Yathin S Krishnappa

Thanks gran! Insomniac oldies could save you from waking up in a bear's mouth

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A healthy mixture of early birds, night owls and wakeful elderly people may have evolved as a clever way of protecting the community from wild beasts and dangerous environments during the night, according to a US study. By tracking the sleep activity of modern day hunter-gatherers in Tanzania, the researchers found that, over a period of twenty days, there were only eighteen minutes when no-one was awake. This strategy may explain why there is still a wide variety in the sleeping habits in modern day humans, they say.

Journal/conference: Proceedings of the Royal Society B

Organisation/s: Duke University, USA

Funder: National Geographic (grant no. 9665-15)

Media Release

From: The Royal Society

Chronotype Variation Drives Nighttime Sentinel-Like Behaviour in Hunter-Gatherers

Sleep is essential for survival, yet also represents a time of extreme vulnerability. The sentinel hypothesis proposes that group-living animals share the task of vigilance during rest periods. To test this in humans, we investigated sleep patterns among Hadza hunter-gatherers of Tanzania. We show that asynchronous sleep is common, with one or more individuals awake during 99.8% of the rest period. We found that variation in chronotype facilitates this effect, and is itself influenced by age. Thus, chronotype variation and wakeful older individuals in modern humans may be a legacy of natural selection acting to reduce the dangers of sleep.


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