The Freakonomics guys recently had a post about how children are basically an addiction for parents - they create surges of oxytocin at unpredictable times by occasionally being nice, so the parent puts up with all the negative behaviour in order to get the rewards when they say "I love you".
Having 2 small (somewhat rambunctious, shall we say) children, this makes a lot of sense to me.
So perhaps the issue is that when the rational brain takes over it is more powerful than the chemical addictions. This could also then apply to non-parents (i.e. nobody would get "broody" when seeing other, well behaved children, becuase the chances are they would have also seen kids behaving like monsters). One would assume that the people on the drug in the story would also not get involved with other (addictive) drugs - not having kids would simply be an extension of that.
Must try and get hold of that story though ... especially as I've always been a Pohl fan!
Edit to include link: http://freakonomics.blogs.nytimes.com/2010/11/16/the-parent-trap-addiction/
Minor proofreading correction: Second to last para: People show interest(ed)
I can't help thinking that route 1 dooms us. Since the planet isn't run by the intellectual elite. Indeed I'm fairly sure I read a study recently which showed the intellectual elite shy away from politics - not becuase they want to get involved but because it is now more about who can make the mud stick than it is about issues. That would mean the world would be steered by the sub-90 IQs rather than the 130-plus IQs. So "popular" support is necessary, to ensure that rational solutions actually get to see the light of day!