By altered state of mind, I'm identifying states of mind in which one is experiencing sensory hallucinations. (Incidentally, the neuroscientist G. Tonini has described normal consciousness as a waking dream, so in that regard, all experience would be a hallucination.)
Thus, roughly, a non-altered state of mind would be a state of mind in which ones experiences correlated strongly with their current environment. (Of course we could have a field day with that statement, so lets have at it, haha.)
Re: prove/disprove a capacity to experience altered states as an adaption.
My understanding is that evolution acts on individuals, not species, so this idea is already on shaky ground. Unless one were to consider that a capacity to experience altered states (hallucinations) was adaptive at the individual level.
Im sure an argument could be made; I consider dreams altered states, and I think important learning happens during dreams, so there's that. If humans couldnt dream, what then? (I did read about a man who went decades without sleeping; I wonder what effects this may have had on him, other than being grouchy all the time. Damn.)
Other than some type of cruel animal studies, no, I'm not sure it could be (dis)proved.
