Ancient Biphasic Sleep: How Our Ancestors Slept Twice a Night
For centuries, the night was not a single, uninterrupted stretch of sleep. Long before electric lights illuminated homes and streets, human life was governed by the natural rhythm of daylight and darkness. As the sun set and darkness enveloped the world, people adjusted their routines accordingly, leading to a widespread practice now known as biphasic sleep.
The Historical Norm of Two Sleep Phases
Historical records from diverse regions, including Europe, Africa, and Asia, indicate that individuals frequently engaged in two distinct phases of sleep. This was not an unusual habit or cultural anomaly but a standard part of daily life shaped by the absence of artificial light. People would retire to bed shortly after sunset, wake spontaneously in the middle of the night, remain awake for a brief period, and then return to sleep until morning.
During this quiet interval, often lasting an hour or two, individuals engaged in various activities. They might check on livestock, read by candlelight, pray, or converse with family members. For hundreds of years, this segmented nighttime routine was the norm, deeply embedded in societal structures and personal habits.
The Shift to Continuous Sleep
The transition to a single, continuous sleep pattern occurred primarily over the last two centuries, driven by technological advancements. The proliferation of artificial lighting—from oil lamps and gas lights to electricity—fundamentally altered how people experienced night and time. Suddenly, the darkness was no longer a barrier to activity, enabling extended wakefulness and reshaping sleep schedules.
Scientific insights reveal that light exposure before bedtime can delay the production of melatonin, the sleep hormone, thereby suppressing natural awakenings. Additionally, the Industrial Revolution introduced rigid factory schedules and early shifts, promoting the ideal of eight uninterrupted hours of sleep as a societal goal.
Evidence from Ancient Texts and Modern Studies
References to biphasic sleep appear casually in ancient literature, such as the works of Homer and Virgil, who mentioned "the hour that ends the first sleep." This historical documentation suggests the practice was commonplace and accepted.
Modern research supports the biological basis of this pattern. A 2017 study of Madagascan farmers without electricity found that most still slept in two segments, waking around midnight. Laboratory experiments where volunteers live without clocks or light cues often show a natural drift back to biphasic rhythms, indicating the pattern remains ingrained in human biology, though suppressed in contemporary life.
Implications for Modern Sleep Health
Waking in the middle of the night is not inherently problematic; sleep experts note that brief awakenings are normal, often occurring near REM sleep stages. However, without the cultural acceptance of "first and second sleep," these moments can feel prolonged, leading to anxiety or boredom. Cognitive behavioural therapy for insomnia (CBT-I) frequently advises leaving bed if awake for 20 minutes or more, engaging in a quiet activity under dim light before attempting to sleep again.
Nights were historically designed as two blocks, with the pause offering opportunities for calm, reflection, and connection. Perhaps waking at 3 a.m. is not a disorder but a remnant of an older, more natural sleep rhythm.
