The Frenetic Code
For some unknown reason a third stage of meiosis begins to occur at conception worldwide wherein extra crossing-over of chromosomes occurs, creating mutations with EVERY conception. It extrapolates the normal genetic diversity that occurs in sexual reproduction and makes it go wild. Every birth results in either an improvement in the human (rare, resulting in a minority of supermen each with different characteristics) or a monster (common, resulting in a marauding majority population of bizarre creatures who, with their own collection of different characteristics) don't take kindly to the new us-vs.-them paradigm. Enclaves of supermen fight for survival in a civilization of ruins, trying to establish a game plan for re-igniting the human race without the genetic homicidal malcontents, all the while staying alive and one step ahead of their stalkers.
This take on the end-of-the-world can have elements of horror, drama, futurism, terror, sci-fi, fantasy, psychological thriller (my favorite--see my book, SLIDER). Needs a novel length.