Irregular Sleep Patterns May Have Kept Early Humans Safe from Predators, According to Science

We finally know why we're always getting up at the same time every night.

You wake up with a jolt and take a look outside. The moon is still out, the sun isn’t quite up, and you still have a few hours to go before starting your day. In an ideal world, you would have slept cleanly through the night. (By the way, you can make these eight little changes to sleep better in just one day.)

The above situation is shared by modern humans and their more ancient ancestors, according to a new study from UNLV, Duke University and the University of Toronto.

Irregular sleep patterns, as it turns out, may have been a sort of defense mechanism for early humans to protect themselves from potential dangers lurking in the dark of night. If at least one person is awake at all times, the likelihood of an attack by a wild animal could be much lower.  


The new study was conducted among the Hadza people of northern Tanzania. The Hadza are modern hunter/gatherers and sleep in groups of 20 to 30 people. Thirty three  healthy Hadza men and women agreed to wear a watch-like device which would monitor their sleep patterns.

Some participants were early to bed and early to rise, and some were not. The staggered bedtimes paired with periodic awakenings from individual members of the group resulted in very rare instances when everyone was asleep at the same time.

All told, out of 220 total hours of study observation, there was only 18 minutes in which the entire group was asleep, or just over 0.1 percent of the time.

So, next time you wake up in the middle of the night, consider yourself lucky that you don’t have to face off against a Wooly Mammoth in your PJ’s. 

(And if you’re having trouble sleeping, check out these 13 secrets for better sleep.)

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