In modern society, we leave the lights on and stay up late. We watch Netflix or scroll news stories on our smartphones until the wee hours of the morning.
We blame societal expectations and technology for these sleep habits, but new research suggests keeping awake long past sundown might just be human nature.
A sleep tracker study of three hunter-gatherer populations shows that ‘primitive’ communities sleep as much or even less than modern societies. The findings detail a paleo lifestyle that comes with fewer sleep disorders, but also point to a way to trigger sleep outside of just turning off the lights.
To make these insights, UCLA neuroscientist Jerome Siegel and his colleagues visited three hunter-gatherer populations: the Hadza of Tanzania, the San of Namibia, and the Tsimane of Bolivia.
“Has sleep decreased because of electronics and electricity?” said Siegel, who directs UCLA’s Center For Sleep Research. “There’s no way to go back before artificial light, to the mid-1800s,” he said, but certain hunter-gatherer societies maintain a pre-industrial lifestyle that can give scientists insight into natural sleep patterns.
The researchers monitored 94 people among these groups by handing out wrist devices that track physical activity but also light levels. There have been thousands of studies using these devices to measure sleep, and they’ve been found to be quite accurate, Siegel said. In this study, the gadgets worked around the clock to log over 1,165 days of data.
Rather than hit the pillow when night fell, these outdoors communities stayed awake up to four hours after sunset. For comparison, the sun will set in Washington D.C. today around 6:30 pm, so these folks would pass out just after most local TV news programs.
But then, instead of sleeping late, these communities often climbed out of bed before sunrise. On average, the three groups only slept between 5.7 and 7.1 hours per night. (Note: The National Sleep Foundation in the United States recommends 7-9 hours for adults.)
“Their sleep is actually on the low end of what’s been recorded in our modern society. There’s been speculation that humans basically used to sleep when it got dark, which would mean they’d sleep 10, 11, even 12 hours. It turns out that that’s not the case,” Siegel said.
But they can nap whenever they want, right?
Nope. They rarely napped. On cold winter days, the team caught napping activity in only seven percent of afternoon recordings among the San. During the warmer summers, nap frequency increased to 22 percent of the days.
This observation was one of many suggesting a seasonal change in sleeping behavior among these hunter-gatherer groups. This pattern led Siegel’s team to conclude that temperature, rather than light, plays a defining role in the sleep-wake cycles of these three groups.
So should you throw off your comforter at night and live the “paleo” way? Maybe.
According to in-person interviews, the San didn’t seem to suffer from sleep disorders, like insomnia. Their fitness levels could be a factor, for instance, the Hazda make long treks to hunt food by bow and arrow. None of the participants in this study had a body mass index over 30, and obesity has been tied to poorer sleep quality.
Alternatively, the differences between western and paleo sleep patterns might be due to culture and societal demands. We may nap and sleep late because of the high-energetic demands of busy work and school schedules. Or central heating and warm apparel in Western culture, like light exposure, might keep people from falling asleep.
“It depends on the demands of that particular society, their climate, what time of year it is,” said Max Hirshkowitz, chair of the National Sleep Foundation. “Actual physiological sleep time probably hasn’t changed that much, if at all [historically]. What has changed over the years is the amount of time people allocate to get their sleep.”
Yet it is apparent that sleep patterns in western culture are often off-kilter for both teens and adults.
“It’s an uphill battle, because for many, many years people have been encouraged to sleep less so they could spend more time doing their other things,” Hirshkowitz said. “Whether it’s by choice or whether or not they’re being urged, or even coerced in that direction, this is a culture. We need to change that culture.”
Editor’s note: Are we more sleep deprived than our ancestors? On tonight’s PBS NewsHour, Hari Sreenivasan reports on questions raised by new sleep research.