Centennial (10 page)

As soon as he was gone, the scavengers moved in—reptiles from the sky, crocodiles from the lagoon, two kinds of dinosaurs from land and the unnoticed mammals from the roots of the ginkgo tree. By nightfall the dead diplodocus, all thirty-three tons of him, had disappeared and only his massive skeleton lay on the beach.

Wounded diplodocus and the four young dinosaurs that had witnessed this massacre now swam back to the lagoon. In the days that followed, she began to experience the last inchoate urge she would ever know. Sharp pains radiated slowly from the place where allosaurus had ripped her. She found no pleasure in association with the other members of the herd. She was drawn by some inexplicable force back to the swamp at the chalk cliff, not for purposes of recreating the family of which she was a part but for some pressing reason she had never felt before.

For nine days she delayed heading for the swamp, satisfying herself with half-sleep in the lagoon, poling herself idly half-submerged from one warm spot to another, but the pain did not diminish. Vaguely she wanted to float motionless in the sun, but she knew that if she did this, the sun would destroy her. She was a reptile and had no means of controlling body heat; to lie exposed in the sun long enough would boil her to death in her own internal liquids.

Finally on the tenth day she entered the river for the last time. stepping quietly like some gracious queen. She stopped occasionally to browse on some tree, lifting her head in a glorious are on which the late sun shone. Her tail extended behind, and when she switched it for some idle purpose it gleamed like a scimitar set with jewels.

How beautiful she was as she took that painful journey, how gracefully coordinated her movements as she swam toward the chalk cliff. She moved as if she owned the earth and conferred grace upon it. She was the great final sum of millions of years of development. Slowly, swaying from side to side with majestic delicacy, she made her way to the swamp that lay at the foot of the cliff.

There she hesitated, twisting her great neck for the last time as if to survey her kingdom. Thirty feet above the earth her small head towered in one last thrust. Then slowly it lowered; slowly the graceful arc capsized. The tail dragged in the mud and the massive knees began to buckle. With a final surge of determination, she moved herself ponderously and without grace into a deep eddy.

Its murky waters crept up her legs, which would never again be pulled forth like reeds; this was the ultimate capture. The torn side went under; the tail submerged for the last time, and finally even the lovely arc of her neck disappeared. The knobby protuberance holding her nose stayed aloft for a few minutes, as if she desired one last lungful of the heavy tropical air, then it too disappeared. She had gone to rest, her mighty frame imprisoned in the muck that would embrace her tightly for a hundred and thirty-six million years.

It was ironic that the only witness to the death of diplodocus was the little pantothere that watched from the safety of a cycad tree, for of all creatures who had appeared on the beach, he was the only one that was not a reptile. The dinosaurs were destined to disappear from earth, while this little animal would survive, its descendants and collaterals populating the entire world, first with prehistoric mammals themselves destined to extinction—titanotheres, mastodons, eohippus—and subsequently with animals man would know, such as the mammoth, the lion, the elephant, the bison and the horse.

Of course, certain smaller reptiles such as the crocodile, the turtle and the snake would survive, but why did they and the little mammal live when the great reptiles vanished? This remains one of the world’s supreme mysteries. About sixty-five million years ago, as the New Rockies were emerging, the dinosaurs and all their immediate relations died out. The erasure was total, and scholars have not yet agreed upon a satisfactory explanation. All we know for sure is that these towering beasts disappeared. Triceratops with its ruffed collar, tyrannosaurus of the fearful teeth, ankylosaurus the plated ambulating tank, trachodon the gentle duck-billed monster—all had vanished.

Ingenious theories have been advanced, some of them captivating in their imaginativeness, but they remain only guesses. Yet because the mystery is so complete, and so relevant to man, all proposals merit examination. They fall into three major groups.

The first relates to the physical world, and each argument has some merit. Since the death of the dinosaurs coincided with the birth of the New Rockies, there may have been a causal relationship, with the vast lowland swamps disappearing. Or temperatures may have risen to a degree that killed off the great beasts. Or plant life may have altered so rapidly that the dinosaurs starved. Or the disappearance of the extensive inland sea changed water relationships and dried up lagoons. Or mountain building somehow involved loss of oxygen. Or a combination of changes in plant food doomed the reptiles. Or a single catastrophic sun flare burned the dinosaurs to death, while the mammals, with their built-in heat-adjusting apparatus, survived.

The second theory is more difficult to assess, because it deals with psychological factors, which, even though they may be close to the truth, are so esoteric that they cannot be quantitatively evaluated. Classes of animals, like men, empires and ideas, have a predestined length of life, after which they become senescent and die out. Or the dinosaurs had overspecialized and could not adapt to changes in environment. Or they became too large and fell of their own weight. Or they reproduced too slowly. Or their eggs became infertile. Or carnivores ate the vegetarian dinosaurs faster than they could reproduce and then starved for lack of food. Or for some unknown reason they lost their vital drive and became indifferent to all problems of survival.

The third combines all the reasons that relate to warfare between a declining reptilian world and a rising mammalian one. Mammals ate the eggs of the dinosaurs at such a rate that the reptiles could not keep producing enough to ensure survival. Or mammals of increasing size killed off the smaller reptiles and ate them. Or mammals preempted feeding grounds. Or mammals, because of their warm blood and smaller size, could adjust more easily to the changes introduced by the mountain building or other environmental shifts. Or a world-wide plague erupted to which the reptiles were subject while the mammals were not.

For each of these theories there are obvious refutations, and scholars have expounded them. But if we reject these proposals, where does that leave us in our attempt to find out why this notable breed of animal vanished? We must know, lest the day come when we repeat their mistakes and doom ourselves to extinction.

The best that can be said is that an intricate interrelationship of changes occurred, involving various aspects of life, and that the great reptiles failed to accommodate to them. All we know for sure is that in rocks from all parts of the world there is a lower layer dating back seventy million years in which one finds copious selections of dinosaur bones. Above it there is an ominous layer many feet thick in which few bones of any kind are found. And above that comes a new layer often crowded with the bones of mammal predecessors of the elephant, the camel, the bison and the horse. The dead reach of relatively barren rock, representing the death of the dinosaurs, has not yet been explained.

Long after they disappeared, and after man had risen to the point where he could search out the fossilized skeletons of the dinosaurs, it would become fashionable to make fun of the great reptiles which had vanished through some folly of their own. The lumbering beasts would be held up to ridicule as failures, as inventions that hadn’t worked, as proof that a small brain in a big body makes survival impossible.

Facts prove just the opposite. The giant reptiles dominated the earth for one hundred and thirty-five million years; man has survived only two million and most of that time in mean condition. Dinosaurs were some sixty-seven times as persistent as man has so far been. They remain one of the most successful animal inventions nature has provided. They adjusted to their world in marvelous ways and developed all the mechanisms required for the kind of life they led. They are honored as one of the world’s longest-lived species, and they dominated their vast period of time just as man dominates his relatively brief one.

Fifty-three million years ago, while the New Rockies were still developing and long after diplodocus had vanished, in the plains area, where the twin pillars formed, an animal began to develop which in later times would give man his greatest assistance, pleasure and mobility. The progenitor of this invaluable beast was a curious little creature, a four-legged mammal, for the age of reptiles was past, and he stood only seven or eight inches high at the shoulder. He weighed little, had a body covering of part-fur, part-hair and seemed destined to develop into nothing more than a small inconsequential beast.

He had, however, three characteristics which would determine his future potential. The bones in his four short legs were complete and separate and capable of elongation On each foot he had five small toes, that mysteriously perfect number which had characterized most of the ancient animals, including the great dinosaurs. And he had forty-four teeth, arranged in an unprecedented manner: in front, some peg-like teeth as weak as those of diplodocus; then a conspicuous open space; then at the back of the jaw, numerous grinding molars.

This little animal made no impression on his age, for he was surrounded by other much larger mammals destined for careers as rhinoceroses, camels and sloths. He lived carefully in the shady parts of such woods as had developed and fed himself by browsing on leaves and soft marsh plants, for his teeth were not strong and would quickly have worn down had they been required to eat rough food like the grass which was even then beginning to develop.

If one had observed all the mammals of this period and tried to evaluate the chances of each to amount to something, one would not have placed this quiet little creature high on the list of significant progenitors; indeed, it seemed then like an indecisive beast which might develop in a number of different ways, none of them memorable, and it would have occasioned no surprise if the little fellow had survived a few million years and then quietly vanished. Its chances were not good.

The curious thing about this little forerunner of greatness is that although we are sure that he existed and are intellectually convinced that he had to have certain characteristics, no man has ever seen a shred of physical evidence that he really did exist. No fossil bone of this little creature has so far been found; we have tons of bones of diplodocus and her fellow reptiles, all of whom vanished, but of this small prototype of one of the great animal families, we have no memorials whatever. Indeed, he has not yet even been named, although we are quite familiar with his attributes; perhaps when his bones are ultimately found—and they will be—a proper name would be ‘paleohippus,’ the hippus of the Paleocene epoch. When word of his discovery is flashed around the world, scholars and laymen in all countries will be delighted, for they will have come into contact with the father of a most distinguished race, one which all men have loved and from which most have profited.

Perhaps thirteen million years after ‘paleohippus’ flourished, and when the land that would contain the twin pillars had begun to form, the second in line and first-known in this animal family appeared and became so numerous that in the land about the future pillars hundreds of skeletons would ultimately be laid down in rock, so that scientists would know this small creature as familiarly as they know their own puppies.

He was eohippus, an attractive small animal about twelve inches high at the. shoulder. He looked more like a friendly dog than anything else, with small alert ears, a swishing tail to keep insects away, a furry kind of coat and a longish face, which was needed to accommodate the forty-four teeth, which persisted. The teeth were still weak, so that the little creature had to content himself with leaves and other soft foods.

But the thing that marked eohippus and made one suspect that this family of animals might be headed in some important direction was the feet. On the short front feet, not yet adapted for swift movement, the five original toes had been reduced to four; one had only recently disappeared, the bones which had once sustained it vanishing into the leg. And on the rear foot there were now three toes, the two others having withered away during the course of evolution. But the surviving toes had tiny hoofs instead of claws.

One could still not predict what this inconspicuous animal was going to become, and the fact that he would stand second in the sixty-million-year process of creating a noble animal seemed unlikely. Eohippus seemed more suited for a family pet than for an animal of distinction and utility.

And then, about thirty million years ago, when the land that was to form the twin pillars was being laid down, mesohippus developed, twenty-four inches high at the shoulders and with all the basic characteristics of his ancestors, except that he had only three toes on each of his feet. He was a sleek animal, about the size of our collie or red fox. The forty-four teeth kept his face long and lean and his legs were beginning to lengthen, but his feet still contained pads and small hoofs.

Then, about eighteen million years ago, a dramatic development took place which solved the mystery. Merychippus appeared, a most handsome three-toed animal forty inches high, with bristly mane, extended face and protective bars behind the eye sockets.

He had one additional development which would enable the horse family to survive in a changing world: his teeth acquired the remarkable capacity to grow out from the socket as they wore down at the crown. This permitted the proto-horse to quit browsing on such leaves as he found and to move instead to grazing on the new grasses that were developing on the prairies. For grass is a dangerous and difficult food; it contains silica and other roughnesses that wear down teeth, which must do much grinding in order to prepare the grass for digestion. Had not merychippus developed these self-renewing grinders, the horse as we know it could have neither developed nor survived. But with this almost magical equipment, he was prepared.