Segmented Sleep in Preindustrial Societies

Extract

I was intrigued to learn of the study conducted of three pre-industrial cultures, without access to electric lighting, by a team of researchers led by Dr. Jerome Siegel in an effort to determine how humans slept “before the modern era.” Titled “Natural Sleep and Its Seasonal Variations in Three Pre-industrial Societies,” it appears in the November issue of Current Biology.¹ Having written on the predominance of “segmented sleep” in preindustrial Europe,² I was particularly surprised by the discovery reported by Yetish et al.¹ that the members of all three of these equatorial societies did not “regularly awaken for extended periods in the middle of the night.” In short, these individuals did not experience a “bimodal sleep pattern.” The authors conclude, “by extension,” that this pattern was “probably not present before humans migrated into Western Europe. Rather, this pattern may have been a consequence of longer winter nights in higher latitudes.” Not only is this broad inference highly questionable, but significant historical and ethnographic evidence also exists to suggest the prevalence of segmented sleep in preindustrial equatorial cultures.