Restless Development: Bad Sleep May Be Evolutionary Survival Tool, Study Finds

Poor sleep is often regarded as a modern affliction linked to our sedentary lifestyles, electric lighting and smartphones on the bedside table. However, new research suggests that fitful sleep could be an ancient survival mechanism designed to guard against nocturnal threats. The study, which tracked the sleep patterns of a modern-day hunter-gatherer tribe in northern Tanzania, found that frequent night-time waking and differing sleep schedules between the young and old ensured that there was nearly always at least one tribe member awake. “They tell an important part of the human evolutionary story because they live a lifestyle that is the most similar to our hunting and gathering past,” said Alyssa Crittenden, an associate professor of anthropology at the University of Nevada, Las Vegas, and one of the study’s co-authors. “They sleep on the ground and have no synthetic lighting or controlled climate.” Of over 220 total hours of observation, there were just 18 minutes when all adults were sound asleep simultaneously. On average, more than a third of the group was alert, or dozing very lightly, at any given time.

The authors claim that the misalignment of sleep schedules of the young and elderly could be an evolutionary adaptation that kept our ancestors safe when sleeping in mixed-age groups.

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