Top Threats to Humanity?

The purpose of this topic is to survey the experts for what they consider the top threats to humanity to be, and why.

Initial Motivation

Dr Stuart Armstrong is a research fellow at Oxford University's Future of Humanity Institute. His job is to think about future threats to the human race and how to confront them. He was recently featured in a Wired article entitled AI uprising: humans will be outsourced, not obliterated. Stuart includes AI as one of the top threats to humanity, while pointing out there are others with different points of view on this and various related issues.