The pressure is on us to start interstellar space travel. We don't know how to do it. Hello?
What? People are going to stop having babies? I don't think so. They might start wars over resources and that might keep the population down. But then that sounds kind of familiar....
War, disease, famine. The population will stay down to the level supported by the food supply. The food provided by a plot of land depends upon how you are using it. If you don't have much technology, you won't get much food. That means you won't have that many people. Slowly, as your technology improves, your food supply improves and your population density can rise. You can have cities, specialists, schools, and even more technology. Success generates more success after a while, but it takes a lot of groundwork before you get a real visible liftoff.
I shake my head at how you support creation, Dan.