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Sleeping troubles might be an evolutionary survival tool

Many people complain about having trouble sleeping. What they might not know, however, is that their insomnia might be traced back to prehistoric times, when people had to stay awake to guard the cave at night.

A study published in the journal Proceedings of the Royal Society B found that age-related differences in sleep patterns ensure that at least one person is awake during night, according to CBS. The study was performed on modern hunter-gatherers in Tanzania, named the Hazda, who still live in groups. “The idea that there’s a benefit to living with grandparents has been around for a while, but this study extends that idea to vigilance during nighttime sleep,” study co-author David Samson said in a Duke University news release.

The hunter gatherers live and sleep in groups of 20 to 30 people and follow day/night cycles the same way humans did for hundreds of thousands of years before agriculture began developing. “They are as modern as you and me. But they do 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,” study co-author Alyssa Crittenden, an associate professor of anthropology at the University of Nevada, Las Vegas, said. “They sleep on the ground, and have no synthetic lighting or controlled climate — traits that characterized the ancestral sleeping environment for early humans,” Crittenden noted.


The Hazda don’t post sentinels to watch the cave throughout the night, because individual sleep patterns and restless sleep among older members of the group ensure that at lest one person is guarding. Over a thirs of the group was alert or dozing lightly at any given time, and “that’s just out of the healthy adults; it doesn’t include children, or people who were injured or sick,” according to Samson.

“A lot of older people go to doctors complaining that they wake up early and can’t get back to sleep,” Nunn observed. “But maybe there’s nothing wrong with them. Maybe some of the medical issues we have today could be explained not as disorders, but as a relic of an evolutionary past in which they were beneficial.”


Daisy Wilder