Our Ancestors Probably Got Less Sleep Than We Do

The San peoples of Namibia are one of the few hunter-gatherer communities left. LUCARELLI TEMISTOCLE/Shutterstock
Josh Davis 16 Oct 2015, 15:15

We regularly hear that the near ever-present glow of our smartphones, televisions, and street lights is disrupting our natural sleep patterns and causing us to sleep less. This deprivation has been linked to a rise in mental illnesses, obesity, and insomnia, especially in the Western world. But a new study looking into the sleeping patterns of hunter-gatherers, well away from the reach of phones and tablet computers, has found that they actually sleep for less time on average than we do.

While we’re often told that for a healthy lifestyle we should be getting between seven and nine hours kip a night, many scientists agree that this is a fairly modern phenomenon. Plenty of evidence suggests that in the past, people used to sleep in two shifts. The first happened a couple of hours after sunset and lasted for around four hours. People would then get up and read, pray, or have sex, then return to bed for another few hours. This was standard practice, it was thought, until the Industrial Revolution brought with it a shift that saw it become the norm to sleep for eight hours straight.

But a team of researchers decided to go back even further, and see if they could work out how much sleep our hunter-gatherer ancestors might have managed to get. To test this, they studied the sleep patterns of 98 people from three of the few remaining hunter-gatherer societies left: the Hadza of Tanzania, the San of Namibia, and the Tsimane of Bolivia. And what they found surprised them. On average, for all three communities, they only got around 6.5 hours of sleep a night, which they did in one go.

“The short sleep in these populations challenges the belief that sleep has been greatly reduced in the ‘modern world,’” says Jerome Siegel, who co-authored the paper published in Current Biology. “This has important implications for the idea that we need to take sleeping pills because sleep has been reduced from its 'natural level' by the widespread use of electricity, TV, the Internet, and so on.”

What’s more, they found that sleep in these societies wasn’t driven by light either, with many of them staying up late into the night. On average, members of the three groups went to bed 3.3 hours after the Sun went down, despite lacking any light other than fires. What the researchers did find, however, was that the pattern was seemingly driven by temperature. It seems that they were sleeping during the coldest parts of the night, then waking up before sunrise to get on with the new day.

The fact that the three hunter-gatherer societies lived thousands of kilometers apart with differing genetics, histories and environments, yet still showed the same pattern of sleeping, probably means that this was also characteristic of our ancient ancestors, too. The researchers note that the hunter-gatherers did not report feeling tired, and two of the groups even lack words for insomnia. They suggest that perhaps by mimicking aspects of the pattern shown by these communities, it might be possible to treat modern sleep disorders experienced in the Western world.

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