The long road I have in mind is the long road of evolution,—the road you and I have traveled in the guise of humbler organisms, from the first unicellular life in the old Cambrian seas to the complex and highly specialized creature that rules supreme in the animal kingdom to-day. Surely a long journey, stretching through immeasurable epochs of geologic time, and attended by vicissitudes of which we can form but feeble conceptions.
The majority of readers, I fancy, are not yet ready to admit that they, or any of their forebears, have ever made such a journey. We have all long been taught that our race was started upon its career only a few thousand years ago, started, not amid the warrings of savage elemental nature, but in a pleasant garden with everything needed close at hand. This belief has faded a good deal in our time, especially among thoughtful persons; but in a modified form, as the special creation theory, it held sway in the minds of the older naturalists like Agassiz and Dawson, long after Darwin had launched his revolutionary doctrine of our animal origin, putting man in the same zoological scheme as the lower orders.
We are slow to adjust our minds to the revelations of science, they have been so long adjusted to a revelation, so-called, of an entirely different character. It gives them a wrench more or less violent when we try to make them at home and at their ease amid these new and startling disclosures. To many good people evolution seems an ungodly doctrine, like setting up a remorseless logic in the place of an omnipresent Creator. But there is no help for it. Science has fairly turned us out of our comfortable little anthropomorphic notion of things into the great out-of-doors of the universe. We must and will get used to the chill, yea, to the cosmic chill, if need be. Our religious instincts will be all the hardier for it.
When we accepted Newton's discovery of the force called gravitation, we virtually surrendered ourselves to the enemy, and started upon a road, the road of natural causation, that traverses the whole system of created things. We cannot turn back; we may lie down by the roadside and dream our old dreams, but our children and their children will press on, and will be exhilarated by the journey.
It is at first sight an unpalatable truth that evolution confronts us with, and it requires courage calmly to face it. But it is in perfect keeping with the whole career of physical science, which is forever directing our attention to common near-at-hand facts for the key to remote and mysterious occurrences.
It seems to me that evolution adds greatly to the wonder of life, because it takes it out of the realm of the arbitrary, the exceptional, and links it to the sequence of natural causation. That man should have been brought into existence by the fiat of an omnipotent power is less an occasion for wonder than that he should have worked his way up from the lower non-human forms. That the manward impulse should never have been lost in all the appalling vicissitudes of geologic time, that it should have pushed steadily on, through mollusk and fish and amphibian and reptile, through swimming and creeping and climbing things, and that the forms that conveyed it should have escaped the devouring monsters of the earth, sea, and air till it came to its full estate in a human being, is the wonder of wonders.
In like manner, evolution raises immensely the value of the biological processes that are everywhere operative about us, by showing us that these processes are the channels through which the creative energy has worked, and is still working. Not in the far-off or in the exceptional does it seek the key to man's origin, but in the sleepless activity of the creative force, which has been pushing onward and upward, from the remotest time, till it has come to full fruition in man.
It is easy to inject into man's natural history a supernatural element, as nearly all biologists and anthropologists before Darwin's time did, and as many serious people still do. It is too easy, in fact, and the temptation to do so is great. It makes short work of the problem of man's origin, and saves a deal of trouble. But this method is more and more discredited, and the younger biologists and natural philosophers accept the zoological conception of man, which links him with all the lower forms, and proceed to work from that.
When we have taken the first step in trying to solve the problem of man's origin, where can we stop? Can we find any point in his history where we can say, Here his natural history ends, and his supernatural history begins? Does his natural history end with the pre-glacial man, with the cave man, or the river-drift man, with the low-browed, long-jawed fossil man of Java,—Pithecanthropus erectus, described by Du Bois? Where shall we stop on his trail? I had almost said "step on his tail," for we undoubtedly, if we go back far enough, come to a time when man had a tail. Every unborn child at a certain stage of its development still has a tail, as it also has a coat of hair and a hand-like foot. But could we stop with the tailed man—the manlike ape, or the apelike man? Did his Creator start him with this appendage, or was it a later suffix of his own invention?
If we once seriously undertake to solve the riddle of man's origin, and go back along the line of his descent, I doubt if we can find the point, or the form, where the natural is supplanted by the supernatural as it is called, where causation ends and miracle begins. Even the first dawn of protozoic life in the primordial seas must have been natural, or it would not have occurred,—must have been potential in what went before it. In this universe, so far as we know it, one thing springs from another; the sequence of cause and effect is continuous and inviolable.
We know that no man is born of full stature, with his hat and boots on; we know that he grows from an infant, and we know the infant grows from a fetus, and that the fetus grows from a bit of nucleated protoplasm in the mother's womb. Why may not the race of man grow from a like simple beginning? It seems to be the order of nature; it IS the order of nature,—first the germ, the inception, then the slow growth from the simple to the complex. It is the order of our own thoughts, our own arts, our own civilization, our own language.
In our candid moments we acknowledge the animal in ourselves and in our neighbors,—especially in our neighbors,—the beast, the shark, the hog, the sloth, the fox, the monkey; but to accept the notion of our animal origin, that gives us pause. To believe that our remote ancestor, no matter how remote in time or space, was a lowly organized creature living in the primordial seas with no more brains than a shovel-nosed shark or a gar-pike, puts our scientific faith to severe test.
Think of it. For countless ages, millions upon millions of years, we see the earth swarming with life, low bestial life, devouring and devoured, myriads of forms, all in bondage to nature or natural forces, living only to eat and to breed, localized, dependent upon place and clime, shaped to specific ends like machines,—to fly, to swim, to climb, to run, to dig, to drill, to weave, to wade, to graze, to crush,—knowing not what they do, as void of conscious purpose as the thorns, the stings, the hooks, the coils, and the wings in the vegetable world, making no impression upon the face of nature, as much a part of it as the trees and the stones, species after species having its day, and then passing off the stage, when suddenly, in the day before yesterday in the geologic year, so suddenly as to give some color of truth to the special creation theory, a new and strange animal appears, with new and strange powers, separated from the others by what appears an impassable gulf, less specialized in his bodily powers than the others, but vastly more specialized in his brain and mental powers, instituting a new order of things upon the earth, the face of which he in time changes through his new gift of reason, inventing tools and weapons and language, harnessing the physical forces to his own ends, and putting all things under his feet,—man the wonder-worker, the beholder of the stars, the critic and spectator of creation itself, the thinker of the thoughts of God, the worshiper, the devotee, the hero, spreading rapidly over the earth, and developing with prodigious strides when once fairly launched upon his career. Can it be possible, we ask, that this god was fathered by the low bestial orders below him,—instinct giving birth to reason, animal ferocity developing into human benevolence, the slums of nature sending forth the ruler of the earth. It is a hard proposition, I say, undoubtedly the hardest that science has ever confronted us with.
Haeckel, discussing this subject, suggests that it is the parvenu in us that is reluctant to own our lowly progenitors, the pride of family and position, like that of would-be aristocratic sons who conceal the humble origin of their parents. But it is more than that; it is the old difficulty of walking by faith where there is nothing visible to walk upon: we lack faith in the efficiency of the biologic laws, or any mundane forces, to bridge the tremendous chasm that separates man from even the highest of the lower orders. His radical unlikeness to all the forms below him, as if he moved in a world apart, into which they could never enter, as in a sense he does, is where the difficulty lies. Moreover, evolution balks us because of the inconceivable stretch of time during which it has been at work. It is as impossible for us to grasp geological time as sidereal space. All the standards of measurement furnished us by experience are as inadequate as is a child's cup to measure the ocean.
Several million years, or one million years,—how can we take it in? We cannot. A hundred years is a long time in human history, and how we pause before a thousand! Then think of ten thousand, of fifty thousand, of one hundred thousand, of ten hundred thousand, or one million, or of one hundred million! What might not the slow but ceaseless creative energy do in that time, changing but a hair in each generation! If our millionaires had to earn their wealth cent by cent, and carry each cent home with them at night, it would be some years before they became millionaires. This is but a faint symbol of the slow process by which nature has piled up her riches. She has had no visions of sudden wealth. To clothe the earth with soil made from the disintegrated mountains—can we figure that time to ourselves? The Orientals try to get a hint of eternity by saying that when the Himalayas have been ground to powder by allowing a gauze veil to float against them once in a thousand years, eternity will only have just begun. Our mountains have been pulverized by a process almost as slow. In our case the gauze veil is the air, and the rains, and the snows, before which even granite crumbles. See what the god of erosion, in the shape of water, has done in the river valleys and gorges—cut a mile deep in the Colorado canyon, and yet this canyon is but of yesterday in geologic time. Only give the evolutionary god time enough and all these miracles are surely wrought.
Truly it is hard for us to realize what a part time has played in the earth's history,—just time, duration,—so slowly, oh, so slowly, have the great changes been brought about! The turning of mud and silt into rock in the bottom of the old seas seems to have been merely a question of time. Mud does not become rock in man's time, nor vegetable matter become coal. These processes are too slow for us. The flexing and folding of the rocky strata, miles deep, under an even pressure, is only a question of time. Allow time enough and force enough, and a layer of granite may be bent like a bow. The crystals of the rock seem to adjust themselves to the strain, and to take up new positions, just as they do, much more rapidly, in a cake of ice under pressure. Probably no human agency could flex a stratum of rock, because there is not time enough, even if there were power enough. "A low temperature acting gradually," says my geology, "during an indefinite age would produce results that could not be otherwise brought about even through greater heat." "Give us time," say the great mechanical forces, "and we will show you the immobile rocks and your rigid mountain chains as flexible as a piece of leather." "Give us time," say the dews and the rains and the snowflakes, "and we will make you a garden out of those same stubborn rocks and frowning ledges." "Give us time," says Life, starting with her protozoans in the old Cambrian seas, "and I will not stop till I have peopled the earth with myriad forms and crowned them all with man."
Dana thinks that had "a man been living during the changes that produced the coal, he would not have suspected their progress," so slow and quiet were they. It is probable that parts of our own sea-coast are sinking and other parts rising as rapidly as the oscillation of the land and sea went on that resulted in the laying down of the coal measures.
An eternity to man is but a day in the cosmic process. In the face of geologic time, man's appearance upon the earth as man, with a written history, is something that has just happened; it was in this morning's paper, we read of it at breakfast. As evolution goes, it will not be old news yet for a hundred thousand years or so, and by that time, what will he have done, if he goes on at his present rate of accelerated speed? Probably he will not have caught the gods of evolution at their work, or witnessed the origin of species by natural descent, these things are too slow for him; but he will certainly have found out many things that we are all eager to know.
In nature as a whole we see results and not processes. We see the rock strata bent and folded, we see the whole mountain-chains flexed and shortened by the flexure; but had we been present, we should not have suspected what was going on. Our little span of life does not give us the parallax necessary. The rock strata, miles thick, may be being flexed now under our feet, and we know it not. The earth is shrinking, but so slowly! When, under the slow strain, the strata suddenly give way or sink, and an earthquake results, then we know something has happened.
A recent biologist and physicist thinks, and doubtless thinks wisely, that the reason why we have never been able to produce living from non-living matter in our laboratories, is that we cannot take time enough. Even if we could bring about the conditions of the early geologic ages in which life had its dawn, which of course we cannot, we could not produce life because we have not geologic time at our disposal.
The reaction which we call life was probably as much a cosmic or geologic event as were the reactions which produced the different elements and compounds, and demanded the same slow gestation in the womb of time. During what cycles upon cycles the great mother-forces of the universe must have brooded over the inorganic before the organic was brought forth! The archean age, during which the brooding seems to have gone on, was probably as long as all the ages since.
How we are baffled when we talk about the beginning of anything in nature or in our own lives! In our experience there must be a first, but when did manhood begin; when did puberty, when did old age, begin? When did each stage of our mental growth begin? When or where did the English language begin, or the French, or the German? Was there a first English word spoken? From the first animal sound, if we can conceive of such, up to the human speech of to-day, there is an infinite gradation of sounds and words.
Was there a first summer, a first winter, a first spring? There could hardly have been a first day even for ages and ages, but only slowly approximating day. After an immense lapse of time the air must have cleared and the day become separated from the night, and the seasons must have become gradually defined. Things slowly emerge one after another from a dim, nebulous condition, both in our own growth and experience and in the development of the physical universe.
In nature there is no first and last. There is an endless beginning and an endless ending. There was no first man or first woman, no first bird, or fish, or reptile. Back of each one stretches an endless chain of approximating men and birds and reptiles.
This talk about the time and place where man began his existence seems to me misleading, because it appears to convey the idea that he began as man at some time, in some place. Whereas he grew. He began where and when the first cell appeared, and he has been on the road ever since. There is no point in the line where he emerged from the not-man and became man. He was emerging from the not-man for millions of years, and when you put your finger on an animal form and say, This is man, you must go back through whole geologic periods before you reach the not-man. If Darwin is right, there is no more reason for believing that the different species or forms of animal life were suddenly introduced than there is for believing that the soil, or the minerals, gold, silver, diamonds, or vegetable mold and verdure were suddenly introduced.
If we know anything of the earth's past history, we know that the continents were long in forming, that they passed through many vicissitudes of heat and cold, of fire and flood, of upheaval and subsidence—that they had, so to speak, their first low, simple rudimentary or invertebrate life, that they were all slow in getting their backbones, slower still in clothing their rock ribs with soil and verdure, that they passed through a sort of amphibian stage, now under water, now on dry land, that their many kinds of soils and climes were not differentiated and their complex water-systems established till well into Tertiary times—in short, that they have passed more and more from the simple to the complex, from the disorganized to the organized. When man comes to draw his sustenance from their breasts, may they not be said to have reached the mammalian stage?
The fertile plain and valley and the rounded hill are of slow growth, immensely slow. But any given stage of the earth has followed naturally from the previous stage, only more and more and higher and higher forces took a hand in the game. First its elements passed through the stage of fire, then through the stage of water, then merged into the stage of air. More and more the aerial elements—oxygen, carbon, nitrogen—have entered into its constituents and fattened the soil. The humanizing of the earth has been largely a process of oxidation. More than disintegrated rock makes up the soil; the air and the rains and the snows have all contributed a share.
The history of the soil which we turn with our spade, and stamp with our shoes, covers millions upon millions of years. It is the ashes of the mountains, the leavings of untold generations of animal and vegetable life. It came out of the sea, it drifted from the heavens; it flowed out from the fiery heart of the globe; it has been worked over and over by frost and flood, blown by winds, shoveled by ice, —mixed and kneaded and moulded as the house-wife kneads and moulds her bread,—refining and refining from age to age. Much of it was held in solution in the primordial seas, whence it was filtered and used and precipitated by countless forms of marine life, making a sediment that in time became rocks, that again in time became continents or parts of them, which the aerial forces reduced to soil. Indeed, the soil itself is an evolution, as much so as the life upon it.
We probably have little conception of how intimate and cooperative all parts of the universe are with one another,—of the debt we owe to the farthest stars, and to the remotest period of time. We must owe a debt to the monsters of Mesozoic and Caenozoic time; they helped to fertilize the soil for us, and to discipline the ruder forces of life. We owe a debt to all that has gone before: to the heavens above and to the earth-fires beneath, to the ice-sheets that ground down the mountains, and to the ocean currents. Just as we owe a debt to the men and women in our line of descent, so we owe a debt to the ruder primordial forces that shaped the planet to our use, and took a hand in the game of animal life.
The gods of evolution had served a long apprenticeship; they had gained proficiency and were master workmen. Or shall we say that the elements of life had become more plastic and adaptable, or that the life fund had accumulated, so to speak? Had the vast succession of living beings, the long experience in organization, at last made the problem of the origin of man easier to solve?
One fancies every living thing as not only returning its mineral elements to the soil, but as in some subtle way leaving its vital forces also, and thus contributing to the impalpable, invisible store-house of vital energy of the globe.
At first among the mammalian tribes there was much muscle and little brains. But in the middle Tertiary the mammal brain began suddenly to enlarge, so that in our time the brain of the horse is more than eight times the size of the brain of his progenitor, the dinoceras of Eocene times.
Nature seems to have experimented with brains and nerve ganglia, as she has with so many other things. The huge reptilian creatures of Mesozoic time—the various dinosaurs—had ridiculously small heads and brains, but they had what might be called supplementary brains well toward the other end of the body,—great nervous masses near the sacrum, many times the size of the ostensible brain, which no doubt performed certain brain functions. But the principle of centralization was at work, and when in later time we reach the higher mammalian forms, we find these outlying nervous masses called in, so to speak, and concentrated in the head.
Nature has tried the big, the gigantic, over and over, and then abandoned it. In Carboniferous times there was a gigantic dragon-fly, measuring more than two feet in the expanse of wings. Still earlier, there were gigantic mollusks and sea scorpions, a cephalopod larger than a man; then gigantic fishes and amphibians and reptiles, followed by enormous mammals. But the geologic record shows that these huge forms did not continue. The mollusks that last unchanged through millions of years are the clam and the oyster of our day. The huge mosses and tree-ferns are gone, and only their humbler types remain. Among men giants are short-lived.
On the other hand, the steady increase in size of certain other species of animals during the later geologic ages is a curious and interesting fact. The first progenitors of the elephant that have been found show a small animal that steadily grew through the ages till the animal as we now find it is reached. Among the invertebrates this same progressive increase in size has been noted, a small shell in the Devonian becoming enormous in the Triassic. Certain species of sharks of medium size in the lower Eocene continue to increase till they attain the astounding dimensions in the Miocene and Pliocene of over one hundred feet long. A certain fish appearing in the Devonian as a small fish of seven centimetres in length, becomes in the Carboniferous era a creature twenty-seven centimetres in length. Among the mammals of Tertiary times this same law of steady increase in size has been operative, as seen in the Felidae, the stag, and the antelope. Man himself has, no doubt, been under the same law, and is probably a much larger animal than any of his Tertiary ancestors. In the vegetable world this process, in many cases, at least, has been reversed, and the huge treelike club-mosses and horsetails of Carboniferous times have dwindled in our time to very insignificant herbaceous forms.
Animals of overweening size are handicapped in many ways, so that nature in most cases finally abandons the gigantic and sticks to the medium and the small.
Can we fail to see the significance of the order in which life has appeared upon the globe—the ascending series from the simple to the more and more complex? Can we doubt that each series is the outcome of the one below it—that there is a logical sequence from the protozoa up through the invertebrates, the vertebrates, to man? Is it not like all that we know of the method of nature? Could we substitute the life of one period for that of another without doing obvious violence to the logic of nature? Is there no fundamental reason for the gradation we behold?
All animal life lowest in organization is earliest in time, and vice versa, the different classes of a sub-kingdom, and the different orders of a class, succeeding one another, as Cope says, in the relative order of their zoological rank. Thus the sponges are later than the protozoa, the corals succeed the sponges, the sea-urchins come after the corals, the shell-fish follow the sea-urchins, the articulates are later than the shell-fish, the vertebrates are later than the articulates. Among the former, the amphibian follows the fish, the reptile follows the amphibian, the mammal follows the reptile, and non-placental mammals are followed by the placental.
It almost seems as if nature hesitated whether to produce the mammal from the reptile or from the amphibian, as the mammal bears marks of both in its anatomy, and which was the parent stem is still a question.
The heart started as a simple tube in the Leptocardii; it divides itself into two cavities in the fishes, into three in the reptiles, and into four in the birds and mammals. So the ossification of the vertebral column takes place progressively, from the Silurian to the middle Jurassic.
The same ascending series of creation as a whole is repeated in the inception and development of every one of the higher animals to-day. Each one begins as a single cell, which soon becomes a congeries of cells, which is followed by congeries of congeries of cells, till the highly complex structure of the grown animal with all its intricate physiological activities and specialization of parts, is reached. It is typical of the course of the creative energy from the first unicellular life up to man, each succeeding stage flowing out of, and necessitated by, the preceding stage.
How slowly and surely the circulatory system improved! From the cold-blooded animal to the warm-blooded is a great advance. In the warm-blooded is developed the capacity to maintain a fixed temperature while that of the surrounding medium changes. The brain and nervous system display the same progressive ascent from the brainless acrania, up through the fishes, batrachia, reptiles, and birds to the top in mammals. The same with the skeletons in the invertebrates, from membrane to cartilage, from cartilage to bone, so that the primitive cartilage remaining in any part of the skeleton is considered a mark of inferiority.
According to Cope, there has been progressive improvement in the mechanism of the body—it has become a better and better machine. The suspension of the lower jaw, so as to bring the teeth nearer the power,—the masseter and related muscles,—was a slow evolution and a great advance. The fin is more primitive than the limb; the limbs themselves display a constantly increasing differentiation of parts from the batrachian to the mammalian. There was no good ankle joint in early Eocene times. The model ankle joint is a tongue and groove arrangement, and this is a later evolution. In Eocene times they were nearly all flat. The arched foot, too, comes in; this is an advance on the flat foot. The bones of the palms and soles are not locked until the later Tertiary. The vertebral column progressed in the same way, from flat to the double curve and the interlocking process, thus securing greatest strength with greatest mobility. In the earliest life locomotion was diffused, later it became concentrated. The worm walks with its whole body.
If we figure to ourselves the geologic history of the earth under the symbol of a year of three hundred and sixty-five days, each day a million years, which is probably not far out of the way, then man, the biped, the Homo sapiens, in relation to this immense past, is of to-day, or of this very morning; while the origin of the first vertebrates, the fishes, from which he has arisen, falls nearer the middle of the great year. Or, dividing this geologic year into four divisions or seasons, primary, secondary, tertiary, and quaternary, the fishes fall in the primary, the reptiles in the secondary, the mammals in the tertiary, and man in the early quaternary.
If the fluid earth hardened, and the seas were formed in the first month of this year, then probably the first beginning of life appeared in the second month, the invertebrate in the third or fourth,—March or April,—the vertebrates in May or June, the amphibians in July or August, the reptiles in August or September, the mammals in October or November, and man in December,—separated from the first beginnings of life by all those millions upon millions of years.
If life is a ferment, as we are told it is, how long it took this yeast to leaven the whole loaf! Man is evidently the end of the series, he is the top of the biological tree. His specialization upon physical lines seems to have ended far back in geologic time; his future specialization and development is evidently to be upon mental and spiritual lines. Nature, as I have said, began to tend more and more to brains in the early Tertiary,—the autumn of the great year; her best harvest began to mature then, her grain began to ripen. Indeed, this increased cephalization of animal life in the fall of the great year does suggest a kind of ripening process, the turning of the sap and milk, which had been so abundant and so riotous in the earlier period, into fibre and fruit and seed.
May it not be that that long and sultry spring and summer of the earth's early history, a time probably longer than has since elapsed, played a part in the development of life analogous to that played by our spring and summer, making it opulent, varied, gigantic, and making possible the condensation and refinement that came with man in the recent period?
The earth is a pretty big apple, and the solar tree upon which it hangs is a pretty big tree, but why may it not have gone through a kind of ripening process for all that? its elements becoming less crude and acrid, and better suited to sustain the higher forms, as the eons passed?
At any rate, the results seem to justify such a fancy. The earth has slowly undergone a change that may fairly be called a ripening process; its soil has deepened and mellowed, its harsher features have softened, more and more color has come to its surface, the flowers have bloomed, the more succulent fruits have developed, the air has cleared, and love and benevolence and altruism have been born in the world.
Life had to creep or swim long before it could walk, and it walked long before it could fly; it had feeling long before it had eyes, and it no doubt had eyes long before it could hear or smell. It was capable of motion long before it had limbs; it assimilated food long before it had a mouth or a stomach. It had a digestive tract long before it had a spinal cord; it had nerve ganglia long before it had a well-defined brain. It had sensation long before it had perception; it was unisexual long before it was bisexual; it had a shell long before it had a skeleton; it had instinct and reflex action long before it had self-consciousness and reason. Always from the lower to the higher, from the simple to the more complex, and always slowly, gently.
Life has had its foetal stage, its stage of infancy, and childhood, and maturity, and will doubtless have its old age. It took it millions upon millions of years to get out of the sea upon dry land; and it took it more millions upon dry land, or since the Carboniferous age, when the air probably first began to be breathable,—all the vast stretch of the Secondary and Tertiary ages,—to get upright and develop a reasoning brain, and reach the estate of man. Step by step, in orderly succession, does creation move. In the rising and in the setting of the sun one may see how nature's great processes steal upon us, silently and unnoticed, yet always in sequence, stage succeeding stage, one thing following from another, the spectacular moment of sunset following inevitably from the quiet, unnoticed sinking of the sun in the west, or the startling flash of his rim above the eastern horizon only the fulfillment of the promise of the dawn. All is development and succession, and man is but the sunrise of the dawn of life in Cambrian or Silurian times, and is linked to that time as one hour of the day is linked to another.
The more complex life became, the more rapidly it seems to have developed, till it finally makes rapid strides to reach man. One seems to see Life, like a traveler on the road, going faster and faster as it nears its goal. Those long ages of unicellular life in the old seas, how immense they appear to have been; then how the age of invertebrates dragged on, millions upon millions of years; then the age of fishes; the Palaeozoic age, how vast—put by Haeckel at thirty-four millions of years, adding rock strata forty-one thousand feet thick; then the Mesozoic or third period, the age of reptiles, eleven million years, with strata twelve thousand feet thick. Then came the Caenozoic age, or age of mammals, three million years, with strata thirty-one hundred feet thick. The god of life was getting in a hurry now; man was not far off. A new device, the placenta, was hit upon in this age, and probably the diaphragm and the brain of animals, all greatly enlarged. Finally comes the Anthropozoic or Quaternary age, the age of man, three hundred thousand years, with not much addition to the sedimentary rocks.
Man seems to be the net result of it all, of all these vast cycles of Palaeozoic, Mesozoic, and Caenozoic life. He is the one drop finally distilled from the vast weltering sea of lower organic forms. It looks as if it all had to be before he could be—all the delay and waste and struggle and pain—all that long carnival of sea life, all that saturnalia of gigantic forms upon the land and in the air, all that rising and sinking of the continents, and all that shoveling to and fro and mixing of the soils, before the world was ready for him.
In the early Tertiary, millions of years ago, the earth seems to have been ripe for man. The fruits and vegetables and the forest trees were much as we know them, the animals that have been most serviceable to us were here, spring and summer and fall and winter came and went, evidently birds sang, insects hummed, flowers bloomed, fruits and grains and nuts ripened, and yet man as man was not.
Under the city of London is a vast deposit of clay in which thousands of specimens of fossil fruit have been found like our date, cocoanut, areca, custard-apple, gourd, melon, coffee, bean, pepper, and cotton plant, but no sign of man. Why was his development so tardy? What animal profited by this rich vegetable life? The hope and promise of the human species at that time probably slept in some lowly marsupial. Man has gathered up into himself, as he traveled his devious way, all the best powers of the animal kingdom he has passed through. His brain supplies him with all that his body lacks, and more. His specialization is in this highly developed organ. It is this that separates him so widely from all other animals.
Man has no wings, and yet he can soar above the clouds; he is not swift of foot, and yet he can out-speed the fleetest hound or horse; he has but feeble weapons in his organization, and yet he can slay or master all the great beasts; his eye is not so sharp as that of the eagle or the vulture, and yet he can see into the farthest depths of siderial space; he has only very feeble occult powers of communication with his fellows, and yet he can talk around the world and send his voice across mountains and deserts; his hands are weak things beside a lion's paw or an elephant's trunk, and yet he can move mountains and stay rivers and set bounds to the wildest seas. His dog can out-smell him and out-run him and out-bite him, and yet his dog looks up to him as to a god. He has erring reason in place of unerring instinct, and yet he has changed the face of the planet.
Without the specialization of the lower animals,—their wonderful adaptation to particular ends,—their tools, their weapons, their strength, their speed, man yet makes them all his servants. His brain is more than a match for all the special advantages nature has given them. The one gift of reason makes him supreme in the world.
We have a stake in all the past life of the globe. It is no doubt a scientific fact that your existence and mine were involved in the first cell that appeared, that the first zoophyte furthered our fortunes, that the first worm gave us a lift. Great good luck came to us when the first pair of eyes were invented, probably by the trilobite back in Silurian times; when the first ear appeared, probably in Carboniferous times; when the first pair of lungs grew out of a fish's air-bladder, probably in Triassic times; when the first four-chambered heart was developed and double circulation established, probably with the first warm-blooded animal in Mesozoic times.
These humble forms started the brain, the nervous system, the circulation, sight, hearing, smell; they invented the liver, the kidneys, the lungs, the heart, the stomach, and led the way to every organ and power my body and mind have to-day. They were the pioneers, they were the dim remote forebears, they conserved and augmented the fund of life and passed it along.
All their struggles, their discipline, their battles, their failures, their successes, were for you and me. Man has had the experience of all the animals below him. He has suffered and struggled as a fish, he has groveled and devoured as a reptile, he has fought and triumphed as a quadruped, he has lived in trees as a monkey, he has inhabited caves with the wolf and the bear, he has roamed the forests and plains as a savage, he has survived without fire or clothes or weapons or tools, he has lived with the mastodon and all the saurian monsters, he has held his own against great odds, he has survived the long battles of the land and the sea, he weathered the ice-sheet that overrode both hemispheres, he has seen many forms become extinct. In the historic period he has survived plague and pestilence, and want and famine. What must he have survived in prehistoric times! What must he have had to contend with as a cave-dweller, as a tree-dweller, as a river-drift man! Before he had tools or weapons what must he have had to contend with!
Nature was full of sap and rioted in rude strength well up to Quaternary times, producing extravagant forms which apparently she had no use for, as she has discontinued them.
In all these things you and I had our part and lot; of this prodigal outpouring of life we have reaped the benefit; amid these bizarre forms and this carnival of lust and power, the manward impulse was nourished and forwarded. In Eocene times nearly half the mammals lived on other animals; it must have been an age of great slaughter. It favored the development of fleetness and cunning, in which we too have an interest. Our rude progenitor was surely there in some form, and escaped the slaughter. Then or later it is thought he took to the trees to escape his enemies, as the rats in Jamaica have taken to the trees to escape the mongoose. To his tree-climbing we probably owe our hand, with its opposing thumb.
In all his disguises he is still our ancestor. His story reads like a fairy book. Never did nimble fancy of childhood invent such transformations—only the transformations are so infinitely slow, and attended with such struggle and suffering. Strike out the element of time and we have before us a spectacle more novel and startling than any hocus-pocus or legerdemain that ever set the crowd agape.
In every form man has passed through, he left behind some old member or power and took on some new. He left his air-bladder and his gills and his fins with the fishes; he got his lungs from the dipnoans, the precursors of the amphibians, and from these last he got his four limbs; he left some part of his anatomy with the reptile, and took something in exchange, probably his flexible neck. Somewhere along his line he picked up the four-chambered heart, the warm blood, the placenta, the diaphragm, the plantigrade foot, the mammary glands—indeed, what has he not picked up on the long road of his many transformations? He left some of his superfluous forty-four teeth with his ancestral quadrumana of Eocene times, and kept thirty-two. He picked up his brain somewhere on the road, probably far back in Palaeozoic times, but how has he developed and enlarged it, till it is now the one supreme thing in the world! His fear, his cunning, his anger, his treachery, his hoggishness—all his animal passions—he brought with him from his animal ancestors; but his moral and spiritual nature, his altruism, his veneration, his religious emotions, his aesthetic perceptions—have come to him as a man, supplementing his lower nature, as it were, with another order of senses—a finer sight, a finer touch, wrought in him by the discipline of life, and the wonder of the world about him, beginning de novo in him only as the wing began de novo in the bird, or the color began de novo in the flower—struck out from preexisting potentialities. The father of the eye is the light, and the father of the ear is the vibration of the air, but the father of man's higher nature is a question of quite another sort. About the only thing in his physical make-up that man can call his own is his chin. None of the orders below him seem to have what can strictly be called a chin.
Man owes his five toes and five fingers to the early amphibians of the sub-carboniferous times. The first tangible evidence of these five toes upon the earth is, to me, very interesting. The earliest record of them that I have heard of is furnished by a slab of shale from Pennsylvania, upon which, while it was yet soft mud, our first five-toed ancestor had left the imprint of his four feet. He was evidently a small, short-legged gentleman with a stride of only about thirteen inches, and he carried a tail instead of a cane. He was probably taking a stroll upon the shores of that vast Mediterranean Sea that occupied all the interior of the continent when he crossed his mud flat. It was raining that morning—how many million years ago?—as we know from the imprint of the raindrops upon the mud. Probably the shower did not cause him to quicken his pace, as amphibians rather like the rain. Just what his immediate forbears were like, or what the forms were that connected him with the fishes, we shall probably never know. Doubtless the great book of the rocky strata somewhere holds the secret, if we are ever lucky enough to open it at the right place. How many other secrets, that evolutionists would like to know, those torn and crumpled leaves hold!
It is something to me to know that it rained that day when our amphibian ancestor ventured out. The weather was beginning to get organized also, and settling down to business. It had got beyond the state of perpetual mist and fog of the earlier ages, and the raindrops were playing their parts. Yet, from all the evidence we have, we infer that the climate was warm and very humid, like that of a greenhouse, and that vegetation, mostly giant ferns and rushes and lycopods, was very rank, but there was no grass, or moss, no deciduous trees, or flowers, or fruit, as we know these things.
A German anatomist says that we have the vestiges of one hundred and eighty organs which have stuck to us from our animal ancestors,—now useless, or often worse than useless, like the vermiform appendix. Eleven of these superannuated and obsolete organs we bring from the fishes, four from amphibians and reptiles. The external ear is a vestige—of no use any more. Our dread of snakes we no doubt inherited from our simian ancestors.
How life refined and humanized as time went on, sobered down and became more meditative, keeping step, no doubt, with the amelioration of the soil out of which all life finally comes. Life's bank account in the soil was constantly increasing; more and more of the inorganic was wrought up into the organic; the value of every clod underfoot was raised. The riot of gigantic forms ceased, and they became ashes. The giant and uncouth vegetation ceased, and left ashes or coal. The beech, the maple, the oak, the olive, the palm came in. The giant sea serpents disappeared; the horse, the ox, the swine, the dog, the quail, the dove came in. The placental mammals developed. The horse grew in size and beauty. When we first come upon his trail, he is a four-hoof-toed animal no larger than a fox. Later on we find him the size of a sheep with one of his toes gone; still later—many hundred thousand years, no doubt—we find him the size of a donkey, with still fewer toes, and so on till we reach the superb creature we know.
The creative energy seems to have worked in geologic time and in the geologic field just as it works here and now, in yonder vineyard or in yonder marsh,—blindly, experimentally, but persistently and successfully. The winged seeds find their proper soil, because they search in every direction; the climbing vines find their support, because in the same blind way they feel in all directions. Plants and animals and races of men grope their way to new fields, to new powers, to new inventions.
Indeed, how like an inventor Nature has worked, constantly improving her models, adding to and changing as experience would seem to dictate! She has developed her higher and more complex forms as man has developed his printing-press, or steam-engine, from rude, simple beginnings. From the two-chambered heart of the fish she made the treble-chambered heart of the frog, and then the four- chambered heart of the mammal. The first mammary gland had no nipples; the milk oozed out and was licked off by the young. The nipple was a great improvement, as was the power of suckling in the young.
Experimenting and experimenting endlessly, taking a forward step only when compelled by necessity,—this is the way of Nature,—experimenting with eyes, with ears, with teeth, with limbs, with feet, with toes, with wings, with bladders and lungs, with scales and armors, hitting upon the backbone only after long trials with other forms, hitting upon the movable eye only after long ages of other eyes, hitting on the mammal only after long ages of egg-laying vertebrates, hitting on the placenta only recently,—experimenting all around the circle, discarding and inventing, taking ages to perfect the nervous system, ages and ages to develop the centralized ganglia, the brain. First life was like a rabble, a mob, without thought or head, then slowly organization went on, as it were, from family to clan, from clan to tribe, from tribe to nation, or centralized government—the brain of man—all parts duly subordinated and directed,—millions of cells organized and working on different functions to one grand end,—cooperation, fraternization, division of labor, altruism, etc.
The cell was the first invention; it is the unit of life,—a speck of protoplasm with a nucleus. To educate this cell till it could combine with its fellows and form the higher animals seems to have been the aim of the creative energy. First the cell, then combinations of cells, then combinations of combinations, then more and more complex combinations till the body of man is reached, where endless confraternities of cells, all with different functions, working to build and sustain different organs,—brain, heart, liver, muscles, nerves,—yet all working together for one grand end—the body and mind of man. In their last analysis, all made up of the same cells—their combinations and organization making the different forms.
Evolution touches all forms but tarries with few. Many are called but few are chosen—chosen to lead the man-impulse upward. Myriads of forms are left behind, like driftwood caught in the eddies of a current. The clam has always remained a clam, the oyster remained an oyster. The cockroach is about the same creature to-day that it was untold aeons ago; so is the shark, and so are many other forms of marine life. Often where old species have gone out and new come in, no progress has been made.
Evolution concentrates along certain lines. The biological tree behaves like another tree, branches die and drop off (species become extinct), others mature and remain, while some central shoot pushes upward. Many of the huge reptilian and mammalian branches perished in comparatively late times.
As nothing is more evident than that the same measure of life or of vital energy—power of growth, power of resistance, power of reproduction—is not meted out equally to all the individuals of a species, or to all species, so it is evident that this power of progressive development is not meted out equally to all races of mankind, or to all of the individuals of the same race. The central impulse of development seems to have come from the East, in historic times at least, and to have followed the line of the Mediterranean, to have culminated in Europe. And this progress has certainly been the work of a few minds—minds exceptionally endowed.
For the most part the barbarian races do not progress. Their exceptional minds or characters do not lead the tribes to higher planes of thought, In all countries we still see these barbarous people which man in his progress has left behind. Our civilization is like a field of light that fades off into shadows and darkness. There is this margin of undeveloped humanity on all sides. Always has it been so in the animal life of the globe; the higher forms have been pushed up from the lower, and the lower have remained and continued to multiply unchanged.
It seems as if some central and cherished impulse had pushed on through each form, and by successive steps had climbed from height to height, gaining a little here and a little there, intensifying and concentrating as time went on, very vague and diffuse at first, embryonic so to speak, during the first half of the great geologic year, but quickening more and more, differentiating more and more, delayed and defeated many times, no doubt, yet never destroyed, leaving form after form unchanged behind it, till it at last reached its goal in man.
After evolution has done all it can do for us toward solving the mystery of creation, much remains unsolved.
Through evolution we see creation in travail-pains for millions of years to bring forth the varied forms of life as we know them; but the mystery of the inception of this life, and of the origin of the laws that have governed its development, remains. What lies back of it all? Who or what planted the germ of the biological tree, and predetermined all its branches? What determined one branch to eventuate in man, another in the dog, the horse, the bird, or the reptile?
From the finite or human point of view we feel compelled to say some vaster being or intelligence must have had the thought of all these things from the beginning or before the beginning.
It is quite impossible for me to believe that fortuitous variation—variation all around the circle—could have resulted in the evolution of man. There must have been a predetermined tendency to variation in certain directions. To introduce chance into the world is to introduce chaos. No more would the waters of the interiors of the continents find their way to the sea, were there not a slant in that direction, than could haphazard variation, though checked and controlled by natural selection, result in the production of the race of man. This view may be only the outcome of deep we dive or high we soar.
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