I wouldn't know if DMT has a function in the whole mind-body system. The human body produces many tryptamines adn some of them are psychedelic, but it is unclear what their function is. If they where initially just by products or products produced when the body metabolizes the initial usefull tryptamines, it is likely that during human evolution they 'aquired' a function, since this tendency towards efficience is something that's seen throuhout evolution. To me the real question here would not as much be what the function is of DMT, but more what the function would be of the various states of mind that could be assosciated with DMT (and other hallucinogen's) effects; dreaming, daydreaming,religious experience, NDE's, etc. I don't believe, like some people, that we're evolving towards a DMT consciousness instead of a serotonin consciousness. I would think that in our mind-body system we need a balance between the very well known rational states of mind (the serotonin state), and the 'creative' states of mind, the 'objective' way of looking at the world and the 'subjective' way.

I think that we're most likely to see answers to this questions during our lifetime, since many research is being done currently to the function dreaming has in our system. That dreaming is of vital importance to us, seems evident by now.

If DMT itself would not proof to actually have a function, it still makes sense to asume that these type of substances in disrupting the 'normal' serotonergic system, trigger a natural proces to switch back into another natural state of mind. most other substances that have effects as dramatic as psychedelic tryptamines do this by at the same time causing a serious intoxication.