“It’s no great surprise that as Witnesses we are drawn to bottlenecks. They are the times of maximum danger for mankind, maximum drama — and yet of maximum flux and opportunity.”

Alia stared at Michael Poole, his troubled face trapped in stillness inside her Witnessing tank. In this incident Poole was outdoors, in a strange landscape. In hot dense sunlight, he was climbing over a vast heap of wreckage, of smashed and abandoned machines. “Here he is aged fifty-two,” she said. “He is entering the most critical time of his life.”

“He looks troubled.”

“He often does,” she said wryly. “Poole knew the dangers of his age very well. Most educated people of the time did, I think. But after the danger his son encountered, Poole came to grasp the implications better than most. He worked on a geoengineering project after all.”

“And he was a Poole,” Reath said, somewhat reverently.

“But they were all so limited — all the people of his time, even Poole himself. The best you can say about them is that they were beginning to understand how little they did know.”

“And is it the problems of the Earth that are depressing him so?”

“More than that,” she said. “His own work isn’t going well. And it is a difficult time in his personal life…” She skimmed the projection back and forth; Poole stayed steady at the center of the flickering images while people appeared and imploded around him.

When she was young Alia had focused her Witnessing on the more accessible moments of Poole’s life: his joyous childhood, his discovery of love as a young man. With Reath’s gentle coaxing she had been trying to concentrate on this period, the most difficult time of his life — Poole’s own Bottleneck, perhaps.

But it was very hard for her to get into the head of a fifty-two-year-old man from the middle of the twenty-first century. Everything about his life was so different. Her fifties would be the start of her young adulthood, a time of opportunity and growing command over her destiny. For Poole, more than half his life — and the more productive, enjoyable part — had already gone. He was rapidly running out of future.

Sometimes, when she studied Poole, all she seemed to see was his smallness. He was a dark, unhappy creature, shut in on himself, trapped in a world so impoverished of stimulus and capability it was a wonder people didn’t simply die of boredom and frustration. “He knows so little,” she said. “He will die knowing so little. He suffers so much. And yet he will shape history.”

Reath touched her shoulder. “This is just as Witnessing is meant to be. As you come to understand the life of another embedded in the past, you come to understand yourself better.

“But you must try to keep a sense of perspective, Alia. Mankind did pass through this terrible Bottleneck. And the future of this limited little species was remarkable indeed…”

After its long Earthbound prologue, mankind erupted off the planet, “like a flock of birds lifting from a tree,” said Reath.

There followed a wave of exploration, colonization, and conquest, in which Michael Poole’s descendants played a significant part. But after the startling discovery of a Galaxy full of alien cultures, many of them ancient and malevolent, it was a wave of expansion that was pushed back several times. Once that reverse reached all the way back to Earth itself.

With the alien occupation of Earth overthrown, mankind re-emerged strong, united, focused — pathologically so, perhaps, Reath said. The government of the time, the most powerful central authority ever to emerge in human history, was known as the Coalition. A new expansion, a froth of war, conquest, and assimilation, swept across the face of the Galaxy. It took twenty-five thousand years, but at last the center of the Galaxy itself lay in human hands, and legends of the victorious warriors, the “Exultant generation,” resonated down the ages that followed.

Alia said, “ ‘Pathological’? That’s a strange word to choose.”

“But it was a pathology, of a sort,” Reath said. “Think about it. The Coalition controlled mankind for twenty-five thousand years! That’s a period that was comparable to the age of the species itself, at the time. For all that time the Coalition controlled culture, politics — even the genetic destiny of mankind. The soldiers who finally broke into the Galaxy’s Core were as human as Michael Poole, save for some superficialities. It was unnatural, Alia! That’s why I say it was pathological. A kind of madness gripped mankind, as we became defined solely by the war.”

“But it was a successful madness.”

“Oh, yes!”

When the war was won, the center could no longer control a Galactic mankind. Reath said darkly, “It was as if a truce had been called among humans, for the purposes of the war against the aliens. But with the Galaxy won history resumed — history of the usual bloody sort.”

The great expansion that had climaxed in the Exultant victory had cleaned out or marginalized most nonhuman life-forms, leaving the Galaxy an empty stage for a new human drama. New ideologies emerged, and successor states sprouted like weeds in the rubble of empire, each of them claiming legitimacy from the collapsed Coalition. The long age of conquest had bequeathed a Galaxy well stocked with the machinery of conflict, and the wars that followed, motivated by economics and ideology, glory and ambition, consumed millennia and countless lives.

“It was not a noble age,” Reath said, “though it threw up plenty of heroes. And it was played out in the shadow of the monumental achievements of the Exultant generation. Many were afflicted with a sense of shame at what they had become. But there was always somebody else to blame for the squabbling, of course.

“And time exerted its power. We are fleeting creatures, we humans!”

The river of time flowed on, bloodied by war, thousand-year empires bubbling like spindrift. The Coalition and its works were forgotten. And humans, flung upon a million alien shores, morphed and adapted. This was the Bifurcation of Mankind.

There were still wars, of course. But now different human species confronted each other. Some were so different that they no longer competed for the same resources — “they no longer shared the same ecological niche,” as Reath put it. But a more fundamental xenophobia fueled genocidal wars.

“So much suffering,” Alia said. “How terrible it all was.”

Reath said, “I wonder what Michael Poole would have thought of it all, if he could have looked forward. Was all his struggle worth it, merely to enable so much suffering to follow?”

“Michael Poole gave those who followed the opportunity to live their lives,” she said. “He can’t take responsibility for what they did with that opportunity.”

Reath nodded. “When your children leave home, you can’t live their lives for them. But you always worry.”

Alia wondered briefly if Reath had any children of his own. He said very little about his past — indeed she knew far more about Michael Poole, dead half a million years, than she did about the man who had come to share her life.

The age of Bifurcation ended abruptly.

Ninety thousand years after the time of Michael Poole, genetic randomness threw up a new conqueror. Charismatic, monstrous, carelessly spending human life on a vast scale, the self-styled Unifier saw only opportunity in the fragmentation of mankind. By using one human type as a weapon against another — and, somehow, by inspiring loyalty in soldiers as unlike each other as it was possible to be and yet still be called human — he built an empire. In the end he was defeated by the sheer scale of the Galaxy. One of his many enemies took his life, and his empire disintegrated, evanescent.

And yet the Unifier’s project had a long-lasting impact. If only briefly he had spread a common culture across a significant fraction of the Galaxy’s geography. Not since the collapse of the Coalition had the successors of mankind recalled that they all once shared the same warm pond.