We now understand how very complex and even apparently intelligent phenomena, such as genetic coding, the immune system, and low-level visual processing, can be accomplished without a trace of consciousness. But this seems to uncover an enormous puzzle of just what, if anything, consciousness is for. Can a conscious entity do anything for itself that an unconscious (but cleverly wired up) simulation of that entity couldn't do for itself?

"The Evolution of Consciousness," Consciousness and Emotion in Cognitive Science: Conceptual and Empirical Issues (1998) ed. Josefa Toribio & Andy Clark