Media ReleaseFrom: 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.