There is increasing evidence that humans are not living sustainably. There are three major drivers of the unsustainable approach: population, consumption and the growth economy. There is widespread denial about these issues, but they clearly need to be addressed if we are to achieve any of the possible sustainable futures. The first and second versions of the ‘World Scientists Warning to Humanity’ both highlight the problem of increasing human population, as do the IPCC and IPBES reports. However, all have been largely ignored. The size of an ecologically-sustainable global population is considered, taking into account the implications of increasing per capita consumption. The paper then discusses the reasons why society and academia largely ignore overpopulation. The claim that discussing overpopulation is ‘anti-human’ is refuted. Causal Layered Analysis is used to examine why society ignores data that do not fit with its myths and metaphors, and how such denial is leading society towards collapse. Non-coercive solutions are then considered to reach an ecologically-sustainable human population.