It really feels like we as a society are getting much worse at sleep. All we want to do when we hit the pillow is drift off to a pleasant land of dreams, where fluffy dogs can talk and everyone gives you free brownies. But the older you get, the trickier that becomes.
Generally, the blame is apportioned to flickering smartphone screens suppressing our natural melatonin. Late-night Twitter scrolls and Reddit rabbit holes are bad, say the experts.
But what if restless sleep is an evolutionary tool that once upon a time protected us from nocturnal predators and enemy ambushes? That’s the suggestion from scientists at the Duke University in North Carolina, who for three weeks closely observed the sleeping patterns of modern-day hunter-gatherers in northern Tanzania.
33 members of the Hazda tribe, aged between 20-60 and in good health, were asked to wear motion sensors for the duration of the study. They found that over the course of 220 hours, everyone slept at the same time for only 18 minutes. The younger people tended to go to bed later, while the elderly tribe members were more likely to rise early. But the important thing was that, due to the wide range of age groups, there was nearly always at least one person awake at any given time.
During the day, the men and women would go off to forage for tubers, berries, honey and meat, before reuniting with the rest of the tribe in the evening. Typically, they’d all sleep together either outside or in huts made of branches and grass. Nobody had their natural sleep cycle interrupted by Rocket League or glowing Facebook statuses, yet the researchers still observed inconsistent sleep. In fact, we in the west are probably getting more kip, despite being permanently attached to gadgets.
“They tell an important part of the human evolutionary story because they live a lifestyle that is the most similar to our hunting and gathering past,” said co-author Alyssa Crittenden, an associate professor of anthropology at the University of Nevada.
“They sleep on the ground, and have no synthetic lighting or controlled climate traits that characterised the ancestral sleeping environment for early humans.”
The researchers said that that differing sleep schedules, rather than insomnia or technology overkill, could be down to vigilance. If you’re in a lighter sleep you’re better equipped to respond to any sudden threats, which would have been necessary thousands of years ago. Perhaps this is something all human beings have inherited, and they believe it could help explain why people tend to have more sleep-related problems as they get older.
“A lot of older people go to doctors complaining that they wake up early and can’t get back to sleep,” said Charlie Nunn, also a co-author of the study. “But maybe there’s nothing wrong with them.”
“Maybe some of the medical issues we have today could be explained not as disorders, but as a relic of an evolutionary past in which they were beneficial.”
So there you have it. Don’t blame Instagram and Simpsons memes for your lack of shut-eye, but your ancestors.