Professor of Natural History in the University of Aberdeen.
In seeking to discover Darwin's relation to his predecessors it is
useful to distinguish the various services which he rendered to the
theory of organic evolution.
(I) As everyone knows, the general idea of the Doctrine of Descent
is that the plants and animals of the present-day are the lineal
descendants of ancestors on the whole somewhat simpler, that these again
are descended from yet simpler forms, and so on backwards towards the
literal "Protozoa" and "Protophyta" about which we unfortunately know
nothing. Now no one supposes that Darwin originated this idea, which in
rudiment at least is as old as Aristotle. What Darwin did was to make
it current intellectual coin. He gave it a form that commended itself
to the scientific and public intelligence of the day, and he won
wide-spread conviction by showing with consummate skill that it was
an effective formula to work with, a key which no lock refused. In
a scholarly, critical, and pre-eminently fair-minded way, admitting
difficulties and removing them, foreseeing objections and forestalling
them, he showed that the doctrine of descent supplied a modal
interpretation of how our present-day fauna and flora have come to be.
(II) In the second place, Darwin applied the evolution-idea to
particular problems, such as the descent of man, and showed what a
powerful organon it is, introducing order into masses of uncorrelated
facts, interpreting enigmas both of structure and function, both
bodily and mental, and, best of all, stimulating and guiding further
investigation. But here again it cannot be claimed that Darwin was
original. The problem of the descent or ascent of man, and other
particular cases of evolution, had attracted not a few naturalists
before Darwin's day, though no one (except Herbert Spencer in the
psychological domain (1855)) had come near him in precision and
thoroughness of inquiry.
(III) In the third place, Darwin contributed largely to a knowledge of
the factors in the evolution-process, especially by his analysis of what
occurs in the case of domestic animals and cultivated plants, and by
his elaboration of the theory of Natural Selection, which Alfred Russel
Wallace independently stated at the same time, and of which there had
been a few previous suggestions of a more or less vague description.
It was here that Darwin's originality was greatest, for he revealed to
naturalists the many different forms--often very subtle--which natural
selection takes, and with the insight of a disciplined scientific
imagination he realised what a mighty engine of progress it has been and
is.
(IV) As an epoch-marking contribution, not only to Aetiology but to
Natural History in the widest sense, we rank the picture which
Darwin gave to the world of the web of life, that is to say, of
the inter-relations and linkages in Nature. For the Biology of the
individual--if that be not a contradiction in terms--no idea is more
fundamental than that of the correlation of organs, but Darwin's most
characteristic contribution was not less fundamental,--it was the idea
of the correlation of organisms. This, again, was not novel; we find
it in the works of naturalist like Christian Conrad Sprengel, Gilbert
White, and Alexander von Humboldt, but the realisation of its full
import was distinctively Darwinian.