First or "deep" or "dead" sleep, as it was sometimes called, often seems to have taken place shortly after sunset, or at least before 10 in the evening. After two to four hours of the night's deepest rest, people would wake up for an hour or two, then resume sleep for another stretch before rising with the light.
During this waking period, people would relax, ponder their dreams, or have sex.
Many might find the later a good description of teenage behavior. Couple that with the physiological fact that
For men, levels of testosterone are highest during sleep and require at least three hours sleep to reach this peak. [2]
And just maybe teenagers are reverting to form.
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[1] At Day's Close: Night in Times Past - Ekirch (2006)
[2] https://www.sciencealert.com/chemical-messengers-how-hormone...