Part 2

Not only do we know that a creating God is a mere guess; that he is unthinkable in quantity or quality, that he bears no conceivable mark of reality; not only do we know that the creation of a universe out of nothing is wholly unintelligible; but the evidence of astronomy points clearly to the conclusion that our planet has been evolved by condensation from a nebula—from the raw material of which worlds are made; the evidence of geology portrays the fact that the earth has become what it is through a process of continuous change covering many millions of years; and the evidence of botany and of biology, studied in living forms and in fossil remains, proves conclusively that the plants and animals of the world have acquired their present character and mould as a result of infinite variations from and improvements upon the first simple forms of life that arose in the primeval world.

Not creation, then, but evolution, is the secret of the world’s infinite diversity of things. Nothing was made; everything has grown. Perfection is not at the beginning, but at the end of nature’s efforts. All things have been fashioned by a process of endless transformation—blind, boundless, staggering, stumbling—at times falling back, but on the whole moving forward, pressed by the relentless forces inherent in substance and shaped in accordance with immutable law. Such a process has covered the earth with its amazing display of vegetation, and with its strange and wondrous population of things that swim and creep and fly and run.

In sketching the story of evolution, as that story is revealed to us by science, let us begin with the evolution of the starry heavens, that we may learn how the world was born.

As the giant telescope sweeps the abysmal depths of space over a distance of at least 4,000 billion miles, it reveals here and there among the hundred million stars, vast patches of cloud-like material. This material is called nebula, and it is the original substance of which all suns and planets are made. One hundred and twenty thousand of these nebulæ come within the range of the great Crossley Reflector at the Lick Observatory. The telescope photographs the nebula—celestial photography is one of the most interesting and instructive branches of modern astronomy—and when you look at a picture of a nebula, you see an actual photograph of an object that marks the beginning of Nature’s work.

According to Sir Robert Stawell Ball, the nebula in Orion (Fig. 1), one of the most beautiful objects revealed by the telescope, covers an area more than a million times larger than that occupied by our entire solar system. Many of the nebulæ are of the spiral form, which shows their whirling motion. To the astronomer, the Great Spiral Nebula (Fig. 2) represents a mighty sun and system of planets in process of formation. Fig. 3 shows an elongated, irregular nebula, from the Constellation Cygnus. This sketchy streak of nebulous material, although it is still many millions of miles wide, is but the remaining thread of a once mighty nebula that has condensed and is still condensing into the surrounding stars.

The nebulæ represent various stages of evolution into suns and worlds. Some resemble great clouds of rarified matter; some are distinctly spiral in form; some show advanced condensation into stars with attendant planetary systems. The stars, too, exhibit various degrees of progress from their birth in the nebula. Some are white, which shows that they are young; some are yellow, which indicates that they have reached middle age; some are red, which is the mark of their declining years.

So the stars, the glowing suns, grow old and die, and, lifeless, wheel in space, like mighty cinders cold and dark, reflecting, like the moon, the light that shines on them from brilliant orbs.

The moon (Fig. 4) is a dead star. Its light and heat are gone. It wheels in space, an extinct cinder, and by the borrowed light which enables us to see the craters on its surface, it prophesies for us the fate that one day will overtake the earth. But that will be millions of years from now; so we need not worry!

But how is the nebula formed? The cluster in the constellation Hercules (Fig. 5), if it is not in fact a colossal nebula, shows that some of the stars are very close together. Now, these immense objects, that in blind fury dash through space, may come into collision with one another and explode into a nebulous cloud; or they may plough through dense swarms of meteorites, with a resultant explosion on a smaller scale; or, torn by internal convulsions, they may burst into fragments and scatter their dead dust over the abyss of space. In one or all of these ways the nebula is born, to begin again the recurring cycle of Nature’s life.

Is there further evidence of this? There is. On the night of February 21, in the year 1901, a luminous object appeared in the constellation Perseus. From a region where all was darkness the night before, a new and wondrous body now blazed forth its treasures of light. To the astronomers, who with lively curiosity watched the new birth for months, it meant that a tremendous conflagration had taken place in the heavens. A new nebula had been given to the universe, not, however, on the night when its light was first seen, but when Napoleon was dazzling the world with his victories; for the glowing mass was 500 billion miles away, and its messenger light, flying across space with the awful velocity of 186,000 miles a second, had been hurrying ninety-nine years to bring the news to our world!

Science now warrants a further step—one which reveals the origin and nature of matter—the ultimate source of the nebula itself.

Ether fills all space. It penetrates even the most solid substances. The universe of matter swims in an ocean of ether. Only by the presence of ether is the force of gravitation made possible—it must have ether upon which to act. The wings of ether alone transmit to us the light of the sun and stars. Now science is telling us that this indispensable ether, this infinitely attenuated and invisible substance, is the birthplace of matter—that atoms of matter are composed of minute centres of energy, or electrons, in ether. The atom is built of thousands of electrons whirling with inconceivable velocity in the space of their tiny, invisible universe; just as the visible universe is composed of myriads of suns and planets rushing forward through the boundless etherial ocean. Matter, then, whether nebulous or solid, was evolved out of the ether.

FIG. 6.—A PILLAR OF STRATIFIED ROCKS.

This illustration and others in this book are reproduced from Dennis Hird’s excellent work, “A Picture Book of Evolution,” with the kind permission of the publishers, Watts & Co., London.]

Millions of ages ago, a collision or an explosion produced a nebula in the region now occupied by our solar system. That nebula spread out over thousands of millions of miles of space. Here and there, in its mighty body, a more solid nucleus drew to itself volumes of the surrounding substance. In this manner the planets arose, leaving the sun, with his giant mass, in the center of the field. As the nebula revolved in one direction, mathematical necessity imparted to all the forming bodies a whirling motion around the central sphere. The smaller bodies cooled rapidly, so to speak, and crusted over; but the sun, owing to his immense bulk, has continued to glow through all these countless ages, and still sends forth enough light and heat to illuminate and warm many billions of worlds like ours. How long a time has elapsed since the earth began to condense from the nebula, the human mind cannot conceive; but Sir G. H. Darwin, the son of Charles Darwin, declares it is not unreasonable to suppose that from five hundred to a thousand million years have passed away since the moon was detached from the earth.

4, morula; 5, section through blastula showing hollow sphere; 6, gastrula showing outer layer of cells (epiblast) and inner layer (hypoblast); the 6 is at the mouth of the cavity (enteron) of the gastrula. From Dr. D. Kerfoot Shute’s “A First Book in Organic Evolution.” Courtesy of The Open Court Publishing Co.]

When the moon was born, the earth was in a plastic state, and many millions of years had yet to elapse before anything like a solid surface could begin to appear upon it. When, at length, the cooling globe did begin to form a crust, that crust was from time to time shattered to fragments by violent eruptions from within. Later, the immense quantities of hydrogen and oxygen that were in the atmosphere combined into molecules of water, and torrents of rain settled upon the hot surface of the earth. Owing to the large admixture of carbonic acid gas which it contained, the atmosphere was then fifty times heavier than it is to-day; but notwithstanding this great pressure upon it, the water that settled on the hot crust of the earth could not remain, and was sent, hissing, into the air in clouds of steam. The time came, however, when the cooling surface of the planet no longer offered such vigorous resistance to the water that fell upon it, and gradually as the rain fell, the earth became almost entirely covered with a boiling ocean. But the hot earth, even under the enormous weight of its ocean and its dense air, was restless, and as time passed away, great stretches of land emerged. Upon this new land, the rain now poured down in floods. This caused a great washing of debris into the surrounding sea. There the debris settled, and beneath the tremendous pressure of the ocean, it became solidified into the oldest stratified rocks.

The rock pillar (Fig. 6) represents the rock formation of the crust of the earth. It gives us an idea of what a cross-section of the earth’s crust would look like, if all the rock deposits could be found superimposed one above the other in any one place. These rocks, built up layer upon layer, by sedimentary deposits in the ocean, are believed by geologists to reach a depth of more than forty miles; and it is held that it must have required at least a hundred million years—perhaps a thousand million years—to lay down all the strata, all the series of layers of rock, that form the crust of the globe.

That these immense depths of rock have been formed by a slow process of growth, of gradual up-building, is certain. The world was not made in a day. It has grown through innumerable ages. It is still growing. At the present time, the rivers of England are carrying away thousands of tons of land every year and depositing it on the floor of the sea. Every year the Mississippi river carries four hundred million tons of solid material into the Gulf of Mexico. This one stream alone displaces more than a million tons of solid matter every day. Similar things are occurring, in greater or less degree, in every part of the world. Everywhere rivers are widening and deepening their channels, cutting their way into mountains, depositing sediment for rock formations, or overflowing and fertilizing soil; everywhere mountains and hills are being worn down by the action of the elements; continents are crumbling into the ocean; island surfaces are rising above or falling beneath the waves. Nature is ever flowing. Throughout her infinite domain there is everlasting movement. Her trademark is eternal change. Nowhere is she at rest. Her labors never cease. To-day, as in the past, she builds and destroys. In her endless process of evolution, every day is a day of creation.

This illustration and several others used in this book are reprinted from J. A. S. Watson’s “Evolution.” Courtesy of The Frederick A. Stokes Co.]

These rocks contain fossils, the skeletons of creatures that lived during the periods when the rocks were being formed. This fact is one of the keys to the temple of evolution; for when we know the kind of fossils the different rocks contain, as we rise from the lower to the higher, we know the kind of creatures that lived in the various periods when those rocks were formed. Let myth-makers say what they will, Nature does not lie.

As the crust of the earth cooled, the enveloping ocean gradually lost its high temperature, and having fallen far below the boiling point, continued to be warm for ages. In that warm primeval ocean, where the various elements entered into all sorts of combinations, the necessary elements combined in the proper proportions, and, as a result of that happy combination, life was born into the world. Just as the requisite proportions of charcoal, sulphur and saltpeter unite in making gunpowder—a high explosive, vastly different from its constituent elements—so, simple elements, uniting in due proportions, produced the phenomenon of living matter.

Whether life is still being evolved from non-living matter, or whether its origin was confined to a peculiar set of favorable conditions—very high temperature, and unusual chemical and electrical conditions—in the early world, remains as yet unknown. On this question, the most distinguished biologists entertain diverse opinions. Among those who hold that the evolution of life is still one of the ordinary processes of Nature’s day’s work may be mentioned Professor Benjamin Moore, F.R.S., whose views are set forth in his excellent little work, “The Origin and Nature of Life.”

All living things, from the blade of grass to the giant oak, from the worm to the philosopher, are composed of cells, and all cells are composed of protoplasm. Protoplasm is, therefore, the physical basis of life. This wonderful substance is a compound of carbon, hydrogen, nitrogen and oxygen, and the story of the evolution of living things spells the limitless transformations of which this vital substance is capable.

In the world of to-day, we see the finished forms that have been beaten out, as it were, upon the anvil of the evolutionary process; and if we would appreciate the progressive march that life has made, from the simple forms of early days to the highly developed and complex creatures of to-day, we must trace the story of evolution through the numberless ages of the past.

The first living things consisted of a single cell—the Protozoa. As this cell grew, it divided into two; the two, having grown somewhat, divided into four; the four into eight; the eight into sixteen, and so on. In this way, the growing cells increased their numbers by division, and what was at first a single cell became an organized group of cells. Fig. 7 illustrates the process of division and growth from the single cell—the fertilized ovum—to the gastrula. This division is the law of life. Every living creature begins its existence in this way.

Gradually, some cells specialized in the performance of the simplest animal functions, like the catching of food and digestion; and in the course of time, such simple forms of life as sponges and marine worms appeared. From flat worms, life advanced to the annelid or ringed worms—little creatures with a food canal and a body cavity filled with blood. In the worm begins the first development of the brain. A few sensitive cells in the fore end of the body, that beginning of mental life, is a far-flung prophecy of the genius that will one day thrill the world. Primitive depressions, lined with pigment cells, in the worm-like head, represent Nature’s first reaching for eyes; two other sensitive nerve pits are the beginning of the nose; yet a further pair of susceptible concave surfaces are destined to develop into the ears of land animals. Creatures with these primitive structures still exist among Nature’s lowly forms.

Australian Lung Fish, Ceratodus (top); South African Lung Fish, Protopterus (middle); South American Lung Fish, Lepidosiren (bottom).]