Almost a year after Jupiter, Andres called her ’council’ of twelve together in the amphitheatre at the base of the Ship. This big chamber had been stripped of its acceleration couches, and the dozen or so of them sat on temporary chairs in the middle of an empty grey-white floor.

Andres told them she wanted to discuss a little anthropology.

In her characteristic manner she marched around the room, looming over her crew. ‘We’ve had a good year, for which I thank you. Our work on the Ship isn’t completed - in a sense it never will be completed - but I’m now satisfied that Mayflower will survive the voyage. If we fail in our mission, it won’t be the technology that betrays us, but the people. And that’s what we’ve got to start thinking about now.’

Mayflower was a generation starship, she said. By now mankind had millennia of experience of launching such ships. ‘And as far as we know, every last one of them has failed. And why? Because of the people.

‘The most basic factor is population control. You’d think that would be simple enough! The Ship is an environment of a fixed size. As long as every parent sires one kid, on average, the population ought to stay stable. But by far the most common causes of mission loss are population crashes, in which the number of crew falls below the level of a viable gene pool and then shuffles off to extinction - or, more spectacularly, explosions in which too many people eat their way to the hull of their ship and then destroy each other in the resulting wars.’

Diluc said dryly, ‘Maybe that proves it’s just a dumb idea. The scale of the journey is just too big for us poor saps to manage.’

Andres gazed at him challengingly. ‘A bit late to say that now, Diluc!’

‘Of course it’s not just numbers but our population’s genetic health that we have to think about,’ pointed out Ruul. This lanky, serious man was the Ship’s senior geneticist. ‘We’ve already started, of course. All of us went through genetic screening before we were selected. There are only two hundred of us, but we’re as genetically diverse a sample of Port Sol’s population as possible. We should avoid the founder effect - none of us has a genetically transmitted disease to be spread through the population - and, provided we exert some kind of control over breeding partnerships, we should be able to avoid genetic drift, where defective copies of a gene cluster.’

Diluc looked faintly disgusted. “‘Control over breeding partnerships”? What kind of language is that?’