Why humans once slept in two shifts and how modern life changed it
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For much of history, people didn’t sleep in one long block.
Instead, night-time rest was split into two sessions – often called a “first sleep” and “second sleep” – with an hour or two of wakefulness in between.
Records from Europe, Africa, and Asia describe families going to bed soon after dark, waking around midnight, then returning to sleep until morning.
That middle interval was used for quiet chores, reading, prayer, reflection – and sometimes intimacy.
Literature from Homer and Virgil even refers to the gap between the two sleeps, showing how common the pattern once was.
The shift to a single eight-hour sleep is relatively recent. Artificial lighting in the 18th and 19th centuries gradually pushed bedtimes later and weakened the biological urge to wake halfway through the night.
As industrial work routines spread, the system reinforced a culture of one consolidated sleep. By the early 20th century, the two-sleep rhythm had faded in most industrialised societies.
Yet when people are kept in long darkness with no clocks or screens, they still often revert to segmented sleep – a sign it’s deeply ingrained.
Light shapes our body clock, mood, and sense of duration. Dim evenings and dark winters slow time perception.
In experiments and in polar regions, people can lose track of time when natural light cues disappear. However, people adapt better to the lack of light cues and loss of time perception when the entire community shares a regular daily schedule.
This all offers a different view of those 3 am awakenings that many people worry about. Short wake periods are natural. It’s the reaction – checking the clock, panicking about minutes passing – that often keeps people alert.
Sleep clinicians suggest getting out of bed if you’re awake for a while, doing something calming in low light, and returning to bed when sleepy.
Understanding that continuous sleep is a modern invention – not the historical norm – may make those midnight wakeups feel less alarming, and more like something humans have always done.