In 2001, historian Roger Ekirch of Virginia Tech published a seminal paper, drawn from 16 years of research, revealing a wealth of historical evidence that humans used to sleep in two distinct chunks.
His book At Day’s Close: Night in Times Past, published four years later, unearths more than 500 references to a segmented sleeping pattern – in diaries, court records, medical books and literature, from Homer’s Odyssey to an anthropological account of modern tribes in Nigeria.
Roger Ekirch says this 1595 engraving by Jan Saenredam is evidence of activity at night
Much like the experience of Wehr’s subjects, these references describe a first sleep which began about two hours after dusk, followed by waking period of one or two hours and then a second sleep.
— The myth of the eight-hour sleep, BBC. Tu vois, c’est pas grave si tu te réveilles la nuit; On est fait pour un sommeil en deux parties avec entracte.