you would be looking at technology that can manipulate things at the molecular level, and a much deeper understanding of how genes express as actual people. this would also provide perfect birth control, so there may be some fucking going on but the babies would be made on purpose. especially after you get a generation or two of engineered humans, they will probably be snobby as fuck and for good reasons. it will be a scifi version of your hindu caste system. the differences will probably be somewhat subtle at first, just better looking, smarter, healthier people, of all kinds, but once they form any sort of breakaway society the differences will be profound.
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