One of the first works to put sleep squarely on the critical map was A. Roger Ekirch’s fascinating essay “Sleep We Have Lost: Pre-Industrial Slumber in the British Isles,” originally published in The American Historical Review in 2001, and expanded and reprinted in his 2005 book At Day’s Close: Night in Times Past. Ekirch’s research revealed that across a wide range of nationalities and social classes in early modern Europe and North America, the standard pattern for nighttime sleep was to do it in two shifts of “segmented sleep.” These two sleeps — sometimes called first and second sleeps, sometimes “dead sleep” and “morning sleep” — bridged an interval of “quiet wakefulness” that lasted an hour or more. During this period, different cultures elaborated rituals — of prayer, lovemaking, dream interpretation, or security checks — and while the rituals varied, the pattern itself was so pervasive as to suggest, according to Ekirch, an evolutionary basis that somehow became disrupted in the modern West. He offered a straightforward explanation for the sudden loss of segmented sleep, and thus the dramatic and unprecedented rise of the eight-hour, lie-down-and-die model that became an unquestioned norm by the late 19th century: the spread of powerful artificial light. He cited as evidence experiments conducted at the National Institute of Mental Health, in which depriving subjects of artificial lighting for several weeks led them to patterns of segmented sleep.
Ekirch’s findings have had a significant impact on popular understandings of sleep: he followed up with essays in The New York Times and Harper’s, he has been interviewed dozens of times, and the work has been cited (uncritically) by science writers and journalists by the score. “Sleep We Have Lost” is also one of the rare historical works to interest scientists: Ekirch has given keynote addresses at the National Sleep Foundation’s annual conference, as well as several other sleep science meetings, and he has conducted follow-up research with neuroscientist Daniel Buysse.
Ekirch’s claim that segmented nighttime sleep is something of an anthropological constant (he cites references to similar sleep patterns in African societies as well as in ancient Greece) has taken hold more firmly in popular media than in the humanities. This may be because, as Steven Pinker has noted, humanities disciplines’ central dogma is the “blank slate,” that is, the notion that there is no “human nature” until culture writes up the recipe. Easier for such blank-slaters to accept is the corollary of Ekirch’s argument: that what we have been led to believe is normal sleep is in fact a recent invention, practiced nowhere in the world before the 19th-century West. Ekirch’s mechanistic explanation of artificial light and its effects on the circadian rhythms of humans has been useful to scientific researchers who are trying to isolate the effects of different kinds of light exposure on sleeping patterns; but to many in the humanities such explanations are “reductive” — a dirty word for them, but usually a compliment in science. Nonetheless, Ekirch’s work made clear that a shift in dominant sleeping patterns took place; and if one were to add to the “light” thesis that 19th- and 20th-century sleep was also altered by the shift of labor outside of the home, the development of industrial time discipline, new patterns of travel, noise pollution from trains and factories, the spread of caffeine and opium, changes in diet, the rise of universal schooling, changing medical conceptions of sleep, and the entrance of electronic media into the home, then one has a research agenda rather than a uniform explanation.