So--I've been rewatching TOS, and I'm starting to hit the episodes I'm not too crazy about. For me, The Apple is mainly about laughing at redshirts falling like flies.
While I was watching it, the whole discussion of whether or not the PD should be violated seemed moot to me, as this wasn't a PD situation. It was a self-defense situation for the Enterprise. There was no alternative but to destroy Vaal.
BUT, after our intrepid non-security survivors left, that's when it me: these people (the Gamma Triangulans) had NO idea of how to deal with childbirth. Kirk leaves them with a "you'll figure it out," and we, the audience, are supposed to just chuckle and think only about the fun and pleasure of the conception and not what happens 9 months later (or however many months the Gamma Triangulans' fetuses will gestate).
But with not a clue about what childbirth is, heavy infant and mother mortality are inevitable, and there aren't that many of them to begin with--and no Vaal to keep them healthy or perform whatever miracles Vaal might have performed. Can this population possibly survive? Hell---will they even understand what it means when the mothers' abdomens start to grow? Will there be horrific attempts to excise what will first appear to be unknown growths? Eeesh.
And let's say they get past the point of childbirth--is there ANY way to avoid inbreeding and the fixing of lethal recessives plus all kinds of chromosome breakage, with a population this small? At least they might have avoided the worst pairings, if they'd had a little instruction from the crew.
And not even McCoy says a word about staying a little while to give them some basic sex ed.