The history of human sleep reveals a fascinating evolution shaped by culture, environment, and spiritual beliefs.

Sleep Patterns and Rhythms For much of Western history, people experienced "segmented" or biphasic sleep, dividing their rest into a "first" and "second" sleep separated by an hour or two of wakefulness used for prayer, reflection, or socializing. However, this may not be a universal biological default. Recent studies of modern hunter-gatherer societies (such as the Hadza, San, and Tsimane) reveal they typically sleep in a single, continuous block of 5.7 to 7.1 hours. Their sleep is heavily regulated by natural elements, generally beginning several hours after sunset and ending at the daily nadir (lowest point) of ambient temperature.

The Material Culture of Sleep The physical environment of sleep has varied widely. Ancien ...