asexually; then they become sexual, or chiefly characteristic of males; then they rapidly evolve in the males while being arrested in development in the females; finally, they become in some of the animals dominant characteristics to which all others bend.”  Nature seems to throw out these new characters and then lets them take their chances in the clash of forces and tendencies that go on in the arena of life.  If they serve a purpose or are an advantage, they remain; if not, they drop out.  Nature feels her way.  The horns proved of less advantage to the females than to the males; they seem a part of the plus or overflow of the male principle, like the beard in man—­the badge of masculinity.  The titanothere is traceable back to a hornless animal the size of a sheep, and it ended in a horned quadruped nearly as large as an elephant.  It flourished in Wyoming in early Tertiary times.  Nature did not seem to know what to do with horns when she first got them.  She played with them like a child with a new toy.  Thus she gave two pairs to several species of mammals, one pair on the nose and one pair on the top of the skull—­certainly an embarrassment of weapons.

The first horns appear to have been crude, heavy, uncouth, but long before we reach our own geologic era they appear in various species of quadrupeds, and become graceful and ornamental.  How beautiful they are in many of the African antelope tribe!  Nature’s workmanship nearly always improves with time, like that of man’s, and sooner or later takes on an ornamental phase.

The early uncouth, bizarre forms seem to be the result of the excess or surplus of life.  Life in remote biologic times was rank and riotous, as it is now, in a measure, in tropical lands.  One reason may be that the climate of the globe during the middle period, and well into the third period, appears to have been of a tropical character.  The climatic and seasonal divisions were not at all pronounced, and both animal and vegetable life took on gigantic and grotesque forms.  In the ugliness of alligator and rhinoceros and hippopotamus of our day we get some hint of what early reptilian and mammalian life was like.