you're certainly on to something with that intuition, that I've long shared. but it's also a lot more complicated than that IMHO. one the one hand, it's more likely multiple rather than two; on the other, they're probably so intricately intertwined that one may easily perceive them as one. it's not at all unusual for control systems to have opposite forces balancing each other towards a desired equilibrium. lots of dimensions for impulse vs suppression. consider a hungry animal watching another larger animal eating, trying to find the right moment in which going for the remnants won't turn itself into food right away. consider the conflict between the impulse to breath while underwater, vs the awareness and other perceptions that you are underwater and breathing there is not such a great idea, and then the further overrider on top of that out of the awareness and understanding that, despite feeling under water, seeing water all around, it's still safe to breathe because you know there's a air supply. layers and layers and layers of impulse and suppression piled on and on over billions of years of evolution got us this. I can't seriously consider the notion that this only came up a couple of million years ago.