I don't understand sleep.
Before, I naively thought it was related to some kind of 'energy' or 'wakefulness' resource that gets depleted as time goes by without rest.
But that's not it, higher activity levels don't make you sleep sooner, they might make you more fatigued and it might correlate with sooner sleep onset but the relation is not 1:1, more activity doesn't equate to earlier sleep, in fact many times it might do the oposite.
Even plants follow some regular pattern of higher and lower activity levels, but seems more related to the environment and resources available.
Maybe we sleep because of the day-night cycle? we adapted to live in daylight, so by specializing we focus our biological resources, and during the night what we do is sleep to limit the consumption of those resources (metabolic rate slows down during sleep) because doing anything else is not useful, we are not adapted for being nocturnal.
So basically sleep is like some kind of instinctual behavior, sleep is induced by the body, the body actively makes us sleep. But then, why do perform so poorly if we don't sleep? a consequence of our adaptations to that day-night pattern? If sleep is only an induced physiological behavior, Why if we stay awake a lot we risk our health? is this dependence on sleep an accident then?
My question is this. If we consider sleep as a behavior actively induced by the body, akin to an instinct, rather than the depletion of a physiological resource (I think this is true), why does insufficient sleep result in adverse health effects, such as those observed in conditions like fatal familial insomnia?