I recall a book I read (late '70s, early '80s) in which an individual had a spontaneous mutation that gave him something like particularly aggressive sperm in acid seminal fluid and a 'repackaged' penis (possibly a penile/vaginal combo?) that in all but the most deliberate circumstances made rape (of males, as exclusive preference I think) fatal. When done
carefully, though, the introduced genetic material would transform (Crispr-ise?) the recipient into a compatible aggressively-biological hermaphroditic member of the new mutation (now capable of safe mutual impregnation to conceive 'natuural' nu-numans).
This book was from the library, the few shelves of sci-fi/fantasy shelves between the children's section and the mainstream adult fiction room, which I was totally devouring at the time (where I encountered the first couple of Discworld novels, and got hooked*). I suppose it (the shelving) was aimed at what these days would be termed Young Adult. Which doesn't explain how on Earth such a blatantly homoerotically-themed novel found itself within easy reach of unsuspecting readers of delicate ages. One assumes it never survived
Clause 28, if it even survived long enough for that without some more prudish reader complaining about it.
(I'd been crossing the corridor into the (age-wise) adult sections of the library for years before I was actually adult - there weren't any borrowing restrictions such as adult/child-specific library tickets. But I'd taken far too long to discover the
interesting shelves with the SF on them.)
But as this is the Science thread and not a Reading Matters or Sexuality thread, maybe you could pick holes in the whole fully-formed in-vivo Horizontal Gene Transfer mechanism (and delivery system!) somehow evolving into reality in a single birth.
Without deliberate (and competent?) design behind it.
* Plus L Ron Hubbard's fictional works, like the Mission Earth decalogy. Which had some of Elron's stranger ideas I later heard had been ploughed into his 'church' (see also Battlefield Earth) but also some rather extreme scenes of perversion that I probably shouldn't describe
beyond the "Earth prostitute becomes sex-tutor on alien world" and "mad (alien) plastic surgeon basically creates human(sic) centipedes", because both those are
dodgier than I've actually explained them. Anyway, all that livened my reading list up, certainly. Better than Piers Anthonthy.