Evolution

by Stephen Baxter

  But the comet wind didn’t care about that, not at all.

  The wind hit the nest first. The rock ledge was swept bare, the nest smashed to fragments. The bones of the pterosaurs’ victims — including those of Second — were sent whirling into the air with the rest of the debris. The chicks flew: if only briefly, if only once, if only to their deaths.

  And then, for the mother azhdarchid, it was as if she had flown into a wall of dust and spray, and even bits of vegetation and wood and rock. She felt her fragile bones snap. She was tumbled over and over, helpless as a dead leaf.

  Once more the suchomimus struggled to her feet. She ached in her legs, arms, back, tail, and head, where she had been struck by bits of flying debris, the wreckage of a world.

  Again the beach had become an utterly unfamiliar place. The ground was now littered by debris from inland, bits of smashed trees and crushed animals, dead or dying pterosaurs and birds, even lake-bottom ooze. Nothing moved — nothing but dying creatures, and the suchomimus.

  She remembered the fish she had been about to eat. The fish was gone.

  Above her, dark banks of cloud whipped across the sky, like a curtain being drawn. The sun disappeared; it would not be seen again for a long time.

  And to the south, the lid of sky began to glow an eerie orange. A breeze wafted a sharp, distinctive smell to her nose. Ozone. The smell of the sea. She thought of lapping water, the glittering fish of the shallows. She must get to the sea. She had always made her living from the sea; there she would be safe. With a mournful lowing even she couldn’t hear, she began to blunder in the direction of the scent, ignoring the grisly detritus under her feet.

  The sea turtle had been fortunate. When the comet hit, she was cruising the sea bottom far from the impact zone.

  Her kind was among the most primitive of the great reptile dynasties. But, primitive or not, this turtle was an effective hunter. Her body was undemanding, requiring only a twentieth as much food as a dinosaur of the same weight. Heavily protected by her powerfully reinforced shell, cautious even as a hunter, the only risks she ran in her life were the annual assaults she had to make on the beaches to lay her eggs, before hurrying back to the safety of the water.

  Her brain was small, her consciousness dim. She lived alone, in a world of colorless monotony. She had no bonds with her parents or siblings, no real understanding that the eggs she laid would produce a new generation. But she was ancient, wary, enduring.

  Now, though, something disturbed her blue, lonely world. A monstrous current began to drag the sea toward the south.

  Grimly the turtle paddled at the water, heading downward. Her instincts, honed by millions of years of tropical storms, primed her with a simple instruction: dive deep, get to the bottom, find shelter.

  But this was like no current she had ever experienced. Through the increasingly muddy and turbulent water she glimpsed much larger creatures, even giant pliosaurs, being dragged backward by this mighty tide. And as she descended she was battered by debris, helpless ammonites, clams, squid, even rocks torn from the floor.

  At last she found soft mud. All her four fins working, she began to work her way into the dirt, ignoring the hail of objects that clattered off her shell. Eventually she would have to surface, for air and warmth; but she could last for a long time, perhaps until this monstrous storm had passed away.

  But now the sea’s glimmering meniscus descended toward her — and the sea drained away — and she found herself in sunlight, with moist mud hissing all around her. Something like shock lit up her small mind. The world had turned upside down; this made no sense.

  And now the sea bottom mud, exposed, began to shake.

  By the shifting, strange light, at last the suchomimus saw the sea. With a hoarse cry of relief, she hurried forward.

  But the sea ran away from her, exposing glistening mud. And as fast as she pursued it, the sea ran faster.

  A fish flopped at her feet. She stopped and plucked it out of the dirty mud and popped it into her mouth. In the fish’s tiny awareness was a kind of relief; this death was quick compared to the grisly suffocation it had endured on the new beach.

  The sea bottom, uncovered for the first time in millions of years, was a glistening floor of life. It was littered with clams, crustaceans, squid, fish, ammonites of all sizes, all of them drowning in the air.

  Further south there were giant shapes. The suchomimus saw a giant plesiosaur, stranded like the rest. Eight meters long, it lay gasping on the mud with its four huge flippers splayed and broken around it. It struggled, tons of marine carnivore flipping this way and that, huge fins waving, savage teeth snapping in rage at the fate that had stranded it.

  On any other day it would have been a remarkable sight. The suchomimus turned away, bewildered.

  When she looked north to the land, she could see creatures creeping out of the devastated forests, the wind-scoured marshland. Many of them were ankylosaurs and other armored creatures, protected thus far by the heavy armor that had evolved to fend off the teeth and claws of tyrannosaurs. They crawled toward the exposed seabed, seeking sanctuary, to drink, to feed.

  But now the ankylosaurs opened their mouths and began to retreat once more. The suchomimus watched them, baffled. They were bellowing, but she couldn’t hear them.

  She turned back to face the sea. And then she saw what had frightened them.

  As air, so water.

  From the impact site, powered by the immense pulse of heat, a circular shock wave now marched outward through the body of the ocean. Its destructive power was limited because the impact had not occurred in deep ocean water. Still, as it neared the coastline of North America, the wave was already some thirty meters high. And as it reached the shallower water of the Texas coast, the tsunami gathered itself, rearing ten to twenty times its initial height.

  Nothing in the suchomimus’s evolutionary heritage had prepared her for this. The returning sea was like a moving mountain range, hurtling out of the retreated ocean. She could not hear it, but she could feel how it made the exposed seabed shudder, smell the sharp stink of salt and pulverized rock. She stood upright and bobbed her head, baring her teeth defiantly at the approaching tsunami.

  The water towered above her. There was an instant of pressure, of blackness, a huge force that compressed her. She died within a second.

  The tsunami rolled landward, dwarfing the lumbering ankylosaurs before crushing them, armor and all. On it went, ramming its way into the ancient, long-dried sea way. When it receded, the water left behind debris, great banks of it dredged from the sea bottom. It had been an immense slosh, from the stone thrown into this Cretaceous pond.

  On the land, in Texas, nothing survived.

  In the sea, only a handful of creatures lived through the oceanic catastrophe.

  One of them was the sea turtle. She had burrowed deep enough into the mud for the tsunami waters to spare her. When she could sense that something like calm was restored, she struggled out of the mud, and ascended up through water cloudy with debris and bits of dead animals and plants.

  The turtles, ancient, had already passed the zenith of their diversity. But where more spectacular creatures had perished en masse, the turtle had survived. In a dangerous world, humility made for longevity.

  The impact had sent an energy pulse through the body of the Earth. In North and South America, across thousands of kilometers, faults gaped and landslides crashed, as the shocked ground shuddered. The rocky waves weakened as they propagated, but the Earth’s internal layers acted like a giant lens to refocus the seismic energy at the impact’s antipode, the southwestern Pacific. Even there, the width of the planet away, the ocean floor heaved in swells ten times higher than the 1906 San Francisco earthquake.

  The shock waves would continue to pass through the planet’s body, crossing, interfering, reinforcing. For days, the Earth would ring like a bell.

  Seen from space, a glowing wound was spreading out over the Earth around the still-burning impact
point. It was a great cloud of molten rock, hurled into space.

  In the vacuum the scattered droplets were beginning to cool and condense into hard specks of dust. Some of this material would be lost to the planet forever, joining the thin drizzle of material that swam between the planets: In a few millennia fragments of Yucatan seafloor would fall as meteors on Mars and Venus and the Moon. And some of the space-borne material would, through chance configurations, enter orbit around the planet, making a temporary ring around the Earth — dark, unspectacular — that would soon disperse under the shifting gravitational tweaks of the sun and Moon.

  But most of the ejecta would fall back to Earth.

  Already the great hailing had begun. The first to fall was the coarser debris from the perimeter of the crater, much of it fragments of smashed-up ocean-bottom limestone. These chunks had not been melted by the heat pulse of the initial impact. But as they fell back into the Earth’s warm pond of air, they began to glow brightly. Streaks of light hundreds of kilometers long were drawn across the sky, like an insane geometrical exercise. Some of the debris chunks were large enough to crack open as they heated, and secondary tracks fanned out from sparking explosions.

  Of all the creatures within a few thousand kilometers of the impact, the great aerial whale had been least affected so far.

  He had watched the great light descend over the Yucatan Peninsula — had seen that stabbing laser beam of vaporized seabed and comet, had even glimpsed the formation of the crater, as great ripples of rock pulsed through the exposed seabed before congealing into place in a great chthonic clench. Had he been able to describe what he saw, the whale could have provided posterity with a compelling eyewitness account of the catastrophe, the most violent impact since the end of the formative bombardment four billion years earlier.

  But the whale cared nothing for that. The whale had not even been troubled by the wind; he flew too high, and had been able to continue feeding as the great sheets of discolored air fled across the ground far beneath him. Distant lights in the sky, trouble on the ground — like the creamy-swirl weather systems that often crossed the land and oceans — meant nothing to a creature who flew at the fringe of space. So long as the wispy aerial plankton that fed him continued to drift up from the lands below, he prowled his thin niche untroubled.

  But this storm was different.

  The air whale was used to meteors. They were just streaks of light in the purple-blue sky above. Almost all of the billions of bits of cosmic debris that fell to Earth burned up far above the stratosphere, the whale’s realm.

  But some of these tracks were reaching down into Earth’s thicker air, passing far below him. The whale had no hearing — he had no need of it in this thin, silent air, where no predators worked — but if he had he might have made out the thin howl of the meteors as they plunged back to the planet from which they had so recently been flung. He could even see where the first sea-bottom chunks fell: On the ground, far below, sparks of light bloomed like tiny flowers, one after the other. It was like the view from a high-altitude bomber.

  For the first time since he was a chick the whale began to know fear. Suddenly this was no aerial light show but a rain of light and fire. It was a rain that was falling all around him — and it was getting thicker. Belatedly he turned. With a slow flap of his immense wings, he headed north.

  Light pulsed.

  The white-hot rock fragment was just a scrap. After the encounter with the whale it continued its descent toward the thick Cretaceous forests, only a fraction of its kinetic energy expended. But the whale’s complex nervous system brought his small brain messages of agonizing pain. When he turned his great head to the right, he saw that the surface of his wing was torn and scorched.

  If the meteor had hit near the center of the wing, it might have made no more than a puncture, and the whale might have lived a little longer. But the whale had been unlucky. The meteor had punched through the joint of an immense, fragile flight finger. The wing began to fold up in great sections around the broken segment of bone.

  The blue-gray Earth tipped over. Though he thrashed inelegantly with his good wing, the whale was already falling away from the horizontal — falling out of control, out of the sky. Still he remained conscious, slowly twisting, crumpling like a broken toy kite. But the meteor hail thickened. Bulletlike meteors tore tunnels through the fine caverns of his body, ripping open air sacs, smashing his delicate, light-as-air filigree skeleton, further puncturing his magnificent wings.

  The pain became overwhelming. His mind filled with comforting, creamy memories of gliding high over an undisturbed Earth. He died long before the remnants of his torso reached the ground, his lungs crushed by the thick air.

  Giant was struggling to get back to his feet.

  Before him a stegoceras lumbered, bewildered, the scarlet-coated cap of bone and flesh on his head absurd. Thanks to a chance sheltering in a dense crop of araucaria this young male had survived the tornado, suffering no worse injury than a snapped rib. But his clan was gone, scattered by the wind. He lifted his head and howled, a great mournful lowing. It was like a chick’s call of distress, a lost call.

  It wasn’t his mother who responded, but two huge carnivores, giganotosaurs, who came stalking slowly toward him, their heads bobbing, their eyes fixed on him. Even now, the game of predator and prey continued.

  But through the adrenaline-induced fear that flooded his system, the stegoceras noticed something strange. A third giganotosaur, as big and powerful as the rest, was showing no interest in him. The third monster was head-bobbing, threatening, reacting to something that approached from out of the sky. Confused, fearful, the stegoceras turned to the south, where a lowering cancerous orange continued to spread through the racing black clouds.

  The first meteor screamed overhead like a glowing hornet. It flew low over the smashed forest and slammed against a foothill beyond. Young volcanic stone exploded, and a secondary shower of steaming fragments hailed out, pattering against the debris-strewn ground. All the dinosaurs turned that way, shocked and startled, their innate animosity briefly forgotten.

  And the second meteor passed through the stegoceras’s body, like a high-velocity bullet. A fraction of a second later, on meeting the impenetrable ground, the meteor dumped the last of its energy into the rock. The explosion burst apart the stegoceras’s body before it had time to fall. In the brief rain of blood, Giant cringed, uncomprehending.

  Now the meteors began to land in the remains of the smashed forest. Fire splashed.

  Giant and his brothers panicked and ran. But still the meteor rain thickened. The meteors pounded the ground around the giganotosaurs, digging shallow craters and starting fires even in the scattered undergrowth. It was as if the brothers were running through an artillery barrage.

  Purga, too, could smell the smoke.

  The primates could ride out fires in their burrows, buried deep in the cool earth, to emerge into the debris of a charred and ruined forest. But, Purga’s instincts warned her, this time was different. She pushed past her cowering mate and her pups, past the grisly severed head of the troodon. She emerged into daylight. She was immediately dazzled, her sensitive night-adapted eyes unable to cope with the unaccustomed flood of light. But she could nevertheless make out the main features of the terrible day: the spreading fires in the smashed blanket forest, the continual, incomprehensible rain of meteors.

  She could not stay here. But where to go?

  With much of the obstructing forest already demolished by the winds she could see the shoulders of the Rockies with their clouds of volcanic smoke lingering at their summits. And where the comet winds had pushed warm, moist air up the flanks of the rising ground, thick cumulus clouds clung to the mountain’s upper slopes.

  Shade. Darkness. Perhaps there would even be rain.

  She took a step further into the open, whiskers twitching. She moved in rapid jerks, pausing every few paces, flattening herself against the ground.

  She
looked back. Beyond the fallen head of the troodon, she could see her mate and pups, three sets of wide eyes peering after her. Instincts honed across a hundred million years urged her to return to the cool earth, or to clamber into the trees where she would find safety, for otherwise the terrible claws and teeth and feet of this giant world would surely claim her. But the trees were smashed and broken, her burrow no longer a sanctuary.

  She scurried away, toward the cloud-draped mountains.

  Her mate followed, more cautiously. One of the pups followed him. The second, terrified, bewildered, bolted back into the recesses of the burrow. There was nothing Purga could do for the second pup. She would never see him again.

  So the three tiny, shrewlike creatures — carrying all the potential of mankind within them — made their way slowly across the battered, smoldering plain while meteors rained around them.

  The fire fed on itself. The scattered pockets of fire were beginning to link up. As the temperature of the air rose even the damp undergrowth was starting to burn. A wind began to gather, the smoke to spiral overhead. Here, and all over North and South America, the fires began to exert a logic of their own, becoming self-feeding, self-perpetuating systems.

  Thus the firestorms began. Everything that could burn did so: every scrap of vegetation, even lake plants still soaked from their immersion. Animals simply burst into flame: Raptors burned like saplings and great armored herbivores cooked in their own monstrous shells.

  The three giganotosaurs burst at last from the forest. They had come to a clearing centered on a large lake. They were overheated, their great mouths gaping, their heads filled with the stink of the smoke.

  The open sky was extraordinary. A lid of blackness was rushing up from the southeast, as if a great curtain were closing. That eerie orange glow was spreading too, growing brighter and ascending to yellow. And still the meteors hammered into the muddy ground.