For any living species the population is self-regulated by the ecosystem. We're no different. We've been able to change our ecosystem with technology and thus

For any living species the population is self-regulated by the ecosystem. We're no different. We've been able to change our ecosystem with technology and thus greatly expand our population. But there are limits, always. And we're lucky that this self-regulation is still operating (I think that the housing market is acting as the signal for us) otherwise we would have to endure an ecosystem collapse at some point.