The 8-Hour Consolidated Sleep: Just A Modern Adaptation
- Pinay Sleep Doctor
- Jul 21
- 4 min read
Updated: Jul 29
Do you know that the 8-hour sleep that we now impose on ourselves has not always been the norm? Believe it or not, this single period of consolidated night sleep started only 200 years ago, and it seems it was due to industrialization, rather than an inherent biological improvement in sleep consolidation.
In research using over 2,000 preindustrial sleep documents from Europe, America, Africa, the Middle East, South Asia, and Latin America, Prof. Roger Ekirch, from Virginia Tech, showed that SEGMENTED or BIPHASIC SLEEP was a common pattern of rest.
There were generally two main types of biphasic sleep:
1. "First and Second Sleep" (Night-segmented sleep): This is the historical pattern that was prevalent before the widespread use of artificial lighting. People would go to sleep shortly after dusk for a "first sleep" lasting a few hours. Then wake up in the middle of the night for an hour or two, engaging in quiet activities such as reading, praying, reflecting, doing light chores, socializing, or sexual activity before returning to bed for a "second sleep" that lasts until dawn. This was considered a normal and natural way to sleep, and historical records, literature, and medical texts from pre-industrial Europe are full of references to it. The period of wakefulness was often calm and introspective.
2. "Siesta Sleep" (Night sleep + midday nap): This is the more commonly recognized form of biphasic sleep today. It involves a longer sleep period at night (typically 5-7 hours) followed by a substantial nap in the afternoon (ranging from 20 minutes to 1.5 hours or more). The nap serves to refresh the individual, especially in cultures where midday heat can make activity difficult, or simply to provide a restorative break.
Why Did Bi-Phasic or Segmented Sleep Evolve/Exist?
Absence of Artificial Light: Before the advent of electricity, human activity was largely dictated by natural light cycles. Going to bed shortly after dark was practical, but the long hours of darkness before dawn, especially during winter, made a single, continuous sleep challenging, if not unnecessary. Waking in the middle of the night provided a natural break during those long, dark hours.
Safety and Vigilance: In ancient communities, having some members awake during different parts of the night (as explained by varying chronotypes) could have offered a continuous watch against predators or intruders, enhancing group survival.
Cultural and Religious Practices: Some religious practices (like certain Muslim prayers before dawn) or monastic traditions naturally aligned with segmented sleep patterns.
Adaptation to Climate: In hot climates, the midday nap (siesta) became an effective strategy to avoid the most intense heat of the day, allowing people to work or be active during cooler morning and late afternoon/evening hours. And again, a break from long, cold, and dark winter nights.
Spain is perhaps the country most famously associated with the “siesta”. And because of our colonization for 300 years, Filipinos naturally inherited this practice. Spanish lunch was typically the main meal of the day, eaten between 2:00 PM and 3:00 PM, and could last 1.5 to 2 hours, sometimes even longer. Many businesses, especially smaller shops and public offices, closed during this period (often from 2 PM to 5 PM). This break allowed people to go home, eat a substantial meal, and spend time with family. While not everyone napped during this time, it provided the opportunity for a short rest or to de-stress. The Spanish workday often extended until 7 or 8 PM, which pushed dinner back to 9 or 10 PM, and social life continued late into the night.
The transition away from these Segmented Sleep patterns was primarily driven by the introduction of new lighting technologies and the economic demands of industrialization, rather than an inherent biological improvement in consolidated sleep. The traditional 2- or 3-hour-long siesta is largely being abandoned, especially among the working adult population. Modern work schedules, increased commuting, and globalization have prompted many companies to adopt continuous workdays (e.g., 9 AM to 6 PM). The traditional siesta is now more likely to be observed only in smaller and rural communities, particularly during the peak of high summer temperatures. Older generations, though, probably still continue the habit. Children may also have designated nap times in schools or at home. For those who do nap, it's often a short power nap (20-30 minutes) taken on a sofa rather than a bed. It's seen as a way to "recharge" and avoid burnout from long working days.
This once-common pattern was "largely lost to the modern world," implying a societal redefinition of "normal" sleep, greatly influenced by the new capabilities afforded by artificial light. This underscores that our current consolidated sleep pattern is a relatively recent cultural and technological adaptation, rather than an ancient biological imperative.
How about you? Do you practice segmented sleep, or would you like to try it? What we know now is that the need for sleep varies between individuals and can also differ from one night to the next for a given person. Recent scientific evidence has shown, though, that adults chronically sleeping <6 hours per night are at high risk of a host of diseases. Only 1–5% of the population comprises the “short sleepers,” who are characterized by a genetic mutation, like ADRB1, that enables them to function well on only 4–6 hours of sleep per night.
To determine your Basal Sleep Need, sleep without any pre-existing debt for two weeks, until you find yourself waking up spontaneously without an alarm clock. I highly recommend camping outdoors, following the rhythm of the sun.
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