deepthinking:

Today, most people seem to have adapted quite well to the eight-hour sleep, but Ekirch believes many sleeping problems may have roots in the human body’s natural preference for segmented sleep as well as the ubiquity of artificial light.

This could be the root of a condition called sleep maintenance insomnia, where people wake during the night and have trouble getting back to sleep, he suggests.

The condition first appears in literature at the end of the 19th Century, at the same time as accounts of segmented sleep disappear.

“For most of evolution we slept a certain way,” says sleep psychologist Gregg Jacobs. “Waking up during the night is part of normal human physiology.”

The idea that we must sleep in a consolidated block could be damaging, he says, if it makes people who wake up at night anxious, as this anxiety can itself prohibit sleeps and is likely to seep into waking life too.

I’m one of those people who will wake up after 4 hours of sleep. When I told this to someone talking about stress at my work they considered it unhealthy and were convinced I should seek medical treatment because “everyone knew you needed eight” hours of sleep…I knew she was full of it and this confirms it.