I'm surprised the article doesn't talk more about the population dynamics of any animal with a fixed amount of space: it either consumes everything it needs to survive and goes extinct, or it approaches an equilibrium population.

I have to imagine that pre-agrarian humans occasionally made the wrong choice there and the whole tribe starved, so genes for population regulation were likely selected for. Less sex as a response to less space (at your parents house or in the tiny apartment that you can barely afford) seems like the straightforward and favorable way for those genes to express.