....assuming the sub-replacement rate continues forever, which is a hefty assumption. It's quite certain that a greater-than-replacement rate can't continue for

....assuming the sub-replacement rate continues forever, which is a hefty assumption. It's quite certain that a greater-than-replacement rate can't continue forever (eventually, the mass of the humans would be greater than the mass of the planet), though that has been the world we've lived in up to now.