The evolution of human sleep

Are you a night owl? Do you want to get up in the middle of the night and head out into the quiet streets? Maybe sit at the counter in an 24-hour diner in companionable silence with the wait staff – then stroll home and slip back between the sheets for another four-hour slumber?

If so, you’re not weird (we promise) – your DNA just contains a throw-back switch to an earlier bi-modal sleep pattern,” according to researcher Dr. A. Roger Ekirch from Virginia Tech

Sleeping through the night is a “new thing” for humans.

In his book, “At Day’s Close: Night in Times Past” (W.W.Norton, 2006), Professor Ekirch describes how many people, prior to the Industrial Revolution (1760), had “segmented sleep”. This was four hours of slumber – then awake for 1 – 3 hours – then back to sleep again for another four hours. 

He found that many 18th Century European regal courts – like those of Louis XVI and Marie Antoinette – did not wind down for the evening. For those of a bi-modal sleep nature, there were delights and diversions, like card games and harpists playing, available at all hours in Versailles’ salons.  

How circadian rhythms work

In a piece for the BBC, Professor Russell Foster, chair of circadian neuroscience at Oxford University, explained how the arrival of electricity and light bulbs changed our circadian rhythms. Once agricultural workers would rise with the dawn, work all day in the natural light, then come home as darkness fell; now office-based workers in artificially-lit environments struggle to form a decent sleep pattern. 

Here’s an animation that Professor Foster’s team prepared to explain how our circadian rhythms work.

Everyone’s sleep patterns are different.

If you don’t sleep through the night, don’t despair. Maybe you’re a bi-modal sleep pattern person. Perhaps you need that wide awake break in the middle of two blocks of four hours of sleep to process your dreams, write down stuff that’s bothering you or take a stroll (safely) around your neighborhood. 


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