There was no other activity, and after five minutes the scene suddenly faded out. The crystal was no more than a glimmering outline in the darkness; Moon-Watcher shook himself as if awaking from a dream, abruptly realized where he was, and led the tribe back to the caves.

He had no conscious memory of what he had seen; but that night, as he sat brooding at the entrance of his lair, his ears attuned to the noises of the world around him, Moon-Watcher felt the first faint twinges of a new and potent emotion. It was a vague and diffuse sense of envy – of dissatisfaction with his life. He had no idea of its cause, still less of its cure; but discontent had come into his soul, and he had taken one small step toward humanity.

Night after night, the spectacle of those four plump man-apes was repeated, until it had become a source of fascinated exasperation, serving to increase Moon-Watcher's eternal, gnawing hunger. The evidence of his eyes could not have produced this effect; it needed psychological reinforcement. There were gaps in Moon-Watcher's life now that he would never remember, when the very atoms of his simple brain were being twisted into new patterns. If he survived, those patterns would become eternal, for his genes would pass them on to future generations.

It was a slow, tedious business, but the crystal monolith was patient. Neither it, nor its replicas scattered across half the globe, expected to succeed with all the scores of groups involved in the experiment. A hundred failures would not matter, when a single success could change the destiny of the world.

By the time of the next new moon, the tribe had seen one birth and two deaths. One of these had been due to starvation; the other had occurred during the nightly ritual, when a man-ape had suddenly collapsed while attempting to tap two pieces of stone delicately together. At once, the crystal had darkened, and the tribe had been released from the spell. But the fallen man-ape had not moved; and by the morning, of course, the body was gone.

There had been no performance the next night; the crystal was still analyzing its mistake. The tribe streamed past it through the gathering dusk, ignoring its presence completely. The night after, it was ready for them again. The four plump man-apes were still there, and now they were doing extraordinary things. Moon-Watcher began to tremble uncontrollably; he felt as if his brain would burst, and wanted to turn away his eyes. But that remorseless mental control would not relax its grip; he was compelled to follow the lesson to the end, though all his instincts revolted against it.

Those instincts had served his ancestors well, in the days of warm rains and lush fertility, when food was to be had everywhere for the plucking. Now times had changed, and the inherited wisdom of the past had become folly. The man-apes must adapt, or they must die – like the greater beasts who had gone before them, and whose bones now lay sealed within the limestone hills.

So Moon-Watcher stared at the crystal monolith with unblinking eyes, while his brain lay open to its still uncertain manipulations. Often he felt nausea, but always he felt hunger; and from time to time his hands clenched unconsciously in the patterns that would determine his new way of life.

As the line of warthogs moved snuffling and grunting across the trail, Moon-Watcher came to a sudden halt. Pigs and man-apes had always ignored each other, for there was no conflict of interest between them. Like most animals that did not compete for the same food, they merely kept out of each other's way.

Yet now Moon-Watcher stood looking at them, wavering back and forth uncertainly as he was buffeted by impulses which he could not understand, Then, as if in a dream, he started searching the ground – though for what, he could not have explained even if he had had the power of speech. He would recognize it when he saw it.

It was a heavy, pointed stone about six inches long, and though it did not fit his hand perfectly, it would do. As he swung his hand around, puzzled by its suddenly increased weight, he felt a pleasing sense of power and authority. He started to move toward the nearest pig.

It was a young and foolish animal, even by the undemanding standards of warthog intelligence. Though it observed him out of the corner of its eye, it did not take him seriously until much too late. Why should it suspect these harmless creatures of any evil intent? It went on rooting up the grass until Moon-Watcher's stone hammer obliterated its dim consciousness. The remainder of the herd continued grazing unalarmed, for the murder had been swift and silent.

All the other man-apes in the group had stopped to watch, and now they crowded round Moon-Watcher and his victim with admiring wonder. Presently one of them picked up the blood-stained weapon, and began to pound the dead pig. Others joined in with any sticks and stones that they could gather, until theirt target began a messy disintegration.

Then they became bored; some wandered off, while others stood hesitantly around the unrecognizable corpse – the future of a world waiting upon their decision. It was a surprisingly long time before one of the nursing females began to lick the gory stone she was holding in her paws.

And it was longer still before Moon-Watcher, despite all that he had been shown, really understood that he need never be hungry again.

The tools they had been programmed to use were simple enough, yet they could change this world and make the man-apes its masters. The most primitive was the hand-held stone, that multiplied manyfold the power of a blow. Then there was the bone club, that lengthened the reach and could provide a buffer against the fangs or claws of angry animals. With these weapons, the limitless food that roamed the savannas was theirs to take.

But they needed other aids, for their teeth and nails could not readily dismember anything larger than a rabbit, Luckily, Nature had provided the perfect tools, requiring only the wit to pick them up; First there was a crude but very efficient knife or saw, of a model that would serve well for the next three million years. It was simply the lower jawbone of an antelope, with the teeth still in place; there would be no substantial improvement until the coming of steel. Then there was an awl or dagger in the form of a gazelle horn, and finally a scraping tool made from the complete jaw of almost any small animal.

The stone club, the toothed saw, the horn dagger, the bone scraper – these were the marvelous inventions which the man-apes needed in order to survive. Soon they would recognize them for the symbols of power that they were, but many months must pass before their clumsy fingers had acquired the skill – or the will – to use them.

Perhaps, given time, they might by their own efforts have come to the awesome and brilliant concept of using natural weapons as artificial tools. But the odds were all against them, and even now there were endless opportunities for failure in the ages that lay ahead.

The man-apes had been given their first chance. There would be no second one; the future was, very literally, in their own hands.

Moons waxed and waned; babies were born and sometimes lived; feeble, toothless thirty-year-olds died; the leopard took its toll in the night; the Others threatened daily across the river – and the tribe prospered. In the course of a single year, Moon-Watcher and his companions had changed almost beyond recognition.

They had learned their lessons well; now they could handle all the tools that had been revealed to them. The very memory of hunger was fading from their minds; and though the warthogs were becoming shy, there were gazelles and antelopes and zebras in countless thousands on the plains. All these animals, and others, had fallen prey to the apprentice hunters.