It’s easy to blame all of our sleep problems on our not-so-healthy lifestyle habits. And it’s true that our tendencies to stare at glowing screens, drink caffeine or alcohol, not get enough exercise, and not eat a healthy diet can negatively impact our quality of sleep.
Sleep quality, however, is influenced by much more than just our lifestyle habits. In a recent study, researchers were able to confirm a sentinel hypothesis from decades ago, which proposed that animals living in groups shared the task of keeping each other safe by taking shifts to watch for potential signs of danger. This suggests that our sleep patterns (including many of the disruptions we experience throughout the night) are rooted in human evolution and the survival techniques our ancestors used to protect themselves against nighttime threats.
To examine sentinel-like behavior in humans as they sleep, the researchers tracked the activity patterns of members of a hunter-gatherer tribe in Tanzania. Thirty-three men and women were given activity tracker wristbands to monitor their sleep and wake periods throughout the night over a three-week period.
By the end of the three weeks and with over 13,000 tracked minutes, the researchers found that every member of the tribe had slept simultaneously for only 18 minutes. In fact, 40 percent of the group on average was awake or in a light doze at any time of the night.
Previous studies have shown similar findings in other animals like mice and birds. This, however, is the first study to confirm these types of sleep pattern behaviors in humans who live a lifestyle that most closely resembles that of our ancestors.
The researchers also found that tribe members’ ages influenced their sleep patterns. Younger members typically stayed up later while older members went to sleep earlier and woke up earlier in the mornings due to a poorer night’s sleep.
In Western society, we tend to think of these types of disruptive patterns as something we need to fix, but the study findings suggest that they’re what helped our ancestors survive. The researchers also made sure to point out that poorer sleep quality as we age might indeed stem from this survival advantage.
Although we don’t face the same threats in the west as our ancestors or those living in hunter-gatherer tribes today, we do face our own modern day versions of threats to our survival. It’s possible that our adaptive sleep select-ability could be partly to blame for the sleep disruptions that occur due to the subconscious effects of our perceived problems related to finances, job security, relationships and other modern day realities.
The next steps involve studying the sleep patterns of self-contained human populations of other cultures in other geographical areas. The team of researchers will continue their investigation next in the Arctic, to find out whether differences in light, temperature and latitude may have contributed to the evolution of human sleep patterns.
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