Dr Neil Stanley Independent Sleep Expert
Ekirch AR. Segmented Sleep in Preindustrial Societies. Sleep. 2016 Mar 1;39(3):715-6 here Reference 1 References 2,3,4 Reference 5 Reference 6 Reference 7 Reference 8 Reference 9 Reference 10 & 11 Reference 12 Reference 13 Reference 14 As the respected journal, Sleep, printed Ekirch’s letter, even though, surprisingly, it was dealing with a paper that was not actually printed in said journal, I decided to write a letter of my own pointing our the weakness of Ekirch’s case, unfortunately Sleep rejected my letter without giving a reason, and so for the sake of clarity I reprint below the letter that I submitted Evidence of ‘segmented sleep’ in ‘preindustrial’ societies In his recent letter1 Roger Ekirch argues that examples from anthropological sources support his contention that biphasic ‘segmented sleep’ existed in ‘preindustrial societies’. While it is true that in his work2,3 he has quoted a number of occurrences of the phrase ‘first sleep’ in descriptions of ‘preindustrial’ societies, it is important to note that a search of the eHRAF World Cultures database4 reveals that this phrase is only mentioned in the descriptions of 7 of the 301 societies achieved. The only description of what might be ‘preindustrial’ ‘segmented’ sleep given by Ekirch is a single case of the use of both ‘first’ and ‘second’ sleep in one society. Referencing the work of Bohannan5 Ekirch states that “The Tiv even employs the terms "first sleep" and "second sleep" as traditional intervals of time”. However it is unclear what these terms actually signify given the actual description given by Bohannan is more nuanced than the interpretation given by Ekirch; “The Tiv are much less specific about time during the night. The time between dusk and about 10 o'clock is called "sitting together" (teman imongo). After that follows "the middle of the night" (helato tugh), which overlaps with the "time of the first sleep" (icin i mnya mom); "the time of the second sleep" (acin a mnya ahar) is about 3 AM or a bit later. The pre-dawn breeze (kiishi) gives its name to the period just before dawn”. The full quote gives the impression that ‘first’ and ‘second’ sleep are merely intervals of time rather than signifiers of distinct, separate, periods of sleep. Support for this interpretation comes from the work of Aubert and White6 who surveyed the anthropological reports on numerous ‘primitive societies’ including the Tiv. Aubert and White stated that “All societies surveyed showed regular and continuous sleep during the night. This holds, however, only if “sleep” includes activities such as urinating, spasmodic chatting, smoking and other intermittent behaviour considered part of the cultural pattern of sleep.” It is also somewhat problematic to Ekirch’s conception that ‘preindustrial’ ‘segmented sleep’ was/is biphasic that a more recent source states that the Tiv also have a phrase for the “time of the third sleep”7 which also occurs before Kishi (the pre-dawn breeze) (Ichin imya mon - time of first sleep; Ichin imya ahar- time of second sleep; Ichin imya atar - time of third sleep). Therefore the only occurrence of ‘first’ and ‘second’ sleep in the anthropological literature does not offer convincing evidence for the existence of biphasic ‘preindustrial’ ‘segmented’ sleep in non-western societies. Thus we perhaps should not be too surprised that to date researchers have not found scientific evidence for ‘segmented’, or biphasic sleep, in studies of sleep under real-life ‘preindustrial’ conditions8,9,10,11  References 1 Ekirch AR. Segmented Sleep in Preindustrial Societies. Sleep. 2016 Mar 1;39(3):715-6. 2 Ekirch AR. Sleep we have lost: pre-industrial slumber in the British Isles. American Historical Review. 2001 Apr 1;106(2):343-86. 3 Ekirch AR. The Modernization of Western Sleep: Or, Does Insomnia have a History?. Past & Present. 2015 Feb 1;226(1):149-92. 4 Human Relations Area Files, World Cultures accessed March 2016 here  5 Bohannan P. Concepts of time among the Tiv of Nigeria. Southwestern Journal of Anthropology. 1953 Oct 1:251-62. 6 Aubert V and White H, Sleep: A Sociological Interpretation. I Acta Sociologica 1959 4(2) 46-54 7 Gbenda JS Eschatology in Tiv Traditional Religious Culture: An Interpretative Enquiry, Nairobi, Chuka Educational Publishers, 2005 p55 8 Wright KP, McHill AW, Birks BR, Griffin BR, Rusterholz T, Chinoy ED. Entrainment of the human circadian clock to the natural light-dark cycle. Current Biology. 2013 Aug 19;23(16):1554-8. 9 Piosczyk H, Landmann N, Holz J, Feige B, Riemann D, Nissen C, Voderholzer U. Prolonged sleep under Stone Age conditions. J Clin Sleep Med. 2014 Jul 15;10(7):719-22. 10 Horacio O, Fernández-Duque E, Golombek DA, Lanza N, Duffy JF, Czeisler CA, Valeggia CR. Access to Electric light is associated with shorter sleep duration in a traditionally hunter-gatherer community. Journal of biological rhythms. 2015 342-350 11 Yetish G, Kaplan H, Gurven M, Wood B, Pontzer H, Manger PR, Wilson C, McGregor R, Siegel JM. Natural sleep and its seasonal variations in three pre-industrial societies. Current Biology. 2015 25(21):2862-8.
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