Evolution (6 page)

Second longed only to get out of this cage of scaly flesh, back to the ground and his burrow. He thrashed at the talons that contained him, and tried to bite into the flesh; but the scales of the huge creature defied his small teeth.

And the pterosaur squeezed until small primate ribs cracked.

The pterosaur was an azhdarchid. She was the size of a hang glider. Her massive, toothless head, with a pointed triangular beak at the front and an elaborate crest at the rear, was sculpted to serve as an aerodynamic aid. Her hollow bones and porous skull made her remarkably light, and her body was tiny. She was nothing but wings and head. She looked like a sketch by Leonardo da Vinci.

The spar of each pterosaur wing was a single tremendous finger. Three remnant fingers created a small claw in the middle of the leading edge. The wing was held open by her hind legs. With all four limbs occupied in controlling the aerodynamic surfaces, the azhdarchid’s relatives could never diversify, like the birds, into running or aquatic forms. But the pterosaurs had been astonishingly successful. Along with birds and bats, they had been one of only three groups of backboned animals to have mastered flight— and they had been the first. By now pterosaurs had darkened Earth’s skies for more than a hundred and fifty million years.

The azhdarchid was capable of taking fish from shallow waters, but made most of her living as a scavenger. She rarely took live mammals. But Second— who had been engrossed in devouring a worm he was pulling from the sand— had not realized how visible the bright comet light had made him. He was not the only animal whose rhythms and instincts were disturbed by the new light in the sky. He had been an easy capture.

Second lay still, encased in pain, as cold air washed over him.

He could see the great outstretched wings above him, comet light shining blue through the translucent skin. Tiny creatures squirmed: a pterosaur’s wing was an enormous expanse of almost hairless skin packed with blood vessels, a powerful lure for parasitic insects. Every square centimeter of the pterosaur’s wing surface was controlled by an underlying mat of muscle fabric, enabling the azhdarchid to control her aerodynamics with exquisite precision; her body was a better engineered glider than any manufactured by human hands.

The azhdarchid banked to avoid a smudge of volcanic cloud that hung above the young mountains. It would be fatal for her delicate wings to be caught in such foul air. She was expert at spotting upwelling fountains of warm air— marked by cumulus clouds or over the sun-facing slopes of hills— that she could exploit for free lift. To her the world was a three-dimensional web of invisible conveyor belts, capable of carrying her anywhere she wanted to go.

The azhdarchid’s nest was in a foothill of the Rockies, above the tree line. A steep wall of young rock soared above a guano-stained ledge littered with eggshells and bones and beaks. Chicks stalked noisily around this confined area, scattering the bits of shells from which they had emerged a few weeks earlier. There were three of them; they had already devoured a weakling fourth sibling.

The parent worked a spur of bone in her wrist that changed the shape of the wings’ membrane: like air brakes, this enabled her to slow without stalling. She came to a halt a meter above the ledge, and dropped onto her hind legs. She stowed her delicate wing membranes, folded her flight fingers across her back, and walked forward, her knees bent outward and her elbows bent.

Second was dropped. He clattered against bare rock. He glimpsed the adult azhdarchid flap away. He scrabbled at the rock, but it was too hard to burrow into.

And little monsters closed in on him, blue-black in the comet light. Fed by their parents’ proteinaceous offerings of fish and meat, the chicks were growing quickly. But their wings were still undeveloped, and their bodies and heads were relatively large. They looked like miniature dinosaurs.

The first beak nipped at Second’s hind leg, almost playfully. The scent of his own blood evoked sudden memories of the burrow. He experienced a kind of regret. He bared his teeth. The ravenous chicks closed around him. It was over in a heartbeat, his warm body torn apart.

But now something moved, far above the mother azhdarchid. She twisted her sketch of a head to peer upwards. In these tall Cretaceous skies, fueled by the oxygen-rich air, a pyramid of predators had erected itself, with all the savagery of its landbound analogues. But when she saw the vast sprawled shadow, skimming over the comet-bright sky
above
the lowest of the clouds, she knew she was in no danger.

It was only an air whale.

The largest flying animal ever discovered by humans was a type of azhdarchid christened Quetzalcoatlus. Its wingspan of fifteen meters was four times that of the largest birds, condors; it had looked like a light airplane.

But the greatest pterosaur of all was an order of magnitude larger again.

The air whale’s tremendous, delicate wings were one
hundred
meters across. His bones were little more than sketches, strut-filled and hollow, astonishingly light. His mouth was vast, a translucent cavern. His main danger was overheating in the unfiltered sunlight of the high air, but his body had a number of mechanisms to compensate, including the capacity to vary the flow of blood in his tremendous wings, and air sacs placed in his body that enabled his internal organs to lose heat.

He lived his life in that thin, high layer of air called the stratosphere, higher than the mountains, above most of the clouds. But even this far from the ground there was life: a thin ethereal plankton of insects and spiders, windblown. Sometimes mating swarms of midges, or even locusts, could be blown up into this lofty realm. This was the whale’s thin bounty, which he scooped endlessly into his vast mouth.

Far below, if he had chosen to look, the air whale might have glimpsed the little drama of Second, the azhdarchid chicks, and the pterosaur. But from up here such remote events were of little interest. When he looked down over his airy domain, the whale could see the curve of the Earth: the fat blue band of thicker air that marked the horizon, and the glimmering of the sea in the light of the comet. The sky above faded to violet at the zenith. He was so high that there was too little air to scatter the light effectively; despite the brightness of the comet, he could see stars.

The air whale was capable of circumnavigating the globe, following the stratospheric winds and seeking updrafts, without once touching the ground. His kind made up a thin population— the aerial plankton could sustain no more— but they were scattered all over the planet. Three or four times in his life he had mated, summoned to the planet’s highest mountain peaks by innate timing mechanisms triggered by the motion of the sun. Mating was perfunctory and uninteresting; such huge, delicate creatures couldn’t afford the displays and courtship rituals of more terrestrial species. Nevertheless ancient instincts did sometimes come to the fore. There could be fights, often savage, almost always lethal, and when that happened, huge flimsy bodies would rain out of the skies, to baffle ground-based scavengers.

The whale was the end product of a brutal evolutionary competition, mostly aimed at removing weight; everything that had been surplus to requirements had, over the generations, been selected out or shriveled to insignificance. And, since nothing ever happened up here in the cool stratosphere, those diminished organs included the whale’s brain. The whale was at once the most spectacular but among the most stupid of his great family; his brain, though a fine control center for his elaborate flight systems, was little more than an organic adding machine. So the magnificent astronaut’s eye view before him meant nothing.

Only the warm oxygen-laden air of the late Cretaceous would allow such immense, delicate creatures to escape from gravity’s clutches, and never again would there be a gene bank like the pterosaur’s to supply raw material for similar evolutionary experiments. Never again would any creature fill this particular ecological niche, and in the future windblown insects would sail in peace.

And human paleontologists, piecing together this remote era from fragments of bone and fossilized plant, would learn little of the true giants. Most pterosaur bones found would be of marine and lakeland species, because that was where fossils were most easily preserved. By comparison the creatures that dominated the roof of the world, the upland areas and mountaintops, left few traces, for their habitats were subject to ferocious uplift and erosion. The highest mountains of the human era, the Himalayas, did not even exist in the Cretaceous.

The fossil record was patchy and selective. All through time there had been monsters and wonders that no human being would ever know had existed— like this immense flyer.

With the most delicate of touches from his immense extended forefingers the whale banked his wings and soared toward a particularly rich layer of aerial plankton.

The cruel night was not yet done with Purga.

Despite the loss of Second, she continued to forage. There was no choice. Death was common; life continued. There was no time to grieve.

But when she returned to her burrow a small, narrow face came pushing out of the dark toward her, a twitching, mobile snout, bright black eyes, quivering whiskers: one of her kind, another male.

She hissed and backed out of the burrow entrance. She could smell blood. The blood of her pups.

It had happened again.
Without hesitation Purga launched herself at the male. But he was fat and strong— evidently a good forager— and he pushed her away easily.

In despair she ran out into the dangerous dawn, where mountainous dinosaurs were starting to stir, the air resonating to the first long-distance calls of the hadrosaurs. She made for an old fern she knew, around whose roots the ground was dry and crumbling. Quickly she dug herself in, ignoring the moist squirms of the worms and beetles. Once she was safe in her cocoon of soil she lay there trembling, trying to shut out of her head the dread stink of her pups’ blood.

The strange male, on discovering Purga’s scent marks— the scent of a fertile female— had followed them back to the burrow, carefully covering over her marks with his own in order to hide her from any other males.

When he had entered the burrow the pups had clustered around the stranger, his same-species smell overwhelming his warning aura of not-of-my-family. He could smell from the traces of fur and dung that a healthy, fertile female lived here. The female was of use to him, but not the pups. They did not smell of him; they were nothing to do with him. Without them, the female would have that much more incentive to raise the litter he would give her.

For the male, it was all utterly logical. The two larger pups had mouthed his belly, seeking milk, even as the male had consumed their younger sister.

The night after that the male found her again, having tracked her scent. He still stank of her dead babies, of the lost part of her. She fought him off savagely.

It took her two more nights before she accepted his courtship. Soon her body would begin to incubate his young.

It was hard.

It was life.

It would have been of no consolation to Purga to know that this brutal landscape, which had swallowed up two of her broods, would soon be overwhelmed by a wave of suffering and death to dwarf anything she had endured.

Earth was now
inside
the comet’s swelling coma, the loose cloud of gases that swathed the nucleus itself.

All over the night side of Earth the tail could be seen stretching away from the sun. It was as if the planet had drifted into a sparkling tunnel. The sky glittered with meteors, tiny bits of comet falling harmlessly into the high atmosphere, creating a light show glimpsed by uncaring dinosaurs.

But the comet’s nucleus was bigger than any meteor. It moved at twenty kilometers per second, at interplanetary speeds. It had already crossed the orbit of the Moon.

From where it would take just five more hours to reach Earth.

All night long, the birds and pterosaurs sang their confusion; during the day, they slumped with exhaustion. There was no room in their neural programming for a new light in the sky, and they were disturbed at a deep cellular level. In the shallow seas, too, the unending light had disturbed the plankton and larger creatures like crab and shrimp; the cynical hunters of the reef fed well.

Only the great dinosaurs were unperturbed. The comet light made no difference to the air temperature, and when true night had fallen they slipped into their usual torpor. On the last night of a reign that had lasted nearly two hundred million years, the rulers of the Earth slept untroubled.

If not for the tyrannosaur eggs, the young giganotosaur would have spotted the disturbed troodon earlier. In the lee of the mountains, he stalked silently through the green shadows. His name meant Giant.

The forest here was sparse, spindly araucaria and tree ferns, scattered over a ground littered with sharp-edged volcanic rocks. Nothing moved. Anything that could hide had already hidden; anything else lay still, hoping for the shadow of death to pass by.

He came to a pile of moss and lichen. Superficially it looked like a heap of debris piled up at random by wind or the passage of animals. But Giant recognized the characteristic scrapings, the lingering smell of meat eater.

It was a nest.

With a rumble of anticipation, he fell on the nest and began to dismantle it with his stubby forearms. When he had exposed the eggs, Giant dug his clawed thumb, with a surgical precision, into the top of the largest. He pulled out the embryo head first. As the mucus and yolk drained from it, lurid colors bright, Giant saw the chick squirm feebly, even saw its tiny heart beat.

Just as the embryos of chimps, gorillas, humans would all be disturbingly similar, so dinosaur fetuses all looked alike. There was no way to know that this chick would have been a female tyrannosaur. Blind, deaf, immature, the embryo struggled to open her mouth, dimly imagining the hulking shape of a mother who would feed her. Giant flicked the embryo into his mouth and swallowed it without chewing. The chick’s life ended in crushing, acidic darkness.