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The Hazards Of The Past
by
Evolution thus makes the world over for us. It shows us in what a complex web of vital and far-reaching relations we stand. It gives us an outlook upon the past that is startling, and in some ways forbidding, yet one that ought to be stimulating and inspiring. If we look back with a shudder we should look forward with a thrill. If the past is terrible, the future is in the same degree cheering and inviting. If we came out of those lowly and groveling forms, to what heights of being may we not be carried by the impetus that brought us thus far? In fact, to what heights has it already carried us!
II
That the hazards of the past, to many forms of life, at least, have been real and no myth, is evident from the vast number of forms that have been cut off and become extinct; various causes, now hard to decipher, have worked together to the end, such as changed geographical conditions, changes of climate, affecting the food-supply, extreme specialization, like that of the sabre-toothed tiger whose petrified remains have been found in various parts of this continent, and who apparently was finally handicapped by his huge dental sabre. Probably many more species of animals have become extinct than have survived, but none of these could have been in the line of man’s descent, else the human race would not have been here. If the Eocene progenitor of the horse, the little four-toed eohippus, had been cut off, would not the world have been horseless to-day? The horse in America became extinct, from some cause only conjectural, many tens of thousands of years ago. Had the same fate befallen the horse in Europe and Asia, it seems probable that our civilization would have been far less advanced to-day than it is.
The fate of every species of mammal in our time seems to have been in the keeping of a single form in early Tertiary times. The end of the Cretaceous or chalk period saw the extinction of the giant reptiles both of sea and of land, at the same time that it saw the appearance of a great many species of small and inconspicuous mammals, among which doubtless were our own humble forebears. Extreme specialization in any direction may narrow an animal’s chances of survival; they have but one chance in the game of life, whereas an animal with a more generalized organization has many chances. Man is one of the most generalized of animals; no special tools, no special weapons–his hand many tools and weapons in one. Hence he is the most adaptable of animals; all climes, all foods, all places are his; he is master of the land, of the sea, of the air.
Animal life is often curiously interdependent. I asked our guide in the Adirondacks if there were any ravens there. “Not nearly as many as there used to be,” he said, and his explanation of their disappearance seems thoroughly scientific; it was that the wolves and the panthers kept them in meat, and now that these animals had disappeared, the ravens had little to feed upon. If the moose were compelled to graze from off the ground, like a sheep or a cow, the species would probably soon become extinct. Osborn thinks it probable that the huge beast called titanothere finally became extinct early in Tertiary times owing to the form of its teeth, which were of such a type that they could not change to meet a change in the flora upon which the creature fed. Of course we shall never know what narrow escapes our race had from extinction in the remote past; some forms have ended in a blind alley, like the sea-urchin and the oyster. Arthropoda have continued to evolve and have reached their high-water mark of intelligence in bees and ants. The vertebrates went forward and have culminated in man. Bergson thinks that in the vertebrates intelligence has been developed at the expense of instinct, and that in the invertebrates instinct has been perfected at the expense of intelligence.