Why do we
We may not always think about the reason we sleep,
but most of us know, that at some level, sleep makes us feel better. We
are more alert, more energetic, happier, and better able to complete
tasks, if we have a good night of sleep. The fact that sleep makes us
feel better and lack of it makes us feel worse only begins to explain
why sleep might be necessary.
A way to think about sleep is to compare it to
eating. Hunger is a protective mechanism that ensures we eat the
nutrients our bodies need to grow, repair itself, and function properly.
Although it may be pretty easy to see why we eat, sleeping is not much
Sleeping and eating are both regulated by internal
drives. Going without food makes you feel hungry. The longer you go
without food, the worse your hunger grows. And just as eating relieves
hunger, sleeping relieves sleepiness. Sleeping ensures we get the sleep
we need. Why do we need sleep at all? There are many theories being
tested to help understand this question.
One of the earliest theories of sleep suggests that
inactivity at night is an adaptation that served a survival function by
keeping organisms out of harm’s way at times when they would be
vulnerable. The theory suggests that animals that were able to stay
still and quiet during these periods of vulnerability had an advantage
over other animals that remained active. These animals did not have
accidents during activities in the dark, and were not killed by
predators. Through natural selection, the behavioral strategy presumably
evolved to become what we now recognize as sleep.
A simple counter-argument to this theory is that it
is always safer to remain conscious in order to be able to react to an
emergency, even if lying still in the dark at night; therefore, there
does not seem to be any advantage of being unconscious and asleep if
safety is the most important.
Is it to refresh your body? Researchers have yet to
find any vital biological function that sleep restores. As far as anyone
can tell, muscles don’t need sleep, just periods of relaxation. The rest
of your body goes along with really “knowing” whether the brain is
asleep or not.
Is it to refresh the mind? The brain benefits from
a good night’s sleep, but brain researchers do not agree as to what kind
of benefit sleeping gives your brain. One theory is that sleep allows
the brain to review and compact the vast amount of information it
gathered while awake. Another suggests that we sleep in order to allow
the brain to stock up on fuel and flush out wastes. A third is that
sleep operates in some mysterious way to help you master various skills,
such as how to play the piano and ride a bike.
Although these theories remain theories, science
has made advances in discovering what happens during sleep and what
controls the cycles of sleep and wakefulness that help define our lives.
While this research does not directly answer the question, “Why do we
sleep?” it does set the stage for putting that question in a new context
and generating new knowledge about this essential part of life.