> The counter argument "but won't population growth drop by itself" is false, because the population is not monolithic. If some group decides to limit procreation, that group will simply (and quickly) be replaced by one that won't. And if necessary, by another species.
You made the exact counter argument I provided in my post, and the reason it is invalid was already stated. To delve a bit more deeply :
This is not true. Now before you point out the statistics : it currently appears true. But here's the key : there is nothing in evolution theory that states any particular situation cannot deviate from the predicted value. Large groups can reduce in number. However exceptions (like the one we're currently in) become increasingly unlikely with their duration.
It's similar to the second law of thermodynamics. There is no law of physics preventing a billard player from sinking n balls in a single shot, but as n increases it becomes increasingly unlikely. The same is true here.
The issue is confused by a specific large population currently choosing to have few kids (mostly because of living space limitations and state support imho), and another population being forced into reproductive limits (Han Chinese). I would argue, therefore, that if you look deeper, the numbers actually support the idea that population growth always happens until it runs into limits.
There are other exceptions. There is no law of physics that says that a gas body cannot suddenly drop 100 degrees in temperature without losing any energy at all. This is simply extremely unlikely to happen (what needs to happen is that the collisions between the gas and it's surroundings drops. That is a random occurence, which has an average likelihood that's pretty constant, but nevertheless that drop can just happen for no reason at all).
TLDR: If you don't force population to drop, "in the limit", it will increase. No exceptions. There are large random fluctuations that can obscure this over any short timeframe though.