LFor a long time, we went to bed early, but mostly several times a day. The sleep of a draft, called monophasic (it’s the evening, we fall asleep and poof, it’s the morning), seems to be, on the scale of humanity, a recent invention. It would date from the industrial revolution, with the artificial light in the cities which would have made it possible to lengthen the working days in the factory, and therefore delayed bedtime. A sentence that remains conditional because studies are rare and diverge on the practice of polyphasic sleep (divided into several phases) according to continents and cultures.
Predators sleep deeper than their prey, which can wake up more easily to escape danger
One thing is certain, mammals, in an overwhelming majority, sleep several times in twenty-four hours. And even those who are diurnal allow themselves one or more naps. The neurobiologist Michel Jouvet, a pioneer in sleep medicine, has highlighted the variations according to animal species. Predators have deeper sleep than their prey, which splits more and can wake up more easily to escape danger. This is how we find horses sleeping upright, birds sleeping while flying, dolphins sleeping while swimming.
And the man? As doctors Magali Sallansonnet-Froment and Thierry de Greslan remind us, in The Mini-nap (Rustica editions, 2017), Standing man chose to leave the trees to sleep on the ground, exposing itself to predators and becoming the “monkey” with the shortest sleep duration.
Multiple stages of sleep
For the rest, we must rely on the work of Roger Ekirch, a teacher at Virginia Tech University, in the United States. In his book, published in France in January 2021, by Amsterdam editions, The Great Sleep Transformation, it shows that sleep has long been divided into two phases. We find references to a “first sum” and a “second sum” in the Middle Ages, but also in Erasmus, Plutarch or in theOdyssey of Homer. Here’s how it was: people would go to bed shortly after sunrise, around 9 or 10 p.m., only to wake up after midnight and go about their business for an hour or two, before going back to sleep until morning. During this waking moment, they could meditate, bathe, have intimate relations or watch the animals.
The siesta has been mentioned since Antiquity in the form of a meridian break
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