There’s a Strange Reason Why You Sleep Less as You Get Older

And no, it has nothing to do with technology.

ShutterstockYou can officially quit blaming the blue light on your smartphones for your sleepless nights (though here’s why they could be a culprit, too!). According to researchers from the University of Toronto, the reason you sleep less as you age could date back for centuries.

Just take it straight from the Hadza people in Tanzania, who still live traditional hunter-gatherer lifestyles. A fascinating new study examined their sleeping patterns, tracking the 33 group members on sleep monitors for 20 days and nights.

According to the results, all of the tribe’s members slept at the same time for only 18 minutes—and they were watched for a period of more than 200 hours. A median number of eight individuals were awake at any one time, which made up 40 percent of the group. Most importantly, the young teens were more likely to stay up late—dubbed “night owls”—while the elderly members started their days early and tended to sleep less.

Makes sense, right? Centuries ago, someone always needed to stay awake to watch for predators and other rival groups while everyone else slept. And humans aren’t the only ones to follow this pattern; animals like meerkats still do the same thing. The study, published in the journal Proceedings of the Royals Society B, dubbed this idea the “sentinel hypothesis.”

“Researchers have theorized that one of the reasons grandparents live so long past their reproductive years is that their function is to take care of grandchildren,” co-author David Samson said in a statement. “Our hypothesis is that their lark behavior and shorter sleep times serve a function: the elders serve as sentinels at the times of day when others are sleeping. Therefore, it’s important to have people of all ages in any population.”

There’s a scientific explanation why you can’t fall asleep on Sunday nights, too.

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