Stranded out of their environment, the people might have died out within a generation, if they hadn't adapted.

It had started innocently. A woman, Harpoon's remote grandmother, had wandered as far as she could up the river valley and on to drier land. Here, on the floodplains and in the seasonal swamps, the well-watered, silty soil supported many annuals, herbs, legumes, vines, lilies, and arrowroots. After years in the swamp she had grown adept at using crude wooden tools and her bare hands to harvest food from soggy, unpromising terrain. She had already filled her belly, and was gathering clumps of roots to take home to her children.

Then she came upon the stranger. The man, from another group further upriver, was using a knife of basalt to skin a rabbit. The two of them stared at each other, one with meat, the other with roots. They might have fled, or tried to kill each other. They did not.

They traded: meat for roots. And they went their separate ways.

A few days later the same women returned to the same spot. Again the man returned. Scowling, suspicious, their tongues mutually incomprehensible, they traded again, this time shellfish and barnacles from the river's mouth for a couple of basalt knives.

That was how it began. The people of the swamp, unable to find everything they needed to stay alive in the scrap of land they had inherited, exchanged the produce of the sea, the swamp, and the floodplain for meat, skin, stone, and fruit from the interior.

After a couple of generations they migrated out, and began a new kind of life. They became true nomads, following the great natural highways, the coasts and the inland water courses. And everywhere they went they traded. As they moved, so they fissured and spread, and tentative trading networks grew. Soon it was possible to find bits of shaped rock hundreds of kilometers from where they had been formed and seashells deep in the interior of the continent.

Living like this was a challenge, though. Trading meant building up a new kind of map of the world. Other people were no longer just passive features of the landscape, like rocks and trees. Now a track had to be kept of who lived where, what they could offer, how friendly they were- and how honest. There was a ferocious pressure on the swamp people to get smarter, fast.

The design of their heads changed drastically. Their skulls enlarged to make room for bigger brains. And changing diets and lifestyles had a dramatic effect on their faces. No longer used to chew tough, uncooked food or to treat leather, their teeth became more feebly rooted. As chewing muscles withered, the upper tooth row shrank back. The lower jaw was left jutting, and the face tilted back, so that these hominids lost the last trace of their ancient apelike muzzles. The declining muzzle and ballooning foreheads provided new anchoring surfaces for the muscles of the face, and the old projecting browridges disappeared.

Meanwhile, as they got smarter, they didn't need to be as strong. Their bodies shed much of the robustness of their immediate ancestors, and reverted to something like the graceful litheness of Far's people.

Pebble's first impression, that Harpoon had seemed childlike, was not accidental. With the proportions of their faces and their thinned bones these new people, compared to ancestral stock, were in some ways like children arrested in their growth. Once again, under ferocious selection pressure, the genes had reached for variations that could be implemented quickly: Adjusting the comparative growth rates of skeletal features was comparatively easy.

All of these changes had been essentially complete within a few millennia. After this process Harpoon, anatomically, was all but identical to a human of Joan Useb's time, even in her skull and the gross features of her brain. And it had been trading, a new way of dealing with other people, that had made them what they were.

But even Harpoon was not yet human. human.

There was a little more invention, a little more organization in her life. Her kind built hearths, for instance. But her tool kit was scarcely more advanced than that of Pebble and his ancestors. Her language was the same unstructured babbling. Much of the way she lived her life, like her sexuality, had been inherited with little change from the kinds of people who had gone before. There were still rigid barriers in her mind, a lack of connections in the neural wiring of her brain. A true human of Joan Useb's age, stranded in this age of her ancestors, would quickly have been driven crazy by the sameness, the routine, and ritual, the lack of art and language- the boring, drab poverty of life.

And, human form or not, these folk had not been dramatically successful. Though they had spread across Africa from their origins in that southeastern swamp, their lifestyle remained marginal. It was difficult to trade if there was nobody like you to trade with. Even now the new nomads' survival was chancy, and most extant groups, around the continent, would not survive.

The children of Harpoon were destined to pass through this bottleneck, but their genes would always bear the imprint of that narrow passage. In the future, the swarming billions who would spring from this unpromising seed would be virtually identical, genetically; every human would be a cousin.

Pebble's relationship with Harpoon came to a head during a hunt.

One day, Pebble found himself in a blind, upwind of a herd of giant horse who cropped the long grass peacefully. The blind was just a lean-to frame of saplings, loosely woven together and covered with palm fronds and grass. Here Pebble huddled, his thrusting-spear at his side, peering out at the big, lame animal that was their target. And Harpoon was at his side. He was tense, adrenaline pumping, and the heat of the day and the sweat scent of the horse filled his head.

Suddenly he felt her fingers on his face.

He turned. Her skin seemed to glow in the green gloom. She traced the vertical ocher stripes he still wore. And then her fine fingers moved to his arm, the long-healed cuts he had inflicted there. Her every touch was startling, as if her fingers were made of ice or fire.

He ran his fingers down her arm. His fist enclosed her forearm easily, as if it were a bird's leg. He felt he could snap the bone with a gesture. Suddenly it was just as it had been on the first day he had met her, on the beach. His mouth dried, his throat tightened.

He didn't understand his lust: the lust that had never gone away. He thought of the clever tools she made, her long, easy stride across the ground, the food she had brought his people- and that harpoon, the exquisite harpoon point, unimaginable before he had seen it that first day. There was something in her his body wanted; the longing was unbearable.

He rolled on his back. In the rustling shade of the blind, she straddled him and smiled.

IV.

Each lump of flint was a miniature cemetery. In some long-vanished sea the corpses of crustaceans had settled into sediment, and minute glassy needles that had once formed the skeletons of sponges became the nuggets of flint embedded inside the gathering chalk seams.

Pebble had always loved the feel of flint. He turned the smooth-faced, brittle rock over in his hands, sensing its structure. Flint knappers got to know all of the stone's subtle properties. The more a flint was exposed to the elements the more likely it was to contain fractures, caused by frost or a battering by river or ocean currents. But this flint lacked the patina of exposure. It was fresh and clean. It had only recently been dug out of its chalk matrix, after a cliff had collapsed. You couldn't get such flint in this area, anywhere within the people's old range. Pebble had missed good flint, in the long years on this beach, before Harpoon had walked into his life.

These days he was never more content than when working stone- or, rather, he was never less discontented.

Seven years had elapsed since his first encounter with Harpoon. At twenty-six, his body was already declining, battered and scarred by the cumulative challenges of a life that continued to be very hard, despite his people's collaboration with the newcomers.

He had embraced Harpoon, and he had embraced the newness and changes she had brought- but those changes themselves had become bewildering. Pebble's mind was immensely conservative. And as he grew older he increasingly relished these moments alone with the stone, when he could retreat into the recesses of his roomy mind.

But this moment of peace didn't last.

"Hai, hai, hai! Hai, hai, hai!"

Here came his son and daughter, squat Sunset and spindly Smooth, running along the beach side by side, jabbering in the patois that had resulted as a merger of Pebble's tongue and Harpoon's. "Come, come, come here with us!" The children, naked, their skin crusted with salt and sweat, wanted him to come work on the logs that Ko-Ko and others were pushing into the sea.

He pretended not to hear them until they were almost on top of him. Then he grabbed them both with a roar, and all three of them rolled in the sand, wrestling. At last Pebble relented. He put aside his flint, got to his feet, and lumbered after the kids along the beach.

The morning was bright, the sun hot, and the air filled with the scent of salt and ozone. As the children flew ahead of his own lumbering gait, Smooth quickly outstripping her brother, Pebble felt briefly joyful at their youthful energy. This place would never be home to him, but it had its pleasures.

Ko-Ko, Hands, and Seal were making a kind of raft. Harpoon was here, her hands resting on a belly that was already showing a bump. She grinned fiercely as Pebble came up.

The men had cut down two stout palms from the inland forests, stripped them of their branches, and lashed them together with lianas and plaited vine. Now Hands and Seal were hauling this crude construction across the sand and down to the water. There was much straining and jabbering: "Push, push, push!" "Back back, no, back, back..." "Hai, hai!" "Hai, hai!"

Pebble joined Hands and Seal at their task. Even with three of them it was hard work, and Pebble was soon sweating like the rest, his legs coated with stinging hot sand. Ko-Ko tried to help, but for sheer brute strength the robust folk had no match. And they were helped, and hindered, by the two children, and by Harpoon's wolf companion who ran around their legs, barking.

The wolf, raised from a captured cub, was all but feral. This was just the start of a relationship longer than any other between people and animals, a relationship that would ultimately shape both species.

Pebble had never forgotten his determination to reach the island. At last, as he sat brooding on his beach, he had watched skinny youngsters playing on bits of driftwood in the water- and a connection had closed in his mind.

In their mangrove swamp the ancestors of Harpoon, no better swimmers than Pebble, had been forced to find ways of crossing crocodile-infested water. After much trial and error- with every error punishable by maiming or death- they had hit on a way of using cut mangrove logs. You could ride on such a log by lying flat on it and paddling with your hands. Through all their journeying, the skinnies had not forgotten that basic technique. And that was what Pebble had seen the children trying to do out on their bits of driftwood. At last he saw a way to get to the island.

But paddling a log across the still waters of a mangrove swamp was one thing. Mastering the choppy surface of an ocean channel was a different challenge.

After a few spectacular failures, Ko-Ko's inventive mind had come up with the notion of strapping two logs together. That way at least you got a little more stability. But these miniature rafts were still too vulnerable to tipping over.

At last they got the logs into the water. They floated, tied together to make a stable surface.

Ko-Ko and Hands threw themselves forward, splashing heavily. They both lay flat on the logs, legs stretched behind them, and began to paddle. Slowly they pulled away from the shore. But the waves tipped the logs up and down- and eventually over, pitching both men into the water. And then the logs' bindings came loose.

Hands came staggering back, spluttering and growling. With Ko-Ko, he hauled the logs back out of the water onto the beach.

Pebble knew that there had been no danger, for the water here was shallow enough to walk out to shore. But further away it deepened quickly- and that was where they must travel, if they were to reach the island.

So they kept working, trying different combinations, over and over.

Much had changed in Pebble's life in seven years.

Gradually those who had come with him from Flatnose's village faded out of the world. Hyena had never recovered from his stab wound, and they had put him in the ground. And not long after that they had had to put Dust in the ground too. Gradually Pebble's mother had seemed to have grown fond of Harpoon, this peculiar stranger who lay with her son. But at last her growing frailty overcame her strength of will.

But where life was lost, so new life was created. His two children were close in age- six and seven years old- but they were quite different.

Sunset was the younger, at six. The boy was the result of Pebble's reluctant union with Cry, who had continued to pursue him long after he had formed his bond with Harpoon. Sunset was squat, round, a ball of energy and muscle, and above a thick, shadowing browridge his hair was still the startling red it had been when he was born, Ice-Age-sunset red.

Sunset had brought poor Cry no pleasure, though. She had died in giving him birth, to the end protesting about the presence of the new people among them.

Pebble's other child, Smooth, had come from Harpoon. Though she had something of her father's chunkiness, she was much more like her mother's kind. Already she was taller than Sunset. Every time he saw her, Pebble was struck by Smooth's flat face, and the ridgeless brow that swept up above her clear eyes.

Pebble had had no reason to be surprised when his sexual contact with Harpoon had resulted in a child. Now, in fact, she was pregnant again. The changes between the ancestral stock and Harpoon's generation, though they were so striking, were not yet so fundamental that the two kinds of people could not crossbreed- and indeed their hybrid children would not be mules. They would be fertile.

Thus Harpoon's modified genes, and her new body plan and way of life, had begun to propagate through the wider population of robust folk. Thus the thread of genetic destiny would pass on through Smooth, child of human-form and robust, into the future.

As the long afternoon wore on, driven by Pebble's determination, they kept on trying to make the logs work.

It was frustrating. They had no way of discussing their ideas. Their language was too simple for that. And even the new folk were not particularly inventive with technology, for the compartment walls in their highly specialized minds denied them full awareness of what they were doing. They weren't able to think it through. It was something like trying to learn a new body skill, like riding a bicycle; conscious effort didn't help. And besides the work was uncoordinated, and only progressed when somebody was passionate enough to bully the rest.

But at last, quite suddenly, Ko-Ko hit on a solution. He splashed into the water. "Ya, ya!" "Ya, ya!" With frantic yells and blows, he forced the swimmers to hold on to a single log and let it float. Then he went to the far end and, swimming strongly himself, guided the log out through the choppy inshore waves to the calmer waters beyond. With frantic yells and blows, he forced the swimmers to hold on to a single log and let it float. Then he went to the far end and, swimming strongly himself, guided the log out through the choppy inshore waves to the calmer waters beyond.

Pebble watched, amazed. It worked. Rather than riding the log, they used it as a float to help these nonswimmers swim. Soon the log was so far from the shore that all he could see was a row of bobbing heads and the black stripe of the log between them.

By clinging to the log and paddling for all they were worth even the robusts, too heavy to swim, were able to cross the water, far out of their depth. It was obvious to everybody that at last they had found a way to cross the strait that had baffled Pebble for years.

Pebble hollered his triumph. His sons ran to him. He picked up Smooth and whirled her, squealing, through the sunlit air, while Sunset pulled at his legs, clamoring for attention.

The raiding party landed on a little crescent of shell-strewn sand that nestled beneath walls of eroded blue-black rock. They staggered out of the water and lay gasping on the beach. Pebble saw immediately that everybody, robust and skinny alike, had made it to the shore.

The crossing had been harder than Pebble could have imagined. He would never be able to forget that awful sensation of being suspended over the blue-black depths where unknown creatures swam. But it was over now.

And already Ko-Ko was at work. Leading by example he was having the logs hauled to the shore. The warriors- a dozen robusts, a dozen skinnies- began to unpack their gear. Some of the weapons had been carried strapped to their backs or in pouches of netting, and some- the skinnies' long throwing spears, for example- had been tied to the logs themselves.

Harpoon stroked her belly and gazed out to sea, back the way they had come. She touched the vertical ocher stripes on Pebble's face, just as she had the first time they had coupled. But now she wore the same ferocious marking as he did- as did all the people, skinnies and robusts alike. He grinned, and she grinned back.

United by their symbols, two kinds of people prepared to make war on a third.

A woman cried out. Pebble and Harpoon whirled. A heavy basaltic rock had fallen onto the beach, pinning a skinny woman's leg. When the rock was pulled away, her foot was revealed, a smashed and bloody mess. She began to keen, tears streaking the ocher stripes on her cheeks.

People were jabbering, pointing at the cliffs. "Hai, hai!" "Hai, hai!"

Pebble peered up, shielding his eyes. Something moved up there: a head, narrow shoulders. The rock had not fallen, Pebble realized. It had been pushed, or thrown.

So it had begun. He grabbed his thrusting spear and roared defiance, and ran along the beach. The people followed him.

A few hundred meters along, this sheltered beach gave way to a more open stretch of dunes and grassland. And on the open land Pebble saw a group of wraithlike hominids. There were more than twenty of them- women, men, children, infants. They had gathered around the carcass of a fallen eland. When they saw Pebble they stood up, their heads swiveling.

Pebble hurled himself forward, yelling.

Some of the hominids turned and ran- mothers with infants, some of the men. Others stood their ground. They picked up rocks and began to hurl them at the intruders, as if trying to drive off marauding hyenas. These people were tall, slender, naked, their bodies superficially similar to Harpoon's. But their heads were quite different, with squat forward-thrusting faces, strong browridges and flat crania.

They were a late variety of Homo erectus. Homo erectus. This group had wandered on to this island when a glacial surge had lowered sea levels sufficiently for it to be joined to the mainland. When the sea had returned, they had survived while the rest of their kind had fallen, because nobody else had figured out how to cross the choppy strait to take the island from them. This group had wandered on to this island when a glacial surge had lowered sea levels sufficiently for it to be joined to the mainland. When the sea had returned, they had survived while the rest of their kind had fallen, because nobody else had figured out how to cross the choppy strait to take the island from them.

Nobody until now, that is.

One male, more burly than the rest, grabbed a huge, heavy hand ax and came running toward Hands. The big robust roared in response, his heavy thrusting spear grasped in his fists. With blurring speed the male sidestepped Hands's charge and brought his hand ax slamming down on the back of Hands's neck. Blood gushed, and Hands faltered and fell face first. Still he fought. He twisted on to his back, his blood soaking into the dirt, and he tried to raise his thrusting spear. But the big male stood over him, ax raised.

Pebble, enraged, drove his own spear hard through the male's back. With this weapon Pebble was capable of piercing the hide and rib cage of a baby elephant, and he had little trouble driving his heavy spear point through hominid skin, ribs, heart. He raised the male's body high, like a speared fish. It flopped, blood spouting from its mouth and back, and sticky crimson gushed down the spear's shaft and over Pebble's arms.

When it was done Pebble knelt beside Hands. But the big man was unmoving, his massively muscled limbs splayed in the dirt. Grief spasmed in Pebble: another companion gone. He stood up, his hands and arms running with blood, seeking the next battle.

But the wraithlike naked ones were running. The skinnies were hurling their spears of fire-hardened wood, spears that rained down on the fleeing hominids.

Pebble shuddered, grateful that it was not him who these skinnies were pursuing with such deadly joy. But he picked up his thrusting spear and ran after his allies, abandoning Hands's body to the hyenas.

Systematic murder of one troop by another was common among many social and carnivorous species- ants, wolves, lions, monkeys, apes. In this, the behavior of the people was, as in many other things, no more than a derivation of deeper animal roots.

But among wolves, apes, pithecines, even the walkers, such campaigns had been inefficient. Without effective weapons, killings could be achieved only with overwhelming numbers, and it could take years for a war between two competing bands of thirty or forty pithecines to resolve itself. Even during the long age of the sedentary robusts, there had been little large-scale slaughter. Isolated strangers were killed, but there were no wars for lebensraum.

But now, as the genetic definition of Harpoon's new nomadic people continued to spread, that was starting to change. Harpoon's kind had accurate long-range weapons, and heads increasingly capable of systematic, orderly thinking; they were able to perform mass killing with unprecedented thoroughness. But there was a feedback effect. Warfare with other groups would force hominids to come together in increasingly large bands, with all the social complications that followed. The killing would shape the killers, too: If love was evolving, so was hate.

After cleaning out one particularly dense nest, Ko-Ko and the others had a kind of party. They dragged the bodies of the women, children, and men from the nest to an open space and piled them up- thirty, forty of them, all with ripped-open bellies, cleaved chests, smashed skulls. Then they began a fire, throwing burning branches onto the heap of bodies. Ko-Ko and the others danced around the burning corpses, whooping and hollering.

The skinny hunters dragged forward live captives. They were a mother and child, a spindly boy small enough to carry. The hunters had cornered her by a rock bluff where she had been trying to hide. Skinnies and robusts alike gathered around, hooting and yelling, and thrusting spears were raised before the mother's face.

To Pebble the mother seemed numbed. Perhaps there was a kind of guilt written on that slim, protruding face. She had survived while others had fallen around her, all save her small child, and she was unable to feel anymore.

Ko-Ko stepped forward. With a simple efficient thrust, he drove the point of his thrusting spear into the woman's chest. A black fluid burst from her skin. She convulsed- there was the too-familiar smell of death shit- and she slumped.

Still the infant lived. He was wailing, clinging to his mother and even trying to gnaw at her blood-streaked breast. But, just as a mother chasma had once pushed her pups toward hapless Elephant, so now Harpoon, her swollen belly proud before her, thrust Smooth toward the infant. Pebble's daughter carried a stone chopping tool. With a lithe body so like her mother's, she looked feverish, eager. And she raised the chopping stone over the infant's flat skull.

Though he never shirked the fighting, the killing, suddenly Pebble longed to be away from here, sitting on a beach under a tall sunset, or digging for yams to bring home to his mother.

By the next morning the fire was burned out. The hominids had been reduced to gaunt skeletons, their blackened bodies wizened into fetal postures. Ko-Ko and Smooth stalked amongst the smoking remains, smashing them to pieces with the butts of their heavy thrusting spears.

CHAPTER 11.

Mother's People Sahara, North Africa. Circa 60,000 years before present.

I.

Mother walked alone, a slim, upright figure in a tabletop landscape. The ground was hot under her feet, the dust sharp and prickling. She came to a stand of Hoodia cactus. She crouched down, cut off a stem about the size of a cucumber, and munched on its moist flesh.