The Quaternary is usually subdivided into two periods, the Pleistocene and the Recent. The Recent is very short, perhaps not more than ten thousand years. It represents, geologically speaking, the mere instant which has elapsed since the final disappearance of the great glaciers. It is but little longer than historic time; and throughout the Recent there are encountered only modern forms of man. Back of it, the much longer Pleistocene is often described as the Ice Age or Glacial Epoch; and both in Europe and North America careful research has succeeded in demonstrating four successive periods of increase of the ice. In Europe these are generally known as the Günz, Mindel, Riss, and Würm glaciations. The probable American equivalents are the Nebraskan, Kansan, Illinoian, and Wisconsin periods of ice spread. Between each of these four came a warmer period when the ice melted and its sheets receded. These are the “interglacial periods” and are designated as the first, second, and third. These glacial and interglacial periods are of importance because they offer a natural chronology or time scale for the Pleistocene, and usually provide the best means of dating the fossil human types that have been or may hereafter be discovered ([Fig. 5]).
10. Place of Man’s Origin and Development
Before we proceed to the fossil finds themselves, we must note that the greater part of the surface of the earth has been very imperfectly explored. Africa, Asia, and Australia may quite conceivably contain untold scientific treasures which have not yet been excavated. One cannot assert that they are lying in the soil or rocks of these continents; but one also cannot affirm that they are not there. North and South America have been somewhat more carefully examined, at least in certain of their areas, but with such regularly negative results that the prevailing opinion now is that these two continents—possibly through being shut off by oceans or ice masses from the eastern hemisphere—were not inhabited by man during the Pleistocene. The origin of the human species cannot then be sought in the western hemisphere. This substantially leaves Europe as the one continent in which excavations have been carried on with prospects of success; and it is in the more thoroughly explored western half of Europe that all but two of the unquestioned discoveries of ancient man have been made. One of these exceptional finds is from Africa. The other happens to be the one that dates earliest of all—the same Pithecanthropus already mentioned as being the closest known approach to the “missing link.” Pithecanthropus was found in Java.
Now it might conceivably prove true that man originated in Europe and that this is the reason that the discoveries of his most ancient remains have to date been so largely confined to that continent. On the other hand, it does seem much more reasonable to believe that this smallest of the continents, with its temperate or cold climate, and its poverty of ancient and modern species of monkeys, is likely not to have been the true home, or at any rate not the only home, of the human family. The safest statement of the case would be that it is not known in what part of the earth man originated; that next to nothing is known of the history of his development on most of the continents; and that that portion of his history which chiefly is known is the fragment which happened to take place in Europe.
Fig. 5. Antiquity of man. This diagram is drawn to scale, proportionate to the number of years estimated to have elapsed, as far down as 100,000. Beyond, the scale is one-half, to bring the diagram within the limits of the page.
11. Pithecanthropus
Pithecanthropus erectus, the “erect ape-man,” was determined from the top part of a skull, a thigh bone, and two molar teeth found in 1891 under fifty feet of strata by Dubois, a Dutch surgeon, near Trinil, in the East Indian island of Java. The skull and the thigh lay some distance apart but at the same level and probably are from the same individual. The period of the stratum is generally considered early Pleistocene, possibly approximately contemporary with the first or Günz glaciation of Europe—nearly a million years ago, by the time scale here followed. Java was then a part of the mainland of Asia.