[the_duke]

This seems pretty logical to me.

If we assume that distribution of professions scales linearly with population size, a 2x increase in population means there will be twice as many researchers and inventors that can dedicate their life to finding new solutions.

I would assume that the scaling is not linear. Do we need twice the workers in agriculture to feed twice as many people? With our modern agriculture technology that seems unlikely to me.

One could argue that this is counter-balanced by diminishing returns, as in: 2x the amount of researchers won't have 2x the output.

But it's hard for me to see how "more people = more progress" is false.