It depends on whether everyone will be born into the first and only generation or the random assignment to people has a time component as well. Much like how t

It depends on whether everyone will be born into the first and only generation or the random assignment to people has a time component as well. Much like how the strategies of prisoners dilemma change If you are playing an iterated game. For your birth defect example, consider 2 societies, where 1 bans cousin marriage and the other encourages it. In 50 years time the chance of being born with a birth defect is 5x higher in 1 than the other. That wouldn't matter for the first generation but imagine you will be born to a random generation between now and 1000 years from now. Which do you choose? Once you take into account time, then growth, social institutions and incentives come into play. You may prefer to bet on a much richer, healthier society that had a bit less equality or freedom in the past for a while.