It is therefore probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species are now man’s nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere. But it is useless to speculate on this subject, for an ape nearly as large as a man, namely the Dryopithecus of Lartet, which was closely allied to the anthropomorphous Hylobates, existed in Europe during the Upper Miocene period; and since so remote a period the earth has certainly undergone many great revolutions, and there has been ample time for migration on the largest scale.
It is interesting to note that Darwin considered modern humans more closely related to chimpanzees and gorillas, African apes, than to orangutans and gibbons. This must have led him to include us with the African group and consequently to consider us at least as much an ape as the orangutans and gibbons, which had separated previously from a common root. We would therefore be a highly evolved form of African ape. The same resemblance between us and the African apes had been noted previously in 1863 by Huxley (1959): “It is quite certain that the Ape which most nearly approaches man, in the totality of its organization, is either the Chimpanzee or the Gorilla.” Nevertheless, this did not lead Huxley to group us in the same taxonomic category with the African apes. Rather, it was they who were grouped with the other great ape, the orangutan, along with the lesser apes, the gibbons, in the same category: “The structural differences between Man and the Man-like apes certainly justify our regarding him as constituting a family apart from them.”
The only way that modern humans are included within the group of apes, in which we are considered apes, is if we are more closely related phylogenetically to some of them (the African apes) than to others (the Asian apes). If this were not the case, the apes would form one clade (a natural group with an exclusive common ancestor) and we would form another, the human clade (sister group), connected with them at a lower node. This is what Darwin believed (1871a, p. 197):
If the anthropomorphous apes be admitted to form a natural sub-group, then as man agrees with them, not only in all those characters which he possesses in common with the whole Catarhine group, but in other peculiar characters, such as the absence of a tail and of callosities and in general appearance, we may infer that some ancient member of the anthropomorphous sub-group gave birth to man. It is not probable that a member of one of the other lower sub-groups should, through the law of analogous variation, have given rise to a man-like creature, resembling the higher anthropomorphous apes in so many respects. No doubt man, in comparison with most of his allies, has undergone an extraordinary