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As some theories suggest, most, if not all, biological features in organisms exist due to environmental factors that trigger the organism's eventual adaptation to these factors for survival purposes.

This characteristic of organisms can be tested and retested to be true, so assuming this is the case, why did humans (and disputedly other organisms), develop the process of experiencing dreams?

Not to be confused with conscious imaginations - potentializing events/experiences - what evolutionary purpose does dreaming of unrealistic events/experiences serve?

Also, consider nightmares and their anxiety producing feelings which the organism would most likely avoid if the event/experience were real.

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Most mammals (exception: dolphins, echidnas) have REM sleep and probably dream. They show movements, facial expressions, and make sounds, during REM sleep that clearly relate to waking activities in the same way that human dreamers talk, move or mimic. It has been suggested, but is currently contested, that birds and reptiles dream. They do show REM sleep. – what Oct 9 '13 at 16:37
I like this question, but I am not if it is answerable or would rely on a lot of conjecture. – user3543 Oct 9 '13 at 23:20
If all living beings dream, then dreams are not a result of evolutionary processes. Obviously we can never know if bacteria or insects "dream", but some of the lowest animals at least show REM sleep. I therefore doubt that dreams are a "higher" or specialized function and a result of evolution, but rather suspect that they are nothing more than a side effect of brain activity in general. That, of course, is an assumption, but before you ask for the evolutionary purpose of dreams, you must show that they are indeed limited to certain animals (like not every animal has a thumb). – what Oct 10 '13 at 7:30

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