DMT is also a product of endogenous human metabolism. It's interesting that the most intense of the hallucinogens DMT, which you mentioned, are the ones which are most closely related to our own brain chemistry. So far from these compounds being alien to the brain or being an insult to the physical brain, what they really represent are the shifting of ratios of compounds already present in the ordinary brain. Serotonin is a neurotransmitter, which occurs in all life, and is most concentrated in the higher primates, and most concentrated there in man. So there is a very close structural affinity between this extremely potent and exotic hallucinogen, and the very common basis for ordinary consciousness.