It will be seen that the argument naturally leads up to this expression—Survival of the Fittest—which was here used for the first time. Two years later (July, 1866) Mr. A. R. Wallace wrote to Mr. Darwin contending that it should be substituted for the expression "Natural Selection." Mr. Darwin demurred to this proposal. Among reasons for retaining his own expression he said that I had myself, in many cases, preferred it—"continually using the words Natural Selection." (Life and Letters, &c., vol. III, pp. 45-6.) Mr. Darwin was quite right in his statement, but not right in the motive he ascribed to me. My reason for frequently using the phrase "Natural Selection," after the date at which the phrase "Survival of the Fittest" was first used above, was that disuse of Mr. Darwin's phrase would have seemed like an endeavour to keep out of sight my own indebtedness to him, and the indebtedness of the world at large. The implied feeling has led me ever since to use the expressions Natural Selection and Survival of the Fittest with something like equal frequency.
I am indebted to Mr. [now Sir W.] Flower for the opportunity of examining the many skulls in the Museum of the College of Surgeons for verification of this. Unfortunately the absence, in most cases, of some or many teeth, prevented me from arriving at that specific result which would have been given by weighing a number of the under jaws in each race. Simple inspection, however, disclosed a sufficiently-conspicuous difference. The under jaws of Australians and Negroes, when collated with those of Englishmen, were visibly larger, not only relatively but absolutely. One Australian jaw only seemed about of the same size as an average English jaw; and this (probably the jaw of a woman), belonging as it did to a smaller skull, bore a greater ratio to the whole body of which it formed part, than did an English jaw of the same actual size. In all the other cases, the under jaws of these inferior races (containing larger teeth than our own) were absolutely more massive than our own—often exceeding them in all dimensions; and relatively to their smaller skeletons were much more massive. Let me add that the Australian and Negro jaws are thus strongly contrasted, not with all British jaws, but only with the jaws of the civilized British. An ancient British skull in the collection possesses a jaw almost or quite as massive as those of the Australian skulls. All this is in harmony with the alleged relation between greater size of jaws and greater action of jaws, involved by the habits of savages.
[In 1891 Mr. F. Howard Collins carefully investigated this matter: measuring ten Australian, ten Ancient British, and ten recent English skulls in the College of Surgeons Museum. The result proved an absolute difference of the kind above indicated, and a far greater relative difference. To ascertain this last a common standard of comparison was established—an equal size of skull in all the cases; and then when the relative masses or cubic sizes of the jaws were calculated, the result which came out was this:—Australian jaw, 1948; Ancient British jaw, 1135; Recent English jaw, 1030. "Hence," in the words of Mr. Collins, "the mass of the Recent English jaw is, roughly speaking, half that of the Australian relatively to that of the skull, and a ninth less than that of the Ancient British." He adds verifying evidence from witnesses who have no hypothesis to support—members of the Odontological Society. The Vice-President, Mr. Mummery, remarks of the Australians that "the jaw-bones are powerfully developed, and large in proportion to the cranium.">[
As bearing on the question of the varieties of Man, let me here refer to a paper on "The Origin of the Human Races" read before the Anthropological Society, March 1st, 1864, by Mr. Alfred Wallace. In this paper, Mr. Wallace shows that along with the attainment of that intelligence implied by the use of implements, clothing, &c., there arises a tendency for modifications of brain to take the place of modifications of body: still, however, regarding the natural selection of spontaneous variations as the cause of the modifications. But if the foregoing arguments be valid, natural selection here plays but the secondary part of furthering the adaptations otherwise caused. It is true that, as Mr. Wallace argues, and as I have myself briefly indicated (see Westminster Review, for April, 1852, pp. 496-501), the natural selection of races leads to the survival of the more cerebrally-developed, while the less cerebrally-developed disappear. But though natural selection acts freely in the struggle of one society with another; yet, among the units of each society, its action is so interfered with that there remains no adequate cause for the acquirement of mental superiority by one race over another, except the inheritance of functionally-produced modifications.
Darwin and after Darwin, Part II, p. 99.