Data on sleep habits, collected over several hundred consecutive days, have shown that, in three separate and geographically isolated groups, individuals were sleeping approximately 5.7 to 7.1 hours in a row every night. For Siegel and his collaborators, these results indicate that modern single-man sleep corresponds to a return to a traditional scheme observed in hunter-gatherers.
“They have neither electric light nor heating … [ils] have not changed their environment or their social structure for hundreds of thousands of years, “he said. “There may have been a period in human history when people woke up in the middle of the night, but say that it is the normal scheme contradicts all this data. »»
Although our oldest societies were able to sleep according to a single -phase scheme, Roger Ekirch found traces of segmented sleep dating back to theOdyssey d’Homer, published at the end of 8ᵉ or at the beginning of the 7ᵉ century BCE. By continuing his research, he discovered countless references to a “first” and a “second” sleep in all kinds of archive documents, ranging from newspapers to medical texts.
“The references were formulated as if segmented sleep was perfectly natural and required no explanation,” he said.
In the past, explains Russell Foster, people tended to go to bed earlier, towards nightfall, and sleeping, intermittently, until sunrise. But everything has changed with the arrival of cheap artificial light sources, which have somehow ended our dependence on sunlight, he adds. “We work much later in the evening. We thus go around natural darkness, therefore reducing our sleep possibilities. »»
However, this version of history does not consensus. Niall Boyce, English professor at the University of London, argues that polyphasic sleep may not be the norm. Siegel, too, questions the interpretation of Ekirch, preferring to rely on his data concerning modern hunter-gatherer societies rather than anecdotal evidence from ancient texts.
“The bimodal sleep scheme that would have existed in Western Europe is not present in traditional groups living today in the tropics and, therefore, probably did not exist before humans migrate in Western Europe,” write the authors in their article. “This scheme could rather be a consequence of long winter nights with high latitudes. »»
The existence of polyphasic sleep in modern humans also remains subject to debate. While some defend a strict definition of the phenomenon, others include naps, brief night’s breaks or siestas as contemporary examples of segmented sleep.
As sleep is influenced by the environmental and social context, Buysse believes that the patterns can vary strongly depending on individuals, regions and seasons.
“I especially think that there is not a single sleep scheme specific to human beings,” he concludes. “I think that adaptability is the main characteristic. »»
