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A conversation with David Samson, evolutionary anthropologist and author of The Sleepless Ape , about how to sleep
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.
Samson traveled to Tanzania to hang out with the Hadza because he was trying to untangle what he calls the sleep paradox: Sleep is critical to human functioning, and yet, we sleep fewer total hours than any other ape, and are still arguably the most evolutionarily successful of the primates. This riddle sent him climbing into chimpanzee nests high in the trees and exploring the sleeping huts and practices of communities around Africa and Madagascar.
The stories he collected, people he met, and research findings he uncovered are vividly described in his new book The Sleepless Ape: The Story of Sleep in Human Evolution . I spoke with Samson about what we really need for a good night’s sleep, why we may be on the cusp of a “sleep enlightenment,” and the origins of what he calls the “lie-down-and-die” model of Western sleep.
You can just say, “Oh, here’s where humans are relative to other primates on sleep.” But that misses the deeper evolutionary story. When I was a postdoc at Duke University about a decade ago, new data was emerging showing that even after controlling for brain size, body size, social order, and actual phylogenetic relatedness, humans are weird outliers—we’re the shortest sleeping primates, yet we pack in the most REM sleep relative to this short duration.
This emerged to me as one of these mysteries that I had to sink my teeth into, and it eventually became the thesis of the book. As humans, we all know what it’s like to have a bad night’s sleep. If you have only two or three hours under your belt, your cognition suffers, your capacity to plan ahead suffers, your social regulation suffers. REM sleep functions almost like a nightly behavioral therapist. Sleep deprivation also erodes your ability to resist disease and to resist injury. We know experientially on a day-to-day basis how desperately we need sleep, yet we’re the shortest sleeping primate ever recorded on the planet, by a very far measure. The owl monkey, by contrast, sleeps 17 hours in a 24-hour period. That’s the paradox in a nutshell.