There are some evolutionary biological approaches have been proposed to explain sleeping and dreaming. It’s important to note that earlier evolutionary theories on dreaming didn’t quite address the nature of dreaming as in comparison to sleep. It was hypothesized that sleep’s function is to conserve energy when the organism couldn’t/shouldn’t be operating, primarily during a portion of the diurnal cycle (Williams, 1966). But Aserinsky ; Kleitman (1953) discovered “rapid-eye moment” (REM) sleep increased brain activation upon intervals throughout the night, it’s also noted the high frequency of dreams occurring in this period of sleep as well. As what the finding implies, through one of the external manifestations of this phenomenon, in where, the sleeping organism is flooded with a high dose of rapid-eye activity in their sleep with their body left in a state of paralysis (Cervantes, 2017). With much of the literature finding this period of sleep consistently associated with experiences such as vivid dreams and nightmares (Tsoukalas, 2012), thus, it can be characterized that REM sleep is a regular behavioral responds that is inherently ingrained within the mammalian sleep cycle.