I think I have now shown not only that no other planet in the solar system makes any approach to the possession of the varied and complex adaptations which are essential for a full development of organic life, but also that on the Earth itself the conditions are so numerous and so nicely balanced that very moderate deviations in excess or defect of what actually exists in the case of any one of them—and of others not referred to here—might have rendered it equally unsuitable, so that either no organic life at all, or only a very low type of life, could have been developed or supported.
There is Purpose in our World
If, then, the more superficial indications of design in the relations of animals to their environment, and of man to the universe, have been shown by modern science to have required no special interference of a higher power to bring them about, but that they have been due to natural laws acting in accordance with and in subordination to the deeper laws and forces that determine the very constitution of matter and the unknown power and principle we term “life,”—yet, on the other hand, we find that a more careful study of the outer universe, or cosmos, reveals a new set of adaptations not less wonderful or more easily explicable by chance coincidence than those presented by the organic world.
Even the very brief sketch of the subject here given suggests the idea of purpose in a world so precisely and uniquely adapted to develop organic life, and to support that life during the countless ages required for the completed evolution of man. But that suggestion becomes a logical induction when the whole of the available evidence is set forth, as I have attempted to set it forth in my work on “Man’s Place in the Universe.” I have there shown not only that the cumulative evidence for the earth being the only supporter of a fully-developed organic life within the solar system is irresistible, but that there is some direct, and much more indirect, evidence that this uniqueness extends to the whole stellar universe; and it is certain that no particle of direct evidence for the existence of organic life elsewhere has been, or is likely to be, adduced.
I have also shown (in an appendix to the second edition of my book) that the purely biological argument for the uniqueness of the development of man—as the culminating point of one line of descent throughout the diverging ramifications of the animal kingdom—is overwhelmingly strong; hence the logical conclusion from the whole of the evidence is that man is the one supreme product of the whole material universe.
My object in the present essay has been limited to showing that, besides and beyond the special adaptations of the various kinds of animals and plants to their special environments, there exist in the earth as a planet, in its various physical and cosmical relations, a whole series of adaptations of a very remarkable character which, so far as we can judge, are essential to its function as a life-producing world. The study of these adaptations, therefore, may be considered to be appropriate here, as constituting a preliminary chapter in the natural history of the Earth and of Mankind.
ALFRED RUSSEL WALLACE
IN THE DAYS OF THE SEA MONSTERS
Reproduced from a plate in Hawkins’ “Book of the Great Sea Dragons.”