in traditional societies sleep in eye-opening
By BRUCE BOWER
Ah, the sweet simplicity of
sleep. You tramp into your bedroom with sagging
eyelids and stifle a yawn. After disrobing, you
douse the lights and climb into bed. Maybe a
little reading or television massages the nerves,
loosening them up for slumber's velvet fingers.
In a while, you nod off. Suddenly, an alarm
clock's shrill blast breaks up the dozefest as
the sun pokes over the horizon. You feel a bit
drowsy but shake it off and face the new day.
Images of a dream dissolve like sugar in the
morning's first cup of coffee.
There's a surprising twist,
however, at the heart of this familiar ritual. It
simply doesn't apply to people currently living
outside of the modern Western worldor even
to inhabitants of Western Europe as recently as
200 years ago.
In such contexts, and probably
throughout human evolution, solitary shut-eye
organized around a regular bedtime and a single
bout of sleep proves about as common as stock car
racing or teleconferencing. Surprisingly,
anthropologists have rarely scrutinized the sleep
patterns and practices of different cultures,
much less those of different classes and ethnic
groups in the United States.
An initial attempt to draw back
the veils of sleep in hunter-gatherer groups and
other traditional societies has uncovered a wide
variety of sleep customs, reports anthropologist
Carol M. Worthman of Emory University in Atlanta.
None of these snooze styles, however, looks
anything like what modern Western folk take for
This finding raises profound
questions for the burgeoning discipline of sleep
research, Worthman says. Over the past 50 years,
scientists have avidly delved into slumber's
biology. Early research identified periods of
rapid-eye-movement (REM) sleep, during which
intense dreams often occur. Current efforts
pursue genes involved in wakefulness and sleeping
(SN: 8/14/99, p. 100). Researchers have also
taken strides toward treating insomnia and other
While investigators readily
concede that they don't yet know why people sleep
and dream, they assume that they at least know
how people should sleep: alone or with a partner
for a solid chunk of the night. Sleep studies
therefore take place in laboratories where
individuals catch winks while hooked up to a bevy
of brain and body monitors.
However, the distinctive sleep
styles of non-Western groups may mold sleep's
biology in ways undreamed of in sleep labs,
Worthman suggests. They may influence factors
ranging from sleep-related genes to the brain's
electrical output during various sleep phases.
"It's time for scientists
to get out into natural sleep environments,"
Worthman remarks. "It's embarrassing that
anthropologists haven't done this, and the lack
of such work is impeding sleep research."
A seemingly innocent question
awakened Worthman to her discipline's ignorance
of how people sleep. In 1994, she had a
conversation with pediatrician Ronald E. Dahl of
the University of Pittsburgh School of Medicine,
who studies the effects of mood disorders on
sleep. He asked the Emory scientist to tell him
what anthropologists know about the history and
prehistory of sleep. "[My] bald, if somewhat
overstated, answer was 'zero,'" she says.
Sleep scarcely figures in the
literature on either cross-cultural differences
or human evolution, Worthman realized.
Investigators generally relegate slumber to the
sidelines, treating it as a biological given with
little potential for variation from one place to
another, she holds.
A few researchers have bucked
this trend. For instance, anthropologist James J.
McKenna of the University of Notre Dame in
Indiana has reported that babies in many
countries outside the United States sleep next to
or in the same room as their parents. Contact
with a parent's body helps regulate an infant's
breathing and other physiological functions, he
asserts, perhaps lowering the risk for sudden
infant death syndrome (SN: 12/4/93, p. 380).
McKenna's work should have
roused investigators of traditional societies out
of their sleep-related torpor, Worthman says.
Yet, even seasoned field-workers have tended to
ignore sleepat least in their published
workswhile describing food production,
sexual practices, and other facets of daily life.
So, Worthman contacted seven
researchers who she knew had intimate knowledge
of one or more traditional societies, including
nomadic foragers, herders, and village-based
farmers. Among these far-flung populations, none
of the investigators, by their own admission, had
systematically studied how people sleep. After
plumbing what the researchers had absorbed about
nighttime activities, Worthman has assembled a
preliminary picture of sleep practices in 10
Worthman's findings rip the
covers off any lingering suspicions that people
everywhere sleep pretty much alike. Far from the
wallpapered confines of middle-class bedrooms,
sleep typically unfolds in shared spaces that
feature constant background noise emanating from
other sleepers, various domestic animals, fires
maintained for warmth and protection from
predators, and other people's nearby nighttime
Groups in Worthman's analysis
include Ache foragers in Paraguay, !Kung
hunter-gatherers in Africa, Swat Pathan herders
in Pakistan, and Balinese farmers in Indonesia.
For all these groups and six others, communal
sleep equals safe sleep, because sleepers can
count on there being someone else up or easily
awakened at all hours of the night to warn others
of a threat or emergency.
Adult sleepers in traditional
societies recline on skins, mats, wooden
platforms, the ground, or just about anything
except a thick, springy mattress. Pillows or head
supports are rare, and people doze in whatever
they happen to be wearing. Virtually no one,
including children, keeps a regular bedtime.
Individuals tend to slip in and out of slumber
several times during the night. In these
unplugged worlds, darkness greatly limits
activity and determines the time allotted to
sleep. Folks there frequently complain of getting
too much sleep, not too little.
Many rituals occur at night and
exploit the need to sleep. For instance,
initiation rites often force participants to cope
with sleep deprivation. In other ceremonies,
individuals enter somnolent, or near-sleep,
states in order to magnify an occasion's
psychological impact and to induce spiritual
Consider the communal sleep of
the Gebusi, New Guinea, rainforest dwellers, who
grow fruit in small gardens and occasionally hunt
wild pigs. Women, girls, and babies crowd into a
narrow section of a community longhouse to sleep
on mats. Men and boys retreat to an adjacent,
more spacious longhouse area, where they sleep on
Gebusi females retire at dark
for about 10 hours of rest and sleep. In
contrast, the men stay up later and frequently
conduct rituals. About once a month, everyone
attends an all-night dance and feast, catching up
on sleep the next day.
Each week or two, Gebusi men go
to seances led by a "spirit medium," at
which they try to keep spirits awake throughout
the night. Participants attempt to slip in and
out of a near-sleep state as the medium, who's
usually adept at operating in this half-conscious
condition, sings about the spirit world and other
As in most of the other studied
societies, the Gebusi express concerns about
exposure to ghosts, evil spirits, and witchcraft
during sleep. They consider deep sleep risky,
since a sleeper's spirit may wander off too far
and fail to return. The Gebusi view group slumber
as a way to lessen the danger of spirit loss,
which they view as especially likely while a
Whether or not one believes
that sleeping puts a person's spirit at risk,
slumber appears to have crucial effects on body
and mind. A culture's sleeping style serves as a
growing child's training ground for managing
biologically based systems of attention and
alertness, Worthman contends. Balinese farmers
provide a striking example of this sleep-related
Balinese infants are carried
and held continuously by caregivers so that they
learn to fall asleep even in hectic and noisy
situations. This grooms them to exhibit what the
Balinese call "fear sleep" later in
life, Worthman says. Children and adults enter
fear sleep by suddenly slumping over in a deep
slumber when they or family members confront
intense anxiety or an unexpected fright. They are
literally scared into sleep.
Infants in middle-class
American homes, who usually sleep alone, may not
learn to ground their sleeping and waking cycles
in a flow of sensations that include bodily
contact, smells, and background noises, Worthman
proposes. In fact, babies forced to bounce back
and forth between the sensory overload of the
waking world and the sensory barrenness of dark,
quiet bedrooms may often find it difficult to
relax, fall asleep, wake up, or concentrate, she
Only cross-cultural studies of
children's sleep and behavior can clarify such
issues, Worthman says.
She described her findings and
their implications in June at the annual meeting
of the Associated Professional Sleep Societies in
Sleep researchers at the
meeting expressed considerable excitement about
the potential for cross-cultural studies.
"Worthman is doing innovative and important
work," comments neuroscientist Robert A.
Stickgold of the Massachusetts Mental Health
Center in Boston. "It's awakening us to the
many different ways in which people organize
Stickgold has developed
snug-fitting, electrode-studded caps that people
can wear in their own beds to measure brain
activity linked to REM and other sleep stages.
Worthman plans to take these
"nightcaps," which hook up to mobile
recorders, into the field to study sleep biology
in traditional societies.
"I've been hoping
anthropologists would examine sleep
cross-culturally for the past 20 years,"
remarks psychologist Mary A. Carskadon of the
Brown University School of Medicine in
Carskadon has directed studies
that indicate that the body's so-called
biological clock gets pushed back during
adolescence. Teenagers may require more sleep
than adults and may have a natural tendency to go
to sleep later and wake up later than at other
ages, she says.
A related study, directed by
neuroscientist Louis J. PtĚcek of the University
of Utah in Salt Lake City, finds that a specific
gene yanks the biological clock forward in some
adults. People who have this gene tend to fall
asleep by 8:30 p.m. and to awaken before 5:30
a.m., the researchers report in the September Nature
In modern Western cultures,
teens' backward shift in sleep timing is
considered a nuisance or a sign of rebellion,
while extreme early birds get diagnosed as sleep
disordered. In traditional settings, however,
highly variable sleep schedules among individuals
and age groups prove invaluable, since they allow
for someone to be awake or easily roused at all
times should danger arise, Worthman holds.
If sleeping patterns in
traditional societies remain little known, those
of prehistoric humans are a total mystery. Still,
in settings that roughly mimic ancient nighttime
conditions, sleep undergoes an intriguing shift,
says psychiatrist Thomas A. Wehr of the National
Institute of Mental Health (NIMH) in Bethesda,
When prohibited from using
artificial light from dusk until dawn, people who
formerly slumbered in solid blocks of time begin
to sleep in two periods separated by an hour or
two of quiet rest and reflection.
Wehr and his coworkers asked 15
healthy adults to rest and sleep in darkness for
14 hours (6 p.m. to 8 a.m.) each night for
several weeks. Volunteers slept for 11 hours each
of the first few nights, apparently to catch up
on their sleep. They then settled into a pattern
of lying awake for a couple of hours before
falling asleep for 3 to 5 hours in the evening.
An hour or so of quiet wakefulness ensued,
followed by about 4 more hours of sleep in the
Many mammals sleep in two major
bouts during the night or day, Wehr says. Animals
from rodents to giraffes and the experimental
human sleepers secrete elevated amounts of the
hormone prolactin when they rest quietly, even if
they are not asleep. Prolactin may promote a
state of calmness that accompanies sleep, the
NIMH scientist suggests.
Participants in Wehr's study
usually awoke out of REM sleep to end their first
slumber session. During REM sleep, the brain
becomes about as active as it is when wide awake.
One function of this sleep phase may be to set
the stage for waking up, Wehr holds.
If prehistoric people slept in
two nightly periods, then regularly awakening out
of REM sleep may have allowed them to reflect on
and remember their dreams in a semiconscious
state that's generally unavailable to modern
sleepers. Sleep compressed into a single stint
may thus encourage modern humans to lose touch
with dreams, myths, and fantasies, Wehr argues.
These results, first reported
in 1993, also raise the possibility that people
who wake up once or twice each night don't
necessarily suffer from insomnia. "A natural
human sleep pattern may reassert itself in an
unwelcome world and get labeled as a
disorder," Wehr says.
The two-phase sleep pattern
observed by Wehr corresponds remarkably closely
to the way in which most Western Europeans slept
between 500 and 200 years ago, according to
historian A. Roger Ekirch of Virginia Polytechnic
Institute and State University in Blacksburg.
While doing research for a book on nighttime
behaviors during that era, Ekirch came across
several hundred references to what he identifies
as "segmented sleep."
From country farms and villages
to city apartments, early modern Europeans
usually sank each evening into what they called a
"first sleep," which lasted for several
hours. Shortly after midnight, they awoke and
spent 1 or 2 hours in a "watching
period." A "second," or
"morning," sleep followed.
The watching period presented
many opportunities, Ekirch notes. People coming
out of their first sleep often stayed in bed to
pray, converse with a bedfellow, contemplate the
day's events or the meaning of a dream, or simply
let their minds wander in a semiconscious state
of contentment that was prized at the time.
A 16th-century physician wrote
that many laborers dozed off exhausted at the
start of each night. Sexual intercourse with
their wives typically occurred in the watching
period, after a recuperative first sleep.
These days, Western societies
treat sleep more as an unavoidable stretch of
downtime than as a prelude to sex or a time for
inner reflection. Only intensive investigations
across cultures and classes will illuminate the
lushness of sleep's landscape, Worthman predicts.
Adds Wehr, "We're going to
have to reconceptualize what it means to sleep
Ch. 9 Discussion Questions
1. Why do you
think cross-cultural research has de-emphasized
differences in sleep patterns while extensively
studying differences in other aspects of life?
2. What are some
observed differences in sleep patterns between
Westen societies and other cultures?
3. What could be
one adaptive function of maintaining a varied
sleep schedule from night to night?