The walls were packed hard and worn smooth by the passage of many, many squirming bodies, and she was immersed in the characteristic stink of milk and piss. The tunnels had been built by the mole folk to take their own slim, scrabbling little bodies, and they were too small for Remembrance. She had to crawl on her belly, dragging herself along with arms and legs that soon ached painfully. It was a nightmare of enclosure.

But there was light. Narrow chimneys snaked to the surface. Thin, angled, they were intended to allow the passage of air while excluding any predator. But enough light diffused down to give her partial impressions of what she was passing through.

Tunnels, branching everywhere, a whole network of them. She could hear echoing spaces beneath and around her, chambers and tunnels and alcoves branching away forever. She caught occasional glimpses of the mole folk- a scrabbling limb or retreating rump, or smoothed over eye sockets gazing blindly. branching everywhere, a whole network of them. She could hear echoing spaces beneath and around her, chambers and tunnels and alcoves branching away forever. She caught occasional glimpses of the mole folk- a scrabbling limb or retreating rump, or smoothed over eye sockets gazing blindly.

Fear and dread filled her mind. But she had no choice but to go on.

Without warning she fell through a thin wall, and tumbled through into a crowded chamber. Babies instantly swarmed over her, biting and scratching.

This large chamber was crowded with children, miniature versions of the adults she had first glimpsed. The place stank overwhelmingly of blood and shit and milk and vomit. Struggling, she pushed the babies away. Almost all of them were female. Their soft, hot little bodies were somehow even more repulsive than the adults'. She turned and tried to clamber back up to the tunnel from which she had fallen.

But now adults came tumbling out of the tunnel. These newcomers did not retreat, as had those she had first encountered. These mole folk were soldiers, come to protect the birthing chamber from the intruder.

The first of the soldiers leapt at her, its digging claws extended. Remembrance raised her arm to protect her throat. Under the mole creature's soft weight she fell back into the wriggling heap of infants.

The soldier was an adult, a female. But her breasts were as tiny as a child's, her pudenda undeveloped. She was sterile. Nevertheless, squirming, biting, and scratching, she fought as ferociously as if her own children were at risk.

Remembrance might have succumbed to the soldier's assault, but she got in a lucky kick. The heel of her foot caught the soldier just below her breastbone. The little creature went flying back, colliding with those who were trying to follow her, so they dissolved into a wriggling mass of limbs and claws.

Dimly making out a tunnel mouth on the far side of the chamber, Remembrance hurled herself that way. She went on all fours, wading through mewling infants.

But still the soldiers pursued her. She struggled on through the tunnels, selecting branches at random. She could not tell if she were climbing upward or deeper into the ground. But for now nothing mattered but to flee.

She broke through another wall, fell, landed on something hard, like a heap of rocks. No, not rocks- they were nuts, nuts, big heavy nuts, the nuts of the borametz tree. Stumbling further, she found an immense heap of seed and roots. This huge chamber was crammed full of food. big heavy nuts, the nuts of the borametz tree. Stumbling further, she found an immense heap of seed and roots. This huge chamber was crammed full of food.

Still the soldiers came, swarming, snuffling.

She leapt to the far side of the chamber and dug herself in against the wall, behind a pile of the heavy seeds. She picked up nuts and hurled them as hard as she could. She could hardly miss, and she was rewarded by the crack of the heavy shells on those eyeless heads. There was whimpering and confusion as the front line of the soldiers pushed back into those who followed, trying to get away from this missile-throwing demon.

But not all the soldiers retreated. Several stayed at the mouth of the tunnel, hissing and spitting at her.

Remembrance, exhausted and battered, really didn't care. She couldn't get out of here, but the soldiers couldn't get to her either. She stopped hurling the nuts.

She smelled dampness. She found a place in the earth wall behind her where a thin tree root pushed through. She had broken the root, and now it was dripping a thin, watery sap. She clamped the root to her mouth and began to suck down the sap. It was sweet, and it trickled over her parched throat. She found some tubers under the nut pile. In the near dark, she bit into sweet flesh, sating her hunger.

She lay down over what was left of her stolen roots, with heavy nuts grasped against her chest. Soon the hissing of the impotent soldiers seemed no more disturbing than the noise of a distant rainstorm. Her energy drained, shocked, bewildered, she actually dozed.

But there was movement in the chamber, scrabbling, slithering. Reluctantly she poked her head above the barrier of nuts. She saw mole folk moving around the chamber, but these were not soldiers. They seemed to have forgotten she was here. They were picking up nuts and passing them out of the chamber, into the tunnel entrance. She had no idea what they were doing. She didn't have the intellectual capacity even to formulate the question. All that mattered was that they were no threat to her.

She slumped back into her improvised nest and, nibbling on a bit of root, fell asleep.

The mole folk's underground way of life had started as a response to the aridity of this place- that and the usual ferocious predation. Even the rats couldn't get you if you burrowed in the ground.

Of course there had been prices to be paid. People had shrunk, generation by generation, the better to fit into the growing complexes of burrows. And over time bodies had been shaped by the restrictions of tunnel life: useless eyes were lost, nails became digging claws, body hair evaporated save for vibrissae, whiskers, which sprouted from lengthening muzzles, the better to help them feel their way in the dark.

The aridity had also promoted cooperation.

The mole folk lived off roots and tubers, riches buried in the ground. But in the dryness the tubers grew large and widely spaced. It was better for the plants that way, because big tubers did not desiccate so easily. A solo mole person, however, burrowing away at random, was likely to starve long before stumbling across the scattered bounty. But if you were prepared to share what you found, then having many colony members digging in all directions brought a more likely chance of success for the group as a whole.

All posthumans were social, like their ancestors, but they specialized in the way they had developed that sociality. These mole folk had taken sociality about as far as you could go. They came to live like social insects, like ants or bees or termites. Or perhaps they were like naked mole rats, the peculiar hive-dwelling rodents that had once infested Somalia, Kenya, and Ethiopia, now long extinct.

This was a hive. There was no conscious mind at work here in the hive. But then consciousness wasn't necessary. The hive's global organization emerged from the sum of the interactions of its members.

Most of the inhabitants of the colony were female, but only a few of those females were fertile. These "queens" had produced the infants Remembrance had stumbled upon in the birthing chamber. The rest of the females were sterile- indeed they never entered puberty- and their lives were devoted to the care not of their own children, but of those of their sisters and cousins.

For the genes it made sense, of course. Otherwise it would not have happened. The colony was one vast family, bound together by inbreeding. By ensuring the preservation of the colony, you could ensure that your genetic legacy was transmitted to the future, even if not directly through your own offspring. In fact, if you were sterile, that was the only only way you could pass on your genes. way you could pass on your genes.

More sacrifices. As the bodies of these colony people had shriveled, so had their brains. You didn't need need a brain. The hive would take care of you- rather as the mouse-raptors took care of the elephant folk they farmed. There were better things to be done with your body's energy than fuel an unnecessary brain. a brain. The hive would take care of you- rather as the mouse-raptors took care of the elephant folk they farmed. There were better things to be done with your body's energy than fuel an unnecessary brain.

And, with time, the mole folk were even giving up that most precious of all mammalian inheritances: hot-bloodedness itself. As they rarely ventured out of their burrows, the mole folk did not need such expensive metabolic machinery- and a cold-blooded scout cost less food than a hot-blooded one. It was done without sentiment. With time, the colony folk would grow smaller yet, smaller than any hot-blooded mammal's design could maintain. In another few million years these mole folk would swarm like tiny lizards, competing with the reptiles and amphibians who had always inhabited the microecology.

So the mole folk scuttled through their spit-walled corridors, their whiskers twitching, fearful and ignorant. But in their dreams their residual eyes, covered by flesh, would flicker and dart as they dreamed strange dreams of open plains, and running, running.

She lost track of time. Suspended in the suffocating heat of the chamber, she slept, ate roots and tubers, sucked water from the tree roots. The mole folk left her alone. She was in there for days, not thinking, with no impulse to act save to eat, piss, shit, sleep.

At last, though, something disturbed her. She woke, looked up drowsily.

In the dim, diffuse light, she saw that mole folk were clambering into the chamber, and out again through a narrow passageway in the roof. They moved in a jostling column, the flaccid skin on their pale bodies crumpling as they pressed against each other, their whiskers twitching, clawed hands scrabbling.

Though the mouse-raptor and other dangers lingered at the back of her mind, Remembrance found herself longing for openness- for a glimpse of day, for fresh air, for green. green.

She waited until the mole folk had passed. Then she clambered over the low heapings of roots and pushed her way into the narrow breach in the roof.

It was a kind of chimney that led up toward a crack of purple-black sky. The sight of the sky drove her on, and she wedged her body ever more tightly into the narrow, irregular chimney, scrabbling at the dirt with her hands and feet, knees and elbows, forcing her chest and hips through gaps that seemed far too small for them.

At last her head broke above ground level. She took in great gulps of fresh air and immediately felt invigorated. But the air was cold. The twisted forms of the borametz trees occluded a star-laden sky. It was night, the most natural time for the mole folk to venture to the surface. She forced her arms out of the hole, got her hands onto the surface, and with a tree-climber's strength she pushed herself upward, prizing her body out of the chimney like a cork from a bottle.

The mole folk were everywhere, running on hind legs and knuckles, snuffling, shuffling, and squirming. But their movement was orderly. They moved in great columns that wound through the termite heaps and ant nests, to and from the borametz trees. They were picking off the nuts that grew in clusters at the roots of the trees, nuts that were sometimes as large as their heads. But they did not seem to be trying to break them open, to get at their flesh. They weren't even taking them into their underground stores. In fact, she saw now, they were actually bringing nuts up up from the underground chambers. from the underground chambers.

They were taking the nuts, one at a time, out to the fringe of the borametz grove. There workers dug into the dirt, scattering the thin grass to make little pits into which the nuts were dropped and buried.

Each borametz was the center of a symbiotic community of insects and animals.

Symbioses between plants and other organisms were very ancient: The flowering plants and the social insects had actually evolved in tandem, one serving the needs of the other. And it was the social insects, the ants and termites, who had been the first to be co-opted by the new tree species' reproductive strategies.

Every symbiosis was a kind of bargain. Attendants, insect or mammal, would remove the borametz trees' seeds from their root bases, but they would not devour them. They would store them. And when conditions were right they would transport them to a place suitable for planting, usually at the fringe of an existing grove, where there would be little competition with established trees or grasses. And so the grove would grow. In return for their labors the attendants were rewarded with water: water brought up even in the most arid areas from deep water tables by the borametz's exceptionally deep-growing roots.

It had not been hard for the mole folk, with their cooperative society and still-agile primate hands and brains, to learn how to emulate the termites and the ants and begin to tend the borametz trees themselves. Indeed with their greater sizes, they were able to move larger weights than the insects, and the development of new borametz species with large seed cases had resulted.

For the borametz it was a question of efficiency. The borametz had to expend much less energy on each successful seedling than its competitors. And so it was a reproductive strategy that enabled the borametz to flourish where other tree species could not. Little by little, as their attendants carried their seeds from their orchards into the meadows, the borametz species were moving out into the grasslands. At last, more than fifty million years after the triumph of the grasses, the trees were finding a way to fight back.

The borametz trees embodied the first great vegetable revolution since the flowering plants that had arisen in the days before Chicxulub. And in the ages to come- like the initial emergence of plants on land that had enabled animals to leave the sea, like the evolution of the flowering plants, like the rise of the grasses- this new vegetable archetype would have a profound impact on all forms of life.

As she sat on the ground, still panting, watching the mole folks' baffling behavior, Remembrance heard a familiar soft footstep, an awful hissing breath. She turned her head, slowly, trying to be invisible.

It was the mouse-raptor- the juvenile, the same one that had strayed from its herd of elephant folk to chase her here. It was standing over a line of mole folk who scurried back and forth from tree to planting ground, oblivious to the threat that loomed over them.

It was as if the raptor were taking a small revenge. Few rodents could get through the mighty shells of the borametz nuts. As the borametz spread, the seed-eating stock from which this raptor had sprung- along with birds and other species- would soon be threatened with dwindling food supplies, dwindling ranges- and, in some cases, extinction.

The raptor made its choice. It bent down, balancing with its long tail, and used its delicate front claws to scoop up a bewildered mole woman. The raptor turned her over and stroked her soft belly, almost tenderly.

The mole woman struggled feebly, cut off from the colony for the first time in her life, divorced from its subtle social pressures. It was as if she had suddenly surfaced from an ocean of blood and milk, and she was truly terrified, for the first and last time. Then the raptor's head descended.

Her companions hurried on past the feet of her killer, their flow barely disturbed.

The mouse-raptor turned, its small ears twitching. And it stared straight at Remembrance.

Without hesitation she plunged straight back into her hole in the ground.

Remembrance stayed in the food chamber for several more days. But she was no longer able to settle back into the exhausted fog that had enveloped her.

In the end it was the madness of the mole folk that drove her out.

Even for this arid area, the season had been dry. The mole folk were having increasing difficulty in finding the roots and tubers on which they relied. The stock in the chamber dwindled steadily, and started to be replaced by other vegetation, like the violet leaves of copper flowers. But this unwelcome diet contained toxic elements. Gradually the poisons built up in the bloodstreams of the mole folk.

At last, everything fell apart.

Again Remembrance was startled awake by a rush of mole folk through the nearly empty food store. But this time they did not move in their orderly columns out through the vents. Instead they swarmed madly, surging up and out of the chamber, shattering its roof in their eagerness to be on the surface.

Remembrance, keeping out of the way of blindly scrabbling claws, followed gingerly. She emerged, this time, into full daylight.

All around her the mole folk swarmed. There were many, many of them, running over the ground, a carpet of squirming bare flesh. The air was full of their milky stink, the scraping of their skins against one another. There were far more than could have come from her own colony: Many hives had emptied as a burst of madness swept through the poisoned, half-intoxicated population.

Already the predators were showing interest. Remembrance saw the stealthy form of a rat-cheetah and a pack of doglike postmice, while overhead birds of prey began their descent. For those who sought flesh this was a miracle, as these little packets of meat just bubbled out of the ground.

It was all a response to the shortage of food. The mole folks' overcrowded burrows had emptied as they swarmed everywhere in a mindless search for provision. But in their intoxicated state they were unable to keep themselves from danger. Many of this horde would die today, most in the mouths of predators. In the long run it did not matter to the hives. Each colony would retain enough breeding stock to survive. And it wasn't necessarily a bad thing for their numbers to be reduced in these times of semidrought. Mole folk reproduced quickly, and as soon as the food supply picked up, the empty burrows and chambers would be full again.

The genes would go on: That was all that mattered. Even this periodic madness was part of the grander design. But many small minds would be extinguished today.

As the predators started to feed- as the air filled with the crunch of bone and gristle, the squeals of the dying, the stink of blood- Remembrance slipped away from this place of madness and death, and resumed her long-broken journey toward the distant purple hills.

IV.

Remembrance came at last to a great bay, a place where the ocean pushed into the land.

She clambered down exposed sandstone bluffs. Once this area had been under the sea, and sediment had been laid down over millions of years. Now the land had been uplifted, and rivers and streams had cut great gouges in the exposed seabed, revealing deep, dense strata- in some of which, sandwiched between thick layers of sandstone, were embedded traces of shipwrecks and debris from vanished cities.

At last Remembrance reached the beach itself. She scampered along its upper fringe, sticking to the shade of the rocks and scrub grass. The sand was sharp under her feet and knuckles, and got into her fur. This was a young beach, and the sand was still full of jagged edges, too new to have been eroded smooth.

She came to a freshwater stream that trickled down from the rocks toward the beach. Where the water decanted onto the sand, a small stand of trees clung to life. She ducked down and pushed her mouth into the cool water, sucking up great mouthfuls. Then she clambered into the stream itself and scraped the water through her fur, trying to get rid of the sand and fleas and ticks.

That done, she crawled into the shade of the trees. There was no fruit here, but the leaf-strewn floor, cold and damp, harbored many toiling insects that she popped into her mouth.

Before her the sea lapped softly, the water bright in the high sunlight. The sea meant nothing to her, but its distant glimmer had always attracted her, and it was oddly pleasing for her to be here.

In fact the sea had been the savior of her kind.

Torn by great tectonic forces, Africa's Rift Valley had eventually become a true rift in the fabric of the continent. The sea had invaded, and the whole of eastern Africa had sheared off the mainland and sailed away into what had been the Indian Ocean, there to begin its own destiny. So chthonically slow was this immense process that the mayfly creatures living on this new island had scarcely noticed it happening. And yet, for Remembrance's kind, it had been crucial.

After the fall of mankind, there had been pockets of survivors left all over the planet. Almost everywhere the competition with the rodents had been too fierce. Only here, on this rifted fragment of Africa, had an accident of geology saved the posthumans, giving them time to find ways to survive the rodents' ruthless competitive onslaught.

Once this place, East Africa, had been the cradle that had shaped mankind. Now it was the final refuge of man's last children.

There was something in the water. Cautiously, Remembrance cowered back into the shade.

It was a great black shape, sleek and powerful, swimming purposefully. It seemed to roll, and a fin a little like a bird's wing was raised into the air. Remembrance made out a bulbous head lifting above the water, with a broad sievelike beak. Water showered from two nostrils set in the top of the beak, sparkling in the air, expelled with a sharp whooshing noise. Then the great body flexed and dove back under the surface. She caught a last glimpse of a tail, and then the creature had vanished. Despite its immense bulk, it left scarcely a ripple in the water.

In this giant's wake more slim, powerful bodies leapt from the water, three, four, five of them. They swept through graceful arcs and plunged back into the sea, and then rose to leap again and again. Their bodies were shaped like those of fish, but these dolphinlike creatures were evidently not fish. They were equipped with beaks like birds, stretched into long orange pincers.

Behind the "dolphins," in turn, came more followers, likewise hopping and buzzing over the ocean surface. Much smaller, these were true fish. Their wet scales glistened, and fins like wings fluttered at the sides of their slim, golden bodies as they made their short, jerky flights over the water.

The "whale" was not a true whale, the "dolphins" not dolphins. Those great marine mammals had preceded humanity into extinction. These creatures were descended from birds: In fact, from the cormorants of the Galapagos Islands in the Pacific, which, blown there from mainland South America by contrary winds, had given up flight and taken to exploiting the sea. Their descendants' wings had become fins, their feet flukes, their beaks a variety of specialized instruments- snappers, strainers- for extracting food from the ocean. Some of the species of "dolphin" had even regrown the teeth of their ancient reptilian ancestors: The genetic design for teeth had lain dormant in birds' genomes for two hundred million years, waiting to be re-expressed when required.

Invisibly slow on any human timescale, adaptation and selection were nevertheless capable, given thirty million years, of turning a cormorant into a whale, a dolphin, or a seal.

And, strangely enough, all the swimming birds Remembrance saw were indirect legacies of Joan Useb.

As Remembrance watched, a dolphinlike creature erupted out of the water right in the middle of the cloud of flying fish. The fish scattered, their fin-wings buzzing, but the beak of the "dolphin" snapped closed on one, two, three of them before its sleek body fell back into the water.

The sun was starting its long descent toward the sea. Remembrance stood up, brushed herself free of sand, and resumed her cautious knuckle-walk along the fringe of the beach, but something overhead distracted her. She glanced up at the sky, fearing it was another bird of prey. It was a light like a star, but the sky was still too bright for stars. As she watched, it slid over the roof of the sky.

The light in the sky was Eros.

NEAR, the humble, long-dead probe, had spent thirty million years swimming with its asteroid host through the spaces beyond Mars. Its exposed parts were heavily eroded, metal walls reduced to paper thinness by endless microscopic impacts. At the touch of a gloved astronaut's hand it would have crumbled like a sculpture of dust.

But NEAR had survived this far, among the last of all of mankind's artifacts. If Eros had kept up its eccentric dance around the sun, perhaps NEAR could have survived longer yet. But it was not going to get that chance.

The asteroid's passage through the atmosphere would be mercifully swift. The fragile probe, returning to the planet where it had been made, would flash to vapor only fractions of a second before the great body with which it had long ago rendezvoused was itself destroyed.

Earth's evolutionary laboratories had been stirred many times by monstrous interventions from without. Now, here was another stirring. And over the bright scene on which Remembrance gazed, a curtain would soon be drawn.

Remembrance herself would survive, as would the children she would bear in the future. Once again the great work would begin: Once again the processes of variation and selection would sculpt the descendants of the survivors to fill shattered ecological systems.

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 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. 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 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. 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.