These days, everyone is obsessed with getting those magical eight hours of sleep - I know I am.
Sleep is the one thing we all need that no one gets enough of. It can boost your mood, help control your blood pressure, and even help you lose weight.
So it may surprise you to learn that for centuries almost no one was interested in eight hours of shut-eye.
Instead, our ancestors had a pretty complicated sleep schedule, which kept them feeling well-rested on fewer hours of sleep than we get.
How did our ancestors sleep?
Roger Ekirch, a history professor at Virginia Tech, uncovered a well-recorded but long forgotten fact about historical sleep patterns.
As recently as the 18th century, most people slept in two shifts, sometimes called first sleep and second sleep.
But while it sounds relaxing to lie down for bed twice a night, the system had its drawbacks.
After first sleep, which usually lasted three or four hours, you would wake up.
After spending two or three hours awake, you would lie down for second sleep, which lasted until morning.
Why did we sleep in shifts?
Experts are split about exactly why humans started sleeping in two chunks.
It was definitely useful for doing extra chores, especially for farmers and laborers, but it may have suited our natural rhythms too.
A psychologist named Thomas Wehr kept 15 men in artificial darkness for hours each day to simulate a long, mid-winter's night.
To his surprise, they started sleeping in shifts, and spent hours relaxing in bed between their naps.
But our ancestors were more likely to spend their spare time each night on something useful: chores, praying, reading, or having sex.
Why did we stop sleeping in shifts?
Ekirch blames the end of the split sleep schedule on a number of things, including the invention of street lamps, the rise of indoor lighting, and the growing popularity of coffee.
Instead of locking their doors and hitting the hay as soon as the sun set, people began to spend time out socializing, or staying up with their family.
The length of the actual "night" shrunk from 12 hours or more to the eight or so we spend sleeping today. So the two sleep shifts overlapped, becoming one big snooze.
There's even evidence that doctors and sleep experts started advising people to change their habits.
Sleeping in one long stretch was said to save time and offer "more enjoyment" during the day - although I'd like to meet anyone who enjoys waking up in the morning.
Are there benefits from sleeping in shifts?
It sounds frustrating, but some people actually enjoy getting a first and second sleep every night.
Many people already describe a condition called maintenance insomnia: they and toss and turn - sometimes for hours.
It could be that our bodies are still used to an old-fashioned sleep schedule, and so they wake us up mid-sleep.
While waking up in the early morning makes most people anxious about losing sleep, if you plan to do it the experience can be very relaxing.
One of the biggest advantages of copying your ancestors' schedule is that you'll need to tuck yourself in earlier each night.
To make sure your wakeful period between rests isn't rushed, you may need to lie down for the night an hour earlier than you normally would.
Getting a few hours of rest is nothing to sneeze at either: research shows that simply lying down and relaxing does wonders for your body, just like sleep.
Are there downsides to sleeping in shifts?
Definitely!
Even if sleeping in parts was common for hundreds of years, our world just isn't made for it anymore.
Like the subjects in Wehr's study, it takes weeks in long hours of darkness for your body to change its rhythms.
These days, city lights and cell phones are already interrupting our sleep. Trying to wake yourself up at 1 a.m. will only make things worse.
Like insomniacs who wake up in the night and stare at their clock for hours, losing sleep is bound to make you feel anxious.
To see any benefits from two sleeps a night, you need to overcome that anxiety, which could take months of adjustment.
Also: the benefits of sleep for your health depend on completing multiple cycles of REM sleep, which take about 90 minutes.
Modern sleep experts will tell you that interrupting this cycle and cutting into your precious REM time is a bad idea.
How can I get more sleep each night?
If you really want to practice your ancestor's sleep habits, try going to bed earlier.
According to the National Sleep Foundation, you're probably not getting enough sleep for your age bracket already.
Here's what the organization recommends:
- 1-12 months old: 14-15 hours
- 1-3 years old: 12-14 hours
- 3-6 years old: 10-12 hours
- 7-12 years old: 10-11 hours
- 12-18 years old: 8-9 hours
- 18-65 years old: 7-9 hours
- 65 years old and up: 7-8 hours
Surprised? Yes, even eight hours doesn't cut it for most people.
If you can't squeeze more hours of sleep into your schedule, take another cue from your ancestors and cut out harmful electric lights.
"Blue light" from cell phones, computer monitors and TV screens can keep you awake for hours.
Set a deadline a few hours before bed and don't pick up your phone after that.
Spend those last hours outside your bedroom, doing a relaxing activity like reading. That way you'll only associate your bed with one thing: sleeping.
Finally, try and be as relaxed as your ancestors were about being up in the middle of the night.
Studies show tracking your sleep and getting anxious about losing time only makes you more anxious.
Focus on making a relaxing sleep environment for yourself and cutting out distractions.