http://www.stanford.edu/~dement/delayed.html
http://www.sleepfoundation.org/publications/sma2.3.cfm#2
http://www.sleepdisorderchannel.net/dsps/
http://sleepdisorders.about.com/cs/dsps/a/nightowl.htm
http://www.about-sleep-disorders.com/html/delayed-sleep-phase-syndrome.php3
Having "suffered" from this "syndrome" my whole life I can tell you that it isn't "caused" during adolescence any more than people "turn gay" in their teens. About 1 in 15 people have this "disorder" -- only it is not a disorder, it is a specalized social function. The articles above talk about the difficulty people with DSPS have operating within "societal norms". Right-- because they aren't supposed to. All social species have specialized groups for specific functions. The purpose and function of "night people" seems pretty obivious to me: night people tell the bedtime stories to the rest of the tribe, we watch the fire and keep the wolves at bay, we paint the magical animals in the dark end of the cave for the shamen. Night people perform the mystery plays after dark. Night people are the artists, storytellers, bonfire-builders, festival organizers, and night-watch. The "normal" people depend on the night people for the entertainment and magic that creates the cultural glue that keeps the tribe together, and they depend on the night people to watch over them while they sleep.
Oringinal post: http://mbarrick.livejournal.com/550480.html