Antiquity of Man.--The geological history of man is imperfectly known, although sporadic explorations have already accumulated an interesting series, especially as regards the shape and capacity of skulls. The remains of early quarternary man have been unearthed in various parts of Europe, and the probable existence of man in the tertiary period is generally admitted. As Osborn says, "Virtually three links have been found in the chain of human ancestry." The most primitive pre-human species is represented by portions of the skull and of the leg bones found in Java by the Dutch surgeon Dubois in the year 1890. These remains were found in tertiary deposits, and were baptized under the name of _Pithecanthropus erectus_. The structural position of this fossil is between the chimpanzee, the highest of anthropoid apes, and the "Neanderthal man." With characteristic scientific caution Osborn says that the _Pithecanthropus_ "belongs in the line of none of the existing anthropoid apes, and falls very near, but not directly, in the line of human ancestry." The second link is supplied by the famous Neanderthal skull found in the valley of the Neander, near Düsseldorf, in 1856. The discovery of this skull, with its receding forehead and prominent ridges above the orbits of the eyes, and its small cranial capacity, created a sensation, for it was soon seen that it was intermediate between the skulls of the lowest human races and those of the anthropoid apes. Virchow declared that if the skull was pre-human its structural characteristics were abnormal. This conclusion, however, was rendered untenable by the discovery in 1886 of similar skulls and the skeletons of two persons, in a cave near Spy in Belgium. The "Spy man" and the "Neanderthal man" belong to the same type and are estimated to have been living in the middle of the palæolithic age. [Illustration: Fig. 111.--Profile Reconstructions of the Skulls of Living and Fossil Men: 1. Brachycephalic European; 2. The more ancient of the Nebraska skulls; 3. The Neanderthal man; 4. One of the Spy skulls; 5. Skull of the Java man. (Altered from Schwalbe and Osborn.)] The third link is in the early Neolithic man of Engis. And now to this interesting series of gradations has been added another by the discovery in 1906 of a supposed primitive race of men in Nebraska. The two skulls unearthed in Douglass County in that State indicate a cranial capacity falling below that of the "Australian negro, the lowest existing type of mankind known at present." Fig. 111 shows in outline profile reconstructions of the skulls of some of the fossil types as compared with the short-headed type of Europe.