Parables From Palæontology
IT seems probable that many decades will elapse before the last word will have been said concerning mutations, saltations, germ-plasm, and orthogenesis; but in the meantime it is well established that the Darwinian conception of the survival of the fittest has been a dominant factor in the process of organic evolution. Whatever may have caused new species to originate, there is no doubt that nature has selected for preservation in the struggle for existence those forms of life best adapted to the environmental conditions of time and place. Likewise, it is extremely likely that reams of paper and tons of printers’ ink will be devoted to discussions concerning ‘Virgin Birth’ and resurrection from the dead, before those and kindred subjects will cease to be a fruitful source of controversy. But meanwhile all agree that the keynote of the message brought by the Carpenter of Nazareth was a stirring appeal to demonstrate by conduct that God is the Father of all mankind, to look upon all men with the eyes of a brother, to count it gain to lay down one’s life for a friend.
Underneath the ancient warfare between theology and science, lurking in the distrust of the ‘higher criticism,’ there is an unvoiced, but very real, fear that in the last analysis the doctrine of the survival of the fittest in the struggle for existence is diametrically opposed to the conception of the brotherhood of man; that evolution according to Darwin and Devries and Weissmann is the antithesis of Christianity according to Christ and John and Paul. Subconsciously, that fear drives many a man to trust blindly in the second-century dogma that the coming of the Kingdom of God must be in the nature of a catastrophic innovation through the intervention of a supernatural power. And were that fear justified, all of us would be forced to take that same position, if we still wished to view with optimism the future of man’s world. How else could the heritage of a score of million years be displaced from human life?
This is why the palæontologist makes bold to lay aside for a moment his fossil shells and petrified bones, and to trespass on the precincts of philosopher and preacher. For, after all, it is the palæontologist who must settle the major problems of evolution and in a sense be responsible for the ethical fruits thereof. He is aided and abetted, to be sure, by the embryologist, the anatomist, and the experimenting biometrician; but it is his knowledge which must eventually bring order out of chaos and make clear the path which we, as well as the remotest of our kindred, have trod. He alone can tell of the past inhabitants of our globe, the myriad ancestral types now represented by much-modified offspring, and the many fruitless side-lines which terminated in the total extinction of whole races of creatures. None other can wave his magic wand over a heap of scattered bones and reconstruct a monstrous, sluggish, clumsy dinosaur dining daintily on his half-ton of rushes and herbs each day; or, with a few small teeth and a fragment of jaw as a suggestion, model an insignificant, scrawny, little egg-laying mammal from which was destined to spring, not only man himself, but the majority of domestic animals and the longtoothed, sharp-clawed monarchs of the jungle as well.
Most certainly there are boundaries within which even the palæontologist’s ambitions must be confined. All of us have our limitations. To explain why the processes of evolution have been as they are; to demonstrate whence came the ‘ceaseless urge’ of the lifeimpulse; to suggest the goal toward which it all is tending — these are problems the solutions of which may never be disclosed to him. With Fosdick he must say, ‘The more we know about the world, the more mysterious it is.’ But simply to tell the facts of lifehistory, as interpreted from the hieroglyphics inscribed on rock-ledge and gravel-bank, is no mean contribution to man’s growing fund of wisdom. Knowledge of the habits which have been formed on the long road traversed by mankind in the past cannot fail to be of assistance in lighting the way which beckons toward the future. Information concerning the pitfalls escaped, the quagmires avoided, the blind lanes detected, and the hillsides climbed, may aid in charting safe passage through the unmapped wilderness which lies before us; because narrow is the gate, and straitened the way, which has led to man, and few are those who have found it.
It was Darwin, I believe, who started the gossip about the imperfection of the geologic record; but many others have enlarged upon the same theme. As a matter of fact, the record is in most parts surprisingly complete. So ubiquitous have fossil-hunters become, and so indefatigable are the students of ancient life, that to-day, scarcely a hundred years after the birth of the science of palæontology, a fairly complete picture of organic history has been sketched. The rough outlines have in the main been blocked in. Details without number remain to be inserted; high lights must be toned down, shadows must be worked up; but the preliminary outline is now ready for study.
Experience in the past has ever been to thoughtful men a guide for the present and the future. But it should be noted that, in considering the age-long development of organisms, we are dealing with forces over which man has little or no control. The laws of racial habit are as the laws of the Medes and Persians. Heredity imposes upon all living creatures the limits within which their lives must be cast. That the administration of the universe is going forward according to a consistent plan, is a conclusion reached alike by the man of religion and the man of science. The trend of evolution, which has brought the human family to its present state, can scarcely be expected suddenly to change and work in another direction. As the twig is bent, so the tree is inclined.
Again, the experiences of other races of animals, the vicissitudes which have been met by members of the world of organisms whose development has been cast in other lines, may serve as parables from which man may well profit. The argument by analogy is frequently unsafe; many have come to grief thereby. But in this case the conclusions have a firmer base than that. So far as the palæontologist can judge, exactly the same general principles have controlled the evolution of all classes of organisms at all times in earth-history. Man is too closely related to the ‘lower animals’ to permit him to think for a moment that he is an exception to the rule and exempt from the workings of evolutionary law.
Far back in earth-history, at the time when the first richly fossiliferous rocks were being formed, the trilobites occupied a proud position at the apex of the pyramid of life-development. They were, for the time being, the culminating product of evolution and held rich promise of future possibilities. Not only were their bodies encased in a protective exoskeleton similar to that of their near relatives, the crab and lobster, but they were endowed with highly specialized nervous apparatus, antennæ and eyes, comparable to those of another group of close relatives, the scorpions and spiders. Quick-witted, agile, capable, the trilobites were ‘easily the most distinguished denizens of the early Paleozoic seas.’1 Their only rivals, the gigantic predaceous ancestors of the pearly nautilus, were clumsy slow-moving creatures, no match for the smaller but more highly developed trilobite.
Very early in their development an obscure offshoot, from the main stock climbed out of the water and gave rise to air-breathing insects, but the larger and apparently more virile group remained in the ancestral home. There, life was easy, food was plentiful, enemies were few, and at first upward progress was rapid. Appendages and organs, especially the sense-organs, attained an enviable perfection; there seemed to be no limit to the degree in which the trilobites might subdue the earth and enjoy its fruits. But with victory almost in their grasp, their purpose faltered. Surplus energy was used in the development of spines, excrescences, and ornamental embellishments of all sorts. Verily the trilobite wasted his substance in riotous living. And from that moment his decline was rapid. Opportunity turned her back and passed him by, never to return.
It was from another group of invertebrates, either the arachnid cousins of the trilobites or a more lowly wormlike organism, that there arose animals with a back-bone. Long after the fishes had conquered the earlier inhabitants of the sea, trilobites awoke to the error of their ways and made a last desperate struggle to retrieve the lost ground. The late Paleozoic trilobites returned to the chaste simplicity of their ancient progenitors; but it was then too late. Trilobites have absolutely vanished from the face of the earth for lo! these many years.
Robert Louis Stevenson writes, ’To touch the heart of man’s mystery, we find in him one thought, strange to the point of lunacy: the thought of duty; the thought of something owing to himself, to his neighbor, to his God; an ideal of decency, to which he would rise if it were possible; a limit of shame, below which, if it be possible, he will not stoop.’ The palæontologist, remembering the fate of scores of organic phyla which, like the trilobite, failed ‘to keep the honor of a certain aim,’ and as a consequence were thrust into oblivion, is not surprised to find in man ‘the thought of duty.’ For geologic ages that thought has been persistently nurtured in all his progenitors. His ancestral lineage includes no creature which, when tried in the balance, was found wanting. In his germplasm there is no tainted heritage from nature’s derelicts.
While the death-struggle of the trilobites was taking place in the seas, there arose on land a host of strange, cold-blooded, air-breathing vertebrates, whose bodies were covered with scales or sheathed in bony plates. Descendants from amphibians, which in turn had been derived from ganoid fishes, the reptiles soon outclassed their immediate ancestors and became the rulers of the land.
During the Mesozoic era, as the geologist designates that time of mediæval life, saurians dominated every quarter of the earth, and hence the palæontologist refers to the time as the Age of Reptiles. On the land, reptiles occupied nearly every place taken to-day by warm-blooded mammals. There were predaceous flesh-eaters and peaceloving vegetarians; swift-moving, lightlimbed dwellers of the uplands and clumsy heavy-bodied inhabitants of the marshes and the swamps. Not content with their terrestrial possessions, they early sent down to the sea an expeditionary force recruited from several different families, which quickly gained dominion there. A little later they tried their fortunes in the air, and flying dragons were creatures of fact which would have been fit companions for those creatures of fancy slain by the knights of old. Truly the earth must have presented a strange appearance in those days. Rulers of the land, masters of the sea, and lords of the air, the reptiles, I suppose, may have wept like Alexander because there were no more worlds to conquer.
Early in their history, or possibly even before the transition from amphibians to reptiles was complete, the class was split into two general divisions. A typically reptilian strain led to modern reptiles, birds, and the host of saurians which dominated the Age of Reptiles. In sharp contrast was a mammalian strain which carried the pulse of life upward through an ancient order of reptiles to the egg-laying mammals, and through them in turn to the higher mammals of the present time.
The typically reptilian strain seems to have had everything its own way during the Mesozoic era. The facts which the palæontologist has patiently unearthed concerning them surpass all imagination. Such a spectacle of gigantic creatures on land and sea and in the sky has occurred but that once in earth-history. For wherever they went, whatever their habits, these saurians seem to have had a mania for size. It was nature’s grandest experiment at producing a master race by development along the line of brute strength and massive bulk. As Barrell has pointed out, the mechanism for purifying the blood, which they had inherited from their amphibian ancestors, was so imperfect that their brains were poorly nourished and received only partially oxygenated blood. As a result, there may be seen in a score of museums the skeletons of dinosaurs which, when alive, must have weighed twenty tons, but whose brains were scarcely as large as a man’s fist and weighed perhaps twenty ounces. Others escaped from the congested lands by transforming their limbs into paddles which propelled them far out to sea. Still others acquired bat-like wings and soared into the clear spaces of the sky. But many put their trust in armaments, both offensive and defensive: horns and claws, bony neckfrills, and scaly armor-plate testify to the contest for supremacy in fighting power. An impartial observer inspecting the earth in early Cretaceous time must have concluded that no good thing could ever come from out this welter of selfishness and greed, of worldly lusts and brute rivalry.
And yet the dawn of a better day was already faintly discernible. Scurrying out from under the ponderous feet of herbivorous dinosaurs, hiding among the rocks and underbrush from the predaceous carnivores, the diminutive mammalian descendants of that other and comparatively inconspicuous race of reptiles were eking out a precarious existence. With no hope of even rivaling the dinosaurs in massiveness or armament, they were forced by the adversity of their environment to develop along the line of mental ability.
At the present time, the four-chambered heart of mammals is so constructed that it sends an untainted supply of purified blood to nourish the head and brain. Undoubtedly, it is a product of those early reptile-dominated days when quick wits, superior intelligence, and clear brains were absolutely essential to a continuance of life. Once attained, it enabled the diminutive defenseless prototherians, not only to perpetuate themselves, but eventually to give rise to the more highly developed viviparous mammals.
Mammalian evolution during the Age of Reptiles was retarded, not only by the dead weight of reptilian dominance and by the fact that mental efficiency has always been more difficultly attained than physical prowess, but by the long wait which was necessary before a suitable food-supply was obtainable. Cereals, grasses, nuts, and fruits have ever been the sustenance of the majority of warm-blooded animals, either directly or indirectly. And it was not until the latter half of the Mesozoic era that any of these angiosperms, or plants with ‘covered’ seeds, made their appearance. Not long after that important event, the impetus which it gave is noted in the increasing number of mammalian teeth and jaws which are mingled with dinosaur bones in late Mesozoic strata.
At about the close of the Mesozoic era the downfall of the reptiles is recorded by the complete disappearance of the gigantic saurians from their former domains. Terrestrial, aquatic, and aerial forms alike became extinct, leaving only the relatively insignificant group of turtles, crocodiles, lizards, and snakes. In their places, the higher mammals appeared in force and at once took possession of the evacuated spheres of influence. The triumph of intelligence, agility, and brainpower over brute strength, massive bulk, and sluggish mentality was complete.
Major upward steps in evolutionary progress have always been fraught with danger and essayed by few. Bergson, philosopher and naturalist, says, ‘In a general way, in the evolution of life, just as in the evolution of human societies and of individual destinies, the greatest successes have been for those who have accepted the heaviest risks.’ Clarke, palæontologist and philosopher, adds: ‘Over and over again the dominant race has started on its career as an insignificant minority struggling for its existence against an overburden of mechanical and vital obstacles, armed only with specific virtues which have little by little fought their way into the foreground, and by so doing consummated their upward purpose.’ Progress, in the long run, has frequently resulted from the discarding of apparent advantages, either in method of obtaining food, or in devices for protection against enemies, and the assumption of new duties and obligations, the far-reaching effects of which could scarcely be foreseen. Habits which for the moment have seemed suicidal have eventually been the salvation of the race.
The palæontologic record is absolutely blank concerning the far-distant beginning of life on this planet. The oldest known fossils are of plants and animals already specialized and diversified, organisms which show considerable progress in development as compared with the theoretical primitive plant-animal. Nevertheless, many assertions concerning the first steps in evolution may be safely based upon the known ‘vestiges of creation,’whether they be fossil or living. Apparently the first sacrifice made by animals was the loss of the vegetable ability to transform inorganic carbon and nitrogen into food-elements. As Bergson expresses it, ‘The vegetable manufactures organic substances directly with mineral substances; as a rule, this aptitude enables it to dispense with movement and so with feeling. Animals, which are obliged to go in search of their food, have evolved in the direction of locomotor activity, and consequently of a consciousness more and more distinct, more and more ample.’ Of marked advantage in the end, the new obligation for the time being imposed a distinctly infelicitous hazard upon those who first assumed it. On the one hand was comparative safety because of the never-failing supply of mineral matter needed for sustenance; on the other, great danger resulted from the scarcity of organic nourishment previously synthesized by plants or other animals.
It is a far cry from the single-celled protozoan to the earliest of the airbreathing vertebrates; yet from many points of view the transition among the higher animals, from the gill-breathing to the lung-breathing stage, marks the second great crisis in organic evolution. For long ages, life-development had progressed in an aquatic environment. Several groups of invertebrates had actually developed terrestrial forms or were preparing for expeditions beyond the margin of sea and lake and river; but in mid-Paleozoic, time the fishes were the only vertebrates which had yet appeared. It would seem that they had originated in the fresh waters of the land, but soon migrated to the broader, more richly populated domain of the sea. There they quickly became the dominant form of life and enjoyed a time of great prosperity and ease.
The fishes, like every other group of animals which for a time attained dominance, tried their hand at achieving permanent success by developing huge bulk and protective armament. Sharks from twenty to twenty-five feet long, and arthrodiras, with bony plates two inches thick covering the fore-part of their bodies, were not uncommon in the shallow coastal seas of every continent. These classes formed the prosperous, easy-going majority. They have given rise to no descendants more highly developed than themselves. It was a less conspicuous and more daring class of fishes that developed the accessory breathing apparatus which in their descendants, the amphibians, became functional lungs. The hazards which surrounded those venturesome ‘lung-fishes’ as they, for the first time, trusted their lives to the new environment and new conditions, may easily be imagined.
Whether the change was due, as Barrell puts it, to ‘the compulsion of seasonal dryness,’ or, using Bergson’s term, to ‘an internal push,’ the fact is the same: the second great milestone along life’s road was successfully passed by a numerically trivial but organically unimpaired minority. Self-satisfied complacency always tends to make the majority moribund. It quickly forgets the ordeal of strenuous endeavor through which it gained its laurels, settles down into a state of passivity, and leaves to a vigorous, risk-taking minority the pioneer tasks of gaining for the world of organisms new liberty and increased efficiency.
The recurrent combat between intelligence and brute strength, combined with the ever-renewed struggle of the efficient few against the moribund many, bore fruit throughout the ages in a progressively higher consciousness and more perfect instinct among animals. Muscle and nerve, bone or shell, became more and more completely adapted to external environment and internal impulse; instinctive reactions to stimuli became so complicated and so remarkable that they will be the wonder of naturalists even when, if ever, their mysteries are made clear. But a still higher plane of development awaited. To mould bodyform and innate habits so that they fit perfectly into environment is to retain life by subservience to surroundings. It is the antithesis of utilizing external resources in order that the environment may be so moulded that it is no longer inimical to the body and its impulses. Man is unique among animals and has ‘subdued the earth’ first of all because he manufactures artificial objects. Instinct must give place to reason; brute-consciousness must develop into self-consciousness.
During the middle of the Cenozoic era, or Age of Mammals, somewhere between one million and ten million years ago, there lived in Southern Asia small arboreal anthropoids which were the common ancestors of chimpanzee, gorilla, and man. Their teeth were adapted primarily for eating fruits, nuts, and herbs; secondarily for tearing flesh. Their arms were long and powerful, with hands and feet well fitted for their life in the tree-tops. Their habits were not unlike those of the higher apes of the present time. Their habitat was the well-forested lowland, with its semi-tropical climate, which existed where to-day are the snow-clad peaks of the Himalayas and the bleak plateaus of Thibet.
Then occurred one of the episodes of crustal deformation which have periodically recurred in earth-history. Mountain-making forces slowly uplifted the Himalayan mass, carrying the surface of the land upward to an elevation of many thousand feet above sea-level. At the same time, and perhaps as a result of this and other crustal changes, the climate of the world became progressively cooler. The bleak northern slopes of the new-born mountain range were not only cold, but dry, because the moisture-laden winds from the south lost their water-vapor before they crossed the mountain crest. The forests dwindled almost to disappearance; grassy prairies and occasional rocky cañons characterized the landscape.
Caught in the midst of these adverse surroundings, prevented from southward escape by the well-nigh impassable mountain barrier, the ancestors of man were forced to modify materially their habitual customs if they would escape annihilation. The rolling turf of prairie and upland staged a contest for speed in action, quickness of spring, and supremacy in sustained flight, between hoofed herbivores and clawed carnivores, in which, from the very beginning, all anthropoids were far outclassed. No longer were friendly treetops ever at hand as a place of safety from bloodthirsty enemy. On the treeless steppes the puny ancestors of man could prevent starvation only by competing with a multitude of more powerful food-hunting creatures.
Under the compulsion of such an adverse physical and biologic environment the long-tailed, strong-armed, tree-dwelling anthropoids evolved perforce into tailless, semi-erect bipeds, and at length developed into primitive man — the men of the Old Stone Age. The acquisition of three new characteristics made possible that transition: the habit of coöperation, the use of implements, and the knowledge of fire. Without all three of these no man-like creature could have survived.
It seems perfectly natural, in retrospect, that a creature whose hands were well adapted for locomotion through the tree-tops should have learned to use branches and limbs as clubs for attack or defence. Coöperation in the chase would come readily even to a distant relative of coyote and wolf. The use of fire, first accidentally and then purposefully, would not be a surprising attainment for individuals ingenious enough to utilize the gnarled limbs of scattered trees or the smooth boulders of ice-fed torrents. And yet, there can be no doubt that there were many conservatives who looked with disfavor upon the revolutionary methods of the innovators, and preferred to remain in the comparative safety of temporary shelter in the isolated groves. How should they know that, because the forested areas were annually decreasing in extent, they would eventually disappear? Why should they realize that death was certain for all those who should neglect to form habits independent of the dwindling forests, where safety was temporary and could not, in the very nature of things, be lasting?
Of all animals, man is one of the most gregarious. The social instinct is a part of his very nature. The palæontologist, visualizing the stress of those pre-glacial days in Central Asia, knows that in man’s lineage there can be no member of the anthropoid stock who refused to coöperate with his fellows to the mutual advantage of all. Selfishness was rampant, beyond doubt, but dependence upon others for assistance in getting food and for protection against omnipresent foes was essential to life. Conservation of the scanty resources for shelter afforded by caverns, overhanging cliffs, or occasional groves of trees, completed the introduction of community life and crystallized the clan spirit in imperishable form. From that day to this the tendency toward coöperation among human beings has been intermittently broadening and deepening its influence. Because of it, man has multiplied upon the face of the earth.
Dominion over nature, so far as inanimate objects and non-human organisms are concerned, has well-nigh been accomplished by mankind. The future years hold many triumphs which must patiently be achieved and which will doubtless add many more conveniences to the long list of human attainments; but man already knows how these conquests must be gained. The method is his; results are but a question of time. The supremacy of mind over matter is beyond cavil. But this is by no means equivalent to stating that man has reached his final goal. Evolution is a ceaseless urge; in the past there have always been higher planes to strive for, in the future there may never be such a thing as an ultimate terminal. Success is always temporary; it simply gains new ground from which to start once more out into the unknown. The subduing of the earth has made man master of the external world; but he cannot even hold what he has gained unless he becomes also master of himself.
The dominant, but militaristic, dinosaurs of the Age of Reptiles were forced into extinction quite as much by internecine warfare as by competitive struggle with other races. A house divided against itself cannot stand; the human race, unless it lives in peace and harmony with itself, can never inherit the earth. The consummation of a true human brotherhood which shall embrace all men is devoutly wished by all thoughtful members of society. Some doubt its possibility; many disagree as to how it is to come. Speak to the earth and it will teach thee, for the experience of the past is the only key to unlock the future.
A crisis in evolution as great as any evolutionary crisis of the past is before us. The successful negotiation of the next great upward step in the progress of life will mark the transition from the Cenozoic era to the Psychozoic era. That the step will be taken can never be doubted by anyone who has surveyed the long road which leads from the unfathomable past to the present; how soon it will be accomplished and by which breed of men depends upon the people of to-day.
Far back beyond the earliest records of animal life thus far revealed to us, brute-consciousness and instinct were achieved. The long geologic periods have borne fruit in the comparatively recent attainment of self-consciousness and reason. The measureless ages which stretch out into the future will see the development of race-consciousness and love. The type of the new variety of the human species was presented to us nineteen hundred years ago. The supremacy of this new variety will be gradually accomplished, just as every new group of organisms came into its own by processes of growth. Exactly the same principles of evolutionary law which controlled the changes of the past will determine those of the present and the future.
To-morrow, as yesterday, the fittest will survive in the struggle for existence. But whereas in the past selfishness was the measure of fitness, in the future survival value will be determined by breadth and depth of love. Modern science is teaching as it never was taught before that no man liveth to himself alone. Coöperation between individuals, and then between families, was essential to the life of man when he competed with the brutes of field and forest. Still greater coöperation between clans and nations is now essential to his continued life on the earth. ‘The moving finger writes, and having writ moves on.’ Now, as always, individuals and peoples who are not in line with the great forward movements in the evolutionary trend are doomed to die.
Delving deep into the nature of the life-changes recorded in the rocks, the palæontologist may be like the householder who brings forth out of his treasure things new and old.
- The geologist divides earth-history into five great divisions or eras: Archeozoic, the era of primal life; Proterozoic, the era of primitive life; Paleozoic, the era of ancient life; Mesozoic, the era of mediaeval life; and Cenozoic, the era of modern life. — THE AUTHOR.↩