LITMIR.BIZ

      There are four main methods of determining prehistoric time.10 One is called the (1) geologic method, which is based upon the fact that, in a slowly cooling earth and the action of water and frost, cold and heat, storm and glacier and volcanic eruption, the rocks on the earth are of different ages. If they had never been disturbed from where they were first laid down, it would be very easy to reckon time by geological processes. If you had a stone column twenty feet high built by a machine in ten hours' time, and granting that it worked uniformly, it would be easy to see just at what hour of the period a layer of stone four feet from the bottom, or ten feet from the top, was laid. If, however, in the building of the wall, it should have toppled over several times and had to be rebuilt, it would require considerable study to see just at what hour a certain stone was put in the wall. Studying the geology of the earth in a large way, it is easy to determine what strata of the earth are oldest, and this may be verified by a consideration of the process in which these rocks were being made. Chemistry and physics are thus brought to the aid of geology. It is easy to determine whether a rock has been fused by a fire or whether it has been constructed by the slow action of water and pressure of other rocks. If to-day we should find in an old river bed which had been left high and dry on a little mesa or plateau above the present river bottom, layers of earth that had been put down by water, and we could find how much of each layer was made in a single year, it would be easy to estimate the number of years it took to make the whole deposit. Also if we could find in the lowest layer certain relics of the human race, we could know that the race lived at that time. If we should find relics later on of a different nature, we should be able to estimate the progress of civilization.

      The second method is of (2) paleontology, which is developed along with geology. In this we have both the vertebrate and invertebrate paleontology, which are divisions of the science which treats of ancient forms of animal and vegetable life. There are many other divisions of paleontology, some devoting themselves entirely to animal life and others to vegetable, as, for instance, paleobotany. As plants and animals have gradually developed from lower to higher forms and the earth has been built gradually by formations at different periods of existence, by a comparison of the former development with the latter, that is, comparison with the earth, or inorganic, development to the life, or organic, development, we are enabled to get a comparative view of duration. Thus, if in a layer of earth, geological time is established and there should be found bones of an animal, the bones of a man, and fossilized forms of ancient plants, it would be easy to determine their relative ages.

      The third method is that of (3) anatomy, which is a study of the comparative size and shape of the bones of man and other animals as a method of showing relative periods of existence. Also, just as the structure of the bones of a child, as compared with that of a man, would determine their relative ages, so the bones of the species that have been preserved through fossilization may show the relative ages of different types of animals. The study of the skeletons of animals, including those of man, has led to the science of anthropometry.

      The fourth method is to study the procession of man by (4) cultures, or the industrial and ornamental implements that have been preserved in the river drift, rocks, and caves of the earth from the time that man used them until they were discovered. Just as we have to-day models of the improvement of the sewing-machine, the reaper, or the flying-machine, each one a little more perfect, so we shall find in the relics of prehistoric times this same gradual development – first a stone in its natural state used for cutting, then chipped to make it more perfect, and finally beautified in form and perfected by polishing.

      Thus we shall find progress from the natural stone boulder used for throwing and hammering, the developed product made by chipping and polishing the natural boulder, making it more useful and more beautiful, and so for all the multitude of implements used in the hunt and in domestic affairs. Not only do we have here an illustration of continuous progress in invention and use, but also an adaptation of new material, for we pass from the use of stone to that of metals, probably in the prehistoric period, although the beginnings of the use of bronze and iron come mainly within the periods of historical records.

      It is not possible here to follow the interesting history of the glacial movement, but a few words of explanation seem necessary. The Ice Age, or the glacial period, refers to a span of time ranging from 500,000 years ago, at the beginning of the first glaciation, to the close of the post-glacial period, about 25,000 years ago. During this period great ice caps, ranging in the valleys and spreading out on the plains over a broad area, proceeded from the north of Europe to the south, covering at the extreme stages nearly the entire surface of the continent. This great movement consists of four distinct forward movements and their return movements. There is evidence to show that before the south movement of the first great ice cap, a temperate climate extended very far toward the pole and gave opportunity for vegetation now extinct in that region.

      But as the river of ice proceeded south, plants and animals retreated before it, some of them changing their nature to endure the excessive cold. Then came a climatic change which melted the ice and gradually drove the margin of the glacier farther north. Immediately under the influence of the warm winds the vegetation and animals followed slowly at a distance the movement of the glacier. Then followed a long inter-glacial period before the southerly movement of the returning ice cap. This in turn retreated to the north, and thus four separate times this great movement, one of the greatest geological phenomena of the earth, occurred, leaving an opportunity to study four different glacial periods with three warmer interglacial and one warm post-glacial.

      This movement gave great opportunity for the study of geology, paleontology, and the archeology of man. That is, the story of the relationship of the earth to plant, animal, and man was revealed. The regularity of these movements and the amount of material evidence found furnish a great opportunity for measuring geological time movements and hence the life of plants and animals, including man.

      The table on page 64 will contribute to the clearness of this brief statement about the glacial periods.

THE ICE AGE IN EUROPE11

      Geological time-unit 25,000 years

       Prehistoric Types of the Human Race. – The earliest record of human life yet discovered is the Pithecanthropus Erectus (Trinil), the apelike man who walked upright, found in Java by Du Bois, about the year 1892. Enough of the skeletal remains of human beings were found at this time to indicate a man of rather crude form and low brain capacity (about 885 c.c.), with possible powers of speech but with no probably developed language or no assumption of the acquaintance with the arts of life.12

      The remains of this man associated with the remains of one other skeleton, probably a woman, and with the bones of extinct animals, were found in a geological stratum which indicates his age at about 500,000 years. Professor McGregor, after a careful anatomical study, has reproduced the head and bust of Pithecanthropus, which helps us to visualize this primitive species as of rather low cultural type. The low forehead, massive jaw, and receding chin give us a vision of an undeveloped species of the human race, in some respects not much above the anthropoid apes, yet in other characters distinctly human.

      There

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