‘But, you see, living space is restricted here. The parents must compete for space against their own children. They don’t care about the children. They use them as workers - or even, when there’s an excess, as a cannibalistic resource . . . But there are always one or two children who fight their way through to adulthood, enough to keep the stock numbers up. In a way the pressure from the adults is a mechanism to ensure that only the smartest and strongest of the kids survive. It’s a mixed strategy.’

‘From the genes’ point of view it’s a redundancy mechanism, ’ Rusel said. ‘That’s the way an engineer would put it. The children are just a fail-safe.’

‘Precisely,’ Andres said.

It was biology, evolution: the destiny of the Mayflower had come down to this.

Rusel had brooded on the fate of his charges, and had studied how time had always shaped human history. And he had decided it was all a question of timescales.

The conscious purpose of the Ship had sustained its crew’s focus for a century or so, until the first couple of generations, and the direct memory of Port Sol, had vanished into the past.

Millennia, though, were the timescale of historical epochs on Earth, over which empires rose and fell. His studies suggested that to sustain a purpose over such periods required the engagement of a deeper level of the human psyche: the idea of Rome, say, or a devotion to Christ. If the first century of the voyage had been an arena for the conscious, over longer periods the unconscious took over. Rusel had seen it himself, as the transients had become devoted to the idea of the Ship and its mission, as embodied by his own Virtual. Even Hilin’s rebellion had been an expression of that cult of ideas. Call it mysticism: whatever, it worked over epochs of thousands of years.

That far, he believed, Andres and the other pharaohs had been able to foresee and plan for. But beyond that even they hadn’t been able to imagine; Rusel had sailed uncharted waters.

And as time heaped up into tens of millennia, he had crossed a span of time comparable to the rise and fall, not just of empires, but of whole species. A continuity of the kind that kept the transients cleaning the walls over such periods could only come about, not through even the deepest layers of mind, but through much more basic biological drivers, like sexual selection: the transients cleaned for sex, not for any reason to do with the Ship’s goals, for they could no longer comprehend such abstractions. And meanwhile natural selection had shaped his cradled populations, of transients and Autarchs alike.