Humans used to sleep in two segments (biphasic sleep) for about 8 hours total, with a 1-2 hour waking period in between, a pattern common before the Industrial Revolution and electric lights rewrote our circadian rhythms; this "first sleep" and "second sleep" involved falling asleep after sunset, waking around midnight to socialize or pray, then sleeping again until dawn, unlike the modern, continuous 8-hour night.
The Social Transformation of Nighttime
For much of recorded history, humans have actually slept eight hours, but in two distinct phases of approximately four hours each.
In the early modern era, first and second sleep had generally been of equal duration, approximately three to three and a half hours apiece.
Biphasic sleep
Before the Industrial revolution started in the 19th century, most people practiced two regular sleep cycles throughout the day. This was known as biphasic sleep, also known as segmented sleep.
For most of human history, a continuous eight-hour snooze was not the norm. Instead, people commonly slept in two shifts each night, often called a "first sleep" and "second sleep."
The koala is famous for sleeping around 20-22 hours a day, which is about 90% of the day, due to their low-energy diet of eucalyptus leaves that requires extensive digestion. Other extremely sleepy animals include the sloth (up to 20 hours) and the brown bat (around 20 hours), with some snakes like the ball python also sleeping up to 23 hours daily.
Despite differences in their genetics, histories and environments, all three groups had similar sleep patterns. People in these groups slept slightly less than 6.5 hours a night on average. In comparison, people in industrial societies usually average seven to eight hours per night.
The 3-2-1 bedtime method is a simple sleep hygiene strategy: stop eating 3 hours before bed, stop working 2 hours before bed, and stop using screens (phones, tablets, TVs) 1 hour before sleep, helping your body transition to rest by reducing stimulants and digestive load for better sleep quality. A more detailed version adds 10 hours (no caffeine) and 0 (no snoozing) for a 10-3-2-1-0 rule.
Leonardo da Vinci
He followed a polyphasic sleep pattern with a 20-minute nap every four hours. Given his expertise in so many things -- invention, painting, sculpting, architecture, science, music and more – the unconventional schedule must have worked for him.
Most of us fall in the night owl category because humans have a circadian rhythm with a period slightly longer than 24 hours. This causes many people to stay up and wake up a bit later each day. By staying up later and waking up earlier than our body wants us to, we can develop sleep deprivation.
Purity, chastity, chaste, maiden, flower, and virgin were all terms that originated in the 1200s that meant a woman who has not been touched sexually. Chaste was specifically meant for unlawful sexual intercourse until the 15th century where it came to mean completely sexually pure.
Humans need less sleep than our closest evolutionary relatives. However, we often sleep less than we need. Needing less sleep is a consequence of our ancestors' choices to remain awake longer — a behaviour that led to evolutionary benefits.
In Old Norse, a bed was referred to as a beðr, hvíla, rekkja or sæng. It is believed that breakfast took place around seven o'clock in the morning, when everyone was already on their feet; from some indirect notes from Family sagas, it seems that it was common to go to bed before midnight.
“In 'normal' circumstances — in the absence of a circadian rhythm or sleep abnormalities/disorders and without significant sleep deprivation — [the forbidden zone for sleep] is going to begin around 7 p.m.,” says Dr. Goldstein.
Musk goes to bed around 3 a.m. and gets about 6 hours of sleep every night. Although he's not getting eight hours a night, Musk has upped his sleeping schedule from being nearly nonexistent in the past. In May 2023, Musk told CNBC that he's no longer pulling all-nighters.
We often perceive sleeping during the day as a sign of laziness, but should we? – After all, there is extensive research showing that an afternoon nap is perfectly natural for humans. At the same time, there is solid evidence that sleep deprivation leads to lessened productivity.
It's common knowledge that sleep is good for your brain – and Einstein took this advice more seriously than most. He reportedly slept for at least 10 hours per day – nearly one and a half times as much as the average American today (6.8 hours). But can you really slumber your way to a sharper mind?
Signs of poor core sleep (deep, restorative sleep) include waking up foggy, daytime fatigue/energy crashes, poor concentration, irritability, frequent illness, memory issues, and mood swings, indicating your brain and body aren't fully repairing and consolidating memories. You might also experience increased sugar cravings, slow muscle recovery, and a weakened immune system.
Yes, the Navy SEAL sleep trick (an 8-minute power nap with elevated legs) is a real technique for quick rest, popularized by former SEAL Jocko Willink, that helps improve alertness and reduce fatigue, though its effectiveness depends on individual relaxation skills and it's not a substitute for full nighttime sleep. The method involves lying down, elevating your feet above your heart (on a chair or couch), relaxing facial muscles, dropping shoulders, and clearing your mind for about 8-10 minutes to promote relaxation and blood flow, preventing grogginess.
The military sleep method involves the following steps: Breathe deeply: Close your eyes and focus on your breathing. Take slow, deep breaths. Relax your face: Slowly relax all the muscles in your face, starting from your forehead and then moving downward over your cheeks, mouth, and jaw.
The 80/20 Rule means that you stick to your healthy, consistent sleep schedule 80% of the time. You then can make exceptions to your schedule 20% of the time. The 80/20 Rule allows you to “live life” and enjoy those special moments with your family.
In his piece, he revealed that through his years of research, he's found that rumination is the biggest thing that causes poor sleep. He says that being worried about something at night has affected his own ability to fall asleep.
More sleep is natural in the wintertime, according to the National Sleep Foundation. The normal range is an extra 1.75 to 2.5 hours per night. The key is limiting your sleep between 7–10 hours per night (for healthy adults). Any more can be a symptom of depression, illness, or other underlying issues.
Some people prefer nine hours of sleep. Albert Einstein is said to have slept 10 hours per night, plus regular daytime naps.
We really have no archaeological way of knowing the positions in which people slept. It doesn't leave a recognizable mark on the skeleton, and more to the point, it doesn't make sense. Our non-human primate relatives , never mind countless other species, are more than capable of creating nests / beds for themselves.