Have we thought, as laymen, why we essentially have to switch off ourselves every night (or day, for nocturnal) and succumb to nothingness? Why are we programmed to sleep? Do we need sleep to ‘recharge’ ourselves as many of the battery operated devices need? Aristotle thought that the digestion of food created vapors which naturally rose upward, causing the brain to become drowsy.
Despite the fact that most people spend more time sleeping than in any other single activity, scientists still lack much knowledge about why we need sleep or what triggers it. Serious scientific studies only began about 60 years ago, and several different theories have been developed, none of which have been proven. It is known, however, that the higher the organism on the evolutionary chain (humans being the highest) the more important sleep becomes.
It is not an accident that the approximate and traditional 8-10 hours "sleep" period coincides almost exactly with the daily and approximate 8-10 hour period of total darkness with which the living organisms had to cope. It is widely held that organisms cannot cope psychologically with long and enduring periods of total darkness without going bananas. Hence the evolutionary value for sleep fixes its importance. The heart and brain (as well as other organs) evolved as continuous operation mechanisms that, if adequately supplied with oxygen, require no "sleep" periods. Trees and other plant life do not "sleep" because darkness presents no psychological menace since plant life is not conscious and, other than a pause of photosynthesis, darkness presents no evolutionary catastrophe. Likewise, if ancients could not eliminate total darkness, the escape mechanism evolved to adapt to it. To cope with long periods of utter darkness, primitive animal life, over long periods of time, adapted to the environment by consciously entering into a sort of "stupor" or unconscious state and with the passing times, it became a die-hard habit, the genes got modified or something like that.
Recuperative theory of sleep was widely accepted but there can be failed explanation as to why bats sleep for 20 hours per day, but shrews hardly at all (Allison & Van Twyer, 1970). In addition, Meddis (1975) claims that shrew, swifts and Dall porpoises all survive without sleep.
Much work has been done regarding the basis of its genesis and importance, however, the issue is multifarious. No single foolproof theory has contented all the spectrums of need of sleep and its occurrence is mystifying. There are certain things which our labs are yet to explore, perhaps from the exaggerated lateral thinking. Why our minds are restricted from the light of essential knowledge? The perplexity is there for some reason, waiting to be chased and conquered.