That's a good question. But we don't have a good answer.
We know that sleep is important. Without it, we get tired and irritable. We get headaches and suffer from lack of concentration. Our immune system suffers. After a number of days without sleep, we can hallucinate or even become psychotic.
But we're not the only ones who need sleep. As far as we know, all animals sleep or have sleep-like behaviors. Theres a wide range. Elephants sleep about three hours; platypuses, about fourteen hours. Marine mammals have even evolved the ability to sleep with only one side of their brain at a time. This way they can still go to the surface to breathe.
So sleep is really important. But why is it essential? There are several theories.
Number one, the efficiency theory. Sleeping keeps us from wasting energy, so we're only active when we need to eat, that sort of thing.
Number two, the tune up theory. When we're asleep, our bodies repair damage, eliminate toxins, produce hormones and all kinds of other maintenance activities.
Number three: the brain theory. While asleep, our bodies may be at rest, but our brains are busy processing new information and organizing memories.
So which one is right? Maybe all of them. Or none of them. Scientists are making a lot of progress in sleep studies. But for the moment, they'll have to sleep on it.
Critical thinking challenge: Why is it that sleeping on it helps us solve problems and make decisions?