Sleep is one activity that everyone engages in every night, and yet it remains something of a mystery. Do you have any theories on why it is we sleep?
It is obvious that our sleep schedule is tied to the day/night pattern. It certainly isn’t a coincidence that due to the earth’s rotation, it is dark every night, and we sleep every night.
Moreover, it seems pretty clear that sleep is the product of evolutionary pressures. Our very distant ancestors gained some advantage from being asleep every night that allowed them to survive, and possibly even to thrive.
However, we don’t know what that advantage is.
One possibility is that our senses leave us at a disadvantage to other predators in the dark. Our eyes do not allow us to see as well in the nighttime, nor do our ears hear so well as to make up the difference, compared to some of our animal competitors. Therefore, a survival mechanism is to keep humans inactive during the time when they are disadvantaged — at night — and concentrate their efforts in the daytime.
But why didn’t the eyes or ears evolve to be more sensitive? Other animals did, so why the difference in humans?
Another possibility is that our larger brains required more organization, and processing of information. For humans, this happens during the sleep cycle, in particular during REM sleep. This, in turn, requires long stretches of uninterrupted sleep, and that is easier at night with fewer distractions.
These are just two examples of possible explanations. Do you know of any others, or have a pet theory? In your opinion, why do we sleep?