The conclusions which Darwin arrived at as to the factors in the transformation of species, and in the production of “adaptations,” have been in part supported by the specialists he influenced, in part strengthened, but in part modified and even reversed, so that a great crisis has come about in regard to Darwinism in the strict sense—a crisis which threatens to be fatal to it. We must here attempt to take a general survey of the state of the question and to define our own position.
Darwin’s interpretation is well known. It is the theory of the natural selection of the best adapted through the struggle for existence, which is of itself a natural selection, and results in the sifting out of particular forms and of higher forms. Darwin’s thinking follows the course that all anti-teleological thought has followed since the earliest times. In bringing forth the forms of life, nature offers, without choice or aim or intention, a wealth of possibilities. The forms which happen to be best adapted to the surrounding conditions of life maintain themselves, and reproduce; the others perish, and are eliminated (survival of the fittest). Thus arises adaptation at first in the rough, but gradually in more and more minute detail. This adaptation, brought about by chance, gives _the impression_ of intelligent creative purpose.
In Darwin this fundamental mode of naturalistic interpretation took, under the influence of the social-economic theories of Malthus, the special form of natural selection by means of the struggle for existence, in association with the assumption of unlimited and fluctuating variability in the forms of life. All living beings have a tendency to increase in number without limit. But the means of subsistence and other conditions of existence do not increase at the same rate; they are relatively constant. Thus competition must come about. Any organism that is, by fortuitous variation, more favourably equipped than its fellows maintains itself and reproduces itself; the less favoured perish. For all things living are exposed to enemies, to untoward circumstances, and the like. Every individual favoured above its rivals persists, and can transmit to its descendants its own more favourable, more differentiated, more highly equipped character. Thus evolution is begun, and is forced on into the ever more diverse and ever “higher.”