But life was not infinitely adaptable.
On Remembrance’s Earth, among the new species there were many novelties. And yet they were all variations on ancient themes. All the new animals were built on the ancient tetrapod body plan, inherited from the first wheezing fish to have crawled out of the mud. And as creatures with backbones, they were all part of a single phylum — a great empire of life.
The first great triumph of multicellular life had been the so-called Cambrian explosion, some five hundred million years before the time of mankind. In a burst of genetic innovation, as many as a hundred phyla had been created: each phylum a significant group of species representing a major design of body plans. All backboned creatures were part of the phylum of chordates. The arthropods, the most populous of the phyla, included creatures like insects, centipedes, millipedes, spiders, and crabs. And so on. Thirty phyla had survived life’s first great shaking down.
Since then species had risen and fallen, and life had suffered major disasters and recoveries over and over again. But not one new phylum had emerged, not one, not even after the Pangaean extinction event, the greatest emptying of all. Even by the time of that ancient event, life’s capability for innovation was much constrained.
The stuff of life was plastic, the mindless processes of variation and selection inventive. But not infinitely so. And with time, less.
It was a question of the DNA. As time had worn away, the molecular software that controlled the development of creatures had itself evolved, becoming tighter, more robust, more controlled. It was as if each genome had been redrafted over and over, each time junk and defects were combed out, each time the coherence of the whole was improved — but each time the possibility for major change was reduced. Extraordinarily ancient, made conservative by the inward-looking complexity of the genomes themselves, life was no longer capable of a great innovation. Even DNA had grown old.
This epochal failure to innovate was an opportunity lost. And life could not take many more hammer blows.
The light in the sky was strange. But, Remembrance’s instinctive calculus quickly computed, it was no threat. In this she was wrong. Purga, who had watched the Devil’s Tail similarly slide silently overhead, might have told her that.
Before the sun had touched the horizon she at last reached her forest in the lee of the volcanic hills, her target for many days. Remembrance peered up at the tall trees before her, the canopy that strained up toward the sky. She thought she saw slim shapes climbing there, and perhaps those dull clots of darkness were nests.
They were not her people. But they were people, and perhaps they would be like her.
She pulled herself off the ground and clambered upward into the comforting green of the canopy.
Something fluttered past her head. It was a flying fish, coming from the sea. As she watched, it sailed into the forest canopy, flapping its fin-wings earnestly, and settled clumsily onto a nest, air wheezing into primitive lungs.
CHAPTER 19
A Far Distant Futurity
Montana, Central New Pangaea. Circa 500 million years after present.
I
Ultimate dug listlessly in the dirt, hoping to find a scorpion or beetle. She was a mound of orange-colored fur on the rust-tinged ground.
This was a flat, dry plain of crimson red rock and sand. It was as if the land had been scraped bare by some vast blade, and the bedrock wind-burnished to a copper sheen. Once there had been mountains to the west, purple-gray cones bringing relief to eyes wearied by flatness. But long ago the wind had torn all the mountains down, leaving great fans of scattered rocks over the plains, rocks that had themselves eroded to dust, leaving no trace.
Half a billion years after the death of the last true human, a new supercontinent had assembled itself. Dominated by desert, as red as the ancient heart of Australia, it was like a vast shield fixed to the blue face of the Earth. On this New Pangaea, there were no barriers, no lakes or mountain ranges. Nowadays it didn’t matter where you went, from pole to equator, from east to west. Everywhere was the same. And there was dust everywhere. Even the air was full of red dust, suspended there by the habitual sandstorms, making the sky a butterscotch-colored dome. It was more like Mars than Earth.
But the sun was a ferocious disk, pumping out heat and light, much brighter than in the past. Any human observer would have cowered from that great fire in the sky.
Under that tremendous glare the heat lay heavy on the land, by day and by night. There was no sound save for the wind and the scratching of the few living things, no sense that things had ever been different on this red planet. The land felt empty, a huge place of resonant silence, a stage from which the actors had departed.
As it happened, far beneath the dust where Ultimate dug — buried under half a billion years of deposits, under the salt and the sandstone of New Pangaea — was the place that had been known as Montana. Ultimate was not far above Hell Creek, where the bones of Joan Useb’s mother had at last joined those of dinosaurs and archaic mammals in the strata she had searched so assiduously.
Ultimate had no way of knowing her peculiar place in history, still less of understanding. But she was among the last of her kind.
Ultimate went home. Home was a pit carved in the harder rock. It offered some shelter from the wind. This was where Ultimate and her kind eked out their lives.
The pit looked artificial. Its floor was smooth, its terraced walls steep. The pit was in fact a quarry, made half a billion years earlier by human beings, dug deep into the bedrock. Even after all this time, even as mountains had come and gone, the quarry had survived almost intact, a mute memorial to the workings of man.
Trees grew on the floor of the pit, standing stately and alone, like sentinels, with their satellite termite colonies towering all around. They were stubby, ugly trees with perennial needlelike leaves, defiant of time. Little else lived here save the people, and other symbiotes of the trees, and many, many tiny creatures that toiled in the dust.
As Ultimate clambered down the pit’s walls, the wind changed and began to blow from the west, from the direction of the inland ocean. Gradually the humidity rose. At last, over the ruined mountains to the west, heavy black clouds began to gather.
Ultimate peered into the western sky. It had never rained here, in Ultimate’s lifetime. Most clouds coming from the distant ocean dumped their rainfall long before they reached a place like this, deep in the supercontinent’s interior. It took a mighty storm indeed to breach those immense defenses of arid plain, a once-in-a-lifetime monster. But that was what was approaching now. You could feel it in the air, feel that something was wrong.
The people hurried back to their Tree, and clambered into its welcoming branches. Hurried, yes — but still they moved with a languid slowness, as if they were swimming through the air’s dense heat.
At ten years old, Ultimate looked something like a small monkey. She was long-limbed, with a narrow torso, narrow shoulders: Even now, in these distant descendants of mankind, the basic body plan of the primates persisted. Her slim body was coated in thick fur, bright red, red as the sand. She had a small head with a large brow and a mobile, expressive face — a very human face, in fact. Small flaps of skin, rather like eyelids, could cover her ears, nose, anus, vagina to trap precious moisture. Her brow was swollen, almost as if her kind had re-evolved the big forebrains of the human age, but behind that brow there was only spongy bone, a great system of sinuses that worked as a refrigeration system to keep her brain cool.