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. 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.

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.

She went naked save for a bolt of eland leather tied round her waist. She had a shaped stone in one hand, but carried nothing else. Her face was fully human, her brow smooth and upright, her chin sharp. But her mouth was pinched and her eyes were sunken, her gaze darting suspiciously.

The savannah around her was arid, dismal. The empty shadowless flatness stretched away, dissolving into a ghostly heat haze that obscured the encircling horizon, a flatness broken only by an occasional drought-resistant bush or the remains of an elephant-trampled copse. There wasn’t even any dung to be seen, for the great herbivores passed rarely now, and the beetles had long done their tidy and efficient work.

Clutching the cactus stem, she moved on.

She reached the edge of the lake — or where its edge had been last year, or perhaps the year before that. Now the ground was dry, a patina of dark, heat-cracked mud so hard it didn’t crumble when she put her weight on it. Here and there scrubby grass, yellow white, clung to life.

She cupped her hands over her eyes. The water was still there, but far from where she stood, just a remote shimmer. Even from here she could detect the dank stench of stagnation. On the lake’s far side she glimpsed elephants, black shapes moving like clouds through the glassy heat haze, and animals rooting in the mud — warthogs, perhaps.

But on the lake’s clogged surface she made out waterfowl, a flock roosting peacefully at the center of the water, safe from the hungry predators of the land.

Mother smiled. The birds were just where she wanted them. She turned and walked back from the lake’s barren muddy aureole.