What about drowsiness? If sleep is just a behavior for keeping us out of harm's way, shouldn't we be able to just "switch back on" upon being awaken? Granted, sometimes we do just start awake. But still, staying out of harm's way and resting sounds like a good reason to develop patience, but sleep.
Are there many species that sleep with their eyes and ears open?
Are there many species that sleep with their eyes and ears open?