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A Indications from both science and history suggest that the eight-hour sleep may not be a natural or inborn pattern for humans. In the early 1990s, psychiatrist Thomas Wehr conducted research which implies just that. Wehr kept a group of people in a darkened room for 14 hours a day for a month. It took some time for their sleep to regulate, but by the fourth week the subjects had settled into a very distinct sleeping pattern. Firstly, they slept four hours, then woke for one or two hours before falling into a second four-hour sleep. Though sleep scientists were impressed by the implications of the study, the idea that we must sleep for eight consecutive hours persists amongst the general public.
B In 2001, historian Roger Ekirch of Virginia Tech University in the US published a paper drawn from 16 years of research, revealing historical evidence that humans used to sleep in two distinct periods of time each night. Ekirch's research found more than 500 references to a segmented sleeping pattern in diaries, court records, medical books and literature, from the ancient Greeks to tribes in Nigeria. Much like Wehr's findings, these references describe a first sleep which began not long following sunset. Then there was a waking period of one or two hours and after that a second sleep. During the waking period, people could be quite active. They sometimes got up and moved around the house, although most people stayed in bed, and perhaps read or wrote if they had enough money for candles. In many historic accounts, Ekirch found that people used the time that they were awake between periods of sleep to think about and attempt to analyse their dreams.
In his book, Evening's Empire, historian Craig Koslofsky suggested an explanation for this divided sleep pattern in Europe. ‘Associations with night before the 17th century were not good,’ he writes. He goes on to explain that the streets of cities and towns at night were often populated by thieves or worse. The streets at night consequently scared many people. Even the wealthy, who could afford to light their way, had better things to spend their money on. There was no prestige or social value with going out or staying up late at night.
