_b-c._ 'Older loess' (sandy loess) of the close of Second Interglacial times. _c-f._ The 'sands of Mauer.' _d-e._ An intermediate layer of clay. The white cross (X) indicates the spot at the base of the 'sands of Mauer' at which the jaw of Heidelberg was discovered.] [Illustration: FIG. 47. The Heidelberg jaw, type of _Homo heidelbergensis_. About two-thirds life size. After Schoetensack.] The discovery in 1907 of a human lower jaw in the base of the 'Mauer sands' is one of the most important in the whole history of anthropology. The find was made at a depth of 79 feet (24.10 m.) from the upper surface of a high bluff (Fig. 46), in ancient river sands which had long been known to yield the very old mammalian fauna described above. For years the workmen had been instructed to keep a sharp lookout for human remains. The jaw had evidently drifted down with the river sands and had become separated from the skull, but it remained in perfect preservation. The author's description may first be quoted.(36) The mandible shows a combination of features never before found in any fossil or recent man. The protrusion of the lower jaw just below the front teeth which gives shape to the human chin is entirely lacking. Had the teeth been absent it would have been impossible to diagnose it as human. From a fragment of the symphysis of the jaw it might well have been classed as some gorilla-like anthropoid, while the ascending ramus resembles that of some large variety of gibbon. The absolute certainty that these remains are human is based on the form of the teeth--molars, premolars, canines, and incisors are all essentially human and, although somewhat primitive in form, show no trace of being intermediate between man and the anthropoid apes but rather of being derived from some older common ancestor. The teeth, however, are somewhat small for the jaw; the size of the border would allow for the development of much larger teeth; we can only conclude that no great strain was put on the teeth, and therefore the powerful development of the bones of the jaw was not designed for their benefit. The conclusion is that the jaw, regarded as unquestionably human from the nature of the teeth, ranks not far from the point of separation between man and the anthropoid apes. In comparison with the jaws of Neanderthal races, as found at Spy, in Belgium, and at Krapina, in Croatia, we may consider the Heidelberg jaw as pre-Neanderthaloid; it is, in fact, a generalized type. [Illustration: FIG. 48. Side view of Heidelberg jaw (centre) compared with that of an orang (right) and of an Eskimo (left); the latter an individual of exceptionally large proportions.]