The skull is low, with narrow receding forehead and heavy ridges of bone above the eye sockets—“supraorbital ridges.” The capacity is estimated at 850 or 900 cubic centimeters—half as much again as that of a large gorilla, but nearly one-half less than the average for modern man. The skull is dolichocephalic—long for its breadth—like the skulls of all early fossil men; whereas the anthropoid apes are more broad-headed. The jaws are believed to have projected almost like a snout; but as they remain undiscovered, this part of the reconstruction is conjectural. The thigh bone is remarkably straight, indicating habitual upright posture; its length suggests that the total body stature was about 5 feet 7 inches, or as much as the height of most Europeans.
Pithecanthropus was a terrestrial and not an arboreal form. He seems to have been slightly more similar to modern man than to any ape, and is the most primitive manlike type yet discovered. But he is very different from both man and the apes, as his name indicates: Pithecanthropus is a distinct genus, not included in Homo, or man.
12. Heidelberg Man
Knowledge of Heidelberg man rests on a single piece of bone—a lower jaw found in 1907 by Schoetensack at a depth of nearly eighty feet in the Mauer sands not far from Heidelberg, Germany. Like the Pithecanthropus remains, the Heidelberg specimen lay in association with fossils of extinct mammals, a fact which makes possible its dating. It probably belongs to the second interglacial period, so that its antiquity is only about half as great as that of Pithecanthropus ([Fig. 5]).
The jaw is larger and heavier than any modern human jaw. The ramus, or upright part toward the socket, is enormously broad, as in the anthropoid apes. The chin is completely lacking; but this area does not recede so much as in the apes. Heidelberg man’s mouth region must have projected considerably more than that of modern man, but much less than that of a gorilla or a chimpanzee. The contour of the jaw as seen from above is human (oval), not simian (narrow and oblong).
The teeth, although large, are essentially human. They are set close together, with their tops flush, as in man; the canines lack the tusk-like character which they retain in the apes.
Since the skull and the limb bones of this form are wholly unknown, it is somewhat difficult to picture the type as it appeared in life. But the jaw being as manlike as it is apelike, and the teeth distinctly human, the Heidelberg type is to be regarded as very much nearer to modern man than to the ape, or as farther along the line of evolutionary development than Pithecanthropus; as might be expected from its greater recency. This relationship is expressed by the name, Homo Heidelbergensis, which recognizes the type as belonging to the genus man.
13. The Piltdown Form
This form is reconstructed from several fragments of a female brain case, some small portions of the face, nearly half the lower jaw, and a number of teeth, found in 1911-13 by Dawson and Woodward in a gravel layer at Piltdown in Sussex, England. Great importance has been ascribed to this skull, but too many of its features remain uncertain to render it safe to build large conclusions upon the discovery. The age cannot be fixed with positiveness; the deposit is only a few feet below the surface, and in the open; the associated fossils have been washed or rolled into the layer; some of them are certainly much older than the skull, belonging to animals characteristic of the Pliocene, that is, the Tertiary. If the age of the skull was the third interglacial period, as on the whole seems most likely, its antiquity might be less than a fourth that of Pithecanthropus and half that of Heidelberg man.
The skull capacity has been variously estimated at 1,170, nearly 1,300, and nearly 1,500 c.c.; the pieces do not join, so that no certain proof can be given for any figure. Except for unusual thickness of the bone, the skull is not particularly primitive. The jaw and the teeth, on the other hand, are scarcely distinguishable from those of a chimpanzee. They are certainly far less human than the Heidelberg jaw and teeth, which are presumably earlier. This human skull and simian jaw are an almost incompatible combination. More than one expert has got over the difficulty by assuming that the skull of a contemporary human being and the jaw of a chimpanzee happened to be deposited in the same gravel.