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Does Evolution Explain Why Our Sleep Habits Change With Age?

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Laugh all you want now about Grandma's 8 p.m. bedtime; after reading this, you might just want to thank her. One team of researchers report that older adults' earlier body clocks may have evolved to ensure that at least one person was always awake to watch over a family group. They published their findings in the Proceedings of the Royal Society B.

Scientists believe that many groups of social animals take turns sleeping and standing guard. This sentinel hypothesis, as it's known, is easiest to observe in a line of sleeping ducks; the last duck in a row literally sleeps with one eye open. But we didn't know whether this phenomenon extended to humans.

To find out, researchers collaborated with Hadza people of northwestern Tanzania. Many Hadza maintain a hunter-gatherer lifestyle, working and sleeping far from the noise and light pollution of the cities. The researchers recruited a group of 33 adults between the ages of 20 and 60 and gave each person an actigraphic (movement-tracking) wristband. For 20 nights, the actigraphs recorded participants' tossing and turning, their waking, and their stillness in sleep.

The big-picture results looked a lot like you might expect. Average bed- and wake-up times were around 10 p.m. and 7 a.m., respectively. But those were just the averages. Within even this small group, two familiar chronotypes emerged: the older early birds, who bedded down around 8 p.m. and woke by 6 a.m., and the younger night owls, who were up past 11 p.m. and slept until 8 a.m.

Most compellingly, the researchers say, nobody ever slept through the night. Each person woke several times per sleep period, whether to pee, go for a smoke, soothe a crying baby, or just roll over in bed. The resulting gaps in sleep time meant that someone in the group was awake at almost all times. Out of 20 nights, there were only 18 minutes in which the entire group was sound asleep.

Co-author Charlie Nunn is an evolutionary anthropologist at Duke University. He says the group's early bird/night owl split, combined with the frequent mid-sleep awakenings, may be our bodies' way of keeping our families safe.

"If you're in a lighter stage of sleep, you'd be more attuned to any kind of threat in the environment," he said in a statement.

Nunn and his colleagues suggest that the staggered sleeping shifts are not an accident but an adaptation.

"A lot of older people go to doctors complaining that they wake up early and can't get back to sleep," Nunn said. "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.”

Maybe. Maybe not. It's quite possible that older adults' sleep issues are just that: issues, and signs of an aging body. We'll need a lot more research on the subject before we can say for sure. In the meantime, let's cut Grandma some slack. Evolutionary advantage or no, we all just want to sleep.

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8 of the Weirdest Gallup Polls
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Born in Jefferson, Iowa on November 18, 1901, George Gallup studied journalism and psychology, focusing on how to measure readers’ interest in newspaper and magazine content. In 1935, he founded the American Institute of Public Opinion to scientifically measure public opinions on topics such as government spending, criminal justice, and presidential candidates. Although he died in 1984, The Gallup Poll continues his legacy of trying to determine and report the will of the people in an unbiased, independent way. To celebrate his day of birth, we compiled a list of some of the weirdest, funniest Gallup polls over the years.

1. THREE IN FOUR AMERICANS BELIEVE IN THE PARANORMAL (2005)

According to this Gallup poll, 75 percent of Americans have at least one paranormal belief. Specifically, 41 percent believe in extrasensory perception (ESP), 37 percent believe in haunted houses, and 21 percent believe in witches. What about channeling spirits, you might ask? Only 9 percent of Americans believe that it’s possible to channel a spirit so that it takes temporary control of one's body. Interestingly, believing in paranormal phenomena was relatively similar across people of different genders, races, ages, and education levels.

2. ONE IN FIVE AMERICANS THINK THE SUN REVOLVES AROUND THE EARTH (1999)

In this poll, Gallup tried to determine the popularity of heliocentric versus geocentric views. While 79 percent of Americans correctly stated that the Earth revolves around the sun, 18 percent think the sun revolves around the Earth. Three percent chose to remain indifferent, saying they had no opinion either way.

3. 22 PERCENT OF AMERICANS ARE HESITANT TO SUPPORT A MORMON (2011)

Gallup first measured anti-Mormon sentiment back in 1967, and it was still an issue in 2011, a year before Mormon Mitt Romney ran for president. Approximately 22 percent of Americans said they would not vote for a Mormon presidential candidate, even if that candidate belonged to their preferred political party. Strangely, Americans’ bias against Mormons has remained stable since the 1960s, despite decreasing bias against African Americans, Catholics, Jews, and women.

4. MISSISSIPPIANS GO TO CHURCH THE MOST; VERMONTERS THE LEAST (2010)

This 2010 poll amusingly confirms the stereotype that southerners are more religious than the rest of the country. Although 42 percent of all Americans attend church regularly (which Gallup defines as weekly or almost weekly), there are large variations based on geography. For example, 63 percent of people in Mississippi attend church regularly, followed by 58 percent in Alabama and 56 percent in South Carolina, Louisiana, and Utah. Rounding out the lowest levels of church attendance, on the other hand, were Vermont, where 23 percent of residents attend church regularly, New Hampshire, at 26 percent, and Maine at 27 percent.

5. ONE IN FOUR AMERICANS DON’T KNOW WHICH COUNTRY AMERICA GAINED INDEPENDENCE FROM (1999)

Although 76 percent of Americans knew that the United States gained independence from Great Britain as a result of the Revolutionary War, 24 percent weren’t so sure. Two percent thought the correct answer was France, 3 percent said a different country (such as Mexico, China, or Russia), and 19 percent had no opinion. Certain groups of people who consider themselves patriotic, including men, older people, and white people (according to Gallup polls), were more likely to know that America gained its independence from Great Britain.

6. ONE THIRD OF AMERICANS BELIEVE IN GHOSTS (2000)

This Halloween-themed Gallup poll asked Americans about their habits and behavior on the last day of October. Predictably, two-thirds of Americans reported that someone in their house planned to give candy to trick-or-treaters and more than three-quarters of parents with kids reported that their kids would wear a costume. More surprisingly, 31 percent of American adults claimed to believe in ghosts, an increase from 1978, when only 11 percent of American adults admitted to a belief in ghosts.

7. 5 PERCENT OF WORKING MILLENNIALS THRIVE IN ALL FIVE ELEMENTS OF WELL-BEING (2016)

This recent Gallup poll is funny in a sad way, as it sheds light on the tragicomic life of a millennial. In this poll, well-being is defined as having purpose, social support, manageable finances, a strong community, and good physical health. Sadly, only 5 percent of working millennials—defined as people born between 1980 and 1996—were thriving in these five indicators of well-being. To counter this lack of well-being, Gallup’s report recommends that managers promote work-life balance and improve their communication with millennial employees.

8. THE WORLD IS BECOMING SLIGHTLY MORE NEGATIVE (2014)

If you seem to feel more stress, sadness, anxiety, and pain than ever before, Gallup has the proof that it’s not all in your head. According to the company’s worldwide negative experience index, negative feelings such as stress, sadness, and anger have increased since 2007. Unsurprisingly, people living in war-torn, dangerous parts of the word—Iraq, Iran, Egypt, Syria, and Sierra Leone—reported the highest levels of negative emotions.

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Earth's First-Recorded Interstellar Visitor Gets Its Closeup—And a Name
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In October, scientists using the University of Hawaii's Pan-STARRS 1 telescope sighted something extraordinary: Earth's first confirmed interstellar visitor. Originally called A/2017 U1, the once-mysterious object has a new name—'Oumuamua, according to Scientific American—and researchers continue to learn more about its physical properties.

Fittingly, "'Oumuamua" is Hawaiian for "a messenger from afar arriving first." 'Oumuamua's astronomical designation is 1I/2017 U1. The "I" in 1I/2017 stands for "interstellar." Until now, objects similar to 'Oumuamua were always given "C" and "A" names, which stand for either comet or asteroid.

'Oumuamua moved too quickly through space to orbit the Sun, which led researchers to believe that it might be the remains of a former exoplanet. Long ago, it might have hurtled from an unknown star system into our solar system. Far-flung origins aside, new observations have led some researchers to conclude that 'Oumuamua is, well, pretty ordinary—at least in appearance.

'Oumuamua's size (591 feet by 98 feet) and oblong shape have drawn comparisons to a chunky cigar that's half a city block long. It's also reddish in color, and looks and acts like asteroids in our own solar system, the BBC reports. Its average looks aside, 'Oumuamua remains important because it may provide astronomers with new insights into how stars and planets form.

University of Wisconsin–Madison astronomer Ralf Kotulla and scientists from UCLA and the National Optical Astronomy Observatory (NOAO) used the WIYN Telescope on Kitt Peak, Arizona, to take some of the first pictures of 'Oumuamua. You can check them out below.

Images of an interloper from beyond the solar system — an asteroid or a comet — were captured on Oct. 27 by the 3.5-meter WIYN Telescope on Kitt Peak, Ariz.
Images of 'Oumuamua—an asteroid or a comet—were captured on October 27.
WIYN OBSERVATORY/RALF KOTULLA

U1 spotted whizzing through the Solar System in images taken with the WIYN telescope. The faint streaks are background stars. The green circles highlight the position of U1 in each image. In these images U1 is about 10 million times fainter than the faint
The green circles highlight the position of U1 in each image against faint streaks of background stars. In these images, U1 is about 10 million times fainter than the faintest visible stars.
R. Kotulla (University of Wisconsin) & WIYN/NOAO/AURA/NSF

Color image of U1, compiled from observations taken through filters centered at 4750A, 6250A, and 7500A.
Color image of U1.
R. Kotulla (University of Wisconsin) & WIYN/NOAO/AURA/NSF

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