It wasn’t just the migraine. Mother was suffering from what might have been diagnosed as a kind of schizophrenia. Her symptoms had been triggered by the death of her son. Even in this first flowering of human creativity, Mother foreshadowed many of the flawed geniuses who would illuminate, and darken, human history in the generations that lay in the future.

There was no police force here. But random killers were not welcome in such a small, close-knit community. So they came to seek her out.

But she had gone.

Alone, she walked for days across the savannah, back to the place they had last camped, the place of the dry gorge. The patch of ground was now so weathered and overgrown that surely only she could have recognized it.

She cleared away the vegetation, grass, and scrub. Then she took a digging-stick and, like long-dead Pebble digging for yams, she began to beat her way into the earth.

At last, a meter or so deep, she glimpsed the white of bone. The first fragment she retrieved was a rib. In the harsh sunlight it gleamed white, utterly cleansed of flesh and blood; she was struck by the awful efficiency of the worms. But it wasn’t ribs she wanted. She dropped the bone and dug her hands into the soil. She knew where to look, remembered every detail of that terrible day when Silent had been flung into this bit of ground, how he had fallen with head lolling back and limbs splayed, the stains of his death shit still showing on his thin legs.

Soon she closed her hands on his head.

She lifted the skull into the air, the gaping eyes facing her. A scrap of cartilage held the jaw in place — but then the rotting cartilage gave way, and the jaw creaked open, as if the fleshless child were trying to say something to her. But the gaping smile kept widening, grotesquely, and a fat worm wriggled where the tongue had been, and then the jaw fell off, back into the dirt.

That didn’t matter. He didn’t need a jaw. What were a few teeth? She spat on the cranium and polished it clean of dirt with the palm of her hand. She cradled the skull, crooning.

When she returned to the lake, the people were waiting for her. They were all here, all but the youngest children and the mothers with infants. Some of the adults carried weapons — stone knives, wooden spears — as if Mother were a rogue bull elephant who might suddenly turn on them. But as many of the group were dismayed as were overtly hostile. Here was Sapling, for instance, his spear-thrower slung over his back on a length of sinew, his pale eyes clouded as he watched the woman who had taught him so much. Many of them even wore the markings she had inspired on their flesh or clothes.

Sour’s only surviving child was a girl, thirteen years old. She had always been prone to chubbiness, and that had gotten worse now that she was coming into womanhood; already her breasts were large, pendulous. And her skin was an odd yellow-brown color, like honey, the legacy of a chance meeting with a wandering group from the north a couple of generations back. Now this girl, Honey, Mother’s cousin, stared at Mother with baffled anger, her dirty face streaked with tears.

Hostile, sad, pitying, or confused, they were all uncertain. When she recognized that uncertainty Mother felt a kind of inner warmth. Without yelling, without using violence, without so much as a gesture, she was in control of the situation.

She held up the skull and swiveled it so that its sightless eyes turned on the people. They gasped and flinched — but most looked more baffled than frightened. What use was an old skull?

But one girl turned away, as if the staring skull were looking at her accusingly. She was a skinny, intense fourteen-year-old with wide eyes. This girl, Eyes, had a particularly elaborate spiral design sketched on her upper arms in ocher. Mother made a mental note of her.

One man stepped forward. He was a huge fellow with a ferocious temper, like a cornered ox. Now Ox pointed back at Sour’s shelter. “Dead,” he said. He pointed his ax at Mother. “You. Head, rock. Why?”

For all the control she was exerting on the situation, Mother knew that what she said now would determine her entire future. If she was driven out of the camp she could not expect to survive long.

But she was confident.

She looked at the skull, and smiled. Then she pointed at Sour’s body. “She kill boy. She kill him.”

Ox’s black eyes narrowed. If that was true that Sour had killed the boy, then Mother’s actions could be justified. Any mother, even a father, would be expected to avenge a murdered child.

But now Honey pushed forward. “How, how, how?” Struggling to express herself, her plump belly wobbling, she mimed stabbing, strangling. “Not kill. Not touch. How, how, how? Boy sick. Boy die. How, how?” How is my mother supposed to have done this?

Mother raised her face to the sun, which sailed through a cloudless dome of white-blue sky. “Hot,” she said, wiping her brow. “Sun hot. Sun not touch. She not touch. She kill.” Action at a distance. It isn’t necessary for the sun to touch your flesh for it to warm you. And it wasn’t necessary for Sour to touch my son to kill him.

There was fear in their faces now. There were plenty of invisible, incomprehensible killers in their lives. But the notion that a person could control such forces was new, frightening.

Mother forced herself to smile. “Safe. She dead. Safe now.” I killed her for you. I killed the demon. Trust me. She held up the skull, stroking its cranium. “Tell me.” And so it had been.

Ox glared at Mother. He growled and stamped, and pointed at her chest with his ax. “Boy dead. Not tell. Boy dead.”

She smiled. She nestled the skull in the crook of her arm, like the head of a baby. And as they stared at her, half-believing, she could feel her power spread.

But Honey wouldn’t accept any of this. Crying, jabbering meaninglessly, she lunged at Mother. But the women held her back.

Mother walked away toward her shelter. The people shrank back as she passed, eyes wide.

The dryness intensified. One hot, cloudless day gave way to another. The land dried quickly, the streams shriveling to brownish trickles. The plants died back, though there were still roots to be dug out with ingenuity and strength. The hunters had to range far in search of meat, their feet pounding over dusty baked-dry ground.

These were people who lived in the open, with the land, the sky, the air. They were sensitive to the changes in the world around them. And they all quickly knew that the drought was deepening.

Paradoxically, though, the drought brought them a short-term benefit.

When the dry period had lasted thirty days, the group broke up its encampment and trekked to the largest lake in the area, a great pool of standing water that persisted through all but the most ferocious dry seasons. Here they found the herbivores — elephant, oxen, antelope, buffalo, horses. Driven to distraction by thirst and hunger, the animals crowded around the lake, jostling to get at the water, and their great feet and hooves had turned the lake’s perimeter into a trampled, muddy bowl where nothing could grow. But already some of them were failing: the old, the very young, the weak, those with the least reserves to see them through this harsh time.

The humans settled, watchful, alongside the other scavengers. There were other human bands here — even other kinds of people, the thick-browed sluggish ones you glimpsed in the distance sometimes. But the lake was big; there was no need for contact, conflict.

For a time the living was easy. It wasn’t even necessary to hunt; the herbivores simply fell where they stood, and you could just walk in and take what you needed. The competition with other carnivores wasn’t too intense, for there was plenty for everybody.