Study of tribal folk disputes 8-hour sleep idea
Hunter-gatherers sleep less, don’t need naps, either.
Modern life’s sleep troubles — the chronic bleary-eyed state that many of us live in — have long been blamed on our industrial society of city lights, long work hours, commutes, caffeine, the Internet.
When talking about the miserable state of our ability to get enough rest, sleep researchers have had a tendency to harken back to a simpler time when humans were able to fully recharge by sleeping and waking to the rhythms of the sun.
It turns out that may not be quite right. In fact, it now appears that our ancestors may not have been getting the doctor-recommended eight hours of sleep either.
In an intriguing study published in Current Biology, researchers traveled to remote corners of the planet to scrutinize the sleep patterns of some of the world’s last remaining hunter-gatherers: the Hadza of Tanzania, the San of Namibia and the Tsimane of Bolivia. Cut off from electricity, media and other distractions, these pre-industrial societies are thought to experience the same sort of natural sleep ancient humans enjoyed more than 10,000 years ago.
Located in a woodland-savannah habitat 2 degrees south of the equator, the Hazda gather their wild foods each day. The San are not migratory but interact very little with surrounding villages and live as hunter-gatherers. The Tsimane are hunter-horticulturalist.
Using Actiwatch-2 devices (a kind of a souped-up, medical-grade Fitbit for sleep), researchers recorded the sleeping habits of 94 of these tribespeople and ended up collecting data representing 1,165 days.
What they found was a striking uniformity in their sleep patterns despite their geographic isolation. On average, all three groups sleep a little less than 6.5 hours a night, do not take naps and don’t go to sleep when it gets dark. Like many of us, the Hazda, San and Tsimane spent more than that in bed — from 6.9 to 8.5 hours — than actually sleeping. That computes to a sleep efficiency of between 81 to 86 percent, which is very similar to that for today’s industrial populations.
Jerome Siegel, director of the University of California at Los Angeles’ Center for Sleep Research, and his colleagues explained that this suggests that sleep may not be environmental or cultural, but “central to the physiology of humans” living in the tropical latitudes where our species evolved.
“The short sleep in these populations challenges the belief that sleep has been greatly reduced in the modern world,” Siegel said. “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.”
The findings call into question the untold millions that have been spent on research that tries to get to the bottom of why “short” sleepers only get about 6 hours of sleep a night and the idea that lack of sleep may be a big reason why obesity, mood disorders, and other physical and mental ailments have surged in recent decades.