DMT does ocurr in humans, they've known for a long time that it does. It is present in the urine of a small portion of the population. It is also more commonly found in the urine of schizophrenics than normal people. If you google DMT and schizophrenia you will find scientific papers about it. David Nichols conducted or was involved in one of these studies. It's presence in urine is the whole reason that Strassman tried to find a source of biosynthesis, for which he suggested the pineal because it also produces melatonin, which is structurally quite similar.
A study published last year and conducted by Dr. Steven Barker, who appears in The Spirit Molecule, found that DMT in the pineal gland of rats for the first time. This supports Strassman's theories of course. Personally, I think that anyone who spends a little time studying near death experiences and spontaneous mystical experiences would find remarkable similarities between those and DMT trips. The show I Survived: Beyond and Back often features people describing NDE's involving contact with alien and non-religious specific entities, as well as brightly colored symbols, patterns, tubes and wormholes of light. Not all NDE's sound like DMT trips, but in my research far more than half of them do. The most commonly reported similarities are partial or complete ego-death where people forget who they were, what they were, and just find themselves suspended in the cosmic bliss of the universe. I had had this happen on DMT many times. You can find the whole rat study online, but here's a link to the abstract:
http://www.ncbi.nlm.nih.gov/pubmed/23881860
Strassman was on to something, and now science is catching up. Speaking of science catching up, everyone interested in psychedelics should see Neurons To Nirvana, it's one of the newer psych documentaries and is very scientific and informative. Ends up, psychedelic do expand your awareness by increasing the connectivity between your logical, higher, human brain and your lower, animal parts of your brain. They also limit blood flow to the human parts, so that your subconscious and interpersonal mind can show through. When used with intent, psychedelics can be waking dreams.