As regards the course of this evolution, all we know with any certainty is, that as far as we can trace it back, the human species was already differentiated into distinct races, and that in all probability the present fundamental types were already formed. When and where the primitive stock or stocks may have originated, and the secondary ancestral races may have branched off from it, is at present unknown. All we can say is, that the more we examine the evidence, the more it points to extreme antiquity even for these secondary stocks, and makes it probable that we must go, as in the case of the horse and other existing mammals, at least as far back as into the Eocene to look for the primitive generalized type or types from which these secondary lines of quadrumanous and human evolution have taken their origin. As regards the secondary types themselves, there is no certainty as to the place or time of their origin, but the balance of evidence points rather in favour of polygeny, that is, of their having followed slightly different lines of evolution from the common starting-point, under different circumstances of environment and in different localities; so that when man, as we know him, first appeared, he was already differentiated into races distinct though not very far apart. In conclusion, I may remark that these hotly-contested questions as to monogeny or polygeny, and as to the place of man's first appearance on earth, lose most of their importance when it is realized that human origins must be pushed back at least as far as the Miocene, and probably into the Eocene period. As long as it was held that no traces of man's existence could be found, as Cuvier held, until the Recent period; or even as some English geologists still contend, until the post-glacial, or at any rate the glacial or Quaternary periods, it was evident that the facts could only be explained by the theory of a series of supernatural interferences. Agassiz's theory, or some modification of it, must be adopted, of numerous special creations of life at special centres, as of the Esquimaux and polar bear in Arctic regions, the Negro and gorilla in the tropics, and so forth. This theory has been completely given up as regards animals, in favour of the Darwinian theory of evolution by natural causes, and no one now believes in a multiplicity of miracles to account for the existence of animal species. Is man alone an exception to this universal law, or is he like the rest of creation, a product of what Darwinians call "Evolution," and enlightened theologians "the original impress"?