Unexpected truth about how and how much we need to sleep

It is said that technology prevents us from sleep. It is said that we do not get enough sleep (and how can you argue with that?). But in fact, we may sleep longer than is necessary, and do not even understand why. They say that elephants have a good memory. They also say that one of the functions of sleep - the consolidation of memories. If both of these facts are true, then the elephants would have to sleep a lot. But these massive pachyderm having the largest among the mammalian brain, sleeping only two hours every night.

And while we sleep almost every night of our lives, so we still have not understood why. There are so many common ideas about the dream that most of them is often wrong, as you can see from the example above. You have heard, for example, that due to electric lighting and a faint glow emanating from the screens of smartphones, which we see before going to sleep, we close our eyes are much smaller than our ancestors, hunters and gatherers?

"Many people have heard so much about it in the media, that it is absolutely sure of that," says Jerry Siegel, director of the Center for Sleep Research, University of California at Los Angeles. He admits that the story is fascinating, but that's fundamentally wrong. Maybe. "The problem is that we have absolutely no information on this issue," he says. "The devices that we use to measure sleep, were invented much later, after the start of the use of electric light."

Because it is impossible to find out how much time our ancestors spent on sleep, Segel decided to do something better. He traveled to Tanzania, Namibia and Bolivia, communicating with groups modern hunter-gatherers. These people were born in an environment that would be closer to our ancestors of other modern. Throughout his life, these societies of hunter-gatherers were living - and sleeping - without any modern devices, we are accused of violating their own peace of mind. Between the two groups in Africa - several thousand kilometers; The third came from the group that migrated from Africa, passed through Asia, crossed the Isthmus of Alaska, then to North America and came to South America. Despite these significant recession, all three groups of sleep about the same time during the night: an average of six and a half hours. According to Siegel, there is no reason to believe that our ancestors slept more than that.

For most people - living in modern societies, with all the trappings of technology and electricity - the amount of time they spend in sleep, is six to eight hours a night. So our ancestors not only slept longer than we, they may have slept a little less than some of us.

We are also used to sleep in the comfort of our homes with air conditioning, on comfortable mattresses with soft pillows, surviving mostly just whether sleeping on a mat next to Bobby. Our ancestors slept on stones, mud, on the tree branches, freezing and starved. They did not know what the earplugs, and the mosquitoes were rescued very mediocre. was still they need to worry about a possible attack by a predator or enemy. It is not surprising that they could not sleep more than six hours.

Nevertheless, there is another myth about how our ancestors slept - they dozed for a few short periods of time during the night, rather than one deep sleep. But it is also wrong, said Siegel. This is an erroneous assumption appeared in our heads when we watched the pets. "I think that the origins of this idea go back to the cats and dogs, and to what do cats and dogs - they are exactly and sleep," he says. "But primates - no." We are the last in a long list of species that prefer to sleep in one long sleep every night without waking up hurl. Not that the monkeys did not sleep during the day, sometimes it also happens, or does not wake up at night by accident. But as with our own kind, this is not normal.

Indeed, cross-cultural study of Siegel showed that modern hunter-gatherer groups almost never asleep, and only occasionally in winter - summer seems to be rescued from the wild heat. And even then, he says, the average person slept during the day every five days or so.

And here there is another thorn in this myth. People who have studied Siegel, lived fairly close to the equator. As we move to higher latitudes, the night can last up to 16 hours in winter, so life in such an environment could cause our ancestors from Northern Europe to break his dream this time of year. But despite this, people in Northern Europe even today prefer to sleep in the usual normal length of sleep at night, sometimes waking up to a short time to visit the restroom.

Knowing exactly where the legs grow from two of the most common myths about sleep Siegel decided to turn to other, more fundamental questions about the nature of sleep. Why do we do this?

If sleep plays a role in memory consolidation, or any other functions of the brain, why then a big brown bat sleeps for 20 hours a day, while the giant and very complex (and clever) African elephant sleeping only 2 hours? Instead, Siegel wonders if the dream can not be the biological requirement in itself, but rather an evolutionary way to maximize productivity? The paper in Nature Review Neuroscience he wrote in 2009, that dream may provide a means of "improving the effectiveness of behavior by adjusting its time limits and reducing power consumption when the activity is not useful."

This is the usual method for animals and plants. Some trees shed their leaves in the fall and cease to photosynthesize. You can imagine it as a kind of botanical nap. Bears hibernate to avoid wasting the energy to hunt and search for food when it does not find.

Other mammals like the echidna fall into the dream state known as torpor, when their metabolism slows to almost zero and helps to survive difficult times. Perhaps a dream - it is just our version of the "adaptive inactivity", which allows us to be productive during the day and at the same time to avoid over-voltage - and, historically, not to deal with predators - at night. After all, we can easily wake up, if required.

In short, the dream may be a manifestation of evolutionary laziness.