That Nature should have turned out better and better handiwork as the ages passed; that she either should have improved upon every model or else discarded it; that she should have progressed from the bird, half-dragon, to the sweet songsters of our day and to the superb forms of the air that we know; that evolution should have entered upon a refining and spiritualizing phase, developing larger brains and smaller bodies, is a very significant fact, and one quite beyond the range of the mechanistic conception of life.

Our own immediate line of descent leads down through the minor forms of Tertiary and Mesozoic times—­forms that probably skulked and dodged about amid the terrible and gigantic creatures of those ages as the small game of to-day hide and flee from the presence of their arch-enemy, man; and that the frail line upon which the fate of the human race hung should not have been severed during the wild turmoil of those ages is, to me, a source of perpetual wonder.

III

The hazards of the future of the race must be quite different from those I have been considering.  They are the hazards incident to an exceptional being upon this earth—­a being that takes his fate in his own hands in a sense that no other creature does.

Man has partaken of the fruit of the Tree of Good and Evil, which all the lower orders have escaped.  He knows, and knows that he knows.  Will this knowledge, through the opposition in which it places him to elemental nature and the vast system of artificial things with which it has enabled him to surround himself, cut short his history upon this planet?  Will Nature in the end be avenged for the secrets he has forced from her?  His civilization has doubtless made him the victim of diseases to which the lower orders, and even savage man, are strangers.  Will not these diseases increase as his life becomes more and more complex and artificial?  Will he go on extending his mastery over Nature and refining or suppressing his natural appetites till his original hold upon life is fatally enfeebled?

It seems as though science ought to save man and prolong his stay on this planet,—­it ought to bring him natural salvation, as his religion promises him supernatural salvation.  But of course, man’s fate is bound up with the fate of the planet and of the biological tree of which he is one of the shoots.  Biology is rooted in geology.  The higher forms of life did not arbitrarily appear, they flowed out of conditions that were long in maturing; they flowered in season, and the flower will fall in season.  Man could not have appeared earlier than he did, nor later than he did; he came out of what went before, and he will go out with what comes after.  His coming was natural, and his going will be natural.  His period had a beginning, and it will have an end.  Natural philosophy leads one to affirm this; but of time measured by human history he may yet have a lease of tens of thousands of years.