Our ancestors probably didn’t get more sleep than the average American
Researchers at University of California, Los Angeles (UCLA) surveyed hunter-gather communities in Africa and South America which practice a traditional lifestyle thousands of years old and found they slept an average of six hours and 25 minutes per night.
We sleep a third of our lifetimes. That sounds like a lot of wasted time, but try going without sleep for a day or two and see where it gets you. You can’t think straight, you become clumsy and feel perpetually exhausted — until you catch some rest. Sleep quality is thus essential if we’re to live healthy, balanced lives. With all its gimmicks and enhancements, however, technology may be disrupting sleep patterns. First the advent of electricity meant people could go about their lives even past dusk, then gadgets like TV, smartphones and laptops gave us even more reasons to forgo sleep. Artificial light, however, can fool the body into thinking it’s still daylight outside, and thus disrupts the circadian rhythm — our internal body clocks. The ‘science of sleep’ is vast and still the subject of intense research, so I won’t try to dive in too much detail. But, in a nutshell, scientists say we should stay away from artificial light as much as possible at least an hour before we go to bed. Few people take note, and as such we’re dealing with a sleep deprived populace. According to Gallup, 40% of Americans get less than seven hours of sleep a day, down an hour on average from 1942. But is this necessarily something to worry about?
One caveat of sleep research says that, evolutionary speaking, we humans have universally used more or less the same sleep pattern for thousands of years: dozing off shortly after night fall and waking up right after dawn. A new research, seems to suggest this assumption is in fact a myth. Researchers at University of California, Los Angeles (UCLA) surveyed hunter-gather communities in Africa and South America which practice a traditional lifestyle thousands of years old and found they slept an average of six hours and 25 minutes per night.
The communities involved in the study were the Hadza, the hunter-gatherers of Tanzania, the San, hunter-gatherers in Namibia and the Tsimane, hunter-horticulturalists in Bolivia. For 1,165 days adult volunteers had sensors that measured heart rate and blood pressure and reported their sleep patterns daily. Even though the communities were isolated from one another, separated by tens of thousands of miles, their sleep routines seem to be very similar.
Humans used to sleep more. False. The hunter-gathers surveyed in the study – a proxy for our ancient forefathers – slept on average 5.7 to 7.1 hours each night.
People went to sleep shortly after dusk. False. The traditional people stayed awake in an average of three hours and 20 minutes after sunset.
Napping during the day was common routine, but busy modern lifestyle meant this had to be foregone. False. The study participants rarely took naps.
Jerome Siegel, lead researcher and professor of psychiatry at UCLA’s Semel Institute of Neuroscience and Human Behaviour first got the idea for the study after they came across research detailing the differences in sleep patterns between wild and captive animals.
“While trying to record sleep in wild African elephants, and finding that their sleep was very different from zoo elephants, I thought that what we really needed to do was compare sleep in humans living in the regions and under the conditions in which we evolved with sleep in our society,” said Siegel.
“The challenging parts were getting stuck in water or sand in four-wheel-drive vehicles while trying to get to the villages we studied,” said Siegel.
“Getting to know the San was a transformative experience,” said Siegel. “To see how much is possible without any of the trappings of civilization. To see how smart and happy they are, and also how they must struggle to survive”
The amount of sleep the traditional folk go varied depending on the season, with more during the winter and less in summer.
“In natural conditions, humans sleep [more] during a period of declining temperature,” Siegel said. “In contrast, in most modern settings, while we may turn the temperature down at night, it is not declining.”
“Rather than saying modern culture has interfered with the natural sleep period, this is a case in which modern culture, with its electric light and temperature control, was able to restore the natural sleep period, which is a single period in traditional humans today and therefore likely in our evolutionary ancestors as well,” Siegel said.
By all accounts, hunter gathers – and likewise all humans who used to live thousands of years ago – seem to be healthy and productive on less than seven hours a day. In contrast, the National Sleep Foundation – a panel made up of the leading researchers in the field – makes the following recommendations:
Newborns (0-3 months): Sleep range narrowed to 14-17 hours each day (previously it was 12-18)
Infants (4-11 months): Sleep range widened two hours to 12-15 hours (previously it was 14-15)
Toddlers (1-2 years): Sleep range widened by one hour to 11-14 hours (previously it was 12-14)
Preschoolers (3-5): Sleep range widened by one hour to 10-13 hours (previously it was 11-13)
School age children (6-13): Sleep range widened by one hour to 9-11 hours (previously it was 10-11)
Teenagers (14-17): Sleep range widened by one hour to 8-10 hours (previously it was 8.5-9.5)
Younger adults (18-25): Sleep range is 7-9 hours (new age category)
Adults (26-64): Sleep range did not change and remains 7-9 hours
Older adults (65+): Sleep range is 7-8 hours (new age category)
Of course, if you’re reading this you’re probably not a hunter gatherer. So, while 6 and half hours of shut eye might be enough if you’re hunting game in Tanzania, it might prove insufficient for those writing emails in a cubicle. That’s not to say that we can’t learn a thing or two. For instance, the researchers found that members from all communities received their maximal light exposure in the morning. This suggests that morning light may have the most important role in regulating mood and the suprachiasmatic nucleus, a group of neurons that serve as the brain’s clock.
Tibi is a science journalist and co-founder of ZME Science. He writes mainly about emerging tech, physics, climate, and space. In his spare time, Tibi likes to make weird music on his computer and groom felines.