Our mammalian neural programming has been growing more complex. Not only has cranial capacity been increasing, but it seems that even the degree of crosstalk between the two hemispheres has been increasing. The so-called "bicameral mind" may be scientifically controversial, but if humans 2,000 or 3,000 years ago did have less communication between the hemispheres, it is possible that their sense of self -- a single, fully intact sense of self -- was comparatively weak and they heard voices coming from within. Today's schizophrenics, or more technically multiple-personality disorders, may have similar characteristics. The sense of self -- the awareness of oneself -- is a complex phenomenon that evolved slowly. But it can be argued that to perceive the world in a logically coherent manner you need to possess logically coherent senses.
A sense of self, regardless of baser mammalian programming, would be a necessary condition to make scientific progress. A sense of detachment brought about by hallucinogens may be fascinating, but to the extent that these mental states interfere with our ability to function logically, the sense of detachment would be counterproductive. If hallucinogens can induce various mental states, it shows that we are electrochemical systems, but more importantly, it shows that such states are possible, but not 'normal'. Evolution has rooted out these states, which may once have been the norm! Evolution is moving us forward in a direction that is leading to greater intellectual capacity. Rather than reprogram ourselves by interfering with processes we do not understand, we could let evolution continue to move us forward through processes that have been highly successful to date.