The men sat before the smoldering embers in the hearth. They all had huge bones stuck through the septa of their noses. One of them gestured. “Horn!” The word was unfamiliar, the gesture unmistakable.

Sapling sat on the far side of the fire. He was offered a cooked root to eat and a drink of some thick liquid. As he laid out his goods he cast greedy looks around the hut. The hearth was elaborate — far more so than the simple holes in the ground made by Mother’s people. And there was a pit nearby, skin-lined and filled with water and big flat riverbed boulders. He could immediately see how the water could be heated by dropping in fire-hot stones. There was a structure of clay bricks and straw that he failed to understand: He had never seen a kiln before. There were a few unusual artifacts, like well-made baskets — and a bowl made of what he thought at first was wood, but turned out to be a strange kind of hardened clay.

But most entrancing were the lamps.

They were just clay bowls of animal fat, with bits of juniper twig used as wicks. But they burned steadily, filling the hut with a clear yellow light. He could see now why these huts needed no windows — and his mind raced as he realized that with these lamps it would be possible to have light whenever it was wanted, even in the depths of night, even without a fire.

It was clear that these people were far ahead of his own in toolmaking. But their art was much more limited, although several of them wore strings of the beads he had spotted around the little girl’s neck, beads that turned out to be made of elephant-tusk ivory.

So he wasn’t surprised when the elders were stunned by the array of goods he was able to lay out before them. There were ivory and bone figurines of animals and humans, images, abstract and figurative, carved in relief into shell and bits of sandstone — and one of Mother’s own more extraordinary figures, a creature with the body of a human but the head of a wolf.

It was a reaction he had seen many times before. The art of Mother’s people had advanced hugely in the couple of decades since her own first uncertain fumblings. The people had been ready for it, with their big brains and nimble fingers; all it had taken was for somebody to come up with the idea — just as these river folk’s roomy minds were ready for the art too. It was as if Mother had dropped a grain of dust into a supersaturated solution, and a crystal had immediately formed.

Sapling had no way of communicating with these river folk save for gestures and guessed-at words. But soon the parameters of the discussion were clear. There would be trade: Sapling’s art for these sedentary strangers’ advanced tools and artifacts.

By the time he left to rejoin his hidden companions, about midday the next day, he had a bag full of sample goods. And he had carefully memorized the location of every kiln, every elaborate hearth.

He had done all of this for Mother, as he had carried through so many other similar assignments. But Mother was not here, at his side, sharing the labor and the risks. In his heart he found, somewhat to his surprise, a dark particle of resentment.

Mother sat by the entrance to her shelter. Legs folded under her, hands resting on her knees, her face was in the sun, her back warmed by the remnants of last night’s fire. She was growing old, gaunt, and she seemed to have trouble staying warm. But for now she was comfortable. Oddly satisfied.

Every square centimeter of her skin was covered with tattoos. Even the soles of her feet were adorned with lattice designs. She wore a skin wrap today, as she usually did, so much of her decoration was covered up, but the skin itself was alive with color and motion, leaping animals, darting spears, exploding stars. And on a wooden pillar beside her sat the skull of her long-dead child, stuck back together with a gum made of tree sap.

She watched the people come and go about their daily work. They would glance at her, sometimes nodding respectfully — or else they would turn away hurriedly, avoiding the stare of Mother and her eyeless son — but either way they were deflected, like planets drifting past the gravitational field of some immense black star.

After all, it was Mother who spoke to the dead, Mother who interceded with earth and sky and sun. If not for Mother, the rain would no longer fall, the grass would no longer grow, the animals would stay away. Even sitting here silently she was the most important person in the community.

The latest camp was a riot of color and shape. It was as if Mother had gradually taken the whole of this troop into her head, into her lightning-threaded imagination — and, in a sense, she had. The forms of animals, people, spears, axes — and strange beings that were mixtures of people and animals and trees and weapons — leapt from every surface, from rocks selected for their smooth workability, and from the treated hides that were draped over every shelter. And interlaced with these figurative forms were the abstract shapes that had always marked out Mother’s domain, spirals and starbursts and lattices and zigzags. These symbols were invested with multiple meanings. The image of an eland could represent the animal itself — or people’s knowledge of its behavior — or it could stand for the hunting activity that was required to bring it down, the tool-making, planning, and stalking — or something more subtle yet, the animal’s beauty, or the richness and joy of life itself.

Between the domains of Mother’s mind — and in the minds of those who followed her — the ancient walls were coming down at last. No longer was her full awareness restricted to dealings with other people, while hands and legs and mouths worked independently of thought; no longer was consciousness restricted to its old function of a model of others’ intentions. Now she could think about an animal as if it were a person, a tool as if it were a human to be negotiated with. It was as if the world were populated by new kinds of people — as if tools and rivers and animals, even the sun and the Moon were people, to be dealt with and understood as any other.

After millennia of stasis, consciousness had become a powerful multipurpose tool, reflected in the multiple layers and meanings of the art pieces, like mirrors of a new kind of mind. For the high-browed people this was a time of intellectual ferment.

And Mother wasn’t the only catalyst. Scattered throughout the human range were many others like her. Each of these genius-prophets — if she were not quickly killed by her suspicious fellows — was similarly serving as the focus of a new kind of thinking, new ways of life, a new kind of fire. It was the beginning of an explosive change in the way people interacted with the world around them.

It was the instability of the climate that had driven the development of this new type of mind. The savagely fluctuating environment of this Pleistocene age, like nothing seen in later times, was an unforgiving filter: Only exceptional individuals survived the exceptional harshness, to pass on their genetic legacy. And, not only was the average mind improving, exceptional individuals like Mother were becoming more common — like the prescient technologists who had given the river folk their advanced tool kit. From the point of view of the species it was useful for the mind to be able to produce occasional geniuses. They might wither in the dirt — or they might invent something that would transform human fortunes.

And when such an innovation was made, the roomy heads of their fellows were ready for it. It was as if they longed for it. For seventy thousand years the people had had the necessary hardware. Now Mother, and others like her, supplied the software.

This new way of thinking about the world was already bringing Mother’s people unprecedented new rewards. The encampment, save for its adornment, was the usual jumble of lean-tos. But this latest camp was large; there were twice as many people here now compared to the time before Mother’s awakening. And it was a long time since anybody had suffered the sunken cheeks and swollen belly of hunger. Mother’s ways were successful.