There were males and females alike, some of the women laden with clinging infants. The males also did a great deal of displaying, hooting, aggressive leaping to and fro. Here was something that had not changed down the long years: the structure of primate society was still the same, a flashy male-hierarchy superstructure imposed on top of a network of patient female clans.

In these middle layers of the canopy the taller trees thrust upward past the crowns of their smaller brethren. In this intermediate place, neither low nor high, the people were relatively safe from threats from above and below. And it was here, surrounded by the tall, slim stripes of the great trees' trunks, that they had built their colony.

It was a ball some ten meters across. Its thick wall was made of twigs and dead leaves, crudely crammed together. The leaves had been softened by chewing before being pressed into gaps in the structure. The whole thing was neatly lodged in the crooks of the robust branches of the tree, in which it had been constructed over generations. And it was lived in: A thin stream of shit and piss slid down the tree's great trunk, sewage trickling out of the openings that pocked the colony's base.

This ball of spittle and twigs was the most advanced construction any posthumans were now capable of. But it was the result of instinct, not mind, as empty of conscious planning as a bower bird's nest or a termite mound.

Remembrance could see small faces peering out timidly through gaps in the colony's crude wall. She remembered her time with her own child inside those dank, ill-smelling walls. The colony's basic purpose was to shelter the most vulnerable from the forest's predators: at night the prepubescent young, the old and sickly would cram within its walls. But only the smallest infants and their mothers were allowed to stay in its shelter during the day while the rest risked the open spaces to forage.

And, as stray canopy-filtered rays of sunlight caught the colony, the walls sparkled. Embedded in the packed-together twigs and leaves were bright stones gathered from the forest floor. There were even bits of glass. Across millions of years glass was unstable, becoming opaque as tiny crystals formed within it- but nevertheless these fragments had retained their shapes, bits of windshields or taillights or bottles, now retrieved and gathered to adorn the walls of this shapeless building.

It looked like decoration, but it was not. The glass and bright stones were meant for defense. Even now predators on these postpeople could be deterred by the remnants of buildings, by glittering stones and shining glass, haunted by deep-buried instincts developed in the time of the most dangerous killers who had ever walked the Earth. So Remembrance's folk aped the structures of their ancestors, not even capable of imagining what they were imitating.

Once, of course, the trees had been the domain of primates, where they had been able to roam with little fear of predation. Monkeys and chimpanzees had not needed fortresses of leaf and twig. Times had changed.

As Remembrance lingered, a young male hissed at her. He had a bizarre white patch of fur on his backside, almost like a rabbit's. She knew what he was thinking: He suspected she might be after the patch of bark he was working with his mother and siblings. People's minds were not what their ancestors' had been, but Remembrance was still capable of working out the beliefs and intentions of others.

But White-patch's troop had been weakened today. Since the last time Remembrance had seen them, their elder son had gone. He might have left to seek some other colony, suspended somewhere in the forest's green depths. Or, of course, he might be dead. The family members themselves showed they were still aware of the lost one's absence in the way they looked over their shoulders at nobody, or left a space for a big male who never came. But soon their memories would heal over, and the brother would vanish into the unremembering mists of the past, as lost as had been all the children of man since the construction of the last tombstone.

Remembrance herself would never learn what had become of the other son. This was not an age of information. Nobody told anybody else anything anymore. All she knew for sure was what she saw for herself.

For Remembrance, though, this was an opportunity. She could probably fight this weakened group for a place on their tree. But her poor sleep had left her feeling brittle, restless. It was a mood that had plagued her since the loss of her child. The child's death had been more than a year ago, but so sharp was the pain, so vivid was it still in her kaleidoscopic, unstructured mind, that it might have been yesterday. Like all her kind, Remembrance was a creature not of purposeful planning but of impulse. And today her impulse was not to fight these squabbling folk for the privilege of a place on their crowded branch, to peel back a bit of bark in search of grubs.

She turned away and began to make her way through the tangled levels of trees.

As she swung, clambered, and leapt her way from branch to branch, she began to feel better. The stiffness quickly worked out of her muscles, and it was as if she were coming fully awake. She even forgot, briefly, the loss of her child. She was still young; her kind often lived beyond twenty-five or even thirty years. And, long after a remote ancestor had crawled, baffled, out of a sewer into the greening daylight, her body was well adapted to her way of life, if not yet the deepest chapels of her mind.

So, as she worked in a blur of speed through the trees, she felt a kind of joy. Why not? Much had been lost, but that made no difference to Remembrance. Her brief moment in the light was here, now, and was to be cherished. As she soared through the dense twilight of the forest layers, her lips drew back from her teeth, and she laughed out loud. It was a reflex the children of man had never lost- even though, across Earth's healing face, thirty million summers had flickered and gone.

Remembrance's tropical forest was part of a great belt wrapped around the waist of the planet, a belt broken only by oceans and mountains. The forests were luxuriant- although they had taken thousands of years after the cessation of man's ferocious logging to attain something like their former richness.

The reassembled world, engulfed by forest, had left little room for the descendants of mankind. And so Remembrance's ancestors had left the ground and taken once more to the green womb of the canopies. There had already been primates here: monkeys whose ancestors had evaded the starving humans in the final days, survivors of the great extinction event. At first the posthumans were clumsier than the monkeys. But they were still smart, relatively- and they were desperate. Soon they completed the extinction that their forefathers had begun.

After that they had begun to proliferate. But the pressures that had driven them off the ground continued to pursue them.

Remembrance knew nothing of this. And yet she carried within her a molecular memory, a continuing unbroken line of genetic inheritance that stretched back to the vanished folk who had carved the mighty roadway out of the rock- and back, back far beyond them, to still more distant times when creatures not unlike Remembrance had clambered in trees not unlike this one.

She stopped at a branch laden with fat red fruit. She sat squat on the branch and began to feed briskly, shelling the fruit and sucking down the soft contents, letting the drained husks fall into the darkness below. But as she ate she kept her back to the trunk, her gaze darted fearfully around the shadows, and her motions were fast, furtive.

Despite her watchfulness, she was startled when the first chunk of rind hit her on the back of the head.

Cowering against the trunk, she looked up. Now she saw that the branches above her were heavy with what looked like fruit: fat, dark, pendulous. But those "fruit" were sprouting arms and legs and heads and glittering eyes, and clever hands that hurled rinds and bits of bark and twig down at her. They had probably lain in wait as she approached, and then just as silently converged on her position. They even threw lumps of warm shit.

And now the chattering began. It was a screaming, meaningless jabber that filled her head, disorienting her- as was its purpose. She huddled in the crook of the branch, her hands clapped over her ears.

The Chattering Folk were cousins of Remembrance's kind. They used to be humans too. But the Chatterers lived differently. They were cooperative hunters. All of them, from barely weaned young upward, would work with a cold, instinctive discipline to bring down any prey, or battle any predator. The strategy worked: Remembrance had seen more than one of her kind fall before this treetop army.

Despite their different ways of living, up to a couple of million years ago the two kinds of people could still have crossbred, though their offspring would have been infertile. By now that was impossible. It had been a speciation, one of many. To the Chattering Folk, Remembrance was not kin, nothing but a potential threat- or perhaps, a meal.

She was cut off. There seemed to be a Chatterer on every branch. She could never get past them and reach the sanctuary of another tree. She had only one way off this bare trunk: across the ground itself.

She didn't hesitate. Skittering down the trunk- letting herself fall for long distances, trusting on her reflexes to grab at branches and slow her descent- she escaped toward the deeper gloom of the forest floor.

At first the Chatterers followed her, and their bits of fruit and shit hailed around her, splattering against the bark. She heard them spread out through the tree from which they had ousted her, chattering and screaming their useless triumph.

At last she slid off the trunk. She intended to make for another great tree trunk a couple of hundred meters away, which might be far enough away from the Chatterers to give her a safe passage back to the canopy.

She stepped forward, her eyes wide and alert, walking upright.

Remembrance had narrow hips and long legs, relics of the bipedal days of ground-dwelling savannah apes. She was more upright than any chimp had ever been, more upright than Capo's folk. But even upright, her legs remained slightly bent, her neck sloped forward. Her shoulders were narrow, her arms long and strong, and her feet were long and equipped with opposable toes- all good equipment for climbing, clinging, leaping. Arboreal life had reshaped her kind: Selection had reached back to ancient designs, much modified, their templates never abandoned.

She wasn't comfortable here on the ground. When she looked up she saw layers of foliage, trees competing for the energy of the sun, cutting out all but the most diffuse light. It was like looking up at another world, a three-dimensional city.

By contrast the forest floor was a dark, humid place. Shrubs, herbs, and fungi grew sparsely in the endless twilight. Though leaves and other debris fell in a continual slow rain from the green galleries above, the ground cover was shallow: the ants and termites, whose mounds stood around the floor like eroded monuments, saw to that.

She came to a huge mushroom. She stopped and began to cram its tasty white meat into her mouth. She had eaten little so far that day, and she had used up a lot of energy in fleeing the Chatterers.

Beyond a stand of spindly saplings something moved through the shadows: huge shapes, grunting, snuffling at the dirt. Remembrance ducked behind the mushroom.

The creatures emerged from the shadows, dimly outlined in the gray-green twilight. They had bulky, hairy bodies, stocky heads, and short trunks that scraped at the ground and plucked foliage and fruit from the trees' lower branches. A couple of meters tall at the shoulder, they looked like forest elephants, though they were tuskless.

These browsers' small pointed ears and oddly curling tails gave away their ancestry. They were pigs, descended from one of the few species domesticated by mankind to survive the great destruction, and now shaped into this efficient form. The last true elephants, in fact, had gone with humans into extinction.

More large, hairy creatures shouldered their way into Remembrance's view. They were elephantine forms too, the same size and shape as the pigs. But where the pigs had trunks but lacked tusks, these animals had no trunks, but carried great sweeping horns that curled before them and served as elephants' tusks once had, clearing the ground and upturning roots and tubers. More skittish and aggressive than the pigs, these animals were descended from another generalist survivor of human farmyards, the goats.

The two kinds of browser, pig- and goat-elephants, worked the shallow ground, different enough to be able to share this space, loftily ignoring each other's presence. Remembrance cowered, waiting for a chance to get away from these much-evolved descendants of farm animals.

And then she smelled a breath on her neck: the faintest trace of warmth, the putrid stink of meat.

Immediately she hurled herself forward. Ignoring the elephantine pigs and goats, she ran until she reached a tree trunk and swarmed up, clinging to crevices in the bark. She didn't hesitate for a moment, not even to look back to see what it was that had so nearly crept up on her.

She caught glimpses, though. It was a creature the size of a leopard, with red eyes, long limbs, grasping paws, and powerful incisors.

She knew what it was. It was a rat. When you smelled rat, you ran.

But the rat followed.

To pursue its climbing prey, the rat-leopard's kind had learned to climb too. The rat-leopard had claws, opposable fingers to grasp branches, forelimbs that could swing wide to allow it to hurl itself from branch to branch, even a prehensile tail. It wasn't as good a climber as the best of the primates, like Remembrance. Not yet. But it didn't need to be as good as the best. It only needed to be better than the worst, the weak and the ill- and the unlucky.

And so Remembrance climbed, on and on, ascending into the pale green light of the upper canopy, faster and faster, ignoring the bursting pain in her lungs and the ache in her arms. Soon she was dazzled by the light. She was reaching the upper reaches of the canopy. But still she climbed, for she had no choice.

Until she burst into open daylight.

She almost stumbled, so suddenly had she erupted out of the green. She clung to a narrow branch that swayed alarmingly under her, bright with leaves that, green and lush, drank in the sunlight.

She was perched right on top of the giant tree's uppermost branch. The canopy was a blanket of green that stretched away to the ocean. But she could make out the rocky shoulders of the gorge within which her dense pocket of forest grew, the ancient roadway of her ancestors. She had nowhere to go. Panting, exhausted, her depleted muscles trembling, she could only cling to this spindly branch. The sun beat down, too hot. Unlike her remote ancestors she was not built for the open: Her kind had given up the ability to sweat.

But the rat did not follow her. She thought she glimpsed its red-rimmed eyes, glittering, before it descended back into the gloom of the forest.

For a heartbeat she exulted. She threw back her head and whooped her joy.

Perhaps it was that that gave her away.

She felt a breeze first. Then came an almost metallic rustle of feathers, a swooping shadow over her.

Claws dug deep into the flesh of her shoulders. The pain was immediately agonizing- and grew worse as she was lifted by those claws, her whole weight suspended from scraps of her own flesh. She was flying. flying. She glimpsed the land wheeling beneath her- scraps of forest, swaths of green grassland and brown borametz groves, all laid over a broken, eroded volcanic landscape, and that belt of glimmering sea beyond. She glimpsed the land wheeling beneath her- scraps of forest, swaths of green grassland and brown borametz groves, all laid over a broken, eroded volcanic landscape, and that belt of glimmering sea beyond.

In Remembrance's world there were ferocious predators both above and below, like red mouths all around you, waiting to punish the slightest mistake. In escaping from one peril, she had run straight into the grasp of another.

The bird was like a cross between an owl and an eagle, with a fierce yellow beak and round forward-facing eyes, adapted for its forays into the gloom of the forest canopy. But it was neither owl nor eagle. This ferocious killer was actually descended from finches, another widespread generalist survivor of the human catastrophe.

The finch was hauling her toward a high complex of volcanic plugs, the eroded core of ancient volcanoes. The debris-littered ground nearby was green with grass, here and there browned by groves of borametz trees. And, tucked into the high ledges, Remembrance glimpsed nests: nests full of pink, straining mouths.

She knew what would happen if the finch succeeded in getting her to its nest.

She began to scream and struggle, pounding her fists against the legs and underbelly of the bird. As she fought, the hooked flesh in her shoulder ripped, sending blood streaming down her fur, but she ignored the pulses of agonizing pain.

The finch cawed angrily and flapped its wings, great tents of oily feathers that hammered at her head and back. She could smell the iron staleness of its blood-caked beak. But she was a big piece of meat, even for this giant bird. As she fought they spun toward the ground, hominid and bird tied up in their clumsy midair battle. At last she got her teeth into the softer flesh above the bird's scaly talons. The bird screamed and spasmed. Its claws opened.

And she was falling through sudden silence. The only noise was her own ragged breathing, the buffeting of the air, like a wind. She could still see the bird, a wheeling shadow above her, fast receding. She reached for branches or rocks, but there was nothing to grab.

Oddly, now that she was lost in her own deepest nightmare of falling, she was no longer afraid. She hung limp, waiting.

She smashed into a tree. Leaves and twigs clutched painfully at her skin as she crashed through them. But the foliage slowed her, and she plummeted at last to the grassy ground. Battered, torn, bruised, she was only winded. For a few heartbeats she could not move.

A human's shock would have been deeper. Who was to blame for this sequence of calamities? The rat, the bird of prey, a spell-casting enemy, a malevolent god? Why had this happened? Why me? Why me? But Remembrance asked herself no such questions. For Remembrance, life was not something to be controlled. Life was episodic, random, purposeless. But Remembrance asked herself no such questions. For Remembrance, life was not something to be controlled. Life was episodic, random, purposeless.

That was how things were now, for people. You didn't live long. You didn't get to shape the world around you. You barely understood much of what happened to you. All you thought about was now now: drawing another breath, finding another meal, evading the next random killer.

Seeing what happened next.

When she had got her breath back she rolled to all fours and scuttled into the shade of the tree that had broken her fall.

II.

Remembrance's time might have been called the Age of the Atlantic.

Since the fall of man the continents' chthonic dance had continued. That great ocean, born as a crack in Pangaea over two hundred million years ago, was continuing to widen as new seabed erupted endlessly along the line of the midocean ridge. The Americas had drifted westward, and South America had broken away from North to resume its interrupted career as an island continent. Meanwhile the cluster of continents around Asia had drifted east, so that the Pacific was slowly closing up. Alaska had reached out to Asia, rebuilding the Bering Strait bridge that had been made and undone repeatedly by the Ice Age glaciations.

There had been tremendous, protracted collisions. Australia had migrated north until it rammed itself into southern Asia, and Africa had crashed into southern Europe. It was as if the continents were crowding into the northern hemisphere, leaving the south abandoned save for lonely, icebound Antarctica. But Africa itself had fragmented, as the mighty wound of the ancient Rift Valley had deepened.

Where continents met, new mountain ranges were stitched. Where the Mediterranean had been there was now a mighty mountain range that reached eastward toward the Himalayas. It was the final extinction of the ancient Tethys. No trace of Rome had survived: the bones of emperors and philosophers alike had been crushed, melted, and gone swimming into the Earth itself. But while mountains were built, others evaporated like dew. The Himalayas were eroded to stumps, opening up new migration routes between India and Asia.

Nothing mankind had done in its short and bloody history had made the slightest bit of difference to this patient geographical realignment.

Meanwhile the Earth, left to its own devices, had deployed a variety of healing mechanisms, physical, chemical, biological, and geological, to recover from the devastating interventions of its human inhabitants. Air pollutants had been broken up by sunlight and dispersed. Bog ore had absorbed much metallic waste. Vegetation had recolonized abandoned landscapes, roots breaking up concrete and asphalt, overgrowing ditches and canals. Erosion by wind and water had caused the final collapse of the last structures, washing it all into sand.

Meanwhile the relentless processes of variation and selection had worked to fill an emptied world.

The sun climbed higher. Despite all that had happened to Remembrance, it was not yet midday.

She was stranded on a grassy plain, with purple volcanic hills in the distance, a few sparse stands of trees and shrubs, and a brown patch of borametz, the new kind of tree. Here, in the rain shadow of those purple hills, the rainfall was intermittent and erratic. The soil was habitually dry, and in such conditions trees were unable to establish themselves, and the grasses continued their ancient dominion- almost. Even vegetable communities evolved. And now the grasses had new competitors, in the borametz groves.

The tree that had saved her from the fall was barren of fruit, parched, clinging to life in the dry soil of this grassland. There was nothing to eat here- nothing but the scorpions and beetles that squirmed from beneath the rocks, bugs she popped into her mouth.

She made out a belt of forest, huddled against those remote purple hills, shimmering in the heat haze. Vaguely she realized that if she could get there she would be safer, she might find food, even people of her own kind.

But the forest was far away. Remembrance's distant grandmothers would have easily walked across this stretch of open savannah. But not Remembrance. She was too clumsy a walker. And like Capo, a chimplike ape of a different time, her kind had regrown their hair and forgotten how to sweat.

So she sat there, her mind empty of plans, waiting for something to turn up.

Suddenly a slim head swooped down from the washed-out sky. Remembrance chattered and flinched back against the tree trunk. She saw black round eyes, wide with surprise, set in a slender, fur-covered face, and two long ears that swept back against an elegant neck. It was a rabbit's head- but it was large, as large as a gazelle's.

The rabbit-gazelle evidently decided that the cowering hominid was no particular threat to her. She proceeded to crop at the grass that grew thinly in the shade of the tree.

Cautiously Remembrance crept forward.

Her visitor was one of a herd, she saw now, scattered over the plain and grazing patiently on the grass. They were tall, some twice as tall as she was. Slim, graceful, they looked like gazelles- but they were indeed descended from rabbits, as their long ears and small white tails clearly demonstrated.

The legs of these animals were like gazelles', too. Their forelegs were straight, and could be locked into position to support the animal with little effort. But halfway down their hind legs these rabbits had backward-bending joints that were in fact ankles. The lower leg was like an extended foot- balanced on two hooflike toes- and the knee was up near the torso, hidden in fur. Their back legs held in a permanent sprinter's crouch, the rabbit-gazelles were constantly ready for flight, the most critical task in their lives. As they grazed, the youngest scuttling at the feet of their elders, the herd remained compact, and there was never a time when at least one of the adults was not scanning the grass.

The reason for all of this soon became apparent. One of the bigger bucks startled, went rigid, fled. The rest of the herd followed immediately, in a blur of speed and dust.

From the cover of a bluff of rocks a slim black form darted forward. It was another rat, this one shaped to run with the low-slung power of a cheetah. The rat-cheetah disappeared into the dust, pursuing the rabbit herd.

Stillness resumed. For a time, nothing moved over the grass-covered plain, nothing but the shimmer of the air. The sun slid away from its height. But the heat did not lessen, and thirst clawed at Remembrance's throat.

She crept out of her hiding place. Her very human face, with straight nose, small mouth and chin, wrinkled in the bright afternoon light. She raised herself to her full height and sniffed. She heard a lowing, a clattering of tusks that sounded as if it were coming from the east, away from the sun. And she smelled the tang of water.

She began to run that way. She moved in scurries, hurrying from one patch of covering shade to the next, with frequent drops to an all-fours lope. This daughter of mankind ran like a chimp.

At last she crested a shallow bluff of eroded sandstone. She found herself facing a broad lake. It was fed by streams that snaked from more distant hills, but she could see that it was choked with reeds and fringed by a broad mud pan. She found an acacia to shelter under, and peered out, trying to find a way to get to the water.

Here, just as they always had, the herbivores had gathered to drink.

She saw more rabbits. There were skittish gazellelike creatures of the kind she had seen before. But there were also heavier-built, bisonlike powerhouses- and, running around their feet, smaller creatures that hopped and jumped. The rabbits, widespread and fast breeding, had, after the fall of man, radiated and adapted quickly. But not all of the new species had abandoned the ancient ways. There were still smaller browsers, especially in the forests where small beasts kicked and leapt and hopped as their ancestors always had.

Meanwhile warthogs snuffled and snorted in the muddy fringe of the lake, left all but unchanged by time. If there was no need to adapt, nature was conservative. And Remembrance made out huge, slow-moving creatures, marching serenely through the shallow water. They were related to the goats she had encountered in the forest, but these were giants, with tree trunk legs and horns that curled like mammoth tusks. They lacked trunks- none of these ruminants had evolved that particular anatomical trick- but, giraffelike, they had long necks that let them reach the succulent leaves growing on low-hanging tree branches, or the water of the lake.

A herd of different goat descendants stood knee-deep in the water. They had webbed feet that kept them from sinking in soft mud and sand. Each had a broad bill-like mask before its face. Sculpted from horns, these bills were used for browsing on the soft weeds found at the edge of the lakes. Sucking peacefully at the lakeside vegetation, these goats were like nothing so much as the hadrosaurs, the long-vanished duck-billed dinosaurs.

And, just as the hadrosaurs had been the most diverse group of dinosaurs before the comet fell, so this rediscovery of an ancient strategy was enabling a new radiation. Already many species of the duck-billed goats, subtly distinguished by differences in horn design, size, and diet preferences, were to be found at many of the water courses of the world's tropical regions and elsewhere.

Meanwhile, all around this scene of relatively peaceful herbivorous thirst-quenching- just as there had always been- intent predatory eyes watched the herbivores at work.