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discovered which had peculiar interest because the Neanderthal type of skull was associated with the La Naulette jaw. By this time Haeckel had described a type of man lower than existing men and given thereto the name apeman" (Pithecanthropus). In 1891 in Java part of a skull, a tooth and thigh bone were found which closely corresponded to Haeckel's description and has since been known as Pithecanthropus erectus. This man had an estimated brain capacity of 1,000 c.c. or 400 more than any known ape. In 1907 near Heidelberg, Germany, a most interesting jaw was found, unquestionably human, yet resembling the jaw of an ape, with almost no chin yet with the teeth arranged like those of man. In 1912 in Sussex, England, parts of a skull and jaw bone were found in glacial deposits which again indicated an early type. During the last decade a number of other finds of early man have been made which need not be here described.

It is important to note that the brains of these primitive men are about as large as those of living men. The differences of the face and lower jaw would seem to indicate that we are in some instances dealing with a species different from our own. Our actual knowledge of this great process is still very meager. Very little of the earth's surface has been carefully examined. There is every reason to hope that some day we shall be able to reconstruct the tree of life with comparative accuracy and determine the time factor much more definitely than is possible today. Where man first appeared on earth is very problematical. The earliest forms of life probably appeared near the poles for there the temperature was first reduced to the necessary degree. We know that there was once a continent stretching from Iceland to Java and it is interesting to note that all the discoveries of early man are in Europe and Java. In America there is no evidence of men who were not closely related to the Indians.

How long this great process has taken we can only roughly estimate. The geologists claim that some 50,000,000 years have passed since the first stratified rocks were deposited and recent students believe that man has been on earth upwards of a million years.

The history sketched in this chapter should teach us at least one lesson. It is not proper for man to set limits beyond which his knowledge may not go nor to attempt to prevent research because of confidence in existing belief. From time to time man has solved intellectual difficulties which had seemed beyond his powers. Recognizing frankly then that many problems are yet unsolved, it would seem wise to hope that increased study and experiment may furnish the answers. It is to be regretted that men like Bergson should appropriate present knowledge, show how it improves our conception of the universe, and then assume that further information can not be had and take recourse in some revamped "vital principle." Is it not better to follow the plan of Columbus when facing unknown seas, in spite of the terrors of the deep and the fears of superstition, and "Sail on, and on, and on"?

SUGGESTIONS FOR READING

BERGSON, H. Creative Evolution (English trans.). 1911.
CLODD, E. Pioneers of Evolution. 1897.

CRAMPTON, H. E. The Doctrine of Evolution. 1911.

DARWIN, C. Origin of Species. 1859.

Descent of Man. 1871.

DRAPER, J. W. Conflict Between Religion and Science. 1887. ELLIOTT, G. F. S. Prehistoric Man and His Story. 1914. HUXLEY, T. Evidence as to Man's Place in Nature. 1863.

JORDAN, D. S., and KELLOGG, V. L. Evolution and Animal Life. 1908.

KEITH, A. The Antiquity of Man. 1915.

KELLOGG, V. L. Darwinism To-day. 1907.

LECONTE, J. Evolution and Its Relation to Religious Thought.

1891.

MCCABE, J. The Story of Evolution. 1912.

METCALF, M. M. Organic Evolution. 1904.

MORGAN, T. H.

OSBORN, H. F.

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Evolution and Adaptation. 1903.

From the Greeks to Darwin. 1894. Men of the Old Stone Age. 1915. ROMANES, G. J. Darwin and After Darwin. 1892-1897. SCHMUCKER, S. C. The Meaning of Evolution. 1913. STEWARD, A. C. (Ed.). Darwin and Modern Science. 1909. THOMSON, J. A. Darwinism and Human Life. 1910. WALLACE, A. R. Darwinism. 1889.

WHITE, A. D. Warfare of Science with Theology. 1896.

CHAPTER

HEREDITY

Long before man was willing to admit that there might be some organic relationship between himself and other animals, he clearly recognized that he had a body which was maintained and reproduced in similar fashion to theirs. Barring a few illogical exceptions, he believed that each animal reproduced "after its kind," the offspring of lions were lions; of tigers, tigers; of men, men. He had recognized that special traits sometimes appeared generation after generation. So the Romans applied such names as Capitones, Labiones to families characterized by peculiar heads and lips, and so Tacitus explained the features of the Germans by saying that they had an unmixed line of descent. The Israelites had even undertaken to control the color of their cattle by exposing them to influences considered potent. There was no clear idea of the nature of growth or of the facts of reproduction; but no one questioned the fact. Today our interest centers in the attempts to understand the machinery and analyze the methods by which these changes are produced.

Our evidence on these points has come from three distinct and yet overlapping methods of research: (1) cytology, or the study of the cell; (2) the breeding of plants and animals; (3) statistical study and comparison. We have already seen that one-celled plants (bacteria) and animals (protozoa) were discovered shortly after the invention of the microscope. As early as 1651 William Harvey asserts that all living organisms come from eggs. By 1677 the human spermatozoon is described. In 1665 Robert Hooke, examining a section of cork under the microscope, sees that it is made of "little boxes or cells distinguished from one another." It remained for Wolff (1759) to catch the idea that growth resulted from the multiplication of these small units or cells. In 1831 Robert Brown discovered the nucleus in plant cells. In 1835 Felix Dujardin discovered protoplasm which is today called "the material basis of life" and which always exists in cell form. In 1838 M. Schleiden and Theodore Schwann showed that plant and animal cells were similar in structure. In 1861 Max Schultze said that " a cell is a globule of protoplasm surrounding a nucleus" and in the same year Gegenbauer showed that the eggs of all vertebrates were in reality single cells. This was found to be true of the spermatozoa in 1865.

As a result of these discoveries man learned that all forms of life start as single cells and that growth results from their multiplication through a process of division. But many lowly forms separate when they divide or form mere masses or aggregates with the different cells seemingly identical in structure and function. In the higher forms there is a specialization of parts. Thus we find that in some plants roots, stems, leaves and, in many cases a piece of the root separated from the plant, will grow and produce a complete plant again. A bit of begonia leaf under favorable conditions will do the same while a post of willow stuck in the ground often becomes a tree. Man takes advantage of this fact in the growing of many of his choicest plants for he thus increases them more rapidly than he could from seed, and moreover he

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