Preprint Review Version 2 This version is not peer-reviewed

How The Mammalian Sleep Was Born

Version 1 : Received: 29 November 2019 / Approved: 30 November 2019 / Online: 30 November 2019 (09:59:13 CET)
Version 2 : Received: 18 July 2020 / Approved: 20 July 2020 / Online: 20 July 2020 (10:31:23 CEST)

How to cite: Rial, R.V.; Canellas, F.; Gamundi, A.; Akaârir, M.; Nicollau, M.C.; Martí-Reina, A.; Rubiño, J.A.; Barceló, P. How The Mammalian Sleep Was Born. Preprints 2019, 2019110387 (doi: 10.20944/preprints201911.0387.v2). Rial, R.V.; Canellas, F.; Gamundi, A.; Akaârir, M.; Nicollau, M.C.; Martí-Reina, A.; Rubiño, J.A.; Barceló, P. How The Mammalian Sleep Was Born. Preprints 2019, 2019110387 (doi: 10.20944/preprints201911.0387.v2).

Abstract

The Nocturnal Bottleneck explains how mammals evolved from their reptilian ancestors after inverting the chronotype, form diurnal to nocturnal. Pre-mammals traded-off the excellent visual system of their ancestors for improvements in audition and in olfactory telencephalon, needed for efficient orientation in the dark. This was how the mammalian nocturnal telencephalic wakefulness was born. However, the modified visual system of those pre-mammals became sensitive to the dangerous diurnal light and the exposure would involve a high risk of blindness and death. Therefore, pre-mammals had to remain immobile with closed eyes hidden in lightproof burrows during light time. This was the birth of the mammalian sleep. Typical reptiles distribute their wake time cycling between Basking Behavior, to attain the preferred body temperature, and poikilothermic Goal Directed Behavior, to perform life sustaining tasks. These cycles persisted during the new mammalian sleep. However, as the behavioral output had to be blocked during light time, the paralyzed reptilian Basking Behavior and Goal Directed Behavior cycles became the NREM and REM cycles, respectively. This was how NREM and REM cycles remained incorporated within the mammalian sleep. After the Cretaceous-Paleogene extinction, the environmental pressure for nocturnal life was softened, allowing high variability in chronotype and sleeping patterns. This permitted some mammalian groups, e.g., primates, to begin the quest for diurnal wake.Concluding, sleep constituted an additional bottleneck in the mammalian evolution. The reduced population of pre-mammals that was able to develop sleep during light time, including NREM and REM, became full mammals and survived; the remainder perished.

Subject Areas

evolutionary bottleneck; evolution of sleep; sleep variability; function of sleep

Comments (1)

Comment 1
Received: 20 July 2020
Commenter: Rubén Víctor Rial
Commenter's Conflict of Interests: Author
Comment: The scope of the review has been reduced to deal only with the consequences of the nocturnal bottleneck. We also added two authors
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