One in a series of talks from the 2019 Models of Consciousness conference. Adrian Kent Department of Applied Mathematics and Theoretical Physics, University of Cambridge The scientific consensus is that, although many important details remain to be elaborated, Darwinian evolution can be understood in principle as a consequence of known physical laws. As William James first pointed out, the development of human consciousness, and in particular the fact that it appears to have evolutionarily advantageous features, are hard to explain within a purely materialist Darwinian theory, according to which we would function equally well in the world if we were unconscious zombies or if pleasure and pain qualia were inverted. However, it is difficult to find attractive alternatives that have any more explanatory power. In this talk I describe toy models that are intended to illuminate the space of possibilities and the difficulties. Filmed at the Models of Consciousness conference, University of Oxford, September 2019. Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales; http://creativecommons.org/licenses/by-nc-sa/2.0/uk/