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I'm not very well informed about all the things related to biology and the current achievements of science in this field so if I'm wrong in anything I say, please let me know.

Many times I've come across a theory that the meaning of life itself is procreation - we simply live in order to make our species exist as long as possible. In the light of this theory, units like homosexuals or infertile people are totally useless and there's no really reason for them to exist from biological point of view. Though it's pretty obvious that in order to make us want to reproduce, something like joy of having sexual intercourse and life in general has been created. That's why units who only lack in ability to reproduce do live and most of the time they're fine.

Evolution doing adjustments in us in order to make us feel happy during our life seems to be understandable, but what about death? I've read that during death, a larger amount of DMT substance is being released in the brain - compound which is known from it's psychedelic effects, which in most cases are euphoric. It looks like we're not meant to feel 'bad' while dying, which is nice, but my question is - is it known why? What could be the evolutionary reason to create this mechanism? The unit which is about to die is not going to be useful anymore, so why bother? I'd like to somehow understand logic behind this.

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As with many such questions, it may be impossible for us to infer why this trait evolved. –  Richard Smith-Unna Dec 30 '13 at 16:01

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The issue I suspect you are struggling with is the anthropomorphization of the evolutionary process. Evolution is an optimization process driven by random mechanisms...i.e. there is often not a "reason" for why certain things are the way they are. Evolution is not a conscious "designer" that produces things with a specific goal in mind...it simply "picks" the best random alteration and enhances it. If there is no "best mutation", then there is no selection pressure to drive change overtime.

For example, one can ask, "Why do humans have 5 fingers on each hand, instead of 6 or 4?" There is no answer, because the question itself is nonsensical. Humans have 5 fingers simply because there is no pressure to drive a change to 6 or fingers, and so it boils down to randomness. There is no "reason" humans have 2 arms, as opposed to 4. That particular trait just randomly happened to be the one which became dominant.

So, to return to your question of "Why does the brain release DMT when dying?", the answer is that there IS no answer. There is no selection pressure for or against that trait, it just happens. As to the mechanism itself, I suspect that there is just a global breakdown of function in the brain, leading to a dump of ALL neurotransmitters. When the reuptake pumps fail, the neurons just dump their contents into the extracellular space. The result is pleasant hallucinations, giving the impression that humans are not "meant" to feel pain when dying. Imposing that kind of rationale, however, is simply creating meaning out of chaos. If you watch TV static long enough, your mind will start to see patterns which aren't there, simply because the human mind is "wired" to find patterns in chaos in order to better understand the environment.

To wrap this up, I suppose the answer to your question is that the brain is finding meaning in meaninglessness, simply because that is what the brain does. We look for patterns to make sense out of our environment, which sometimes leads to spurious conclusions. There is no reason that the brain hallucinates when dying, but there IS a reason that this trait appears to be a built-in mechanism.

I hope I was able to shed some light on the issue. Or at the very least, not confuse you further :D

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I disagree with all of this except the part about evolution not being a conscious designer. You are arguing that genetic drift accounts for a large proportion of evolution. This is the opposite of the current understanding informed by genomics and transcriptomics. For example: onlinelibrary.wiley.com/doi/10.1111/j.1558-5646.2007.00308.x. It is highly likely that there is a reason (i.e. a proximate cause) for DMT being released at death, but it may not be direct, and it may be impossible for us to infer it with current information. The same is true for having 5 fingers and 2 arms. –  Richard Smith-Unna Dec 30 '13 at 16:00
    
The point I was trying to get across is not that random genetic drift accounts for the bulk of traits seen in organisms. My point was that assigning a "purpose" to an observed trait is often faulty logic because it presumes a "goal" to evolution. The only goal in evolution is higher reproductive fitness, so attempting to find a cause for other perceived goals is impossible. One could easily imagine humans having 6 fingers per hand, and you would be hard pressed to identify the specific fitness advantage to actively (and specifically) select for 5. –  Andrew Bonnell Jan 30 at 1:50
    
As such, it would be faulty to presume there must be a selection pressure there, when it could just as easily be random. Basically, to argue that a given trait is selected for, you first need to demonstrate how that trait significantly improves that organism's reproductive fitness. I think you would be hard-pressed to identify a reproductive advantage to the "DMT dump" trait. That's not to say it's impossible for there to be an advantage. Just that there is no evidence or hypothesized mechanism for an advantage. –  Andrew Bonnell Jan 30 at 2:46
    
@AndrewBonnell I can't really say I'm satisfied with the answer. I believe it's too much of a coincidence to be happening just because. I might be wrong, but I think it's just not known yet, therefore the best explanation is that it's a random thing. Anyway, thank you very much for the answer. –  Piotr Chojnacki Aug 1 at 6:43

Dimethyltryptamine have been identified as normal constituents of human blood, urine,cerebrospinal fluid.Dimethyltryptamine is an N-methylated indoleamine derivative, a serotonergic hallucinogen.It apparently acts as an agonist at some types of serotonin receptors and an antagonist at others.DMT is traditionally associated with indigenous Amazonian people, who consume a bitter decoction of at least two types of plant material, known as ayahuasca.

DMT is capable of transporting the user, within seconds, to what appears to be a fully autonomous alternate reality.

There is term called consensus reality the world we live in an imagination of our brain. DMT is capable of building this alternate reality with which in normal circumstances we don't feel or perceive it. DMT can cause such dramatic shifts in consciousness, such that completely novel worlds appear.Our brain use various approaches,to create a mental field which gives a unified world and these two can be classified as functional segregation and integration. As humans we are very much visual creatures and the cortex region of our brain helps us in doing that. Our brain continues to develop, changes throughout life and across the span of evolutionary time. It becomes absolutely critical in determining how the brain interprets and categorizes sensory information and thus builds the consensus world and we reach a point where our brain can create or is capable of building worlds without extrinsic influence or data.

These are the findings that were reported from the DMT studies

1.Hallucination—visual, physical, auditory; 2.Entering other realities, sometimes including having contact with other sentient beings, which were described as true or real experiences rather than hallucinations; 3. Lucidity; 4. Affective distortions; 5. Ineffability; 6. Extreme intensity; 7. Spirituality, learning, or being taught about truths of the universe or self; 8. Distortion in sense of time, space, self; 9. Sense of familiarity

This is also being reported by research group. - Merry-go-rounds, fairgrounds, clowns/jesters, circuses; – Mischievous or playful elves/dwarves/imps; – Insectoid and reptilian creatures, aliens; – Futuristic hypertechnological buildings and cities; – Complex machinery, hyper-advanced technology; – Being observed and/or experimented upon; – Unknown places apparently on Earth.

So due all these mechanisms and effect of DMT I can say that when we are on the verge of our death our brain produces DMT in higher amounts in order to ease the pain which I assume and at the same time the alternate reality or the alien reality is something which is not yet thoroughly investigated. So I would say if an alternate world exist where humans go after death then DMT is the molecule which helps in doing it.

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thanks Felix_Sim –  krushna Dec 25 '13 at 20:30
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This doesn't answer the question. The question asks why DMT being released at death would be selected for evolutionarily. –  Richard Smith-Unna Dec 30 '13 at 16:01

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