Fossil fuel emissions are also a human construct. We did fine before fossil fuels, and even coal. Population is a horrible measure because all it captures is if you are keeping people alive. Even North Korea can keep people alive. But people want more than just survival.
But fine, you want to talk about population? You're ignoring the second example I brought up. The EU has 1/3 the population of China and 1/4 the emissions. In other words, China is still the problem.
Edit: I just did the calculation, and North Korea is 4x more "efficient" than China if we are using carbon emissions per capita. I don't think population is a great measure, to say the least