Then he dropped back to all fours and scuttled back into the forest's shadows, his nerve gone.

Capo gave him a sound beating about the head for taking such a risk. Then he led his troop back into the deeper forest.

Capo hauled himself up an acacia tree, seeking fruit and flowers. Capo climbed steadily. He used a kind of shimmying style, pulling himself up with his arms while gripping the tree trunk with his feet to provide a platform.

It was a feat Roamer could not have achieved- or indeed any monkey. Capo's apes had flat chests, short legs, and long arms. They had achieved greater flexibility by moving their shoulder blades to the backs of their bodies, which enabled Capo to reach up above his head. All this was equipment for hauling oneself up a tree trunk. Where Roamer had spent much of her life running along branches, Capo was a climber.

And this re-engineering for climbing had had another side effect, easily visible in Capo's long, narrow body. Working vertically, with a new bone structure and system of balance, Capo was already preadapted to walking on two feet. Sometimes he did this in the trees, holding on to branches for balance, trying to reach the highest fruit- and sometimes his kind would stand up out in the open, as Frond had demonstrated.

As their bodies had been redesigned, the apes had become smarter.

In these tropical climes fruit trees rarely fruited simultaneously. Even when you found a fruiting tree, you might have a long way to travel to the next. So the apes needed to spend much of each day searching for patchy resources, foraging alone or in small groups, collecting together again to sleep in the treetop refuges. This basic architecture of food gathering had shaped their social lives. For one thing they needed to understand their environment very well if they were to find the food they needed.

And, given the way they lived their lives, their bonding was loose. They could split and recombine, forming special relationships with other members of the community, even though they might not see them for weeks at a time. Keeping track of a multileveled, fissile social complexity required increasing smartness. As the apes juggled their relationships, it was as if they were living through a soap opera- but it was a social maelstrom that honed their developing minds.

In the first years after the great split of the archaic anthropoid stock into apes and monkeys, the apes had become the Old World's dominant primates. Though shrinking climate belts restricted them to the middle latitudes, there was plenty of room for them in a continuous band of forest that had spanned the whole of Africa and stretched across Eurasia from China to Spain. Following this green corridor the apes had walked out of Africa and spread through the Old World forests. In fact, they had migrated alongside the proboscideans.

At their peak there were more than sixty ape species. They had ranged from cat-sized to the size of a young elephant. The largest, like the giants, were leaf eaters, the midsized- those the size of Capo- took fruit, but the smallest, weighing under a kilogram or so, were insectivores, like their remote ancestors. The smaller the animal, the faster its metabolism and the higher the quality of the food it demanded. But there was room for everybody. It had been an age of apes, a mighty anthropoid empire.

Sadly for them it hadn't lasted.

As the world continued to cool and dry, the great forest belts had shriveled into isolated islands, like this one. The vanishing of forest connections between Africa and Eurasia had isolated the Asian ape populations, which would develop independently of events in Africa, into the orangutan and its relatives. With the reduced ranges had come a dwindling of numbers. Most ape species had, in fact, already already long gone extinct. long gone extinct.

And then had come the rise of a new competitor.

Capo reached a clump of foliage where, he knew, this particular acacia had an especially productive patch of flowers. But he found the spiny branches already stripped. When he pried them aside he was met by a small, startled black face, fringed by white fur and a gray topknot. It was a monkey- like a vervet- and juice dribbled from its small mouth. It peered into Capo's eyes, squealed, and shot out of sight before he could do anything about it.

Capo rested for a while, scratching his cheek thoughtfully.

Monkeys were a pest. Their great advantage was that they were able to eat unripe fruit. Their bodies manufactured an enzyme to neutralize the toxic chemicals used by the trees to protect their fruit until their seeds were ready to germinate. The apes could not match this. So the monkeys were able to strip the trees before the apes even arrived. They were even moving out into the grasslands, feeding off the nutlike seeds to be found there. To the apes, the monkeys were as tough a competition as the rodents had always been.

High over Capo's head, a slim form moved, swinging gracefully and purposefully. It was a gibbon. It raced through its forest canopy at extraordinary speed. It used its body as a pendulum to gain momentum, and, like a child on a fairground swing, it pumped its legs up and down to build up its speed.

The gibbon's body was a kind of extreme version of the apes' long-armed, flat-chested design. The ball-and-socket joints in its shoulders and wrists had been freed up so that the gibbon could hang from its arms and twist its body through a full circle. With its low weight and extreme flexibility, the gibbon could hang from the outermost branches of the highest trees, and it was able to reach the fruits that grew at the end of the thinnest branches, safe from even tree-climbing predators. And, able to hang upside down from branches, it could reach goodies out of the grasp of other apes, who were too heavy to climb so high, and even the monkeys, who ran along the tops of the branches.

Capo peered up at the gibbon with a kind of envy for a grace, speed, and skill he could not match. But, magnificent though it was, the gibbon was not a triumph for the apes but a relic, forced by the competition it had lost to the monkeys to eke out its living on the ecological margins.

Vaguely disappointed, still hungry, Capo moved on.

At length Capo found another of his favorite resources, a stand of oil palms. The nuts of this tree had rich, oily flesh- but they were enclosed in a particularly hard outer case that rendered them immune to most animals, even the clever fingers of monkeys. But not to apes.

Capo hurled handfuls of the nuts down to the ground, then clambered down after them. He collected the nuts together, carried them to the roots of an acacia he knew, and hid them under a heap of dried palm fronds.

Then he worked his way out toward the perimeter of the forest, to where he had stashed his hammer-stones. These were cobbles that fit neatly into the palm of his hand. He selected one and headed back to his nut stash.

On his way back he passed the adolescent Howl. Briefly he considered mating her again, but Capo's attention once a day was enough of an honor for any female.

Anyhow she was sitting with an infant, an odd-looking male with a peculiarly elongated upper lip: Elephant. He was actually one of Capo's sons. He was sitting on the ground clutching his stomach and moaning loudly. Perhaps he had a worm, or some other parasite. Howl was moaning along with him, as if some of the pain had transferred to her body. She was plucking bristly leaves and making the youngster swallow them; the leaves contained compounds that were toxic to many parasites.

And there were Finger and Frond, he saw, grubbing their way along the forest floor. The young males were aiming for a little light thievery, it seemed to Capo- in fact, he realized angrily, they had their eyes on Capo's own heap of fronds.

Capo contained his impatience. He sat under a tree, dropped his hammer-stone, picked up a stick and began to work methodically to clean out the spaces between his toes. He knew that if he made a dash for his palm nuts the others would get there first and pilfer the nuts. By loitering like this, he was making Frond and Finger believe that no nuts had been hidden at all.

Unlike Roamer, Capo was able to read the intentions of others. And Capo understood that others could have beliefs different from his own, that his actions could affect others' beliefs. It was a capability that even made a limited kind of empathy possible: Howl really had been sharing the suffering of Elephant. But it also made possible ever more elaborate modes of deceit and treachery. He was able, in a sense, to read minds.

This new ability had even made him self-aware, in a new way. The best way to model the contents of another's mind was to be able to study your own: If I saw what she sees, if I believed what she does, what would I do? If I saw what she sees, if I believed what she does, what would I do? It was an inward look, a reflection: the birth of consciousness. If Capo had been shown his face in a mirror he would have known it was It was an inward look, a reflection: the birth of consciousness. If Capo had been shown his face in a mirror he would have known it was him, him, not another ape in a window. His were the first animals since the hunters of Pangaea to have achieved such sophistication. not another ape in a window. His were the first animals since the hunters of Pangaea to have achieved such sophistication.

At last Frond and Finger moved away from the stash. Capo grabbed his hammer-stone and descended on his palm nuts. Capo would deliver beatings to the two of them later anyhow, on principle; they would never quite understand why.

He brushed aside the concealing fronds to expose his favorite anvil stone, a flat rock embedded in the ground. To protect his backside he spread some broad leaves over the moist ground. He sat down, legs tucked up to his chest. He set a palm nut on the anvil, holding it steady with finger and forefinger- and then brought down the hammer, snatching his fingers out of the way at the last moment. The nut rolled a little and squirted sideways unbroken; Capo retrieved it and tried again. It was a tricky procedure that took a lot of coordination. But it took Capo only three goes before he had cracked the first nut and was chewing out its flesh with his teeth.

Twenty-seven million years after Roamer and her habit of slamming nuts against branches, this was the height of technology on Earth.

Capo worked steadily on the nuts, losing himself in the tricky little procedure, pushing out of his mind the obscure worries that niggled him. It was high morning now, and for a time he felt content, satisfied in the knowledge that he had gotten enough food to stave off hunger pains for a few hours at least.

Elephant, drawn by the nuts' rich smell, came to see what was happening. This youngster's stomach problem had evidently been eased by Howl's rough-and-ready bush medicine- or perhaps he had been faking it, to get some attention- and he was starting to feel hungry. He made out bits of nutshell scattered around the anvil stone, and even a few scraps of kernel. The youngster snatched these up and crammed them into his mouth.

Capo, grandly, let this pass.

Now Leaf came by with her infant clinging to her back.

Capo dropped his hammer-rock and reached for Leaf. Gently he began to groom her belly, an attention to which she submitted gracefully. Leaf, a big, gentle creature, was one of his favorite females. In fact she was favored by all of the troop's males, and they would compete for grooming time with her.

But that wasn't Capo's way. Very soon his lumpy penis had sprouted from his fur, and Leaf had had all the grooming she was going to get. Leaf carefully lifted the infant from her back and put her down on the ground. Then she lay back and let Capo enter her. She arched her back as he thrust, so that her head was upside down, her weight balanced on her skull. These apes often mated face to face like this. Empathy again: They could share each others' pleasure in grooming or mating.

Capo and Leaf were close. Though mating was promiscuous, sometimes Capo and Leaf would take themselves off into the forest for days on end- just the two of them- and during such safaris of tenderness, previsioning the sexual privacy of later kinds, most of Leaf's children by Capo had been conceived, including Elephant.

What Capo and Leaf felt for each other at such moments as this was nothing like human love. Each of the apes remained locked inside a wordless prison; their "language" still wasn't much more sophisticated than a cry of pain. But they were among the least lonely creatures on the planet, the least lonely who had ever lived.

Meanwhile young Elephant pored over Capo's tool kit. He started tapping nut against cobble, cobble against anvil.

Capo's apes, as they grew from infancy, had much to learn about their environment. They needed to learn where to find water and food, how to use occasional tools to get at the food, how to apply their simple bush medicine. They had been driven to live this way, in fact, because of competition from the monkeys: They had to figure out how to extract food the monkeys couldn't steal, and that took smarts.

But there was no schooling here. It wasn't that Elephant was trying to figure out what Capo had been doing. But by experimenting, using trial and error and the tools the adults left lying around- all the time driven by the lure of the delicious palm nuts- Elephant would eventually learn how to smash nuts for himself. It would take him three more years before he got it right. Elephant had to figure everything out from scratch himself, as if repeating in his own lifetime the whole intellectual progression of the species.

On and on he pounded at the shells, as if he were the first ape ever to try this trick.

Capo brought himself to a slow, shuddering orgasm, his first of the day. He withdrew from Leaf and rolled onto his back, rather unjustifiably proud of himself, and allowed her to groom him, picking knots from the fur of his belly.

But now his peace of mind was disturbed by a sudden cacophony from deeper into the forest: hooting cries, drumming, the rustle of large bodies clambering and swinging.

Capo sat up. In his world it wasn't good to have too much excitement in which he wasn't involved. He vaulted over a tree stump, drummed on a branch, routinely cuffed Elephant about the head, and loped off toward the source of the noise.

A group of young males were hunting a monkey.

To Capo's eye it looked like the little vervetlike creature he had disturbed munching on acacia flowers earlier. Now it sat cowering at the top of a young palm.

The hunters had spread out around the base of the tree, and were clambering stealthily up neighboring trees. Others, Frond and Finger among them, had gathered around to see the excitement. It was these spectators who were making all the noise; the hunters themselves moved with stealth and silence. But to the monkey the din was terrifying and disorienting.

Capo was unpleasantly surprised when he saw who the hunters were. They were the rowdy young males who had loped off not days before on a foraging trip to another part of the forest clump. Their informal leader, a burly creature called Boulder, had given Capo some trouble in the past with his rebellious ways, and Capo had been happy to see him go: Let him blow off steam, make a few mistakes, even get hurt, and he would soon defer to Capo's authority once more.

But Boulder had been away just days, where Capo had expected weeks to pass. And from the look of his bristling aggression, his jaunt hadn't made him any calmer.

Capo was worried by the hunt, too. Monkey hunting usually happened only when other food was scarce, such as during periods of drought. Why hunt now now?

One of the clambering apes made a sudden leap. Chittering, the monkey jumped the other way- straight into the arms of a waiting hunter. The watching apes hooted and barked. The hunter swung the screaming monkey around and slammed its skull against a tree trunk. Its cries were cut off immediately. Then the hunter hurled the limp carcass to the ground, its smashed head making a bright red splash in the forest's green murk.

That was Capo's moment. He vaulted past Boulder to be first onto the body. He grabbed up the still-warm scrap, got hold of one ankle and twisted, hard, ripping the little limb loose at the knee.

But, to his astonishment, Boulder challenged him. The burly male leapt at him feetfirst, ramming him in the chest. Capo fell sprawling, an ache spreading along his rib cage, the breath knocked out of him. Boulder deliberately picked up the monkey limb and bit into it, blood spurting over his mouth. All the apes were madly excited now, and they hooted and drummed and scrambled over one another.

Ignoring the pain in his chest Capo leapt to his feet with a roar. He couldn't let Boulder get away with this. He scrambled up into the lower branches of a tree, drummed ferociously, hooted loudly enough to disturb birds that roosted high above him, and vaulted back to the ground. He let anger surge through him so that he bristled, and a proud pink-purple erection stuck out before him: a nice touch that, his trademark.

But Boulder kept his nerve. With the monkey limb wielded in his hand like a club, he began his own display, his stamping, leaping, and drumming just as impressive as Capo's.

Capo knew he couldn't afford to lose this one. If he did, given Boulder's circle of blood-stained hunters, he might lose not just his status but his very life.

With an agility that belied his years, he leapt forward, knocked Boulder flat, and sat on his chest. Then he began to batter Boulder about the head and chest as hard as he could. Boulder fought back. But, save for youth, Capo had all the advantages: surprise, experience, and authority. Boulder couldn't shift Capo's weight, and he couldn't bring his own powerful arms and legs fully into play.

Gradually, Capo saw, he was winning the battle in the minds of the rest of the troop, which was just as important as subduing Boulder. The young male's followers seemed to have melted away into the trees, and the whoops of excitement and approval Capo heard now seemed to be directed at him.

But even as he battled to subdue Boulder, a slow deduction worked through Capo's roomy mind.

He thought of the dying trees he had glimpsed beyond the fringe of the forest island, the speedy return of Boulder and his wanderers, their apparent hunger, their need to hunt.

Boulder had found nowhere to go. The forest patch was shrinking. The forest patch was shrinking. That had been true all of Capo's life, and now it was becoming unavoidable. There was no longer enough room for them here. If he tried to keep the group here, the tension between them, as they competed for dwindling resources, would become too intense. That had been true all of Capo's life, and now it was becoming unavoidable. There was no longer enough room for them here. If he tried to keep the group here, the tension between them, as they competed for dwindling resources, would become too intense.

They would have to move.

At last Boulder gave in. He lay limp under Capo, cupped the older male's buttocks, and even briefly stroked his still-erect penis, all gestures of submission. To drive home his point Capo kept battering at Boulder's head for long minutes. Then he clambered off the prone younger male. Still bristling, he made his way into the forest, where he could afford to limp and massage the pain in his chest and nobody could see how he hurt.

Behind him the others fell on the vervet. Their stomachs could not digest flesh well, and later they would pick through their feces for lumps of meat to eat again. It was a digestive system that was going to have to improve, if the descendants of these rummaging creatures were to prosper on the savannah.

II.

Since Roamer's time, grass had remade the world.

The great epochal cooling of the Earth continued. As water was locked up in the Antarctic ice cap, sea levels diminished, and inland seas shrank or became landlocked. But with more continental landmass exposed, there was less sea to buffer the climate from extremes of heat and cold, and the weathering rock drew carbon dioxide from the air, making it less able to retain the sun's heat. Cooler and drier: The planet had developed a vast feedback mechanism, driving its surface to still more arid, chilly conditions.

Meanwhile tectonic collisions created new mountain ranges: the Andes of South America, and the Himalayas of Asia. These new uplifts cast gigantic rain shadows across the continents; the Sahara Desert would soon be born in such a shadow. In the new desiccation, great belts of broad-leaved deciduous woodland spread from south and north toward the equator.

And the grasses spread.

Grass plants- huddling in their great crowds, able to rely on fertilization by windblown pollen- might have been designed for the new open, dry conditions. Grass was able to subsist on the sporadic rainfall that now fell, whereas most trees, with their roots delving ever deeper into the ground, found only dryness and could not compete. But the real secret of grass lay in its stems. The leaves of most plants grew from the tips of shoots, but not grass's. Grass blades grew from underground stems. So grass could be cropped by a hungry animal, right down to the ground, without losing its power to regenerate.

These unspectacular properties had enabled grass to take over a world, and to feed it.

The new grass-eating herbivores developed specialized ruminant guts able to digest the grassy fodder over long periods and hence extract the maximum nutrient from it, and teeth able to withstand the abrasive effect of silica grains in grass blades. Many herbivores learned to migrate, because of the seasonality of the rainfall. These new mammals were larger than their archaic ancestors, lean and long-legged with specialized feet and a reduced number of toes to help them walk and run long distances and at speed. And meanwhile there was a sharp rise in the types of rodents, like voles and field mice, able to eat grass seeds.

New carnivores rose, too, equipped to feast on the new herds of large herbivores. But the rules of the ancient game had changed. In the sparse cover of a grassland, predators could see prey from long distances- and vice versa. So predators and prey began a metabolic arms race, with the emphasis on speed and endurance; they developed long legs and quick reactions.

A new kind of landscape began to spread- especially on the eastern side of the continents that were sheltered from the predominantly westerly winds and the rain they carried: open, grass-covered plains marked by scattered scraps of bush and woodland. And in turn animals who adapted to the new vegetation were rewarded with a guaranteed food source that could spread across hundreds of kilometers.

But their specializations, and the stability of the grasslands, would lock in the grazers to the grasses, the predators to their prey, establishing a close codependency. In this period the deer, cows, pigs, dogs, and rabbits looked little different from their equivalents of human times five million years later- although many of them would have looked surprisingly large; they would later be outcompeted by their smaller, faster cousins.

Meanwhile the opening up of land bridges, caused by the falling sea levels, led to a great crisscross migration of animals. Three kinds of elephants- high-browsing deinotheres, omnivorous gomphotheres, and browsing mastodonts- crossed from Africa to Asia. Along with them traveled the apes, cousins of Capo. And in the other direction came rodents and insectivores, cats, rhinos, mouse deer, pigs, and primitive types of giraffe and antelope.

There were some exotica, especially on the islands and the separated continents. In South America the largest rodents that ever lived were flourishing; there was a kind of guinea pig as large as a hippo. In Australia, the first kangaroos appeared. And what would later be considered tropical animals could be found in North America, Europe, and Asia: In England, the Thames was broad and swampy, and hippos and elephants basked on its floodplain. The world had cooled greatly since Noth's time, but it still wasn't cold cold; the deepest chill would afflict later ages.

But still the drying continued. Soon the older mosaic of grassland and woodland able to support a wide variety of animals lingered only in the equator-straddling Africa; elsewhere the grasslands opened up into arid plains, the savannah, steppe, and pampas. In these coarser, simplified conditions, many species fell away.

This intense evolutionary drama was driven by the endless shifts in Earth's climate- and the animals and plants were as helpless as bits of flux on a great terrestrial forge.

The next morning there was no luxurious ball scratching. As soon as he woke, Capo sat up, hooted softly at the pain of yesterday's lesions and bruises, and voided his bladder and bowels in a fast, efficient movement, ignoring the chitters of protest from below.

He vaulted from his nest and began to shimmy down the tree. Just as yesterday he roused the troop by crashing into their nests, hooting, kicking, and slapping. But today Capo wasn't interested in displaying; this morning his purpose was not dominance but leadership.

His determination was still strong in his mind. The troop had to move. Where they should go wasn't part of his unsophisticated decision making yet. But what was very clear in his head was the pressure of yesterday, his competition with Boulder, what he had sensed of the overcrowding of this little patch of forest.

The troop gathered together on the ground, more than forty of them, including infants clinging to their mothers' bellies or backs. They were sleepy, wary, scratching themselves and stretching. No sooner had Capo gotten them gathered, of course, than they were drifting apart again, plucking at bits of grass and moss on the ground, reaching for low-growing figs and other fruit. Even among the males he saw reserve, rivalry, resentment; they might resist him just to make their own points in the endless plays for dominance. And as for the females, they were a law unto themselves, for all of Capo's noise and violence.

How was he going to be able to lead this lot anywhere?

He wasn't conscious all the time, as a human was. He was conscious intermittently. He was only truly aware of his own thoughts, of himself, when thinking about others in the troop, because that was the primary purpose of consciousness, to model the thinking of others. He wasn't conscious in the same way about other domains of his life, like food-gathering or even tool using: those were unconscious actions, as peripheral to his awareness as breathing or the working of his legs and arms when he climbed. His thinking was not like a human's; it was simplified, compartmentalized.

His mind was a sophisticated machine, basically evolved to handle complex social situations. And he had a good innate understanding of his environment. He had a kind of database in his head of the resources he needed to stay alive and where they could be found. He was even good at dead reckoning navigation, and could easily compute good shortcut courses from one site to another. It was his environmental awareness that had prompted his concern about the shrinking forest patch.

It was hard for him to put together the elements of this puzzle: the danger posed by the shrinking forest, what he needed to do with his troop. But the danger was very real to him, and every instinct screamed at him to get away from here. The troop had to follow him. It was as simple as that; he knew it deep in the fibers of his being. If they stayed here they would surely die.

So he roared to get his blood flowing, and threw himself into the most energetic display he could. He raced up and down among the troop, slapping, punching, and kicking. He tore branches from the trees and waved them over his head to make himself look even bigger. He swung and vaulted over branches and trunks, drummed ferociously on the ground, and- as a climactic gesture to reinforce his victory of yesterday- he threw Boulder to the ground and shoved his own puckered anus in the younger male's face. It was a magnificent spectacle, as good as any Capo had mounted even in his younger days. Males whooped, females flinched, infants cried, and Capo allowed himself a glimmer of pride in his work.

But then he tried to lead them away, toward the fringe of the forest. He walked backward, shaking branches and running back and forth.

They stared. Suddenly he was behaving like a submissive junior male. So he displayed again, drumming, vaulting, and hooting, and went back to the follow-me routine.

At last one of them moved. It was Frond, the spindly young male. He took a couple of tentative knuckle-walk steps. Capo responded with a chattering cry and threw himself at Frond, rewarding him with a burst of intense grooming. Now more came forward: Finger, a few more of the junior males, eager to be groomed in turn. But Capo noticed that Boulder aimed a sly kick at Frond's backside.

And then, to Capo's intense relief, here came Leaf, her infant riding on her back, knuckle-walking grandly if a bit stiffly. Where this most senior female came, others followed, including Howl, the near-pubescent youngster.

But not all the females followed- and not all the males. Boulder stayed behind, sitting squat under a tree with his legs ostentatiously crossed under him. Other males gathered around him. Capo displayed at them furiously. But they huddled and groomed each other as if Capo no longer existed. It was a deliberate snub. If he wanted to maintain his position, Capo was going to have to break up this knot of rebellion, perhaps even face down Boulder once more.