Why we sleep is one of life’s enduring mysteries. Liam Drew dives in.
https://www.newscientist.com/article/mg21729021-700-sleep-and-dreaming-why-cant-we-stay-awake-247/
WE SPEND about a third of our life doing it. If deprived of it for too long we get physically ill. So it’s puzzling that we still don’t really know why it is that we sleep. On the face of it the answer seems obvious: so that our brains and bodies can rest and recuperate. But why not rest while conscious, so that we can also watch out for threats? And if recuperation means things are being repaired, why can’t that take place while we are awake?
Scientists who study how animals eat, learn or mate are unburdened by questions about the purpose of these activities. But for sleep researchers the big “Why?” is maddeningly mysterious.
Sleep is such a widespread phenomenon that it must be doing something useful. Even fruit flies and nematode worms experience periods of inactivity from which they are less easily roused, suggesting sleep is a requirement of the simplest of animals.
But surveying the animal kingdom reveals no clear correlation between sleep habits and some obvious physiological need. In fact there is bewildering diversity in sleep patterns. Some bats spend 20 hours a day slumbering, while large grazing mammals tend to sleep for less than 4 hours a day. Horses, for instance, take naps on their feet for a few minutes at a
time, totalling only about 3 hours daily. In some dolphins and whales, newborns and their mothers stay awake for the entire month following birth.
... Article behind a paywall. Email me for for a copy.