My friend Barry Solow just alerted me to this, Letter of Recommendation: Segmented Sleep, in the NYTimes:
Back when segmented sleep was common, this period between “first” and “second” sleep inspired reverence. The French called it dorveille, or wakesleep, a hypnotic state. English speakers called it “the watch.” I had usually approached the post-midnight hours full-sail, by staying up. Waking into them is different, childlike. The time feels freer. The urge to be busy abates. Conversation has a conspiratorial intimacy, as if you’ve sneaked behind the tent to find the only other smoker at the wedding. Though I preferred the name dorveille, because it sounded glamorous, “the watch” was technically more accurate during those early weeks, when I mainly got up and watched Netflix.In the preindustrial West, most people slept in two discrete blocks and used dorveille for all kinds of purposes. Having sex was popular. Benjamin Franklin liked to “take cold-air baths,” a fancy way of saying “open his windows naked.” Many people wrote in journals or interpreted dreams, which feel more proximate at 3 a.m. than in daylight. You could drink a cup of tea and take a satisfied leak on the embers of your fire. But everyone did something, because dorveille was ubiquitous.We tend to view our basic patterns, like spending the evening out and then lying unconscious for eight hours straight, as belonging to a natural order. But until streetlights, being up late meant wandering town in butt-clenching terror, tripping over stray animals until the wind blew out your lantern and you were set upon by armed bandits. So you went home before dark and went to bed early, waking after midnight.
After all, we're not born to sleep thru the night. Teaching/coaxing/cajoling infants to sleep through the night is one of the major tasks of childhood. As I recall from something I read years ago, we're born to a 3 hour cycle, 90 minutes awake, and the 90s minutes of sleep. That's what has to be shaped to a "normal" sleeping pattern.