The teeth are of the normal human pattern, being small and vertical. Prof. Arthur Keith says they have the same shape as those of the specimen found at Spy. The jaw has an ape-like appearance, due to the extreme recessiveness of the chin. It is also remarkable for its massiveness and the broadness of the ascending rami. Its anomalous character is indicated by the manifest disproportion between the powerful jaw and the insignificant teeth. “One is impressed,” says Prof. George Grant MacCurdy of Yale, “by the relative smallness of the teeth as compared with the massive jaw in the case of _Homo heidelbergensis_.” (Smithson. Inst. Rpt. for 1909, p. 570.) “Why so massive a jaw,” says the late Professor Dwight, former anatomist at Harvard, “should have such inefficient teeth is hard to explain, for the very strength of the jaw implies the fitness of corresponding teeth. Either it is an anomaly or the jaw of some aberrant species of ape.” (_Op. cit._, p. 164.) This fact alone destroys its evidential force; for, by way of anomaly, almost any sort of feature can appear in apes and men, that is, human characters in apes and simian characters in man. “Thus it is certain,” says Dwight, “that animal features of the most diverse kinds appear in man apparently without rhyme or reason, and also that they appear in precisely the same way in animals far removed from those in which they are normal. It is hopeless to try to account for them by inheritance; and to call them instances of convergence does not help matters.” (_Op. cit._, pp. 230, 231.) Kramberger, however, claims that, with the exception of the extremely recessive chin, the features of the Heidelberg jaw are approximated by those which are normal in the modern Eskimo skull. (Cf. _Sitzungbericht der Preuss. Akad. der Wissenschaften_, 1909.) Prof. J. H. McGregor holds similar views. He claims that the greater use of the jaw in uncivilized peoples, who must masticate tough foods, tends to accentuate and increase the recessiveness of the chin. It is also possible that the backward sloping of the chin may have been intensified in certain primitive races or varieties of the human species as a result of factorial mutation. We would not, however, be justified in segregating a distinct human species on the basis of minor differences, such as the protuberance or recessiveness of chins. On the whole, we are hopelessly at sea with reference to the significance of the Heidelberg mandible. Taxonomic allocation must be grounded on something more than a jaw, otherwise it amounts to nothing more than a piece of capricious speculation.