Why do we sleep?

Virtually all living organisms sleep, or its equivalent.  But it has been a puzzle why.  Surely spending a big part of every day unconscious can’t have much survival value.  But scientists have now discovered that sleep is when our bodies repair themselves and when our brain is rejuvenated and, literally, cleansed.

Time has a fascinating article on the subject, linked and excerpted after the jump.  Type-A personalities who brag about how little they sleep so they can work more, party animals who stay up all night, commuters who stay up late and get up early, and college students in general would do well to read it. [Read more...]

Why we sleep

Virtually all animals sleep, but scientists have had a hard time figuring out why that is.  New research has apparently uncovered a major reason why our brains need to go out of consciousness on a regular basis:  While we are asleep, toxins that build up in the brain get flushed out.  Experiments with mice show that their brain cells actually shrink  so that there is 60% more space between them, allowing fluid to wash them more effectively, sweeping out dead cells and Alzheimer’s-causing plaque, as well as chemical toxic wastes.

How lucky we are that so many random mutations came together to make this happen so as to allow us to sleep!  I feel bad, though, about the animals that must have lived for millions of years before one of them, completely by chance, gained this survival advantage and spread it to all other species.  Before they could sleep, living organisms must have been really grumpy.

After the jump, details about the discovery. [Read more...]

First sleep, second sleep

David T. Koyzis points to historical research that shows that people used to sleep differently than we do today.  Instead of sleeping for an 8-hour-or-so block of time, people would sleep three or four hours, wake up for two or three hours, and then sleep again until morning.  It would all take about 12 hours–go to bed when it got dark (say at 8:00 p.m.); wake up at midnight until 2:00 or 3:00 a.m.; then enjoy what they called “second sleep” until 8:00 a.m.

This was the practice in the West from ancient times until the 17th century with the advent of street lights and then the industrial revolution, though it lingered on some places until the 20th century.  (And today in some people’s patterns of insomnia.)

Prof. Koyzis shows how this fact explains certain passages in Scripture.  Also the monastic prayer offices in the middle of the night.  Also, I would add, the various watches of the night, in which sailors, soldiers, and others out in the elements exposed to danger  took three-hour shifts standing guard through the night.   Details after the jump. [Read more...]


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