In a comment to one of my posts on Brave New World, AkodoAkira writes:
“So my question is this: why are their no new Alphas? Maybe I missed it in one of the books, but what’s the deal with it?”
Native alphas come from deltas who have near-death experiences. These people are still affected by the Disappearance Effect that happened in the wake of the Bicentennial Battle. They end up transported to the disappeared Chicago.
Alphas can come into the world from other dimensions, and they can also stick around if they’re protected at the moment of their conversion. This is rare, though, and could only happen through tremendous foresight or providence.
“Also: Why do Deltas begin springing up in the 20th century? My friend is arguing that the tears in the fabric allow the Delats to appear, I am arguing that medical science is allowing them to survive the change. Which one is more accurate?”
Your friend is closer to what I had in mind. I like your idea too. I’d never thought of it that way. It could easily be a combination of the two.