I think it's safe to say those two controls would be a hard sell to a modern citizenry, to say the least. Not to mention the certainty of devastation our modern wars create, that a stone age culture could not even dream of. Regardless, war and murder on any scale is not acceptable to any culture that's moving into the Aquarian age, as an example of how you might frame that evolution. So population control will be achieved via a cognitive self-correction, or we'll be looking at war and infanticide. Which wouldn't make us any more civilized than the islanders.

Birth prevention is accepted by all but the most patriarchal religions, tho. Secular society has been giving lip service to sustainability. In some cases those governments and organizations are actually manifesting real solutions, from education to direct medical care.

We definitely have a very skewed perception of childbirth in the west, in that we have a high survival rate. The almost unbelievable ease with which we raise our kids, compared to the third world, gives us a different perspective on the value of a life.

This will sound a bit controversial, but life has always favored the quick until we came along. Within the space of recorded history, many humans have found ways to survive and reproduce that completely bypass the more physical and intuitive aspects needed by a hunter or warrior, or a gatherer, or a multitasking laborer.

Think of it this way... there's much more than 300 million Americans... there's really something more along the lines of 500 million Americans when you figure at least half that 300 million is taking in 2, 3, 4 times the daily calories they need. And all of us grew up in times of plenty, except for some very aged who remember hard times in the 30s. So nobody really knows what 'lean' means, not even most of the people that are already there by standard definition.