Human extinction, also known as omnicide, is the hypothetical end of the human species due to either natural causes such as population decline from sub-replacement fertility, an asteroid impact, or large-scale volcanism, or to anthropogenic (human) causes. For the latter, some of the many possible contributors include climate change, global nuclear annihilation, biological warfare, and ecological collapse. Other scenarios center on emerging technologies, such as advanced artificial intelligence, biotechnology, or self-replicating nanobots.