Unfortunately, even if we do get people to control their breeding, and the planet settles in at a nice stable say 4 billion humans in 150 – 200 years we will still be fighting evolution.

If there is no direct penalty to having more than the number of kids it takes to replace you (right now about 2.2 per couple), unless having more than that many children results in a direct hit to the survival chances of those children, not future children, or others children … then evolution will favour those people who are reckless, selfish, or stupid enough to have lots of kids.

Oh well, we have to get through the next century without a massive collapse and contraction of civilization before we worry about that, and to me, the chances of that look to be 50/50.

If we don’t control our population, Nature will. And nature isn’t worried about being nice.