A Hadza man sleeps on the ground on an impala skin in northern Tanzania.
Credit: David Samson.
I tell you what, Dave, that impala skin looks an awful lot like a beach towel but we're rolling with it.
It's another intuitive thing when we consider sleeping will be better with the grandparents around since a man knows when his parents are asleep and the kids are abed as well, he has done his job so now he and the little woman have some time to engage in Nature's best sleeping medication.
But you know the scientists want the anthropology of it.
A sound night's sleep grows more elusive as people get older. But what some call insomnia may actually be an age-old survival mechanism, researchers report.
A study of modern hunter-gatherers in Tanzania finds that, for people who live in groups, differences in sleep patterns commonly associated with age help ensure that at least one person is awake at all times.
The research suggests that mismatched sleep schedules and restless nights may be an evolutionary leftover from a time many, many years ago, when a lion lurking in the shadows might try to eat you at 2 a.m.
"The idea that there's a benefit to living with grandparents has been around for a while, but this study extends that idea to vigilance during nighttime sleep," said study co-author David Samson, who was a postdoctoral fellow at Duke University at the time of the study.
Phys.org: Live-in grandparents helped human ancestors get a safer night's sleep
It's the evolutionary consequence of they only come out at night but it was required for survival and we spent far more of our history living in that way than in our modern environments.
Ed: sounds like insomnia is forever
Maybe so, mate. I've got to get up every few hours or so for bladder release so the benefit to the young 'uns is a lion will probably eat me first and maybe they get time to run away.
The Hadza people of northern Tanzania live by hunting and gathering their food, following the rhythms of day and night just as humans did for hundreds of thousands of years before people started growing crops and herding livestock.
The Hadza live and sleep in groups of 20 to 30 people. During the day, men and women go their separate ways to forage for tubers, berries, honey and meat in the savanna woodlands near Tanzania's Lake Eyasi and surrounding areas. Then each night they reunite in the same place, where young and old alike sleep outside next to their hearth, or together in huts made of woven grass and branches.
"They are as modern as you and me. But they do 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, associate professor of anthropology at the University of Nevada, Las Vegas.
- PO
They are as modern as you or me is a bit puzzling but it looks like it means we're the same from an evolutionary standpoint. We're all Cro-Mags or Modern Man but some sleep in a penthouse and others on the ground. We don't need any economics in this context; we're just the same people in different places.
As part of the study, 33 healthy men and women aged 20 to 60 agreed to wear a small watch-like device on their wrists for 20 days, that recorded their nighttime movements from one minute to the next.
Hadza sleep patterns were rarely in sync, the researchers found. On average, the participants went to bed shortly after 10 p.m. and woke up around 7 a.m. But some tended to retire as early as 8:00 p.m. and wake up by 6 a.m., while others stayed up past 11 p.m. and snoozed until after 8 a.m.
In between, they roused from slumber several times during the night, tossing and turning or getting up to smoke, tend to a crying baby, or relieve themselves before nodding off again.
As a result, moments when everyone was out cold at once were rare. Out of more than 220 total hours of observation, the researchers were surprised to find only 18 minutes when all adults were sound asleep simultaneously. On average, more than a third of the group was alert, or dozing very lightly, at any given time.
- PO
Maybe that sounds like a whole lot of people would be bitching about sleep problems but that isn't what happens.
Yet the participants didn't complain of sleep problems, Samson said.
The findings may help explain why Hadza generally don't post sentinels to keep watch throughout the night—they don't need to, the researchers say. Their natural variation in sleep patterns, coupled with light or restless sleep in older adults, is enough to ensure that at least one person is on guard at all times.
- PO
This one spins off for the interested student or just about anyone since many have problems with sleep. The science shows that which is now perceived as a problem wasn't regarded that way during much of our history so the complaints must be coming from trying to adapt to a situation which isn't necessarily natural.
Note: natural in this context is used to mean the way we evolved.
Ed: so insomnia really is forever then
It's only insomnia if you don't have something to do.
Ed: any more Zen and I start shooting!
Enhance your calm, my brother (larfs).
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