In 1871, nearly twelve years after the \'Origin of Species,\' Darwin published his \'Descent of Man.\'

We have seen already that he would fain have avoided the treatment of this difficult and dangerous topic a little longer, so as to let his main theory be fairly judged on its own merits, without the obtrusion of theological or personal feelings into so purely biological a question; but the current was too strong for him, and at last he yielded. On the one hand, the adversaries had drawn for themselves the conclusion of man\'s purely animal origin, and held it up to ridicule under false forms in the most absurd and odious light. On the other hand, imprudent allies had put forth under the evolutionary ?gis their somewhat hypothetical and extravagant speculations on this involved subject, which Darwin was naturally anxious to correct and modify by his own more sober and guarded inferences. The result was the second great finishing work of the complete Darwinian system of things.

Ever since evolutionism had begun to be at all it had been observed that a natural corollary from the doctrine of descent with modification was the belief in[Pg 133] man\'s common ancestry with the anthropoid apes. As early as the middle of the last century, indeed, Lord Monboddo, a whimsical Scotch eccentric, had suggested in his famous book on the origin of language the idea that men were merely developed monkeys. But this crude and unorganised statement of a great truth, being ultimately based upon no distinct physical grounds, deserved scarcely to be classed higher than the childish evolutionism of \'Telliamed\' De Maillet, which makes birds descend from flying-fish and men the offspring of the hypothetical tritons. On this point as on most others the earliest definite scientific views are those of Buffon, who ventured to hint with extreme caution the possibility of a common ancestry for man and all other vertebrate animals. Goethe the all-sided had caught a passing glimpse of the same profound conception about the date of the Reign of Terror; and Erasmus Darwin had openly announced it, though without much elaboration, in his precocious and premature \'Zoonomia.\' Still more specifically, in a note to the \'Temple of Nature,\' the English evolutionist says: \'It has been supposed by some that mankind were formerly quadrupeds.... These philosophers, with Buffon and Helvetius, seem to imagine that mankind arose from one family of monkeys on the banks of the Mediterranean;\' and in the third canto of that fantastic poem, he enlarges upon the great part performed by the hand, with its opposable thumb, in the development and progress of the human species. Lamarck, in his \'Philosophie Zoologique,\' distinctly lays down the doctrine that man is descended from an ape-like ancestor, which gradually acquired the upright position, not even now[Pg 134] wholly natural to the human race, and maintained only by the most constant watchfulness. The orang-outang was then the highest known anthropoid ape; and it was from the orang-outang, therefore, that the fancy of Lyell and other objectors in the pre-Darwinian days continually derived the Lamarckian Adam.

The introduction of the chimpanzee into our European Zoological Gardens gave a fresh type of anthropoid to the crude speculators of the middle decades of the century; and in 1859, Paul du Chaillu, the explorer and hunter of the Gaboon country, brought over to America and Europe the first specimens of the true gorilla ever seen by civilised men. There can be little doubt that the general interest excited by his narrative of his adventures (published in London in 1861) and by the well-known stuffed specimen of the huge African anthropoid ape so long conspicuous in the rooms of the British Museum, and now surviving (somewhat the worse for wear) in the natural history collection at South Kensington, did much to kindle public curiosity as to the nature of our relations with the lower animals. It is no mere accidental circumstance, indeed, that Huxley should have brought out \'Man\'s Place in Nature\' just two years after Du Chaillu\'s \'Explorations and Adventures in Equatorial Africa\' had made the whole world, lay and learned, familiar with the name and features of the most human in outer aspect among the anthropoid family. Thenceforth the gorilla, and not the orang-outang, was popularly hit upon by scoffer and caricaturist as the imaginary type of our primitive ancestors.

On the other hand, during the twelve intervening[Pg 135] years immense strides had been made in every department of anthropological science, and the whole tenor of modern speculation had been clearing the ground for the \'Descent of Man,\' In 1865, Rolle in Germany had published his work on \'Man Viewed by the Light of the Darwinian Theory.\' Two years later, Canestrini in Italy read before the Naturalists\' Society of Modena his interesting paper on rudimentary characters as bearing on the origin of the human species. In 1868, Büchner brought out his rudely materialistic sledge-hammer lectures on the Darwinian principle; and in 1869, Barrago flung straight at the head of the Roman clericals his offensive work on man and the anthropoid apes. Most of these foreign publications were unhappily marked by that coarse and almost vituperative opposition to received views which too often disfigures French and German controversial literature. In England, on the contrary, under our milder and gentler ecclesiastical yoke, the contest had been conducted with greater decorum and with far better results. Wallace had broken ground tentatively and reverently in his essay on the \'Origin of Human Races,\' where he endeavoured to show that man is the co-descendant with the anthropoid apes of some ancient lower and extinct form. Lubbock\'s \'Prehistoric Times\' (1865) and \'Origin of Civilisation\' (1870) helped to clear the way in the opposite direction by demolishing the old belief, firmly upheld by Whately and others, that savages represent a degraded type, and that the civilised state is natural and, so to speak, congenital to man. Tylor\'s \'Early History of Mankind\' (1865) did still more eminent service in the same direction. Colenso\'s \'Pentateuch[Pg 136] and Book of Joshua Critically Examined,\' the publication of which began in 1862, had already shaken the foundations of the Mosaic cosmogony, and incidentally discredited the received view of the direct creation of the first human family. McLennan\'s \'Primitive Marriage\' (1865) and Herbert Spencer\'s articles on the origin of religion had kept speculation alive along other paths, all tending ultimately towards the same conclusion. Darwin\'s own cousin, Hensleigh Wedgwood, and Canon Farrar, had independently endeavoured to prove that language, instead of being a divine gift, might have arisen in a purely natural manner from instinctive cries and the imitation of external sounds. The Duke of Argyll and Professor Max Müller, by the obvious feebleness of their half-hearted replies, had unconsciously aided in disseminating and enforcing the very views they attempted to combat. Bagehot and Flower, Maudsley and Jevons, Vogt and Lindsay, Galton and Brown-Séquard had each in his way contributed facts and arguments ultimately utilised by the great master architect in building up his consistent and harmonious edifice. Finally, in 1868, Haeckel had published his \'Natural History of Creation,\' in which he discussed with surprising and perhaps excessive boldness the various stages in the genealogy of man. These various works, following so close upon Huxley\'s \'Man\'s Place in Nature\' and Lyell\'s conclusive \'Antiquity of Man,\' left Darwin no choice but to set forth his own reasoned opinions on the subject of the origin and development of the human species.

The evidence of the descent of man from some lower form, collected and marshalled together by Darwin, consists[Pg 137] chiefly of minute inferential proofs which hardly admit of deliberate condensation. In his bodily structure man is formed on the same underlying type or model as all the other mammals, bone answering throughout to bone, as, for example, in the fore limb, where homologous parts have been modified in the dog into toes, in the bat into wing-supports, in the seal into flippers, and in man himself into fingers and thumb, while still retaining in every case their essential fundamental likeness of construction. Even the brain of man resembles closely the brain of the higher monkeys; the differences which separate him in this respect from the orang or the gorilla are far slighter than the differences which separate those apes themselves from the inferior monkeys. Indeed, as Huxley conclusively showed, on anatomical grounds alone, man must be classed in the order Primates as only one among the many divergent forms which that order includes within its wide limits.

In his embryonic development man closely resembles the lower animals, the human creature being almost indistinguishable in certain stages from the dog, the bat, the seal, and especially the monkeys. At a very early age he possesses a slight projecting tail; at another, the great toe is shorter than its neighbours, and projects like the thumb at a slight angle; and at a third, the convolutions of the brain reach a point of development about equivalent to that of the adult baboon. In his first stages man himself ............