Diluc showed Rusel a draft of a ‘social contract’ he was preparing to capture all this. ‘First, on reaching adulthood you submit yourself to the needs of the group as a whole. For instance your choice of career depends on what we need as much as what you want to do. Second, you agree to have kids only as the need allows. If we’re short of the optimum population level, you might have three or four or five, whether you want them or not, to bring up the numbers; if we’re over the target, you might have none at all and die childless. Third, you agree to postpone parenthood for as long as possible, and to keep working as long as possible. That way you maximise the investment the tribe has made in educating you. Fourth, you can select your own breeding-spouse, who may be the same as your companionship-spouse—’

‘We were lucky,’ Tila said fervently.

‘But she can’t be closer than a second cousin. And you have to submit to having your choice approved by the Elders. That’s you.’ He grinned at Rusel. ‘Your match will be screened for genetic desirability, and to maximise the freshness of the gene pool - all of that. And finally, if despite everything you’re unlucky enough to have been born with some inheritable defect that might, if propagated, damage the Ship’s chances of completing its mission, you agree not to breed at all. Your genetic line stops with you.’

Rusel frowned. ‘That’s eugenics.’

Diluc shrugged. ‘What else can we do?’

Diluc hadn’t studied Earth history, as Elder-educated Rusel now had, and without that perspective, Rusel realised, that word carried for him none of the horrific connotations it had once borne. As Diluc had implied, they had little choice anyhow given the situation they were in. Besides, eugenics through arranged couplings was lower-tech than genetic engineering: more future-proofing.

Rusel studied the draft contract. ‘And what happens if somebody breaks the rules?’

Diluc was uncomfortable; suddenly Rusel was aware that he was an Elder, as well as this man’s brother. ‘We’ll cross that bridge when we come to it,’ Diluc said. ‘Look, Rus, we don’t have police here, and we don’t have room for jails. Besides, everybody really is essential to the community as a whole. We can’t coerce. We work by persuasion; we hope that such situations will be easily resolved.’

Diluc talked of personal things too: of the progress of his boys at school, how Tomi had always hated the hour’s wall-cleaning he had to put in each day, while little Rus loved it for the friends he was making.

‘They are good kids,’ Rusel said.