Neuroskeptic is a neuroscientist who takes a skeptical look at
his own field and beyond at the Neuroskeptic blog. Why do we
sleep? We spend a third of our lives doing so, and all known
animals with a nervous system either sleep, or show some kind of
related behaviour. But scientists still don’t know what the
point of it is. There are plenty of theories. Some researchers
argue that sleep has no specific function, but rather serves as
evolution’s way of keeping us inactive, to save energy and keep
us safely tucked away at those times of day when there’s not
much point being awake. On this view, sleep is like hibernation
in bears, or even autumn leaf fall in trees. But others argue
that sleep has a restorative function—something about animal
biology means that we need sleep to survive. This seems like
common sense. Going without sleep feels bad, after all, and
prolonged sleep deprivation is used as a form of torture. We
also know that in severe cases it can lead to mental
disturbances, hallucinations and, in som