If we take for granted that consciousness evolved, consciousness would somehow have to promote survival and reproduction in order to be selected for. If consciousness did not promote survival and preproduction, it would not be selected for, and to the extent that it were biologically costly, it would be selected against. The only way consciousness could promote survival and reproduction, moreover, is by virtue of guiding an organism’s actions, prompting it to perform survival and reproduction enhancing actions – and the only way in which consciousness could prompt an organism towards survival and reproduction seems to be by imbuing experiences with a certain valence or a pro/con attitude. Without a valence or a pro/con attitude, it is unclear how an experience would be able to guide an organism’s actions. Evolution, moreover, cares for action, not for experiences as an end in itself. It therefore seems that if consciousness were to ever get going, valence would have to be present from the very start. Otherwise, consciousness would disappear as fast as it occurred. This suggests that hedonic valence phylogentically is as old as consciousness itself, which in turn lends support to the view that hedonic valence lies at the heart of consciousness. This supports dimensionalism, moreover, since according to dimensionalism, pleasure and pain—rather than being two things out of the many things we can experience—imbues all […] our experiences. Indeed, one might, from a dimensionalist approach to consciousness, argue that the first experience any organism ever had was an experience of either pleasure or pain, and that consciousness of the kind our species has today is a more fine-grained version of something that is most fundamentally a pleasure/pain mechanism.
Ole Martin Moen, ‘The Unity and Commensurability of Pleasures and Pains’, Philosophia, vol. 41, no. 2 (June, 2013), pp. 540-541