Document Type
Article
Publication Date
11-2-2015
Abstract
How did humans sleep before the modern era? Because the tools to measure sleep under natural conditions were developed long after the invention of the electric devices suspected of delaying and reducing sleep, we investigated sleep in three preindustrial societies[1–3]. We find that all three show similar sleep organization, suggesting that they express core human sleep patterns, likely characteristic of pre-modern era Homo sapiens. Sleep periods, the times from onset to offset, averaged 6.9–8.5-h, with sleep durations of 5.7–7.1-h, amounts near the low end of those industrial societies[4–7]. There was a difference of nearly 1-h between summer and winter sleep. Daily variation in sleep duration was strongly linked to time of onset, rather than offset. None of these groups began sleep near sunset, onset occurring, on average, 3.3-h after sunset. Awakening was usually before sunrise. The sleep period consistently occurred during the nighttime period of falling environmental temperature, was not interrupted by extended periods of waking and terminated, with vasoconstriction, near the nadir of daily ambient temperature. The daily cycle of temperature change, largely eliminated from modern sleep environments, may be a potent natural regulator of sleep. Light exposure, was maximal in the morning greatly decreasing at noon, indicating that all three groups seek shade at midday and that light activation of the suprachiasmatic nucleus is maximal in the morning. Napping occurred on <7% of days in winter and <22% of days in summer. Mimicking aspects of the natural environment might be effective in treating certain modern sleep disorders.
Recommended Citation
Yetish, G., Kaplan, H., Gurven, M., et al. (2015). Natural sleep and its seasonal variations in three pre-industrial societies. Current Biology, 25(21), 2862-2868. https://doi.org/10.1016/j.cub.2015.09.046
Peer Reviewed
1
Copyright
Elsevier
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Included in
Biological and Physical Anthropology Commons, Economic Theory Commons, Ethnic Studies Commons, Latin American Studies Commons, Other Anthropology Commons, Other Economics Commons, Social and Cultural Anthropology Commons
Comments
NOTICE: this is the author’s version of a work that was accepted for publication in Current Biology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Current Biology, volume 25, issue 21, in 2015. https://doi.org/10.1016/j.cub.2015.09.046
The Creative Commons license below applies only to this version of the article.