Humans Used to Sleep in Two Shifts

Around a third of the population has trouble sleeping, including difficulties maintaining sleep throughout the night. While nighttime awakenings are distressing for most sufferers, there is some evidence from our recent past that suggests that this period of wakefulness occurring between two separate sleep periods was the norm. Throughout history, there have been numerous accounts of segmented sleep — from medical texts, to court records and diaries, and even in African and South American tribes, with a common reference to "first" and "second" sleep. Anthropologists have found evidence that in pre-industrial Europe, sleep onset was determined not by a set bedtime, but by whether there were things to do. Households retired a couple of hours after dusk, woke a few hours later for one or two hours, and then had a second sleep until dawn. During this waking period, people would engage in activities like sewing, chopping wood, or reading. The first and second sleep started to disappear during the late 17th century. Today, there’s still evidence of two sleeps, especially in cultures that take an afternoon siesta. Today's society often doesn't allow for this type of flexibility, but goes by the belief that a continuous 7-to-9-hour unbroken sleep is best. Unfortunately, that schedule may not suit our circadian rhythms. The bottom line is that people have to design a sleep schedule that works for them, rather than following some specific guideline.