what does sleep do out of those two options then?
i'm not sure if i'm saying this right, but i still cant see the real reason for sleep. If it was to replenish your brain why do you need to sleep for your brain to do that?, your brain builds up chemicals and removes waste products when you are awake aswell. If sleep is a low power state to save energy that implies that every animal has evolved to be inefficient at storing energy, and so has to sleep to save this energy. So if an animal evolved to become twice as efficient at using energy than its predecessors it should sleep for half the time. surely thats not correct?