This presentation illustrates that the population expansion that humanity has witnessed since 1950 is the upstream driver of numerous existential threats, from climate change, biodiversity loss, and environmental degradation to water scarcity, poverty, pandemic emergence, and resource-driven wars. This presentation states that if humanity wants to avoid all of these negative phenomena, population growth must be stopped and reversed. This presentation further discusses a crucial study (Ferguson and Rimmer 2017) which explores the hypothetical results of a voluntary, global agreement from 2020 that all families should have either two children or only one child and compares them with current population projections, concluding that only universal one-child families could solve the problem. The presentation concludes by stating that while it is not likely for voluntary one-child ethics to be globally accepted or embraced in the foreseeable future, it should be widely promoted by bioethicists as well as healthcare providers to emphasize that this is ultimately the only ethical solution to our population predicament.