II.
The next question is, how the facts of palæontology agree with these most important results of comparative anatomy and ontogeny. The fossils are the true historical 'medals of creation,' the palpable evidence of the historical succession of all those innumerable organic forms which have peopled the globe for many millions of years. Here the question arises, If the known fossil specimens of Mammalia, and particularly of Primates, give proof of these Pithecometra-theses, do they confirm directly the descent of man from ape-like creatures? The answer to this question is, in my opinion, affirmative.
It is true that the gaps in the palæontological evidence, here as elsewhere, are many and keenly felt. In the order of the Primates they are greater than in many other orders, chiefly because of the arboreal life of our ancestors. The explanation is very simple. It is really due to a long chain of favourable coincidences if the skeleton of a vertebrate, covered as it was with flesh and skin, and containing still more perishable viscera, is petrified at all. The body may be devoured by other creatures, and its bones scattered about; or it rots away and crumbles to pieces. Many animals hide in thick undergrowth when death approaches them; and, leading an almost entirely arboreal life, the Primates are especially likely to disappear without being fossilized. It is only when the body is quickly covered with sand, or is embedded in suitable lime or silica containing mud, that the process of petrifaction can come to pass. Even then it is only by great good luck that we come across such a fossil. Very few countries have been searched systematically, and the areas that have been searched amount to little in comparison with the whole surface of the land, even if we leave out of account the fact that more than two-thirds of the globe are covered by water.
These deplorable deficiencies of empirical palæontology are balanced on the other side by a growing number of positive facts, which possess an inestimable value in human phylogeny. The most interesting and most important of these is the celebrated fossil Pithecanthropus erectus, discovered in Java in 1894 by Dr. Eugène Dubois.[10] Three years ago this now famous ape-like man provoked an animated discussion at the third International Zoological Congress at Leyden. I may therefore be allowed to say a few words as to its scientific significance. Unfortunately, the fossil remains of this creature are very scanty: the skull-cap, a femur, and two teeth. It is obviously impossible to form from these scanty remains a complete and satisfactory reconstruction of this remarkable Pliocene Primate.
The more important points are the following: The remains in question rested upon a conglomerate which lies upon a bed of marine marl and sand of Pliocene age. Together with the bones of Pithecanthropus were found those of Stegodon, Leptobos, Rhinoceros, Sus, Felis, Hyæna, Hippopotamus, Tapir, Elephas, and a gigantic Pangolin. It is remarkable that the first two of these genera are now extinct, and that neither hippopotamus nor hyæna exists any longer in the Oriental region. If we may judge from these fossil remains, the bones of Pithecanthropus are not younger than the oldest Pleistocene, and probably belong to the upper Pliocene. The teeth are like those of man. The femur, also, is very human, but shows some resemblances to that of the gibbons. Its size, however, indicates an animal which stood when erect not less than 5 feet 6 inches high. The skull-cap also is very human, but with very prominent eyebrow ridges, like those of the famous Neanderthal cranium. It is certainly not that of an idiot. It had an estimated cranial capacity of about 1,000 cubic centimetres—that is to say, much more than that of the largest ape, which possesses not more than 600 c.c. The crania of female Australians and Veddahs measure not more than 1,100, some even less than 1,000 c.c.; but, as these Veddah women stand only about 4 feet 9 inches high, the computed cranial capacity of the much taller Pithecanthropus is comparatively very low indeed.[11]
The upper figure represents the outlines of the skull of Pithecanthropus, as restored by Manouvier.[12] The lower figure shows the comparative size and shape of Pithecanthropus, the Neanderthal skull, a specimen of the Cro-Magnon race of neolithic France, and a Young Chimpanzee before the full development of the supraorbital crests.
The final result of the long discussion at Leyden was that, of twelve experts present, three held that the fossil remains belonged to a low race of man; three declared them to be those of a man-like ape of great size; the rest maintained that they belonged to an intermediate form, which directly connected primitive man with the anthropoid apes. This last view is the right one, and accords with the laws of logical inference. Pithecanthropus erectus of Dubois is truly a Pliocene remainder of that famous group of highest Catarrhines which were the immediate pithecoid ancestors of man. He is, indeed, the long-searched-for 'missing link,' for which, in 1866, I myself had proposed the hypothetical genus Pithecanthropus, species Alalus.