But people may be meant to sleep as little as 6 1/2 hours nightly and were doing so long before the advent of electricity and smartphones, researchers say.
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Unable to travel back in time to monitor the sleeping habits of our paleolithic ancestors, Siegel worked with three groups of people who live life much as our forebears did for millennia.
Members of three hunter-gatherer societies who lack electricity-and thus evenings filled with Facebook, Candy Crush, and 200 TV channels-get an average of only 6.4 hours of shut-eye a night, scientists have found. That’s no more than many humans who lead a harried industrial lifestyle, and less than the seven to nine hours recommended for most adults by the National Sleep Foundation.
This goes against common held assumptions that modern life has greatly reduced our sleep and that this is why many of us often feel exhausted. Instead, the hunter-gatherers began to sleep a little more than 3 hours after sunset, on average.
The notion that humans would get more sleep in a world devoid of artificial light, Starbucks and the Internet as is widespread as it is persistent.
Several studies have linked the chronic use of sleeping pills to a shorter life, but the pills might not be to blame.
The research proved hard at times, Siegel said.
Two of these groups are in Africa.
“These three groups all slept less than what you might predict based on the information coming from Western societies … this is very surprising”, says John Peever, professor in the department of cell and systems biology and physiology at the University of Toronto and director of the Centre for Biological Timing and Cognition, who was not involved in the study. “This paper questions, is that data flawed?”
This characteristic could have evolved to save energy by reducing the temperature difference between the body and environment and consequent heat loss.
“When the temperature reaches its minimum and stops falling they wake up – and that is usually near sunrise”.
“Temperature might be an important environmental cue to when people go to sleep and wake up”, says Peever.
Researchers already know that light and temperature play an important role in sleep. Typically, people fell asleep several hours after sunset, and rose an hour before dawn.
According to in-person interviews, the San didn’t seem to suffer from sleep disorders, like insomnia. They slept nearly an hour longer in winter than in summer, whereas the wired sleep about 20 minutes longer. “I think the beauty of this current study is that maybe we shouldn’t be ramming this requirement down [every person’s] throat so to speak”, she says. We may nap and sleep late because of the high-energetic demands of busy work and school schedules. “It’s our activity and diet and stress level”.
“Our findings indicate that sleep in industrial societies has not been reduced below a level that is normal for most of our species’ evolutionary history”, they wrote. “What has changed over the years is the amount of time people allocate to get their sleep”.
Previous research has found that in modern times, many people get sleepy in the midafternoon, leading to speculation that humans naturally want to nap during this time, and that the modern lifestyle suppresses this urge. “There are still many people in our society who do not get enough sleep, who find it hard to get out of bed in the morning”.
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What’s natural for a hunter-gatherer might not be natural for everyone, Siegel agrees. But he’s excited about other possibilities. These people do, however, have lower rates of insomnia, so those who have trouble sleeping might benefit from recreating a few aspects of the hunter-gatherers’ environment. He has a dry wit and no hobbies.
