I read Lights Out, decided to black out my bedroom, and immediately felt
better for it. When possible I try to spend 9 hours in my "dark cave." It
serves as a sort of poor man's sensory deprivation tank, I believe.

HOWEVER I seriously doubt if this is a true reflection of paleo living. I
think cave living was limited and that many, if not most, early humans
lived under the varying light of the moon and the brilliant light of the
stars. Prior to urban pollution it was easily possible to read, even see
colors, from starlight alone, assuming the night was not cloudy.

Years ago I slept in a room exposed to the stars and moonlight and found it
reassuring to be aware of the phases of the moon. When the area around me
developed and neighbors started putting up yard lights I closed the
curtains and haven't been happy about it since.

The contention in the book that even a small amount of light falling on the
skin (the back of the knee, in the cited study) resets melatonin production
is suspect. A cursory search of Medline shows that blind people's melatonin
cycles are completely unsynced with the cycles of light and dark. In other
words, melatonin production is apparently well regulated by light entering
the eyes, but not by light falling on the skin.

Still, I like my dark bedroom. I seem to be more even tempered and have
less food cravings.

John