Embryos of three mammals
(At three corresponding stages of development). B = Bat (Rhinolophus) G = Gibbon (Hylobates) M = Man (Homo)
Skeletons of five anthropoid apes
These skeletons of the five living genera of anthropomorpha are reduced to a common size, in order to show better the relative proportions of the various parts. The human skeleton is 1/20 th natural size, the gorilla 1/18 th, the chimpanzee 1/7 th, the orang 1/7 th, the gibbon 1/9 th. Young specimens of the chimpanzee and orang have been selected, because they approach nearer to man than the adult. No one of the living anthropoid apes is nearest to man in all respects; this cannot be said of either of the African (gorilla and chimpanzee) or the Asiatic (orang and gibbon). This anatomic fact is explained phylogenetically on the ground that none of them are direct ancestors of man; they represent divergent branches of the stem, of which man is the crown. However, the small gibbon is nearest related to the hypothetical common ancestor of all the anthropomorpha to which we give the name of Prothylobates.