On the other hand, think of career politicians and of dictators for life. Later-borns will have a hard time catching up to the experience, life-savviness, networks, and other moats, of the multi-centennials they’re competing against. Also, who will be allowed to have children when the population can’t grow indefinitely? Things could get pretty dystopian.

The basic social structure would have to be completely rethought. A good model might exist, we just don’t know what it is yet.