CHAPTER XV.

THE ORIGIN OF SPECIES (1859).

[Sidenote: THE ORIGIN OF SPECIES.]

It is very interesting to separate the two arguments which occur interwoven in the “Origin”--the argument for evolution and the argument for natural selection. The paramount importance of Darwin’s contributions to the evidences of organic evolution are often forgotten in the brilliant theory which he believed to supply the motive cause of descent with modification. Organic evolution had been held to be true by certain thinkers during many centuries; but not only were its adherents entirely without a sufficient motive cause, but their evidences of the process itself were erroneous or extremely scanty. It was Darwin who first brought together a great body of scientific evidence which placed the process of evolution beyond dispute, whatever the causes of evolution may have been. And accordingly we find that, even at first, natural selection was attacked far more generally than the doctrine of descent with modification.

In Chapter I., Variation under Domestication and man’s power of selection in forming breeds of animals and plants are discussed; in