I
The word ‘evolution’ is so popularly accepted and so generally employed in connection with Darwin’s theories that it will never be displaced; but it is not wholly satisfactory, because it always suggests progress from a lower to a higher and hence involves a difficult and invidious definition of terms. Some such phrase as ‘descent with modification’ would probably be more exact. But whatever the term used, to associate it as a scientific theory or discovery exclusively with Darwin or any other one man would be absurd. The natural hypothesis of earlier thinkers was that divine creative power, in whatever shape, had established the different forms of life on the earth pretty much as they exist to-day. But those who looked more deeply, were inclined to surmise, in view of the close and evident bonds of kinship between all living things, that variety had developed from comparative unity and that the vital impulse, having first appeared in elementary forms, became gradually elaborated into more and more complicated organisms. The vast pains that Darwin took to substantiate this view, together with his particular explanation of how the process came about, have forever bound up the idea of evolution with his name, but he did not originate it nor did he claim to have done so.
The various hints and manifestations of earlier evolutionary theory are admirably elucidated in Professor Osborn’s ‘From the Greeks to Darwin.’ The vast curiosity and reflection of Aristotle anticipated here, as everywhere, and some of his sentences have a striking evolutionary bearing: ‘Variety in animal life may be produced by variety of locality.’[389] ‘Locality will differentiate habits also; for instance, rugged highlands will not produce the same results as the soft lowlands.’[390] And Empedocles suggests Darwin’s views even more directly. Under the régime of Biblical and Christian tradition evolutionary thought naturally made little progress. But with the greater freedom of the eighteenth century, notions of modification by descent again appeared. In England Darwin’s grandfather, Erasmus, the botanical poet, speculated curiously on the subject, and there were various other intimations, notably in Chambers’s ‘Vestiges of Creation,’ while Darwin himself felt that he was much influenced by the geological theories of Lyell. In Germany Goethe became profoundly interested in the metamorphoses of life. Especially in France Buffon and St.-Hilaire led up to the ‘Philosophie Zoologique’ of Lamarck, which propounded the theory of modification in a very definite form, and suggested the mode in which the modification was accomplished. Lamarck’s idea was that plants and animals, by an inborn, vital impulse, adapted themselves to their environment, and that these adaptations were transmitted by inheritance. Thus wading birds acquired webbed feet and the neck of the giraffe was elongated in its effort to obtain its food from the branches of the trees. The great stumbling-block of this theory has always been the difficulty of proving that acquired adaptations are inherited.[A]