Then he hauled her without ceremony back into the forest.

Whiteblood had spotted Roamer- a juvenile female wandering alone, an unusual opportunity. He had stalked her carefully, a fruit eater moving like an experienced hunter. And now the cover of the storm had given him the opportunity he needed to take her. Whiteblood had his own problems- and he thought Roamer might be part of the answer.

Like their notharctus ancestors, anthro females lived in tight supportive groups. But in this seasonless tropical forest, perpetually abundant, there was no need for their breeding cycles to be synchronized. Life was much more flexible, with different females coming into estrus at different times.

That made it easier for a small group of males- even a single male, sometimes- to monopolize a female group. Unlike the notharctus Emperor, it wasn't necessary for an anthro male to try to cover all his females in a single day, or to face the impossible task of keeping other males away. Instead it was enough that he kept rivals away from the small number of females who were fertile at any given time.

Though they were physically larger, anthro males did not "own" the females, or dominate them excessively. But the males, bound to the female group by a genetic loyalty- in a promiscuous group there was always a chance that any child born might be yours yours- would work to protect the group from outsiders and predators. For their part the females were generally content with the loose satellite male communities that accreted around them. Males were occasionally useful, obviously necessary, rarely troublesome.

But recently, for Whiteblood's troop, things had gone wrong.

Ten of the twenty-three females in the group had gone into estrus simultaneously. Soon other males had been attracted, drawn by the scent of blood and pheromones. Suddenly there weren't enough females to go around. It had been an unstable situation, intensely competitive. Already there had been bloody battles. There was a danger the group might fission altogether.

So Whiteblood had gone out hunting females. Juveniles were the preferred target: young and small enough to be handled easily, foolish enough to be easy to separate from their home groups. Of course it meant waiting a year or more before a child like Roamer could be mated. But Whiteblood was prepared to wait: His mind was complex enough for him to act now in the prospect of reward later.

For Whiteblood the situation was quite logical. But for Roamer it was a nightmare.

Suddenly they were swinging and running at a ferocious rate. Whiteblood kept hold of her scruff, seeming to find her no trouble to haul. Roamer had never moved in these great bounds, swoops, and leaps: Her mother and the other females, more sedentary than the males, moved much more cautiously than this. this. And she was being carried a long way; she could smell muddy water, for they were approaching the bank of the river itself. And she was being carried a long way; she could smell muddy water, for they were approaching the bank of the river itself.

And meanwhile the rain clattered down, pelting through the leaves and turning the air into a gray misty murk. Her fur was sodden and water ran into her eyes, making it impossible to see. Far below them, water ran across the sodden ground, rivulets gathering into streams that washed red-brown mud into the already swollen river. It was as if forest and river were merging, dissolving into each other under the storm's power.

Her panic intensified. She struggled to get free of Whiteblood's grasping hand. All she got for her troubles were cuffs on the back of her head, hard enough to make her squeal.

At last they reached Whiteblood's home range. Most of the troop, males, females, and infants, had clustered together in a single tree, a low, broad mango. They sat in rows on the branches, huddled together in sodden misery. But when the males saw what Whiteblood had brought back, they hooted and slapped the branches.

Whiteblood, without ceremony, thrust Roamer at a group of females. One female started poking hard at Roamer's face, belly, and genitals. Roamer slapped her hand away, hooting in protest. But the female came back for more, and now more of them crowded around her, striving to get close to the newcomer. Their curiosity was a mixture of the anthros' usual fascination with someone new, and a kind of rivalry over this potential competitor, a new recruit in the ever-shifting hierarchies.

For Roamer everything was bewildering: the sheets of lightning flashing over the purple sky, the hammering rain on her face, the roar of water below, the damp-fur, unfamiliar stink of the females and young around her. Surrounded by open pink mouths and questing fingers, she was overwhelmed. Struggling to escape, she lunged forward, and found herself briefly dangling over the branch.

And she looked down on strangeness.

Two indricotheres were lurking under the tree. These great creatures were a kind of hornless rhino. Looking like meaty giraffes, they had long legs, supple necks, and hides like those of elephants. They were oddly graceful in a slow-moving way, even if they did mass as much as three times as an African elephant- and so huge they were unused to being threatened by anything. Even now they reached up their thick necks and horselike faces to crop at the tree's soaking foliage.

But they were in danger. Muddy water flowed over the ground, washing around the indricotheres' legs, as if the tree and the indricotheres alike stood in the river itself.

At last a great sheet of muddy soil broke away from the riverbank, right next to the tree's shallow roots, and slid without ceremony into the river. One mighty indricothere lowed, its great flat elephantine feet scrabbling at a ground suddenly turned into a slippery, treacherous slope- and then it fell, fifteen tons of meat flying, its neck twisting and long tail working. It hit the water with a tremendous splash, and in an instant it was gone, swept away into the voracious river.

The second indricothere lowed its loss. But it too was in peril as the ground continued to dissolve under the water's relentless probing, and the bereft animal lumbered backward to safety.

But the tree itself was in trouble. Its roots had been exposed by the sudden erosion of the flash flood, and further undermined by the river's assault on its bank. The trunk creaked once, and shuddered.

And then, with a series of explosive cracks, the roots gave way. The tree began to topple toward the water. Like fruit from a shaken branch, primates of all sizes tumbled out of the tree and fell screaming into the turbulent water.

Roamer howled and clung to her branch as the tree tipped nightmarishly, all the way into the river.

The first few minutes were the worst.

Close to the riverbank the water was at its most turbulent, torn between the fast-flowing current and friction with the land. In this mighty torrent even the great mango tree was like a twig tossed in a brook. It bucked and creaked and twisted. First its foliage slammed into the water, then its roots, clogged with mud and rocks, would claw toward the sky. Roamer was rolled and dunked, plunged into cloudy brown water that forced its way into her mouth and nose, then carried into the air again.

At last the tree slid away from the turbulence near the bank and drifted into the center of the river, where its rocking and twisting quickly damped out.

Roamer found herself stuck underwater. She looked up through muddy murk at a glimmering surface littered with leaves and twigs. Already her mouth and throat were filling up, and panic overwhelmed her. With a bubbling scream she scrambled up through the tangled, broken foliage, clambering toward the light.

She broke through the surface. Light, noise, and the battering rain assaulted her senses. She hauled herself out of the water and lay flat on a branch.

The tree was floating branches first down the river. Its tangled, ripped roots reached up toward the lowering, lightning-strewn sky. Roamer raised her head, peering around for other anthros. It was not easy to recognize them through the thick rain-filled air, so battered and sodden were they, but she made out Whiteblood, the burly male who had abducted her, a couple of other males- and a female with an infant that had somehow hung onto her back, a little bundle of soaked, miserable fur.

Even though she was just as battered and half drowned as before, Roamer felt suddenly better. If she had been left alone it would have been the most unbearable thing of all; the presence of others was comforting. But still, these others were not her family, not her troop.

More displaced vegetation coursed over the surface of the river, clustering along its spine where the water ran deepest. There were more trees and bushes, some of them washed by this precursor of the Congo thousands of kilometers downstream from the very different lands in the center of the continent. There were animals here too. Some of them clung to the floating foliage, like the anthros. She saw the flitting, nervous forms of a couple of crowders, and even a potbelly, sitting squat on the trunk of a walnut. The potbelly, a female, had found a stable place to sit, and the rain didn't bother her. She had already resumed her usual habit of feeding on leaves conveniently delivered to her clutching hands and feet.

But not all the animals in this gruesome assemblage had made it here alive. There was a whole family of fat, piglike anthracotheres, all of them drowned, stuck in the branches of a broken palm like meaty fruit. And the huge indricothere that had been washed into the river just before the fall of the mango was here too, a great carcass drifting in the water, long neck lolling back and powerful legs splayed, just another bit of floating detritus jammed in with the rest.

Gradually, as the river broadened, the subtle currents shoved these fragments together, foliage and roots tangling, and a makeshift raft assembled itself. The animals stared at one another, and at the churning river, as their crude vessel drifted on.

Roamer could see the forest, growing thick and green on shallow riverbank slopes of eroded sandstone. The trees were mangos, palms, a kind of primitive banana. Branches hung low over the water, and lianas and vines looped over the tangled terraces. Her arms ached for a branch to swing from, a way she could climb from here to there. But the forest was separated from her by churning water- and as the vegetable raft continued to sail downstream, those tempting banks receded further, and the familiar forest gave way to the mangroves that dominated the coastal areas.

The rain wasn't done yet. It actually fell harder. Fat droplets hurled themselves out of the leaden sky. The water was stippled with craters that disappeared as soon as they were formed. A white-noise harshness flooded her ears, so that it was as if she were lost in a kind of huge bubble of water, water below and around her, with only this broken mango to cling to. Moaning, chilled to the bone, Roamer burrowed into the branches of the mango and huddled, alone, waiting for everything to go away, and for her to be returned to the world she knew, of trees and fruit and anthros.

That, however, was never going to happen.

The storm, heavy as it was, blew itself out quickly. Roamer saw finger-thin shafts of light pushing into her shelter of foliage. The rain noise had gone, to be replaced by the eerily soft lapping of water.

She struggled out of the branches and clambered on top of the tree. The sun was strong, as if the air had been cleared, and she felt its warmth sink deep into her fur, drying it quickly. For a heartbeat she luxuriated in the warmth and dryness.

But there was no forest here: only this fallen tree and its cluster of broken companions, drifting over a gray-brown sheet of water. There weren't even any riverbanks. On three sides of the tree, all she could see was water, all the way to a knife-sharp horizon. But when she looked back the way the raft had drifted, she spotted land: a line of crowded green and brown, striped over the eastern horizon.

A line that was receding.

The raft of debris had been washed out to sea, out into the widening Atlantic, anthros, potbelly, crowders, and all.

II.

After the days of Noth the geometry of the restless world had continued to evolve, and it continued to shape the destinies of the hapless creatures who rode the continental rafts.

The two great cracks that had doomed ancient Pangaea- the east-west Tethys Sea, and the north-south Atlantic Ocean- closed and opened respectively. Africa was undergoing a slow collision with Europe. Meanwhile India was drifting north to crash into Asia, and the Himalayan Mountains were being thrust into the air. But immediately after the young mountains were born, the rain and the glaciers had begun their work, gouging and eroding, washing the mountains back to the sea: On this turbulent planet, rock flowed like water, and mountain ranges rose and fell like dreams. But as the continents closed, the Edenic flow of the Tethys was doomed, though fragments of the shrinking ocean would survive as the Black, Caspian, and Aral Seas, and in the west as the Mediterranean.

As the Tethys died there was a great drying, right across the belly of the world. Once there had been mangrove forests in the Sahara. Now a great belt of semiarid scrub spread around the old track of the Tethys, across North America, southern Eurasia, and northern Africa.

Meanwhile, the huge land bridge that had closed off the northern Atlantic, spanning from North America to northern Europe via Greenland and Britain, was being severed, and the Atlantic reached up to the Arctic Ocean. As the ancient east-west ocean passage was being closed, so a new channel from south to north was opening.

Thus ocean currents were reshaped.

The oceans were great reservoirs of energy, restless, unstable, mobile. And all the oceans were laced with currents, great invisible Niles that dwarfed any river on land. The currents were driven by the sun's heat and the Earth's rotation; the top few meters of the oceans stored as much energy as the whole of the atmosphere.

Now the huge equatorial currents that had once rolled around the Tethys belt were disrupted. But already the great flows that would dominate the widening Atlantic were in place: A precursor of the Gulf Stream flowed, a mighty river sixty kilometers across, running south to north with the force of three hundred Amazons.

But this change in circulation patterns would reconstruct the planet's climate. For while equatorial currents promoted warming, north-south interpolar currents provoked a vast refrigeration.

To make matters worse, Antarctica had settled over the Earth's southern pole. Now its great ice cap had begun to gather, for the first time in two hundred million years. Vast, cold circumpolar ocean currents gathered in the southern seas, feeding the great northward currents of the Atlantic.

It was a crucial change: the start of a mighty planetary cooling, a downturn of the graph, that would persist to human times and well beyond.

All over the planet, the old climate belts shrank toward the equator. Tropical vegetation types survived only in the equatorial latitudes. In the north, a new kind of ecology appeared, a temperate woodland of mixed conifers and deciduous trees. Vast swaths of it covered the northern lands, stretching across North America, Europe, and Asia from the tropic to the Arctic.

This climatic collapse triggered a new dying- what paleobiologists would later call the Great Cut. It was a drawn-out, multiple event. In the ocean the plankton population crashed repeatedly. Many species of gastropods and bivalves disappeared.

And on the land, after thirty million years of comfortable success, the mammals suffered their first mass extinction ever. Mammalian history was cut in half. The exotic assemblages of Noth's times finally succumbed. But new, larger herbivores began to evolve, with heavy-duty ridged teeth able to cope with the new, coarser vegetation typical of seasonal woodland. By Roamer's time the first proboscideans, properly equipped with trunks and tusks, were already walking the African plains. The trunk, unparalleled for muscular flexibility save for an octopus's arm, was used for stuffing the animal's mouth with the vast quantity of food it needed. These deinotheres had stubby trunks, and odd, downward-curving tusks that they used for stripping the bark from trees. But, unlike their moeritherium ancestors, they looked looked like elephants, and some already grew as tall as the African elephants of later times. like elephants, and some already grew as tall as the African elephants of later times.

And this was a time of success for the horses. The descendants of the timid creatures of Noth's forest world had diversified into many woodland browser types- some of them as large as gazelles, but with tougher teeth than their ancestors had had to take leaves rather than soft fruit- along with longer-legged plains animals slowly adapting to a diet of grass. Most of the horses now had three toes on both their front and back feet, but some plains-living runners were starting to lose their side toes, and were putting all their weight on their central toes. But as the forests shrank this diversity was already falling; soon many of the forest species would disappear. The rodents, too, were diversifying, with the appearance of the first gophers, beavers, dormice and hamsters, a great diversity of squirrels- and the first rats.

But the new conditions were not kind to the primates. Their natural habitat, the tropical forests, had shriveled back to the southern tropics. Many of the primate families had gone extinct. Fruit eaters like Roamer lingered only in the tropical woodlands of Africa and southern Asia, clinging to the year-long food supply these forests still provided. By the time Roamer was born there were no primates left north of the tropics, and- since the rise of the rodents- none in the Americas at all: not a single species.

But that was soon to change.

The sea around Roamer was a sheet of gunmetal gray across which waves rippled, languid as mercury. Roamer was in an utterly baffling place: a sketchy, elemental two-dimensional environment, static yet full of mysterious churning motion, that could not have been more different from the forest.

She felt nervous climbing around on top of the vegetation. She expected some ferocious aerial predator to bite into her skull at any moment. And as she moved she could feel the uneasy raft shift under her, its loosely tangled components rustling with the slow breathing of the sea. It felt as if the whole thing might disintegrate at any moment.

There were just six anthros: three males, two females- including Roamer- and the infant who still clung sleepily to the fur of its mother. These were the only survivors of Whiteblood's troop.

The anthros sat on a tangle of branches, eyeing one another. It was time to form provisional hierarchies.

For the two females the priorities were clear enough.

The other female, the mother, was a burly individual more than a decade old. This child was her fourth and- though she could not know it- now her only surviving offspring. Her most noticeable characteristic was a fur-free patch of scar tissue on one shoulder where she had once been burned in a forest fire. The infant, clinging to Patch's chest, was tiny, small even for its age, just a scrap of fur. Patch, the mother, studied Roamer dismissively. Roamer was small, young, and a stranger, not even remote kin. And, as a nursing mother, Patch would always have priority. So she turned her broad back on Roamer and began to stroke her infant, Scrap.

Roamer knew what she had to do. She scuttled over the branches to Patch, and dug her fingers into fur that was still moist and began to comb out tangles and bits of debris. When she probed at Patch's skin, she found knots of muscle, and places which made Patch wince to be touched.

As Roamer's strong fingers worked, Patch relaxed slowly. Patch, like all of them, had been battered by her precipitate removal from the forest, and was stressed by her sudden dumping into this extraordinary emptiness and the loss of her family. It was as if she could, for a moment, under the magic of the other's touch, forget where she was. Even the infant, Scrap, seemed soothed by the contact between the two females.

Roamer herself was calmed by the simple, repetitive actions of the grooming, and by the subtle social bond she was building up with Patch.

The males' negotiations were more dramatic.

Whiteblood found himself facing two younger males, brothers, in fact. One had a peculiar crest of snow-white hair that stuck up around his eyes, making him look permanently surprised, and the other had a habit of using his left arm predominantly over his right, so much so that the muscles on his left side were much more heavily developed than those on the right, like those of a left-handed tennis player.

Both Crest and Left were smaller and weaker than Whiteblood, and, younger, they had not outranked him back in the forest. But now Whiteblood had lost all of his allies, and together these two might defeat him.

So, without hesitation, he launched into a display. He stood upright, shakily, hooted and shrieked, and threw handfuls of leaves. Then he turned around, spread his backside and blew shit through moist fur.

Left was immediately intimidated. He shrank back, arms folded around himself.

Crest was more defiant, and answered Whiteblood's display with a shrieking tantrum of his own. But he was outsized by Whiteblood and, without the support of his brother, could not hope to best the older male. When Whiteblood began to cuff him about the head and neck, Crest quickly backed down, tumbling onto his back and spreading his arms and legs like an infant, showing his submission. All of this was halted only when an incautious stamp plunged Whiteblood's leg through the foliage and into the cold water. He yelped, pulled back his leg, and sat with legs folded beneath him, subdued.

But he had done enough. The brothers approached him now, their heads bent and postures humble. A brief interval of frantic mutual grooming ensured the new hierarchy was reinforced, and the three males started to pick bits of shit out of each other's fur.

The rough-and-ready communities of Noth had been like street gangs, held together by not much more than brute force and dominance, with each individual aware of little more than her own place in the pecking order. But by now the advantages of social living had driven primate societies to baroque intricacy, and had spurred the development of new types of mind.

Group living required a lot of social knowledge: knowing who was doing what to whom, how your own actions fit in with this, who you had to groom and when, to make your life easier. The larger the group, the greater the number of relationships you had to keep track of, and as those relationships changed constantly, you needed still more computational capacity to handle it all. By allowing their group living to develop to such extremes of complexity, primates continued to get relentlessly smarter.

Not all primates, though.

Through all this the big potbelly had sat on the comfortable branch she had found, methodically stripping it of leaves. She had no interest in the peculiar displays and hairy fiddling of the anthros.

Even among her own kind the potbelly knew little of the society of others. She ignored other females and let herself be bothered by males only when she felt the urge to mate- which, in fact, was on her now. When they were in season anthros like Patch and Roamer showed sexual swellings on their rumps. That would have been of little use to a creature who spent most of her time sitting on her backside, so on the potbelly's chest pinkish blisters had swollen brightly in an unmistakable hourglass shape. But as there was no male potbelly around, nobody was doing anything about it.

Not that the potbelly cared much. She didn't understand where she was and what had become of her any more than the anthros did, but it didn't trouble her. She could see there were plenty of leaves on this fallen tree to last her through the day. She had no real idea that there could be such a thing as a tomorrow different from today, that it might not find her in an endless forest full of nutritious leaves.

Already the anthros were starting to feel hungry; their low-nutrition diet worked through their systems quickly. They broke up their grooming circles and spread out over the branches of the fallen mango. The tree had lost much of its fruit, along with most of its inhabitants, when it fell from the bank. But Crest, one of the brothers, quickly turned up a cluster of fruit that had gotten lodged in an angle of branch and trunk. He hooted to summon the others.

The new miniature society worked efficiently. Though Crest managed to grab one piece of fruit for himself, he was quickly pushed away by Whiteblood. But Whiteblood was in turn usurped by Patch. Though she was not much more than two-thirds of Whiteblood's size, the infant clinging to her chest was like a badge of authority. Whiteblood took one fruit and, grumbling, moved back, giving way to Patch.

While this was going on Roamer, like the brothers, knew that she would get no nearer to the fruit until the dominant ones had taken what they wanted.

Alone, she walked carefully, all four limbs grasping, toward the edge of the raft, where the tangle of branches was a little looser. The two terrified crowders, huddled together, skittered away as she approached. Through the foliage she could see murky brown water, littered with bits of wood and leaf, rippling languidly. The sun glimmered in a hundred places, shining through gaps in the cover of the fallen tree, and the dancing light was entrancing, distracting.

Roamer was hungry, but she was also thirsty. She dipped her hand cautiously into the water- it was cool- and scooped up a mouthful. The water was mildly salty- not bitterly so, for even so far from land the river's powerful outflow diluted the ocean's brine. But as she drank the taste of salt began to build up in her mouth, and she spat out her last mouthful.

Hungry, bored, the brothers came to inspect her as she drank, head bent down into the foliage, arm outstretched, buttocks raised. They sniffed her curiously, but they could smell how young she was, too young to mate.

When the older ones were done, Roamer and the others fell on the fruit.

With their bellies full for now, the anthros were calming down. But already the haphazard raft had drifted out of sight of the land, already the anthros had eaten much of the fruit from the drowned mango tree. And already the potbelly, complacently munching, had stripped half the branches of their leaves.

And none of them had seen the pale gray triangle that slid silently through the water, not meters away.

The shark circled the crude, disintegrating raft. Alerted by the feeding frenzy as the drowned inhabitants of the riverbank forest were washed out to the waiting mouths of the ocean, the shark had been attracted by the scent of stale blood that leaked from the indricothere carcass. But now it sensed motion on the tangled foliage that floated overhead. It circled, calculating, patient.

The shark was not as intelligent as its parallels on land. But then it was not much like an animal at all. The bones of its back were not bone, but tough cartilage that gave the shark better flexibility than more advanced fish. Its jaw was cartilage too, in which were loosely attached teeth, serrated like steak knives, perfect for shearing flesh. Its projecting snout looked crude, but it cut through the water with the precision of a submarine's engineering, and it was equipped with nostrils that could detect minute traces of blood. Beneath the snout was a special organ with extraordinary sensitivity to vibration, enabling it to sense the struggles of a frightened animal across immense distances. Behind its small head, the shark's entire body was made of muscle, designed for power, for forward drive. It was like a battering ram.

Sharks had already been the ocean's top predators for three hundred million years. They had endured through the great extinctions, while families of land predators had come and gone. They had seen off competition from new classes of animals, some much younger, like the true fish. Over that vast period of time, the sharks' body design had barely modified, for there was no need.

The shark was relentless, unable to be deflected by guile, prepared to keep on attacking as long as its senses were appropriately stimulated. It was a machine designed for killing.

The shark could sense the great mass of dead meat drifting at the heart of this raft, but it could also hear the scurrying of live animals on its surface. The dead thing could wait.

Time to attack. It went in headfirst, its jaws open. The shark had no eyelids. But to protect its eyes, it rolled them back, so that they turned white, in the last instant before it struck.

Patch was the first to see the approaching fin, to glimpse the white torpedo body gliding through the water toward the raft, to look into the white eyes. She had never seen such a thing before, but her instincts yelled that this sleek form spelled trouble. She ran over the loose foliage to the raft's far side.