Where Human Sleep Went Wrong

When evolutionary anthropologist David Samson was living and working among the Hadza tribe in northern Tanzania, he noticed something puzzling: Their sleep was highly fragmented, short in duration, and low in “efficiency,” or actual time spent sleeping versus time in bed. This broken sleep was partly the consequence of activity and noise well into the night in the camps. People stayed up late telling stories, sharing food, and dancing. Yet, the Hadza uniformly reported high satisfaction with their sleep. It challenged the so-called Paleo sleep hypothesis, the notion that hunter-gatherer sleep must be optimally long and deep, but also ran counter to the medical orthodoxy that unbroken sleep is essential to a good night’s rest.