On symmetric person-affecting views (PAV), in choosing between actions only necessary people, those who will exist regardless of our immediate choice, count while those whose existence is contingent on our choices are ignored. Chaotic 'butterfly effects' mean that almost any terrestrial action will shortly scramble the genetic makeup and identities of future terrestrial births. Thus philosopher Michael Plant invokes symmetric PAV to say that '[o]n this, roughly speaking, the well-being of future entities, human or non-human, does not count" and to argue in favor of a focus on short-run impacts on long-lived existing creatures (humans and dogs, but not chickens or ants) rather than long-run consequences of altruistic interventions, since vast future populations would be composed of contingent rather than necessary people. However, the empirical underpinnings of this move are questionable: there are reasonable possibilities on which astronomically large populations of necessary people will exist, and credence in such possibilities will mean that they account for the bulk of expected impact on necessary people. I raise three such possibilities: technological life extension, contact with distant aliens, and fission cases.