"Sleep Drives Metabolite Clearance from the Adult Brain The conservation of sleep across all animal species suggests that sleep serves a vital function. We her

"Sleep Drives Metabolite Clearance from the Adult Brain The conservation of sleep across all animal species suggests that sleep serves a vital function. We here report that sleep has a critical function in ensuring metabolic homeostasis ... the restorative function of sleep may be a consequence of the enhanced removal of potentially neurotoxic waste products that accumulate in the awake central nervous system." http://www.sciencemag.org/content/342/6156/373 http://www.sciencemag.org/content/342/6156/373 TL;DR: sleep is necessary, otherwise it probably wouldn't have evolved in so many different species. If you're really lucky (and a dolphin), you can get by with only sleeping one hemisphere of your brain at a time: http://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep http://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep